Add software LiPo UV protection with energy-save boot.

Detect under-voltage on GPIO1/11, persist UV state in NVS, enter a minimal
power mode without ESP-NOW, and recover after charge; expose LED mode 6
battery-low for host testing via goTool.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/ARCHITECTURE.md

@@ -0,0 +1,416 @@
+# Powerpod — Architektur-Spezifikation
+
+Dieses Dokument beschreibt die Firmware-Architektur des ESP32-S3-Projekts: Rollen, Schichten, Datenflüsse und die wichtigsten Implementierungsstellen. **goTool** (Host-CLI) ist bewusst ausgeschlossen — es nutzt nur das UART-Protokoll des Masters.
+
+---
+
+## 1. Systemüberblick
+
+Master und Slave laufen mit **demselben Binary**. Die Rolle wird beim Boot per DIP-Schalter und I2C-IO-Expander festgelegt; danach verzweigt die Initialisierung.
+
+```mermaid
+flowchart TB
+  subgraph host["Externer Host (UART)"]
+    PC[PC / beliebiger UART-Client]
+  end
+
+  subgraph master["Master ESP32-S3"]
+    UART_RX[uart_read_task]
+    Q[cmd_queue]
+    DISP[vCmdDispatcherTask]
+    HAND[cmd/*.c Handler]
+    REG[client_registry]
+    ENOW_M[esp_now_comm Master]
+  end
+
+  subgraph slaves["Slave ESP32-S3 × N"]
+    ENOW_S[esp_now_comm Slave]
+    BMA[BMA456 + LED Ring]
+  end
+
+  PC <-->|UART1 921600 framed + protobuf| UART_RX
+  UART_RX --> Q --> DISP --> HAND
+  HAND --> REG
+  HAND --> ENOW_M
+  ENOW_M <-->|ESP-NOW nanopb| ENOW_S
+  ENOW_S --> BMA
+  ENOW_S -->|Accel/Tap/Battery| ENOW_M
+  ENOW_M --> REG
+```
+
+| Rolle | UART | ESP-NOW | Zentrale Datenhaltung |
+|-------|------|---------|------------------------|
+| **Master** | Ja — einziger Befehlseingang von außen | Discover (Broadcast), Unicast zu Slaves | `client_registry.c` |
+| **Slave** | Nein | Antwort auf Discover, Heartbeat, Events zum Master | `esp_now_slave.c` |
+
+**Einstieg:** `main/powerpod.c` → `app_main()`.
+
+---
+
+## 2. Boot und Konfiguration
+
+### 2.1 Ablauf
+
+```mermaid
+sequenceDiagram
+  participant AM as app_main
+  participant NVS as pod_settings
+  participant I2C as I2C / IO-Expander
+  participant BMA as bosch456
+  participant EN as esp_now_comm
+  participant LR as led_ring
+  participant BI as board_input
+  participant CMD as cmd_handler + uart
+
+  AM->>NVS: pod_settings_init()
+  AM->>AM: GPIO DIP_MASTER → master/slave
+  AM->>I2C: Bus + Expander 0x20 → network 1–8
+  AM->>BMA: init_bma456() (Master + Slave)
+  AM->>AM: app_config_t füllen
+  AM->>BI: board_input_init()
+  AM->>EN: esp_now_comm_init(&app_config)
+  AM->>LR: led_ring_init()
+  alt master == true
+    AM->>CMD: Queue, Dispatcher, UART, Handler registrieren
+  end
+```
+
+### 2.2 `app_config_t`
+
+| Feld | Quelle | Bedeutung |
+|------|--------|-----------|
+| `master` | `DIP_MASTER` (GPIO 4): Low = Master | Steuert UART + Registry-Nutzung |
+| `network` | IO-Expander, Bits 5–8 (nibble reversed) | 1–8 → WiFi/ESP-NOW-Kanal |
+| `running_partition` | `esp_ota_get_running_partition()` | Aktives OTA-Label (`ota_0` / `ota_1`) |
+
+**Dateien:** `main/app_config.h`, `main/powerpod.c`, `main/powerpod.h` (Pins).
+
+---
+
+## 3. Schichtenmodell
+
+```
+┌─────────────────────────────────────────────────────────────┐
+│  Befehlshandler (main/cmd/cmd_*.c)                          │
+│  Decode/Encode: uart_cmd.c, Antwort: uart_proto.c           │
+├─────────────────────────────────────────────────────────────┤
+│  Dispatch: cmd_handler.c (Queue + vCmdDispatcherTask)       │
+├─────────────────────────────────────────────────────────────┤
+│  Transport UART: uart.c (Framing)  │  ESP-NOW: esp_now_comm │
+├─────────────────────────────────────────────────────────────┤
+│  Protokoll: uart_messages.proto    │  esp_now_messages.proto │
+│  Codec: nanopb (proto/*.pb.c)      │  esp_now_proto.c        │
+├─────────────────────────────────────────────────────────────┤
+│  Domäne: client_registry, bosch456, led_ring, ota_*, board  │
+├─────────────────────────────────────────────────────────────┤
+│  ESP-IDF: UART, WiFi, ESP-NOW, I2C, ADC, OTA, NVS, FreeRTOS │
+└─────────────────────────────────────────────────────────────┘
+```
+
+---
+
+## 4. Datenfluss: Commands (Befehle)
+
+Commands sind **asynchron über eine FreeRTOS-Queue** entkoppelt; der UART-Reader blockiert nicht auf Handler-Logik.
+
+### 4.1 Eingang (UART → Handler)
+
+```mermaid
+flowchart LR
+  A[Bytes UART1] --> B[parse_uart_byte]
+  B --> C{Frame vollständig?}
+  C -->|ja| D[uart_enqueue_packet]
+  D --> E["generic_msg_t<br/>msg_id = payload[0]<br/>payload = Rest"]
+  E --> F[cmd_queue xQueueSend]
+  F --> G[vCmdDispatcherTask]
+  G --> H{msg_register_handler}
+  H --> I[cmd_*.c callback]
+  I --> J[free payload]
+```
+
+**Wichtige Stellen:**
+
+| Schritt | Datei | Funktion |
+|---------|--------|----------|
+| Byte-Parser + Timeout 50 ms | `main/uart.c` | `parse_uart_byte()`, `uart_read_task()` |
+| Queue-Eintrag | `main/uart.c` | `uart_enqueue_packet()` |
+| Dispatcher | `main/cmd/cmd_handler.c` | `vCmdDispatcherTask()`, `msg_register_handler()` |
+| Registrierung Master | `main/powerpod.c` | `cmd_*_register()` nach `init_uart()` |
+
+**Nachrichten-ID:** Byte 0 des UART-Payloads = `alox_MessageType` (siehe `main/proto/uart_messages.proto`). Bytes 1… = nanopb-kodiertes `UartMessage` **ohne** wiederholtes Type-Feld — Handler erhalten nur den protobuf-Teil (`msg.payload` ab Offset 1).
+
+### 4.2 Ausgang (Handler → UART)
+
+```mermaid
+flowchart LR
+  H[Handler baut alox_UartMessage] --> U[uart_cmd_send]
+  U --> P[uart_send_uart_message]
+  P --> E[pb_encode + Byte0 = type]
+  E --> F[uart_send_framed]
+  F --> W[uart_write_bytes]
+```
+
+**Wichtige Stellen:**
+
+| Schritt | Datei | Funktion |
+|---------|--------|----------|
+| Handler-Hilfen | `main/uart_cmd.c` | `uart_cmd_decode()`, `uart_cmd_init_response()`, `uart_cmd_send()` |
+| Protobuf + Framing | `main/uart_proto.c` | `uart_send_uart_message()` |
+| XOR-Rahmen | `main/uart.c` | `uart_send_framed()` |
+
+### 4.3 OTA-Sperre (keine parallelen Befehle)
+
+Während einer OTA-Session (`ota_uart_is_active()` oder `ota_espnow_distribution_active()`) lehnt der Dispatcher alle UART-Befehle ab **außer**:
+
+- `OTA_START`, `OTA_PAYLOAD`, `OTA_END`, `OTA_START_ESPNOW`, `OTA_SLAVE_PROGRESS`
+
+Implementierung: `ota_session.c`, Prüfung in `vCmdDispatcherTask` vor Handler-Aufruf.
+
+Auf dem **Slave** verarbeitet `espnow_recv_cb` während `ota_uart_is_active()` nur noch OTA-Nachrichten vom joined Master (kein Discover, Stream, LED, …).
+
+Auf dem **Master** während ESP-NOW-Verteilung nur noch `ESPNOW_OTA_STATUS` aus dem recv_cb.
+
+### 4.4 UART-Request-Decode (strikt)
+
+| Regel | Beispiele |
+|-------|-----------|
+| Leerer protobuf-Body (`len == 0`) erlaubt | `VERSION`, `CLIENT_INFO`, `CACHE_STATUS`, `BATTERY_STATUS` (Defaults) |
+| `len > 0` → Decode muss gelingen, `which_payload` muss passen | `ACCEL_STREAM`, `TAP_NOTIFY`, `RESTART`, OTA, … |
+
+### 4.5 Bridge-Muster: UART-Befehl → ESP-NOW
+
+Viele Master-Handler folgen demselben Muster:
+
+1. `uart_cmd_decode()` → Request aus `UartMessage`
+2. Lokale Aktion und/oder `client_registry_*` aktualisieren
+3. `esp_now_comm_send_*()` mit MAC aus Registry
+4. `uart_cmd_send()` mit Response
+
+```mermaid
+sequenceDiagram
+  participant Host
+  participant UART as uart.c
+  participant CMD as cmd_accel_deadzone.c
+  participant REG as client_registry
+  participant EN as esp_now_comm.c
+  participant SL as Slave
+
+  Host->>UART: Frame ACCEL_DEADZONE
+  UART->>CMD: generic_msg_t
+  CMD->>REG: set_accel_deadzone / lookup MAC
+  CMD->>EN: esp_now_comm_send_accel_deadzone
+  EN->>SL: ESPNOW_SET_ACCEL_DEADZONE
+  SL->>SL: bma456 + NVS
+  CMD->>Host: uart_cmd_send Response
+```
+
+**Beispiel-Implementierung:** `main/cmd/cmd_accel_deadzone.c`  
+**Weitere Bridge-Handler:** `cmd_accel_stream.c`, `cmd_tap_notify.c`, `cmd_led_ring.c`, `cmd_espnow_find_me.c`, `cmd_restart.c`, `cmd_espnow_unicast_test.c`, `cmd_espnow_echo_ping.c`, `cmd/cmd_ota.c` (OTA + `ota_espnow.c`).
+
+**Nur Master / nur Cache (kein Slave-Roundtrip):** `cmd_client_info.c`, `cmd_battery.c`, `cmd_cache_status.c`, `cmd_version.c`, `cmd_set_log_level.c`.
+
+---
+
+## 5. Datenfluss: UART
+
+### 5.1 Rahmenformat (Transport)
+
+Unabhängig von Protobuf — reines Bytestream-Framing:
+
+| Feld | Wert |
+|------|------|
+| Start | `0xAA` |
+| Länge | 1 Byte (1–252) |
+| Payload | `length` Bytes |
+| Prüfsumme | XOR aller Payload-Bytes |
+| Stopp | `0xCC` |
+
+**Parameter:** `main/uart.h` — `UART_NUM_1`, `921600` Baud, TX GPIO **2**, RX GPIO **3**, `MAX_PAYLOAD_SIZE` 248.
+
+### 5.2 Nutzlast (Anwendung)
+
+```
+Payload[0]     = MessageType (enum, 1 Byte)
+Payload[1…]    = nanopb UartMessage (Felder ab type/payload oneof)
+```
+
+**Schema:** `main/proto/uart_messages.proto`  
+**Generiert:** `main/proto/uart_messages.pb.c/h` (`make proto_generate_uart`)
+
+### 5.3 Tasks und Prioritäten
+
+| Task | Stack | Priorität | Datei |
+|------|-------|-----------|--------|
+| `uart_rx` | 4096 | 5 | `uart.c` |
+| `cmd_dispatch` | 8192 | 5 | `cmd_handler.c` |
+
+Queue-Größe Master: **64** Einträge (`powerpod.c`); volle Queue → Warnung, Payload wird freigegeben.
+
+---
+
+## 6. Datenfluss: ESP-NOW
+
+### 6.1 Stack-Initialisierung
+
+`esp_now_comm_init()` (`esp_now_comm.c`) → `esp_now_core` (WiFi/Radio/Send) + Rolle:
+
+1. `client_registry_init()` (Master)
+2. `esp_now_init()`, recv_cb leitet an `esp_now_master_on_recv` / `esp_now_slave_on_recv`
+3. **Master** (`esp_now_master.c`): `espnow_disc`, `espnow_mon`
+4. **Slave** (`esp_now_slave.c`): `espnow_stx`, `espnow_hb`, `espnow_accel`, `ota_slave_work`
+
+**Codec:** Rohes Paket = ein nanopb `EspNowMessage` — **kein** zusätzliches Framing (`main/esp_now_proto.c`).
+
+### 6.2 Discovery und Join (Slave)
+
+```mermaid
+sequenceDiagram
+  participant M as Master espnow_disc
+  participant S as Slave recv_cb
+  participant TX as slave_tx_task
+
+  loop alle 500 ms
+    M->>M: ESPNOW_DISCOVER → FF:FF:…:FF
+  end
+  S->>S: handle_discover (network match)
+  S->>S: s_slave_joined, s_master_mac
+  Note over S,TX: Kein Send aus recv_cb!
+  S->>TX: SLAVE_TX_SLAVE_INFO
+  TX->>M: ESPNOW_SLAVE_INFO
+  S->>TX: SLAVE_TX_BATTERY
+  TX->>M: ESPNOW_BATTERY_REPORT
+  loop alle 1 s
+    S->>M: ESPNOW_HEARTBEAT
+  end
+```
+
+**Registry-Schlüssel:** immer `recv_info.src_addr` (WiFi-MAC des Senders), **nicht** optionales `mac`-Feld in der Protobuf-Nachricht.
+
+**Slave-ID:** `mac[5]` (letztes Oktett) — kann kollidieren; eindeutig ist die volle MAC in der Registry.
+
+**Master-Verlust:** Slave setzt Join zurück, wenn **5 s** kein Discover vom gleichen Master (`SLAVE_MASTER_LOST_MS`).
+
+**Join-Policy:** Master→Slave-Steuerung (Stream, Tap, LED, OTA, `UNICAST_TEST`, `SET_ACCEL_DEADZONE`, …) nur bei `s_slave_joined` und `src_addr == s_master_mac`. Während `ota_uart_is_active()` auf dem Slave verarbeitet der recv_cb nur OTA vom joined Master.
+
+**Slave OTA:** Payload/End/Status-Sends laufen über `ota_slave_work_task` (Queue), nicht im ESP-NOW-recv_cb.
+
+### 6.3 Master → Slave (Unicast)
+
+Alle Master-Sends laufen über `send_message()` / `send_message_ex()`:
+
+1. `esp_now_proto_encode()`
+2. `ensure_peer(dest_mac)`
+3. `esp_now_send()`
+
+Öffentliche API: `main/esp_now_comm.h` (`esp_now_comm_send_*`).
+
+**Empfang Slave:** `espnow_recv_cb()` → Switch auf `which_payload` → Handler (`handle_slave_*`).
+
+### 6.4 Slave → Master (Events)
+
+| Nachricht | Task / Trigger | Master-Ziel |
+|-----------|----------------|-------------|
+| `ESPNOW_ACCEL_SAMPLE` | `slave_accel_stream_task` 16 ms | `client_registry_update_accel()` |
+| `ESPNOW_TAP_EVENT` | BMA456-IRQ → `on_bma456_tap` | `client_registry_update_tap()` |
+| `ESPNOW_BATTERY_REPORT` | Heartbeat + nach Join | `client_registry_update_battery()` |
+| `ESPNOW_SLAVE_INFO` / `HEARTBEAT` | `slave_tx_task` / Heartbeat-Task | `client_registry_heartbeat()` |
+| `ESPNOW_OTA_STATUS` | `ota_espnow_slave_*` | `ota_espnow_master_on_status()` |
+
+**Master recv:** `espnow_recv_cb()` — Presence, Accel, Tap, Battery, OTA-Status.
+
+### 6.5 OTA über ESP-NOW
+
+Nach erfolgreichem UART-OTA auf dem Master (oder `OTA_START_ESPNOW`): `ota_espnow.c` liest gestagte Partition, sendet `OTA_START` / `PAYLOAD` (≤200 B, `send_message_ex` mit ACK-Semaphore) / `OTA_END` an alle **available** Slaves.
+
+Gemeinsamer Flash-Puffer: `ota_uart.c` (4 KiB Blockgröße).
+
+---
+
+## 7. Client Registry (Master-Datenhub)
+
+Die Registry ist die **zentrale Brücke** zwischen ESP-NOW-Echtzeitdaten und UART-Abfragen.
+
+```mermaid
+flowchart TB
+  EN_RX[espnow_recv_cb] --> REG[client_registry]
+  CMD_R[cmd_client_info / battery / cache_status] --> REG
+  CMD_W[cmd_* write paths] --> REG
+  REG --> CMD_R
+  EN_TX[esp_now_comm_send_*] --> MAC[MAC aus Registry]
+```
+
+| Daten | Aktualisiert durch | Gelesen durch UART |
+|-------|-------------------|-------------------|
+| Presence, Version | HEARTBEAT / SLAVE_INFO | `CLIENT_INFO` |
+| Accel-Stream-Samples | `ESPNOW_ACCEL_SAMPLE` | `CACHE_STATUS` |
+| Tap-Events (16 ms Cache) | `ESPNOW_TAP_EVENT` | `CACHE_STATUS` |
+| Batterie | `ESPNOW_BATTERY_REPORT` + Master-ADC | `BATTERY_STATUS` |
+| Konfig-Flags | Handler + ESP-NOW | `CLIENT_INFO`, diverse GET |
+
+**Datei:** `main/client_registry.c`, `main/client_registry.h` (max. 16 Clients, Timeout 3 s ohne Heartbeat).
+
+---
+
+## 8. FreeRTOS-Tasks (Übersicht)
+
+| Task | Rolle | Intervall / Trigger |
+|------|-------|---------------------|
+| `uart_rx` | Master | UART read 20 ms timeout |
+| `cmd_dispatch` | Master | Queue blocking |
+| `espnow_disc` | Master | 500 ms Discover |
+| `espnow_mon` | Master | 1 s Timeout + Master-Battery |
+| `espnow_stx` | Slave | Queue: SLAVE_INFO, Battery nach Join |
+| `espnow_hb` | Slave | 1 s Heartbeat + 30 s Battery |
+| `espnow_accel` | Slave | 16 ms Accel wenn Stream an |
+| `bma456_poll` | Beide | 10 Hz (`bosch456.c`) |
+| `vTaskLedRing` | Beide | LED-Ring-Befehle |
+
+`app_main` endet in `while(1) vTaskDelay(portMAX_DELAY)` — alle Arbeit läuft in Tasks.
+
+---
+
+## 9. Implementierungskarte (wichtige Dateien)
+
+| Bereich | Pfad | Verantwortung |
+|---------|------|----------------|
+| Einstieg / Init | `main/powerpod.c` | Boot-Reihenfolge, Master-Handler-Register |
+| UART Transport | `main/uart.c`, `main/uart.h` | Framing RX/TX |
+| UART Protobuf TX | `main/uart_proto.c` | `uart_send_uart_message` |
+| UART Handler-Boilerplate | `main/uart_cmd.c`, `main/uart_cmd.h` | Decode, Register, Send |
+| Command Dispatch | `main/cmd/cmd_handler.c` | Queue, Dispatcher |
+| UART Commands | `main/cmd/cmd_*.c` | Pro Befehl ein Modul |
+| ESP-NOW | `esp_now_comm.c` Init/Router; `esp_now_core.c` Send/Peer; `esp_now_master.c` / `esp_now_slave.c` Rollenlogik |
+| ESP-NOW Codec | `main/esp_now_proto.c` | nanopb encode/decode |
+| Registry | `main/client_registry.c` | Slave-Tabelle + Caches |
+| BMA456 | `main/bosch456.c` | Sensor, Tap, Deadzone-Filter |
+| LED | `main/led_ring.c` | 95 LEDs, Digit-Maps |
+| OTA UART | `main/ota_uart.c`, `cmd/cmd_ota.c` | A/B-Partition Upload |
+| OTA ESP-NOW | `main/ota_espnow.c` | Verteilung an Slaves |
+| Einstellungen NVS | `main/pod_settings.c` | Accel-Deadzone persistent |
+| Board | `main/board_input.c` | Taster, LiPo-ADC |
+| Protobuf Schemas | `main/proto/*.proto` | Vertrag UART / ESP-NOW |
+| Vendor BMA456 | `components/bma456/` | Nur `bma4.c` + `bma456h.c` gelinkt |
+
+---
+
+## 10. Protokoll-Verträge (Kurzreferenz)
+
+- **UART:** `main/proto/uart_messages.proto` — Host ↔ Master  
+- **ESP-NOW:** `main/proto/esp_now_messages.proto` — Master ↔ Slave  
+
+Regenerierung: `make proto_generate` (siehe `DOCUMENTATION.md`).
+
+---
+
+## 11. Design-Entscheidungen
+
+1. **Eine Queue für UART-Commands** — einziger Eingang vom Host; während OTA nur OTA-Befehle.  
+2. **Kein ESP-NOW-Send im `recv_cb`** — Slave antwortet auf Discover über `slave_tx_task` (Deadlock-/Stack-Risiko vermeiden).  
+3. **Registry-MAC = ESP-NOW-Quelladresse** — Protobuf-MAC ist optional/informativ.  
+4. **Gleiches Binary** — Konfiguration nur Hardware (DIP + Expander); reduziert Release-Komplexität.  
+5. **Nanopb statt vollem protobuf-c** — passend für ESP-RAM/Flash.  
+6. **Master aggregiert Sensor-Daten** — Slaves streamen; Host pollt Cache per UART (`CACHE_STATUS`), kein Durchreichen jedes Accel-Samples über UART.
+
+---
+
+Weitere Details (Befehlsliste, GPIO, Build, BMA456): [`DOCUMENTATION.md`](DOCUMENTATION.md).

docs/DOCUMENTATION.md

@@ -0,0 +1,564 @@
+# Powerpod ESP-Firmware — Dokumentation
+
+Vollständige Referenz für das ESP-IDF-Projekt unter `main/` und `components/`. Diese Doku beschreibt **nur die Firmware** — kein goTool, keine Host-Implementierung.
+
+- **Architektur & Datenflüsse:** [`ARCHITECTURE.md`](ARCHITECTURE.md)  
+- **Neues Feature end-to-end:** [`adding-a-feature.md`](adding-a-feature.md)
+
+---
+
+## Inhaltsverzeichnis
+
+1. [Projektziel](#1-projektziel)
+2. [Hardware und Pins](#2-hardware-und-pins)
+3. [Build und Flash](#3-build-und-flash)
+4. [Boot-Konfiguration](#4-boot-konfiguration)
+5. [UART-Protokoll](#5-uart-protokoll)
+6. [ESP-NOW-Protokoll](#6-esp-now-protokoll)
+7. [Befehlsreferenz (UART)](#7-befehlsreferenz-uart)
+8. [OTA](#8-ota)
+9. [BMA456 Beschleunigungssensor](#9-bma456-beschleunigungssensor)
+10. [LED-Ring](#10-led-ring)
+11. [Board-Input und Batterie](#11-board-input-und-batterie)
+12. [Persistenz (NVS)](#12-persistenz-nvs)
+13. [Protobuf und Code-Generierung](#13-protobuf-und-code-generierung)
+14. [Modulreferenz](#14-modulreferenz)
+15. [Logging-Tags](#15-logging-tags)
+
+---
+
+## 1. Projektziel
+
+**Powerpod** ist Firmware für ESP32-S3-Knoten in einem verteilten System:
+
+- Ein **Master** spricht per **UART** mit einem externen Host und verwaltet bis zu **16 Slaves** über **ESP-NOW**.
+- **Slaves** haben keinen UART-Befehlspfad; sie joinen über periodisches **Discover**, senden Heartbeats und liefern Sensor-/Statusdaten.
+- Master und Slave nutzen **identisches Firmware-Image**; Rolle und Funknetz werden beim Boot erkannt.
+
+Zielbild für den Host: Befehle an den Master senden; der Master steuert Slaves und **cached** deren Telemetrie (`client_registry`) für schnelle UART-Abfragen.
+
+---
+
+## 2. Hardware und Pins
+
+> Pinbelegung ist in `powerpod.h` als vorläufig markiert — mit Schaltplan abgleichen.
+
+| Signal | GPIO | Datei / Modul |
+|--------|------|----------------|
+| DIP Master/Slave | 4 | `powerpod.h` — Low = Master |
+| I2C SCL / SDA | 5 / 6 | IO-Expander `0x20`, BMA456 `0x18` |
+| UART1 TX / RX | **2 / 3** | `uart.h` (Adapter: ESP-TX → Host-RX) |
+| LED-Ring (WS2812) | 7 | `led_ring.c` |
+| BMA456 Interrupt | 10 | `bosch456.c` |
+| Taster | 12 | `board_input.c` |
+| LiPo ADC 1 | 1 | `board_input.c` |
+| LiPo ADC 2 | 11 | `board_input.c` |
+
+**UART (Host-Protokoll):** `UART_NUM_1`, **921600** Baud, 8N1, kein Flow-Control.
+
+**ESP-IDF-Log (Debug):** `esp_log_*` geht auf **UART0** (Standard-Konsole, typisch USB am Dev-Board, **115200** Baud, `CONFIG_ESP_CONSOLE_UART_NUM=0`). Das ist **getrennt** vom Host-UART1 — goTool liest keine `esp_log`-Ausgabe. Ohne angeschlossenes Debug-Kabel werden aktivierte Logs trotzdem formatiert und an UART0 gesendet (CPU-Overhead bleibt); nur `ESP_LOG_NONE` / Level-Filter vermeiden die Arbeit.
+
+**I2C:** 100 kHz, interne Pull-ups, gemeinsamer Bus für Expander und BMA456H.
+
+---
+
+## 3. Build und Flash
+
+**Ziel-Chip:** ESP32-S3 (ESP-IDF).
+
+```bash
+source ~/esp/esp-idf/export.sh   # oder export.fish
+cd /pfad/zu/powerpod
+idf.py build
+idf.py -p /dev/ttyUSB0 flash monitor
+```
+
+- **Git-Hash** wird beim Build in `POWERPOD_GIT_HASH` eingebettet (`main/CMakeLists.txt`).
+- **Firmware-Version:** `POWERPOD_FW_VERSION` (Default `1` in `esp_now_comm.c` / `cmd_version.c`).
+
+**Komponenten:**
+
+| Pfad | Inhalt |
+|------|--------|
+| `main/` | Anwendungslogik |
+| `components/bma456/` | Bosch BMA456H-Treiber (Vendor) |
+| `libs/nanopb/` | Protobuf-Codec für Embedded |
+
+---
+
+## 4. Boot-Konfiguration
+
+### 4.1 Initialisierungsreihenfolge (`powerpod.c`)
+
+1. `pod_settings_init()` — NVS
+2. `board_input_init_adc_only()` — LiPo-ADC
+3. Bei `POWERPOD_BATTERY_UV_ENABLE`: `battery_uv_evaluate_boot()` → ggf. Energiesparmodus (nur LED + ADC, **kein** weiterer Init)
+4. DIP → `app_config.master`
+5. I2C + IO-Expander → `app_config.network` (1–8)
+6. `init_bma456()` — optional, bei Fehler weiter ohne Sensor
+7. `pod_settings_apply_accel_deadzone()` wenn Sensor da
+8. OTA-Partition → `app_config.running_partition`
+9. `board_input_start_lipo_monitor()` + `board_input_init_button()`
+10. `esp_now_comm_init(&app_config)` — **normaler Pfad** (Master + Slave)
+11. `led_ring_init()`
+12. **Nur Master:** `cmd_queue` → `init_cmdHandler` → `init_uart` → alle `cmd_*_register()`
+
+### 4.2 Master vs. Slave
+
+| Funktion | Master | Slave |
+|----------|--------|-------|
+| UART Command-Handler | Ja | Nein |
+| ESP-NOW Discover senden | Ja (Broadcast) | Nein |
+| ESP-NOW auf Discover reagieren | Nein | Ja |
+| `client_registry` für Fremdknoten | Ja | Nein (nur eigener Join-State) |
+
+---
+
+## 5. UART-Protokoll
+
+*(Transport + Anwendung — Datenfluss-Diagramme in [`ARCHITECTURE.md`](ARCHITECTURE.md) §4–5.)*
+
+### 5.1 Rahmen
+
+| Byte | Inhalt |
+|------|--------|
+| 0 | `0xAA` Start |
+| 1 | Länge N (1–252) |
+| 2…N+1 | Payload |
+| N+2 | XOR-Checksum über Payload |
+| N+3 | `0xCC` Stopp |
+
+Implementierung: `uart.c` — `parse_uart_byte()`, `uart_send_framed()`.
+
+### 5.2 Anwendungs-Payload
+
+| Offset | Bedeutung |
+|--------|-----------|
+| 0 | `MessageType` (siehe Enum in `uart_messages.proto`) |
+| 1… | nanopb `UartMessage` (ohne separates type-Feld im protobuf-Teil) |
+
+**Antworten** nutzen dieselbe Struktur: Byte 0 = Response-Typ, Rest = kodierte `UartMessage`.
+
+### 5.3 Handler-Pipeline
+
+1. `uart_read_task` parst Frames → `uart_enqueue_packet`
+2. `generic_msg_t` → `cmd_queue`
+3. `vCmdDispatcherTask` → registrierter `msg_callback_t`
+4. Handler: `uart_cmd_decode(data, len, &msg)` — `data` ist **nur** protobuf-Teil; bei `len > 0` strikt (Decode/`which_payload`-Fehler → Fehlerantwort)
+5. `ota_session_uart_cmd_allowed()` — während OTA nur OTA-Befehle
+6. Antwort: `uart_cmd_init_response()` + Felder setzen + `uart_cmd_send()`
+
+Hilfsmakro für Request-Felder:
+
+```c
+UART_CMD_REQ(&uart_msg, alox_UartMessage_accel_deadzone_request_tag, accel_deadzone_request)
+```
+
+---
+
+## 6. ESP-NOW-Protokoll
+
+*(Join, Tasks, Registry — [`ARCHITECTURE.md`](ARCHITECTURE.md) §6.)*
+
+### 6.1 Grundlagen
+
+- WiFi **STA**, keine AP-Verbindung.
+- **Kanal** = `app_config.network` (1–13).
+- Payload = ein `EspNowMessage` (nanopb), max. `ESP_NOW_MAX_DATA_LEN`.
+- Schema: `main/proto/esp_now_messages.proto`.
+
+### 6.2 Nachrichtentypen
+
+| Type | Richtung | Payload | Zweck |
+|------|----------|---------|--------|
+| `ESPNOW_DISCOVER` | M→Broadcast | `discover.network` | Slaves finden Master |
+| `ESPNOW_SLAVE_INFO` | S→M | `slave_info` | Erste Registrierung |
+| `ESPNOW_HEARTBEAT` | S→M | `heartbeat` | Keepalive 1 s |
+| `ESPNOW_SET_ACCEL_DEADZONE` | M→S | `accel_deadzone` | Deadzone LSB |
+| `ESPNOW_SET_ACCEL_STREAM` | M→S | `accel_stream` | Stream ~16 ms |
+| `ESPNOW_ACCEL_SAMPLE` | S→M | `accel_sample` | x/y/z Roh-LSB |
+| `ESPNOW_SET_TAP_NOTIFY` | M→S | `tap_notify` | Tap-Arten filtern |
+| `ESPNOW_TAP_EVENT` | S→M | `tap_event` | kind 1/2/3 |
+| `ESPNOW_BATTERY_QUERY` | M→S | `battery_query` | On-demand |
+| `ESPNOW_BATTERY_REPORT` | S→M | `battery_report` | mV LiPo 1/2 |
+| `ESPNOW_LED_RING` | M→S | `led_ring` | Wie UART LED_RING |
+| `ESPNOW_FIND_ME` | M→S | `find_me` | LED-Locate |
+| `ESPNOW_RESTART` | M→S | `restart` | Reboot Slave |
+| `ESPNOW_UNICAST_TEST` | M→S | `unicast_test` | Link-Test |
+| `ESPNOW_ECHO_PING` | M→S | `echo_ping` | Latenztest (Host-Timestamp + `master_time_us`) |
+| `ESPNOW_ECHO_PONG` | S→M | `echo_pong` | Echo unverändert zurück zum Master |
+| `ESPNOW_OTA_*` | M↔S | `ota_*` | Firmware-Verteilung |
+
+### 6.3 Zeitkonstanten (`esp_now_comm.c`)
+
+| Konstante | Wert |
+|-----------|------|
+| Discover-Intervall | 500 ms |
+| Heartbeat | 1000 ms |
+| Client-Timeout (Master) | 3 × Heartbeat = 3 s → `available=false` |
+| Master-Verlust (Slave) | 5 s ohne Discover |
+| Accel-Stream | 16 ms |
+| Batterie-Report | 30 s (+ einmal 150 ms nach Join) |
+| Echo-Ping Timeout (Master) | 500 ms (`ESPNOW_ECHO_PING_TIMEOUT_MS`) |
+
+### 6.4 `EspNowSlavePresence`
+
+Felder: `network`, `mac` (6 B), `version`, `slave_id`, `available`, `used`.
+
+- `slave_id` = letztes Oktett der STA-MAC.
+- Registry auf dem Master indexiert über **Sender-MAC** der ESP-NOW-Callback.
+
+---
+
+## 7. Befehlsreferenz (UART)
+
+Nur auf dem **Master** registriert (`powerpod.c`). IDs aus `MessageType` in `uart_messages.proto`.
+
+| ID | Name | Modul | Kurzbeschreibung |
+|----|------|-------|------------------|
+| 1 | ACK | — | Reserviert |
+| 2 | ECHO | — | Reserviert |
+| 3 | VERSION | `cmd_version.c` | FW-Version, Git-Hash, OTA-Partition |
+| 4 | CLIENT_INFO | `cmd_client_info.c` | Liste `client_registry` |
+| 5 | CLIENT_INPUT | — | Geplant |
+| 6 | ACCEL_DEADZONE | `cmd_accel_deadzone.c` | Get/Set Deadzone lokal + ESP-NOW |
+| 7 | ESPNOW_UNICAST_TEST | `cmd_espnow_unicast_test.c` | Link-Test zu Slave |
+| 8 | LED_RING | `cmd_led_ring.c` | Ring lokal / ESP-NOW |
+| 16 | OTA_START | `cmd_ota.c` | UART-OTA beginnen |
+| 17 | OTA_PAYLOAD | `cmd_ota.c` | Chunk ≤200 B |
+| 18 | OTA_END | `cmd_ota.c` | Abschluss + ESP-NOW-Verteilung |
+| 19 | OTA_STATUS | `cmd_ota.c` | Gerät → Host Status |
+| 20 | OTA_START_ESPNOW | `cmd_ota.c` | Nur ESP-NOW aus Staging |
+| 21 | OTA_SLAVE_PROGRESS | `cmd_ota_slave_progress.c` | Fortschritt pro Slave |
+| 22 | FIND_ME | `cmd_espnow_find_me.c` | LED Locate |
+| 23 | RESTART | `cmd_restart.c` | Master oder Slave reboot |
+| 25 | ACCEL_STREAM | `cmd_accel_stream.c` | ESP-NOW Accel-Stream an/aus |
+| 26 | BATTERY_STATUS | `cmd_battery.c` | Cache LiPo Master + Slaves |
+| 27 | TAP_NOTIFY | `cmd_tap_notify.c` | Tap-Weiterleitung konfigurieren |
+| 29 | CACHE_STATUS | `cmd_cache_status.c` | Accel + Tap Cache (ein Round-Trip) |
+| 30 | ESPNOW_ECHO_PING | `cmd_espnow_echo_ping.c` | Timestamp-Echo über ESP-NOW (Latenztest) |
+| 31 | SET_LOG_LEVEL | `cmd_set_log_level.c` | ESP-IDF-Log-Level global (`"*"`) lesen/setzen |
+
+### 7.1 VERSION (3)
+
+- **Request:** nur Typ-Byte `0x03` oder leerer protobuf-Body.
+- **Response:** `version`, `git_hash`, `running_partition`.
+
+### 7.2 CLIENT_INFO (4)
+
+- **Response:** wiederholtes `ClientInfo` pro Registry-Eintrag: `id`, `mac`, `version`, `available`, `used`, `last_ping`, `last_success_ping`, Tap-/Stream-Flags.
+
+### 7.3 ACCEL_DEADZONE (6)
+
+- **Request:** `write`, `deadzone`, `client_id` (0=lokal), `all_clients`.
+- **Write Master:** Registry + `esp_now_comm_send_accel_deadzone` pro Slave; lokal `bma456` + NVS.
+- **Slave-Empfang:** `handle_slave_accel_deadzone` in `esp_now_comm.c`.
+
+### 7.4 ACCEL_STREAM (25)
+
+- Master setzt `client_registry_set_accel_stream` und sendet `ESPNOW_SET_ACCEL_STREAM`.
+- Slave-Task `slave_accel_stream_task` sendet `ESPNOW_ACCEL_SAMPLE` alle 16 ms.
+
+### 7.5 TAP_NOTIFY (27)
+
+- Konfiguriert auf Slave welche Tap-Arten `ESPNOW_TAP_EVENT` auslösen.
+- Tap-Quelle: BMA456-Interrupt → `on_bma456_tap` in `esp_now_comm.c`.
+
+### 7.6 CACHE_STATUS (29)
+
+- **Request:** leer.
+- **Response:** pro Slave mit Stream und/oder Tap-Notify: gecachte Accel-Werte (`age_ms`) und konsumierte Tap-Events (`client_registry_take_tap`).
+
+### 7.7 BATTERY_STATUS (26)
+
+- Liest **nur Cache** — keine ESP-NOW-Roundtrip-Pflicht pro Abfrage.
+- Master-Batterie: `client_registry_set_master_battery` (Monitor-Task).
+
+### 7.8 LED_RING (8)
+
+| mode | Bedeutung |
+|------|-----------|
+| 0 | Clear |
+| 1 | Progress 0–100 % |
+| 2 | Digit 0–10 |
+| 3 | Blink |
+| 4 | Find-me (RGB-Sequenz) |
+| 5 | Solid color |
+
+`client_id=0` nur Master-Ring; `>0` ESP-NOW; `all_clients` Broadcast über Registry.
+
+### 7.9 FIND_ME (22) / RESTART (23)
+
+- `client_id=0`: lokaler Master (`led_ring_find_me` / `pod_schedule_restart`).
+- `client_id>0`: ESP-NOW Unicast zum Slave.
+
+### 7.10 ESPNOW_UNICAST_TEST (7)
+
+Minimaler Master→Slave-Ping; Slave loggt `UNICAST TEST OK`.
+
+### 7.11 ESPNOW_ECHO_PING (30)
+
+Round-Trip-Latenztest zu einem **Slave** (`client_id` > 0, muss in der Registry sein).
+
+**Ablauf:**
+
+1. Host (goTool) setzt `timestamp_us` (Unix-µs) und sendet `EspNowEchoPingRequest` per UART.
+2. Master (`cmd_espnow_echo_ping.c`) löst MAC aus Registry auf, ruft `esp_now_comm_echo_ping()` auf.
+3. Master sendet `ESPNOW_ECHO_PING` mit `host_timestamp_us` und `master_time_us` (`esp_timer_get_time()` kurz vor Send).
+4. Slave (`handle_echo_ping`) antwortet mit `ESPNOW_ECHO_PONG` (Felder unverändert).
+5. Master empfängt Pong, berechnet `esp_rtt_us = esp_timer_get_time() - master_time_us`, antwortet per UART.
+
+**Request:** `client_id`, `timestamp_us` (vom Host gesetzt).
+
+**Response:** `success`, `client_id`, `timestamp_us` (echoed), `esp_rtt_us` (nur bei Erfolg).
+
+| Feld | Quelle | Bedeutung |
+|------|--------|-----------|
+| `timestamp_us` | Host → Slave → Host | Korrelations-ID; muss mit Request übereinstimmen |
+| `esp_rtt_us` | Master | Rohe µs-Differenz von `esp_timer_get_time()` (Ping-Send → Pong-Empfang im `recv_cb`) |
+
+**Implementierung:** `main/cmd/cmd_espnow_echo_ping.c`, `esp_now_comm_echo_ping()` in `esp_now_master.c`, Slave `handle_echo_ping` in `esp_now_slave.c`.
+
+**Host-seitig (goTool):** `rtt_ms` = volle UART-Kette (Send bis Response-Empfang); unabhängig von `esp_rtt_us`.
+
+### 7.12 SET_LOG_LEVEL (31)
+
+Laufzeit-Steuerung des **globalen** ESP-IDF-Log-Levels auf dem Master (`esp_log_level_set("*", …)`). Kein ESP-NOW, kein NVS — nur Master.
+
+**Request:** `write`, `level` (`esp_log_level_t`: 0=NONE, 1=ERROR, 2=WARN, 3=INFO, 4=DEBUG, 5=VERBOSE).
+
+| `write` | Verhalten |
+|---------|-----------|
+| `false` / leer | Aktuelles Level lesen (`esp_log_level_get("*")`) |
+| `true` | Level setzen; ungültige Werte (>5) → `success=false` |
+
+**Response:** `success`, `level` (aktuell bzw. gesetzt).
+
+**Boot-Default:** `CONFIG_LOG_DEFAULT_LEVEL` in `sdkconfig` (aktuell **INFO** = 3). Kann per UART/Web-UI zur Laufzeit geändert werden; nach Reboot gilt wieder der sdkconfig-Wert.
+
+**Ausgabe:** Logs erscheinen auf **UART0** (Debug-USB), nicht auf dem Host-UART1 (goTool).
+
+```bash
+go run . -port /dev/ttyUSB0 log-level
+go run . -port /dev/ttyUSB0 log-level -set -level 3
+```
+
+---
+
+## 8. OTA
+
+### 8.1 UART-OTA (nur Master)
+
+Implementierung: `ota_uart.c`, Steuerung `cmd/cmd_ota.c`.
+
+| Phase | Host → Master | Master → Host |
+|-------|---------------|---------------|
+| Start | `OTA_START` + `total_size` | `OTA_STATUS` preparing → ready |
+| Daten | `OTA_PAYLOAD` ≤200 B, `seq` | `block_ack` je 4096 B Flash |
+| Ende | `OTA_END` | success/failed; startet ESP-NOW-Verteilung |
+
+- Inaktive Partition: `esp_ota_get_next_update_partition()`.
+- LED-Ring zeigt Fortschritt (blau Schreiben, grün Verteilung).
+
+### 8.2 ESP-NOW-OTA (Master → Slaves)
+
+`ota_espnow.c` — gleiche Status-Codes wie UART.
+
+1. `ESPNOW_OTA_START` + `total_size` → Slave `ota_espnow_slave_on_start`
+2. `ESPNOW_OTA_PAYLOAD` bis 200 B → 4 KiB Buffer auf Slave
+3. `ESPNOW_OTA_END` → Boot-Partition setzen
+4. Slave antwortet `ESPNOW_OTA_STATUS` (mit `send_message_ex` + Semaphore auf Master)
+
+Nach Erfolg: **alle Knoten neu starten**.
+
+### 8.3 OTA_SLAVE_PROGRESS (21)
+
+Abfrage laufender oder letzter ESP-NOW-Verteilung: pro Slave `bytes_written`, `status`, `error`.
+
+---
+
+## 9. BMA456 Beschleunigungssensor
+
+| Thema | Detail |
+|-------|--------|
+| Wrapper | `bosch456.c` / `bosch456.h` |
+| Chip-Variante | BMA456**H** (`bma456h.c` im Component) |
+| I2C | Adresse 0x18, 100 kHz |
+| Polling | Task ~10 Hz |
+| Interrupt GPIO 10 | Single/Double/Triple Tap |
+| Deadzone | Software-Filter für Logs/Stream (Default 100 LSB) |
+| API | `bma456_read_accel`, `bma456_set_accel_deadzone`, `bma456_set_tap_handler` |
+
+Ohne Sensor: `bma456_is_ready() == false`, Firmware läuft weiter.
+
+---
+
+## 10. LED-Ring
+
+- **95 LEDs**, WS2812 über RMT (`led_ring.c`).
+- Segment-Karten für Ziffern 0–10 in `digit_lookup[]`.
+- **Kein** lokaler Demo-Loop — Anzeige nur über UART (`cmd_led_ring.c`) oder ESP-NOW `ESPNOW_LED_RING`.
+- Helligkeit: `intensity` 0 → Default ~5 % (`LED_RING_DEFAULT_INTENSITY`).
+- Modi: `0` clear … `5` color, `6` **battery-low** (erste 4 LEDs rot ~10 %, 5 s).
+
+---
+
+## 11. Board-Input und Batterie
+
+`board_input.c`:
+
+- **Taster** GPIO 12 — Logging bei Druck.
+- **LiPo-ADC** GPIO 1 und GPIO 11 (Pin-Spannung in mV).
+- Master: `master_monitor_task` aktualisiert Master-Batterie alle 30 s.
+- Slave: `slave_send_battery_report_to_master` nach Join, Heartbeat und Query.
+
+Spannungen in Millivolt in Registry und `BATTERY_STATUS`-UART.
+
+### Software-UV-Schutz (`battery_uv.c`)
+
+Aktivierbar mit `POWERPOD_BATTERY_UV_ENABLE` in `powerpod.h` (CMake-Override möglich).
+
+| Zustand | ADC-Schwelle | Logik |
+|---------|--------------|-------|
+| UV | < 2300 mV | Ein gültiger Kanal reicht |
+| Geladen | ≥ 3000 mV | Alle gültigen Kanäle |
+
+- NVS-Key `uv_latch` in `pod_settings.c`
+- Boot: ADC früh, bei UV nur LED + ADC-Poll (kein ESP-NOW/WiFi/UART/I2C/Button)
+- Runtime: `battery_uv_poll()` im LiPo-Monitor (2 Samples Debounce)
+- LED-Anzeige: Mode `6` battery-low (`led_ring_show_battery_low`)
+
+---
+
+## 12. Persistenz (NVS)
+
+`pod_settings.c` — Namespace `powerpod`:
+
+| Key | Inhalt |
+|-----|--------|
+| `accel_dz` | Accel-Deadzone LSB |
+| `uv_latch` | Software-UV-Zustand (`1` = Energiesparmodus) |
+
+Gespeichert bei lokalem Set (UART `client_id=0`, ESP-NOW auf Slave). Geladen nach `init_bma456()`.
+
+---
+
+## 13. Protobuf und Code-Generierung
+
+```bash
+make proto_generate        # beide Schemas
+make proto_generate_uart   # nur uart_messages.proto
+make proto_generate_espnow # nur esp_now_messages.proto
+```
+
+**Ausgabe:** `main/proto/*.pb.c`, `*.pb.h`  
+**Optionen:** `main/proto/uart_messages.options` (nanopb max_size etc.)
+
+Includes in generierten `.pb.c` müssen `"uart_messages.pb.h"` heißen (nicht `main/proto/...`).
+
+**Paketname protobuf:** `alox` → C-Prefix `alox_`.
+
+---
+
+## 14. Modulreferenz
+
+### 14.1 Kern
+
+| Datei | Rolle |
+|-------|--------|
+| `powerpod.c` | `app_main`, Init, Master-Register |
+| `app_config.h` | Laufzeit-Konfiguration |
+| `cmd_handler.c` | Queue + Dispatcher |
+| `uart.c` | Framing |
+| `uart_proto.c` | UartMessage send |
+| `uart_cmd.c` | Handler-Hilfen |
+
+### 14.2 Kommunikation
+
+| Datei | Rolle |
+|-------|--------|
+| `esp_now_comm.c` | Init, recv-Router |
+| `esp_now_core.c` | WiFi, Peer, gemeinsamer Send |
+| `esp_now_master.c` | Master-Tasks, Registry, Unicast send |
+| `esp_now_slave.c` | Join, Heartbeat, Accel/Tap send |
+| `esp_now_proto.c` | nanopb für EspNowMessage |
+| `client_registry.c` | Slave-Tabelle + Telemetrie-Cache |
+
+### 14.3 Befehle (`main/cmd/`)
+
+| Datei | UART-Typ |
+|-------|----------|
+| `cmd_version.c` | VERSION |
+| `cmd_client_info.c` | CLIENT_INFO |
+| `cmd_accel_deadzone.c` | ACCEL_DEADZONE |
+| `cmd_accel_stream.c` | ACCEL_STREAM |
+| `cmd_tap_notify.c` | TAP_NOTIFY |
+| `cmd_cache_status.c` | CACHE_STATUS |
+| `cmd_battery.c` | BATTERY_STATUS |
+| `cmd_led_ring.c` | LED_RING |
+| `cmd_espnow_find_me.c` | FIND_ME |
+| `cmd_restart.c` | RESTART |
+| `cmd_espnow_unicast_test.c` | ESPNOW_UNICAST_TEST |
+| `cmd_espnow_echo_ping.c` | ESPNOW_ECHO_PING |
+| `cmd_set_log_level.c` | SET_LOG_LEVEL |
+| `cmd_ota.c` | OTA_* |
+| `cmd_ota_slave_progress.c` | OTA_SLAVE_PROGRESS |
+
+### 14.4 Domäne
+
+| Datei | Rolle |
+|-------|--------|
+| `bosch456.c` | Accelerometer + Tap |
+| `led_ring.c` | LED-Anzeige |
+| `board_input.c` | Taster, ADC |
+| `battery_uv.c` | Software-UV-Schutz, Energiesparmodus |
+| `pod_settings.c` | NVS |
+| `pod_reboot.c` | Verzögerter Restart |
+| `ota_uart.c` | Flash-Puffer UART-OTA |
+| `ota_espnow.c` | OTA Master/Slave; Slave-Work-Queue |
+| `ota_session.c` | OTA-Sperre für UART-Dispatcher |
+
+### 14.5 Protobuf
+
+| Datei | Rolle |
+|-------|--------|
+| `proto/uart_messages.proto` | UART-Vertrag |
+| `proto/esp_now_messages.proto` | ESP-NOW-Vertrag |
+| `proto/pb_encode.c`, `pb_decode.c`, `pb_common.c` | nanopb Runtime |
+
+---
+
+## 15. Logging-Tags
+
+**Level zur Laufzeit:** UART `SET_LOG_LEVEL` (31) oder Dashboard „ESP Log-Level“ — steuert nur die Konsolen-Ausgabe auf UART0, nicht das Host-Protokoll.
+
+| Tag | Modul |
+|-----|--------|
+| `[Main]` | powerpod.c |
+| `[LOG_LVL]` | cmd_set_log_level.c |
+| `[UART]` | uart.c |
+| `[CMDH]` | cmd_handler.c |
+| `[UART_CMD]` | uart_cmd.c |
+| `[ESPNOW]` | esp_now_comm.c |
+| `[CLIENTS]` | client_registry.c |
+| `[BMA456]` | bosch456.c |
+| `[VERSION]` etc. | jeweiliger cmd_* |
+
+Typischer Ablauf bei UART-Befehl:
+
+```
+[UART] received message cmd=0x06 len=…
+[CMDH] trigger command ACCEL_DEADZONE (0x06)
+[ACCEL_DZ] …
+```
+
+---
+
+## Anhang: Neues UART-Kommando hinzufügen
+
+1. `uart_messages.proto` erweitern → `make proto_generate_uart`
+2. `cmd/cmd_neu.c` mit `handle_*` + `uart_cmd_register()`
+3. In `powerpod.c` `cmd_neu_register()` aufrufen (nur Master-Zweig)
+4. Bei Slave-Bedarf: `esp_now_messages.proto` + `esp_now_comm_send_*` + Slave-Zweig in `espnow_recv_cb`
+
+Siehe [`adding-a-feature.md`](adding-a-feature.md) für ein vollständiges Beispiel (Find Me).

docs/adding-a-feature.md

@@ -345,7 +345,7 @@ idf.py build
 
 Ähnliche Features zum Abgucken:
 
-- **Nur Master, kein ESP-NOW:** `main/cmd/cmd_version.c`, `main/cmd/cmd_led_ring.c`
+- **Nur Master, kein ESP-NOW:** `main/cmd/cmd_version.c`, `main/cmd/cmd_led_ring.c`, `main/cmd/cmd_set_log_level.c`
 - **Nur Slave per ESP-NOW (Master leitet nur durch):** `main/cmd/cmd_espnow_unicast_test.c`
 - **Master + alle Slaves / Filter:** `main/cmd/cmd_accel_deadzone.c`
 - **Großer ESP-NOW-Fluss mit Status:** `ota_espnow.c`, `main/cmd/cmd_ota.c`

goTool/Makefile

@@ -0,0 +1,2 @@
+win:
+	GOOS=windows GOARCH=386 go build .

goTool/README.md

@@ -28,13 +28,15 @@ go run . -port /dev/ttyUSB0 clients
 | `tap-notify` | `0x1b` | Get/set which tap kinds (single/double/triple) notify via ESP-NOW (`-set`, `-client`, `-all`, `-single`, `-double`, `-triple`) |
 | `cache-status` | `0x1d` | Subscribed accel + tap cache (`CACHE_STATUS`); one UART round-trip for 16 ms polling |
 | `unicast-test` | `0x07` | Sends ESP-NOW unicast test to one slave (`-client`, `-seq`) |
+| `echo-ping` | `0x1e` | ESP-NOW echo round-trip to one slave (`-client`); prints `rtt_ms` (host UART chain) and `esp_rtt_us` (master ESP-NOW, raw µs) |
 | `test` | — | Run an automated scenario (JSON configs under `testdata/`) |
 | `serve` | — | Web dashboard at `http://localhost:8080` (WebSocket live updates) |
 | `ota` | 16–19 | UART firmware upload to master; firmware then pushes to slaves via ESP-NOW |
 | `ota-progress` | 21 | Query per-slave ESP-NOW OTA progress on the master (`-client N`, default all) |
-| `led-ring` | 8 | LED ring: `-mode clear\|color\|progress\|digit\|blink\|find-me`, `-client`, `-all` |
+| `led-ring` | 8 | LED ring: `-mode clear\|color\|progress\|digit\|blink\|find-me\|battery-low`, `-client`, `-all` |
 | `find-me` | 22 | Locate pod (`-client 0` master, `>0` slave via ESP-NOW) |
 | `restart` | 23 | Reboot master or slave (`-client 0` / `>0`) |
+| `log-level` | `0x1f` | Get/set master ESP-IDF log level for tag `"*"` (`-set`, `-level` 0–5); output on UART0 debug, not host UART |
 
 `clients` requires slaves to have responded to master discover broadcasts first.
 
@@ -86,7 +88,7 @@ If the UART device is unplugged or the port disappears, `serve` keeps running an
 
 | Doc | Content |
 |-----|---------|
-| **[docs/API_WEBSOCKET.md](docs/API_WEBSOCKET.md)** | `ws://…:8081/ws` commands, **`accel` / `tap` push stream** format, dashboard `ws://…:8080/ws` |
+| **[docs/API_WEBSOCKET.md](docs/API_WEBSOCKET.md)** | `ws://…:8081/ws` commands and **`input` push stream** (accel + tap) |
 | **[docs/API_REST.md](docs/API_REST.md)** | REST on `:8080` (dashboard) and `:8081` (battery, LED, service info) |
 
 CLI:
@@ -113,8 +115,24 @@ go run . -port /dev/ttyUSB0 unicast-test -client 16 -seq 42
 
 On success the slave serial log should show `UNICAST TEST OK from master … seq=42`.
 
+```bash
+go run . -port /dev/ttyUSB0 echo-ping -client 16
+go run . -port /dev/ttyUSB0 log-level
+go run . -port /dev/ttyUSB0 log-level -set -level 3
+```
+
+`log-level` controls `esp_log_*` on the master (UART0 USB console). The host protocol UART (GPIO 2/3) is unchanged.
+
+Measures latency to one slave. `rtt_ms` is the full host round-trip (UART + ESP-NOW + UART back). `esp_rtt_us` is the master-side ESP-NOW leg only (`esp_timer_get_time()` delta, raw microseconds from firmware).
+
 Example output:
 
+```
+echo ping: success=true client_id=16 rtt_ms=49.729 esp_rtt_us=18234
+```
+
+`clients` example:
+
 ```
 clients (2):
   [0] id=42 mac=aabbccddeeff ver=1 available=true used=false last_ping=250 last_success_ping=250

goTool/api_serve.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -40,6 +41,19 @@ type unicastAPIResponse struct {
 	Error   string `json:"error,omitempty"`
 }
 
+type echoPingAPIRequest struct {
+	ClientID uint32 `json:"client_id"`
+}
+
+type echoPingAPIResponse struct {
+	Success     bool    `json:"success"`
+	ClientID    uint32  `json:"client_id,omitempty"`
+	TimestampUs uint64  `json:"timestamp_us,omitempty"`
+	RttMs       float64 `json:"rtt_ms"`
+	EspRttUs    uint32  `json:"esp_rtt_us"`
+	Error       string  `json:"error,omitempty"`
+}
+
 type findMeAPIRequest struct {
 	ClientID uint32 `json:"client_id"`
 }
@@ -60,6 +74,17 @@ type restartAPIResponse struct {
 	Error    string `json:"error,omitempty"`
 }
 
+type logLevelAPIResponse struct {
+	Success bool   `json:"success"`
+	Level   uint32 `json:"level"`
+	Error   string `json:"error,omitempty"`
+}
+
+type logLevelAPIRequest struct {
+	Write bool   `json:"write"`
+	Level uint32 `json:"level"`
+}
+
 type otaAPIResponse struct {
 	Success       bool   `json:"success"`
 	BytesWritten  uint32 `json:"bytes_written,omitempty"`
@@ -90,6 +115,13 @@ func mountServeAPI(mux *http.ServeMux, link *managedSerial, hub *wsHub, streamCt
 		}
 		serveUnicastTest(w, r, link)
 	})
+	mux.HandleFunc("/api/echo-ping", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+		serveEchoPing(w, r, link)
+	})
 	mux.HandleFunc("/api/find-me", func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
 			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
@@ -104,6 +136,16 @@ func mountServeAPI(mux *http.ServeMux, link *managedSerial, hub *wsHub, streamCt
 		}
 		serveRestart(w, r, link)
 	})
+	mux.HandleFunc("/api/log-level", func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			serveLogLevelGet(w, r, link)
+		case http.MethodPost:
+			serveLogLevelPost(w, r, link)
+		default:
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		}
+	})
 	mux.HandleFunc("/api/ota", func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
 			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
@@ -146,7 +188,11 @@ func serveOTAUpload(w http.ResponseWriter, r *http.Request, link *managedSerial,
 		if hub != nil {
 			hub.broadcastRaw(OTAProgress{Type: "ota_progress", Phase: "error", Message: err.Error()})
 		}
-		writeJSON(w, http.StatusServiceUnavailable, otaAPIResponse{Error: err.Error()})
+		status := http.StatusServiceUnavailable
+		if errors.Is(err, errOTAInProgress) {
+			status = http.StatusConflict
+		}
+		writeJSON(w, status, otaAPIResponse{Error: err.Error()})
 		return
 	}
 	writeJSON(w, http.StatusOK, otaAPIResponse{
@@ -255,6 +301,43 @@ func applyDeadzoneToSlaves(link *managedSerial, deadzone uint32) (uint32, error)
 	return updated, nil
 }
 
+func serveLogLevelGet(w http.ResponseWriter, r *http.Request, link *managedSerial) {
+	resp, err := link.SetLogLevel(false, 0)
+	if err != nil {
+		writeJSON(w, http.StatusServiceUnavailable, logLevelAPIResponse{Error: err.Error()})
+		return
+	}
+	writeJSON(w, http.StatusOK, logLevelAPIResponse{
+		Success: resp.GetSuccess(),
+		Level:   resp.GetLevel(),
+	})
+}
+
+func serveLogLevelPost(w http.ResponseWriter, r *http.Request, link *managedSerial) {
+	var body logLevelAPIRequest
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeJSON(w, http.StatusBadRequest, logLevelAPIResponse{Error: "invalid JSON"})
+		return
+	}
+	if !body.Write {
+		writeJSON(w, http.StatusBadRequest, logLevelAPIResponse{Error: "write must be true"})
+		return
+	}
+	if body.Level > 5 {
+		writeJSON(w, http.StatusBadRequest, logLevelAPIResponse{Error: "level must be 0–5"})
+		return
+	}
+	resp, err := link.SetLogLevel(true, body.Level)
+	if err != nil {
+		writeJSON(w, http.StatusServiceUnavailable, logLevelAPIResponse{Error: err.Error()})
+		return
+	}
+	writeJSON(w, http.StatusOK, logLevelAPIResponse{
+		Success: resp.GetSuccess(),
+		Level:   resp.GetLevel(),
+	})
+}
+
 func serveRestart(w http.ResponseWriter, r *http.Request, link *managedSerial) {
 	var body restartAPIRequest
 	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
@@ -311,6 +394,30 @@ func serveUnicastTest(w http.ResponseWriter, r *http.Request, link *managedSeria
 	})
 }
 
+func serveEchoPing(w http.ResponseWriter, r *http.Request, link *managedSerial) {
+	var body echoPingAPIRequest
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeJSON(w, http.StatusBadRequest, echoPingAPIResponse{Error: "invalid JSON"})
+		return
+	}
+	if body.ClientID == 0 {
+		writeJSON(w, http.StatusBadRequest, echoPingAPIResponse{Error: "client_id required"})
+		return
+	}
+	result, err := link.EchoPing(body.ClientID)
+	if err != nil {
+		writeJSON(w, http.StatusServiceUnavailable, echoPingAPIResponse{Error: err.Error()})
+		return
+	}
+	writeJSON(w, http.StatusOK, echoPingAPIResponse{
+		Success:     result.Success,
+		ClientID:    result.ClientID,
+		TimestampUs: result.TimestampUs,
+		RttMs:       result.RttMs,
+		EspRttUs:    result.EspRttUs,
+	})
+}
+
 func parseUintQuery(r *http.Request, key string, def uint32) (uint32, error) {
 	s := r.URL.Query().Get(key)
 	if s == "" {

goTool/api_stream.go

@@ -9,55 +9,61 @@ import (
 	"sync"
 	"time"
 
-	"github.com/gorilla/websocket"
 	"powerpod/gotool/pb"
+
+	"github.com/gorilla/websocket"
 )
 
 const (
 	defaultAccelStreamInterval = 16 * time.Millisecond
+	defaultPreFetchMs          = 2
 	minAPIStreamInterval       = 1 * time.Millisecond
 	maxAPIStreamInterval       = 10 * time.Second
 	// How long tap events stay in API push/cache after first sight (matches dashboard).
 	apiTapDisplayMinMs = 2000
 )
 
-// AccelClientSample is one slave's cached accel on the master.
-type AccelClientSample struct {
-	ClientID uint32 `json:"client_id"`
-	Valid    bool   `json:"valid"`
-	X        int32  `json:"x,omitempty"`
-	Y        int32  `json:"y,omitempty"`
-	Z        int32  `json:"z,omitempty"`
-	AgeMs    uint32 `json:"age_ms,omitempty"`
+// InputClientSample is one slave's cached accel + tap state on the master.
+type InputClientSample struct {
+	ClientID   uint32 `json:"client_id"`
+	Valid      bool   `json:"valid"`
+	X          int32  `json:"x,omitempty"`
+	Y          int32  `json:"y,omitempty"`
+	Z          int32  `json:"z,omitempty"`
+	AccelAgeMs uint32 `json:"accel_age_ms,omitempty"`
+	TapKind    string `json:"tap_kind,omitempty"`
+	TapAgeMs   uint32 `json:"tap_age_ms,omitempty"`
 }
 
-// AccelStreamMessage is sent to external WebSocket clients (hello + accel samples).
-type AccelStreamMessage struct {
-	Type            string   `json:"type"` // "hello" | "accel"
+// InputStreamMessage is sent to external WebSocket clients (hello + input samples).
+type InputStreamMessage struct {
+	Type            string   `json:"type"` // "hello" | "input"
 	Serial          string   `json:"serial_port,omitempty"`
 	IntervalMs      int      `json:"interval_ms,omitempty"`
+	PreFetchMs      int      `json:"pre_fetch_ms,omitempty"`
 	TapDisplayMinMs int      `json:"tap_display_min_ms,omitempty"`
 	Commands        []string `json:"commands,omitempty"`
 	Note            string   `json:"note,omitempty"`
 
 	T       int64               `json:"t,omitempty"` // Unix nanoseconds
 	Success bool                `json:"success,omitempty"`
-	Clients []AccelClientSample `json:"clients,omitempty"`
+	Clients []InputClientSample `json:"clients,omitempty"`
 	Error   string              `json:"error,omitempty"`
 }
 
 // StreamStatusMessage is the reply to set_stream / get_stream (this connection).
 type StreamStatusMessage struct {
-	Type         string `json:"type"` // "stream_status"
-	ReceiveAccel bool   `json:"receive_accel"`
-	IntervalMs   int    `json:"interval_ms"`
-	Success      bool   `json:"success"`
-	Error        string `json:"error,omitempty"`
+	Type          string `json:"type"` // "stream_status"
+	ReceiveInput  bool   `json:"receive_input"`
+	IntervalMs    int    `json:"interval_ms"`
+	PreFetch      int    `json:"pre_fetch"`
+	Success       bool   `json:"success"`
+	Error         string `json:"error,omitempty"`
 }
 
-// AccelStreamStatusMessage is the reply to set_accel_stream / get_accel_stream (slave).
-type AccelStreamStatusMessage struct {
-	Type          string `json:"type"` // "accel_stream_status"
+// InputStreamStatusMessage is the reply to set_input_stream / get_input_stream (slave).
+type InputStreamStatusMessage struct {
+	Type          string `json:"type"` // "input_stream_status"
 	ClientID      uint32 `json:"client_id"`
 	Enabled       bool   `json:"enabled"`
 	Success       bool   `json:"success"`
@@ -65,33 +71,6 @@ type AccelStreamStatusMessage struct {
 	Error         string `json:"error,omitempty"`
 }
 
-// TapClientEvent is one tap visible to API clients (fresh or within tap_display_min_ms).
-type TapClientEvent struct {
-	ClientID  uint32 `json:"client_id"`
-	Valid     bool   `json:"valid"`
-	Kind      string `json:"kind,omitempty"` // single | double | triple
-	AgeMs     uint32 `json:"age_ms,omitempty"`
-	ShownAtMs int64  `json:"shown_at_ms,omitempty"` // Unix ms when API first saw this tap
-}
-
-// TapStreamMessage is pushed to external WebSocket clients when receive_tap is on.
-type TapStreamMessage struct {
-	Type    string           `json:"type"` // "tap"
-	T       int64            `json:"t,omitempty"`
-	Success bool             `json:"success,omitempty"`
-	Events  []TapClientEvent `json:"events,omitempty"`
-	Error   string           `json:"error,omitempty"`
-}
-
-// TapStreamStatusMessage is the reply to set_tap_stream / get_tap_stream (this connection).
-type TapStreamStatusMessage struct {
-	Type       string `json:"type"` // "tap_stream_status"
-	ReceiveTap bool   `json:"receive_tap"`
-	IntervalMs int    `json:"interval_ms"`
-	Success    bool   `json:"success"`
-	Error      string `json:"error,omitempty"`
-}
-
 // APIClientInfo is one registered slave (or slot) from CLIENT_INFO.
 type APIClientInfo struct {
 	ID              uint32 `json:"id"`
@@ -101,7 +80,7 @@ type APIClientInfo struct {
 	Used            bool   `json:"used"`
 	LastPing        uint32 `json:"last_ping"`
 	LastSuccessPing uint32 `json:"last_success_ping"`
-	AccelStream     bool   `json:"accel_stream"`
+	InputStream     bool   `json:"input_stream"`
 	TapNotifySingle bool   `json:"tap_notify_single"`
 	TapNotifyDouble bool   `json:"tap_notify_double"`
 	TapNotifyTriple bool   `json:"tap_notify_triple"`
@@ -132,6 +111,7 @@ type accelWSCommand struct {
 	ClientID   uint32 `json:"client_id"`
 	Enable     *bool  `json:"enable"`
 	IntervalMs *int   `json:"interval_ms"`
+	PreFetch   *int   `json:"pre_fetch"`
 	Single     *bool  `json:"single"`
 	DoubleTap  *bool  `json:"double_tap"`
 	Triple     *bool  `json:"triple"`
@@ -144,6 +124,7 @@ type APIInfoResponse struct {
 	SerialPort        string `json:"serial_port"`
 	WebSocket         string `json:"websocket"`
 	DefaultIntervalMs int    `json:"default_interval_ms"`
+	DefaultPreFetchMs int    `json:"default_pre_fetch_ms"`
 	MinIntervalMs     int    `json:"min_interval_ms"`
 	MaxIntervalMs     int    `json:"max_interval_ms"`
 	TapDisplayMinMs   int    `json:"tap_display_min_ms"`
@@ -153,21 +134,28 @@ type APIInfoResponse struct {
 type cachedTapEvent struct {
 	kind    string
 	shownAt time.Time
+	ageMs   uint32
 }
 
 type wsSubscriber struct {
 	conn          *websocket.Conn
-	receiveAccel  bool
-	receiveTap    bool
+	receiveInput  bool
 	interval      time.Duration
-	lastAccelSent time.Time
-	lastTapSent   time.Time
+	preFetch      time.Duration
+	lastInputSent time.Time
+}
+
+type pendingInputCache struct {
+	cache   *pb.CacheStatusResponse
+	readAt  time.Time
+	readErr error
 }
 
 type accelStreamHub struct {
 	mu              sync.RWMutex
 	clients         map[*websocket.Conn]*wsSubscriber
 	defaultInterval time.Duration
+	defaultPreFetch time.Duration
 	configChanged   chan struct{}
 	recentTaps      map[uint32]cachedTapEvent
 }
@@ -176,6 +164,7 @@ func newAccelStreamHub(defaultInterval time.Duration) *accelStreamHub {
 	return &accelStreamHub{
 		clients:         make(map[*websocket.Conn]*wsSubscriber),
 		defaultInterval: defaultInterval,
+		defaultPreFetch: defaultPreFetchMs * time.Millisecond,
 		configChanged:   make(chan struct{}, 1),
 	}
 }
@@ -197,26 +186,39 @@ func clampAPIInterval(d time.Duration) time.Duration {
 	return d
 }
 
+func clampPreFetch(d time.Duration) time.Duration {
+	if d < 0 {
+		return 0
+	}
+	if d > maxAPIStreamInterval {
+		return maxAPIStreamInterval
+	}
+	return d
+}
+
 func (h *accelStreamHub) register(conn *websocket.Conn, portName string) *wsSubscriber {
 	sub := &wsSubscriber{
 		conn:         conn,
-		receiveAccel: false,
+		receiveInput: false,
 		interval:     h.defaultInterval,
+		preFetch:     h.defaultPreFetch,
 	}
 	h.mu.Lock()
 	h.clients[conn] = sub
 	h.mu.Unlock()
 
-	hello := AccelStreamMessage{
+	hello := InputStreamMessage{
 		Type:            "hello",
 		Serial:          portName,
 		IntervalMs:      int(h.defaultInterval / time.Millisecond),
+		PreFetchMs:      int(h.defaultPreFetch / time.Millisecond),
 		TapDisplayMinMs: apiTapDisplayMinMs,
-		Note:            "set_tap_notify configures slave S/D/T only; set_tap_stream enables tap polling/push",
+		Note:            "set_tap_notify configures slave S/D/T only; set_stream enables input polling/push on this connection",
 		Commands: []string{
 			"list_clients",
-			"set_stream", "get_stream", "set_accel_stream", "get_accel_stream",
-			"set_tap_stream", "get_tap_stream", "set_tap_notify", "get_tap_notify",
+			"set_stream", "get_stream",
+			"set_input_stream", "get_input_stream",
+			"set_tap_notify", "get_tap_notify",
 			"set_led_ring", "get_battery",
 		},
 	}
@@ -229,36 +231,25 @@ func (h *accelStreamHub) register(conn *websocket.Conn, portName string) *wsSubs
 func (h *accelStreamHub) unregister(conn *websocket.Conn) {
 	h.mu.Lock()
 	delete(h.clients, conn)
-	anyTap := false
+	anyInput := false
 	for _, sub := range h.clients {
-		if sub.receiveTap {
-			anyTap = true
+		if sub.receiveInput {
+			anyInput = true
 			break
 		}
 	}
-	if !anyTap {
+	if !anyInput {
 		h.recentTaps = nil
 	}
 	h.mu.Unlock()
 	h.notifyConfigChanged()
 }
 
-func (h *accelStreamHub) anyWantsAccel() bool {
+func (h *accelStreamHub) anyWantsInput() bool {
 	h.mu.RLock()
 	defer h.mu.RUnlock()
 	for _, sub := range h.clients {
-		if sub.receiveAccel {
-			return true
-		}
-	}
-	return false
-}
-
-func (h *accelStreamHub) anyWantsTap() bool {
-	h.mu.RLock()
-	defer h.mu.RUnlock()
-	for _, sub := range h.clients {
-		if sub.receiveTap {
+		if sub.receiveInput {
 			return true
 		}
 	}
@@ -270,7 +261,7 @@ func (h *accelStreamHub) minWantedInterval() time.Duration {
 	defer h.mu.RUnlock()
 	var min time.Duration
 	for _, sub := range h.clients {
-		if !sub.receiveAccel && !sub.receiveTap {
+		if !sub.receiveInput {
 			continue
 		}
 		if min == 0 || sub.interval < min {
@@ -283,20 +274,28 @@ func (h *accelStreamHub) minWantedInterval() time.Duration {
 	return min
 }
 
-func (h *accelStreamHub) setStream(sub *wsSubscriber, enable bool, intervalMs *int) StreamStatusMessage {
+func (h *accelStreamHub) setStream(sub *wsSubscriber, enable bool, intervalMs, preFetchMs *int) StreamStatusMessage {
 	h.mu.Lock()
-	sub.receiveAccel = enable
+	sub.receiveInput = enable
+	if !enable {
+		h.recentTaps = nil
+	}
 	if intervalMs != nil {
 		sub.interval = clampAPIInterval(time.Duration(*intervalMs) * time.Millisecond)
 	}
+	if preFetchMs != nil {
+		sub.preFetch = clampPreFetch(time.Duration(*preFetchMs) * time.Millisecond)
+	}
 	ms := int(sub.interval / time.Millisecond)
+	pf := int(sub.preFetch / time.Millisecond)
 	h.mu.Unlock()
 	h.notifyConfigChanged()
 
 	return StreamStatusMessage{
 		Type:         "stream_status",
-		ReceiveAccel: enable,
+		ReceiveInput: enable,
 		IntervalMs:   ms,
+		PreFetch:     pf,
 		Success:      true,
 	}
 }
@@ -306,45 +305,47 @@ func (h *accelStreamHub) getStream(sub *wsSubscriber) StreamStatusMessage {
 	defer h.mu.RUnlock()
 	return StreamStatusMessage{
 		Type:         "stream_status",
-		ReceiveAccel: sub.receiveAccel,
+		ReceiveInput: sub.receiveInput,
 		IntervalMs:   int(sub.interval / time.Millisecond),
+		PreFetch:     int(sub.preFetch / time.Millisecond),
 		Success:      true,
 	}
 }
 
-func (h *accelStreamHub) setTapStream(sub *wsSubscriber, enable bool, intervalMs *int) TapStreamStatusMessage {
-	h.mu.Lock()
-	sub.receiveTap = enable
-	if !enable {
-		h.recentTaps = nil
-	}
-	if intervalMs != nil {
-		sub.interval = clampAPIInterval(time.Duration(*intervalMs) * time.Millisecond)
-	}
-	ms := int(sub.interval / time.Millisecond)
-	h.mu.Unlock()
-	h.notifyConfigChanged()
-
-	return TapStreamStatusMessage{
-		Type:       "tap_stream_status",
-		ReceiveTap: enable,
-		IntervalMs: ms,
-		Success:    true,
-	}
-}
-
-func (h *accelStreamHub) getTapStream(sub *wsSubscriber) TapStreamStatusMessage {
+func (h *accelStreamHub) streamTiming(now time.Time) (needRead, needDeliver bool, waitPreFetch time.Duration) {
 	h.mu.RLock()
 	defer h.mu.RUnlock()
-	return TapStreamStatusMessage{
-		Type:       "tap_stream_status",
-		ReceiveTap: sub.receiveTap,
-		IntervalMs: int(sub.interval / time.Millisecond),
-		Success:    true,
+	for _, sub := range h.clients {
+		if !sub.receiveInput {
+			continue
+		}
+		if sub.lastInputSent.IsZero() {
+			needRead = true
+			needDeliver = true
+			if sub.preFetch > waitPreFetch {
+				waitPreFetch = sub.preFetch
+			}
+			continue
+		}
+		nextPush := sub.lastInputSent.Add(sub.interval)
+		readAt := nextPush.Add(-sub.preFetch)
+		if !now.Before(readAt) {
+			needRead = true
+		}
+		if !now.Before(nextPush) {
+			needDeliver = true
+			if sub.preFetch > waitPreFetch {
+				waitPreFetch = sub.preFetch
+			}
+		}
 	}
+	return needRead, needDeliver, waitPreFetch
 }
 
-func (h *accelStreamHub) ingestTapEvents(incoming []TapClientEvent) []TapClientEvent {
+func (h *accelStreamHub) ingestTapFromCache(cache *pb.CacheStatusResponse) {
+	if cache == nil {
+		return
+	}
 	h.mu.Lock()
 	defer h.mu.Unlock()
 
@@ -352,39 +353,66 @@ func (h *accelStreamHub) ingestTapEvents(incoming []TapClientEvent) []TapClientE
 	if h.recentTaps == nil {
 		h.recentTaps = make(map[uint32]cachedTapEvent)
 	}
-	for _, e := range incoming {
-		if !e.Valid || e.Kind == "" {
+	for _, c := range cache.GetClients() {
+		t := c.GetTap()
+		if t == nil {
 			continue
 		}
-		h.recentTaps[e.ClientID] = cachedTapEvent{kind: e.Kind, shownAt: now}
+		kind := tapKindLabelPB(t.GetKind())
+		if kind == "" {
+			continue
+		}
+		h.recentTaps[c.GetClientId()] = cachedTapEvent{
+			kind:    kind,
+			shownAt: now,
+			ageMs:   t.GetAgeMs(),
+		}
 	}
-	return h.activeTapEventsLocked(now)
+	h.pruneRecentTapsLocked(now)
 }
 
-func (h *accelStreamHub) activeTapEventsLocked(now time.Time) []TapClientEvent {
+func (h *accelStreamHub) pruneRecentTapsLocked(now time.Time) {
 	if len(h.recentTaps) == 0 {
-		return nil
+		return
 	}
 	cutoff := now.Add(-apiTapDisplayMinMs * time.Millisecond)
-	out := make([]TapClientEvent, 0, len(h.recentTaps))
 	for id, ev := range h.recentTaps {
 		if ev.shownAt.Before(cutoff) {
 			delete(h.recentTaps, id)
-			continue
 		}
-		shownAtMs := ev.shownAt.UnixMilli()
-		out = append(out, TapClientEvent{
-			ClientID:  id,
-			Valid:     true,
-			Kind:      ev.kind,
-			AgeMs:     uint32(now.Sub(ev.shownAt).Milliseconds()),
-			ShownAtMs: shownAtMs,
-		})
+	}
+}
+
+func (h *accelStreamHub) inputClientsFromCacheLocked(cache *pb.CacheStatusResponse, now time.Time) []InputClientSample {
+	h.pruneRecentTapsLocked(now)
+	out := make([]InputClientSample, 0, len(cache.GetClients()))
+	for _, c := range cache.GetClients() {
+		sample := InputClientSample{
+			ClientID: c.GetClientId(),
+		}
+		if a := c.GetAccel(); a != nil {
+			sample.Valid = a.GetValid()
+			if a.GetValid() {
+				sample.X = a.GetX()
+				sample.Y = a.GetY()
+				sample.Z = a.GetZ()
+				sample.AccelAgeMs = a.GetAgeMs()
+			}
+		}
+		if ev, ok := h.recentTaps[c.GetClientId()]; ok {
+			sample.TapKind = ev.kind
+			if t := c.GetTap(); t != nil && tapKindLabelPB(t.GetKind()) == ev.kind {
+				sample.TapAgeMs = t.GetAgeMs()
+			} else {
+				sample.TapAgeMs = ev.ageMs + uint32(now.Sub(ev.shownAt).Milliseconds())
+			}
+		}
+		out = append(out, sample)
 	}
 	return out
 }
 
-func (h *accelStreamHub) deliver(msg AccelStreamMessage) {
+func (h *accelStreamHub) deliverInput(msg InputStreamMessage) {
 	data, err := json.Marshal(msg)
 	if err != nil {
 		return
@@ -394,13 +422,13 @@ func (h *accelStreamHub) deliver(msg AccelStreamMessage) {
 	h.mu.Lock()
 	defer h.mu.Unlock()
 	for conn, sub := range h.clients {
-		if !sub.receiveAccel {
+		if !sub.receiveInput {
 			continue
 		}
-		if !sub.lastAccelSent.IsZero() && now.Sub(sub.lastAccelSent) < sub.interval {
+		if !sub.lastInputSent.IsZero() && now.Sub(sub.lastInputSent) < sub.interval {
 			continue
 		}
-		sub.lastAccelSent = now
+		sub.lastInputSent = now
 		if err := conn.WriteMessage(websocket.TextMessage, data); err != nil {
 			delete(h.clients, conn)
 			_ = conn.Close()
@@ -408,155 +436,79 @@ func (h *accelStreamHub) deliver(msg AccelStreamMessage) {
 	}
 }
 
-func (h *accelStreamHub) deliverTap(msg TapStreamMessage) {
-	data, err := json.Marshal(msg)
-	if err != nil {
-		return
-	}
+func runInputStreamer(link *managedSerial, hub *accelStreamHub, dash *wsHub, ctl *accelStreamCtl, tapCtl *tapNotifyCtl, stop <-chan struct{}) {
+	ticker := time.NewTicker(minAPIStreamInterval)
+	defer ticker.Stop()
 
-	now := time.Now()
-	h.mu.Lock()
-	defer h.mu.Unlock()
-	for conn, sub := range h.clients {
-		if !sub.receiveTap {
-			continue
-		}
-		if !sub.lastTapSent.IsZero() && now.Sub(sub.lastTapSent) < sub.interval {
-			continue
-		}
-		sub.lastTapSent = now
-		if err := conn.WriteMessage(websocket.TextMessage, data); err != nil {
-			delete(h.clients, conn)
-			_ = conn.Close()
-		}
-	}
-}
-
-func runAccelStreamer(link *managedSerial, hub *accelStreamHub, dash *wsHub, ctl *accelStreamCtl, tapCtl *tapNotifyCtl, stop <-chan struct{}) {
-	var ticker *time.Ticker
-	var tick <-chan time.Time
-
-	resetTicker := func() {
-		if ticker != nil {
-			ticker.Stop()
-		}
-		interval := hub.minWantedInterval()
-		ticker = time.NewTicker(interval)
-		tick = ticker.C
-	}
-	resetTicker()
-	defer func() {
-		if ticker != nil {
-			ticker.Stop()
-		}
-	}()
+	var pending *pendingInputCache
 
 	for {
 		select {
 		case <-stop:
 			return
 		case <-hub.configChanged:
-			resetTicker()
-		case <-tick:
-			wantAccel := hub.anyWantsAccel() && accelStreamPollingActive(dash, ctl)
-			wantTap := hub.anyWantsTap()
-			if !wantAccel && !wantTap {
+			pending = nil
+		case now := <-ticker.C:
+			if !hub.anyWantsInput() || !inputPollingActive(dash, ctl, tapCtl) {
+				pending = nil
 				continue
 			}
 
-			now := time.Now().UnixNano()
-			cache, err := link.readCacheStatusPoll()
-			if errors.Is(err, errUARTBusy) {
-				if wantAccel {
-					hub.deliver(AccelStreamMessage{
-						Type:    "accel",
-						T:       now,
-						Success: false,
-						Error:   "uart busy",
-					})
+			needRead, needDeliver, waitPreFetch := hub.streamTiming(now)
+
+			if needRead && pending == nil {
+				cache, err := link.readCacheStatusPoll()
+				if err != nil {
+					pending = &pendingInputCache{readErr: err, readAt: now}
+				} else {
+					hub.ingestTapFromCache(cache)
+					pending = &pendingInputCache{cache: cache, readAt: now}
 				}
-				if wantTap {
-					hub.deliverTap(TapStreamMessage{
-						Type:    "tap",
-						T:       now,
-						Success: false,
-						Error:   "uart busy",
-					})
-				}
-				continue
 			}
-			if err != nil {
-				if wantAccel {
-					hub.deliver(AccelStreamMessage{
-						Type:    "accel",
-						T:       now,
-						Success: false,
-						Error:   err.Error(),
-					})
-				}
-				if wantTap {
-					hub.deliverTap(TapStreamMessage{
-						Type:    "tap",
-						T:       now,
-						Success: false,
-						Error:   err.Error(),
-					})
-				}
+
+			if !needDeliver || pending == nil {
 				continue
 			}
 
-			if wantAccel {
-				samples := accelSamplesFromCacheStatus(cache)
-				clients := make([]AccelClientSample, 0, len(samples))
-				for _, s := range samples {
-					clients = append(clients, AccelClientSample{
-						ClientID: s.GetClientId(),
-						Valid:    s.GetValid(),
-						X:        s.GetX(),
-						Y:        s.GetY(),
-						Z:        s.GetZ(),
-						AgeMs:    s.GetAgeMs(),
-					})
+			ts := now.UnixNano()
+			if pending.readErr != nil {
+				errMsg := pending.readErr.Error()
+				if errors.Is(pending.readErr, errUARTBusy) {
+					errMsg = "uart busy"
 				}
-				hub.deliver(AccelStreamMessage{
-					Type:    "accel",
-					T:       now,
+				hub.deliverInput(InputStreamMessage{
+					Type:    "input",
+					T:       ts,
+					Success: false,
+					Error:   errMsg,
+				})
+				pending = nil
+				continue
+			}
+
+			if pending.cache != nil && now.Sub(pending.readAt) >= waitPreFetch {
+				hub.mu.RLock()
+				clients := hub.inputClientsFromCacheLocked(pending.cache, now)
+				hub.mu.RUnlock()
+				hub.deliverInput(InputStreamMessage{
+					Type:    "input",
+					T:       ts,
 					Success: true,
 					Clients: clients,
 				})
-			}
-			if wantTap {
-				events := tapEventsFromCacheStatus(cache)
-				fresh := make([]TapClientEvent, 0, len(events))
-				for _, e := range events {
-					if !e.GetValid() {
-						continue
-					}
-					fresh = append(fresh, TapClientEvent{
-						ClientID: e.GetClientId(),
-						Valid:    true,
-						Kind:     tapKindLabelPB(e.GetKind()),
-						AgeMs:    e.GetAgeMs(),
-					})
-				}
-				visible := hub.ingestTapEvents(fresh)
-				if len(visible) > 0 {
-					hub.deliverTap(TapStreamMessage{
-						Type:    "tap",
-						T:       now,
-						Success: true,
-						Events:  visible,
-					})
-				}
+				pending = nil
 			}
 		}
 	}
 }
 
-func accelStreamPollingActive(dash *wsHub, ctl *accelStreamCtl) bool {
+func inputPollingActive(dash *wsHub, ctl *accelStreamCtl, tapCtl *tapNotifyCtl) bool {
 	if ctl != nil && ctl.Any() {
 		return true
 	}
+	if tapCtl != nil && tapCtl.Any() {
+		return true
+	}
 	return dash != nil && dash.anyAccelStreamEnabled()
 }
 
@@ -586,9 +538,9 @@ func writeLedRingStatus(conn *websocket.Conn, out ledRingAPIResponse) {
 	_ = conn.WriteMessage(websocket.TextMessage, data)
 }
 
-func writeAccelStreamStatus(conn *websocket.Conn, out accelStreamAPIResponse) {
-	msg := AccelStreamStatusMessage{
-		Type:          "accel_stream_status",
+func writeInputStreamStatus(conn *websocket.Conn, out accelStreamAPIResponse) {
+	msg := InputStreamStatusMessage{
+		Type:          "input_stream_status",
 		ClientID:      out.ClientID,
 		Enabled:       out.Enabled,
 		Success:       out.Success,
@@ -602,14 +554,6 @@ func writeAccelStreamStatus(conn *websocket.Conn, out accelStreamAPIResponse) {
 	_ = conn.WriteMessage(websocket.TextMessage, data)
 }
 
-func writeTapStreamStatus(conn *websocket.Conn, msg TapStreamStatusMessage) {
-	data, err := json.Marshal(msg)
-	if err != nil {
-		return
-	}
-	_ = conn.WriteMessage(websocket.TextMessage, data)
-}
-
 func clientInfoToAPI(c *pb.ClientInfo) APIClientInfo {
 	return APIClientInfo{
 		ID:              c.GetId(),
@@ -619,7 +563,7 @@ func clientInfoToAPI(c *pb.ClientInfo) APIClientInfo {
 		Used:            c.GetUsed(),
 		LastPing:        c.GetLastPing(),
 		LastSuccessPing: c.GetLastSuccessPing(),
-		AccelStream:     c.GetAccelStreamEnabled(),
+		InputStream:     c.GetAccelStreamEnabled(),
 		TapNotifySingle: c.GetTapNotifySingle(),
 		TapNotifyDouble: c.GetTapNotifyDouble(),
 		TapNotifyTriple: c.GetTapNotifyTriple(),
@@ -717,28 +661,28 @@ func handleAccelWSCommand(conn *websocket.Conn, sub *wsSubscriber, data []byte,
 			})
 			return
 		}
-		writeStreamStatus(conn, hub.setStream(sub, *cmd.Enable, cmd.IntervalMs))
+		writeStreamStatus(conn, hub.setStream(sub, *cmd.Enable, cmd.IntervalMs, cmd.PreFetch))
 
 	case "get_stream":
 		writeStreamStatus(conn, hub.getStream(sub))
 
-	case "set_accel_stream":
+	case "set_input_stream":
 		if cmd.ClientID == 0 {
-			writeAccelStreamStatus(conn, accelStreamAPIResponse{Error: "client_id required"})
+			writeInputStreamStatus(conn, accelStreamAPIResponse{Error: "client_id required"})
 			return
 		}
 		if cmd.Enable == nil {
-			writeAccelStreamStatus(conn, accelStreamAPIResponse{
+			writeInputStreamStatus(conn, accelStreamAPIResponse{
 				ClientID: cmd.ClientID,
 				Error:    "enable required",
 			})
 			return
 		}
-		writeAccelStreamStatus(conn, applyAccelStreamClient(link, dash, ctl, cmd.ClientID, *cmd.Enable))
+		writeInputStreamStatus(conn, applyAccelStreamClient(link, dash, ctl, cmd.ClientID, *cmd.Enable))
 
-	case "get_accel_stream":
+	case "get_input_stream":
 		if cmd.ClientID == 0 {
-			writeAccelStreamStatus(conn, accelStreamAPIResponse{Error: "client_id required"})
+			writeInputStreamStatus(conn, accelStreamAPIResponse{Error: "client_id required"})
 			return
 		}
 		resp, err := link.AccelStreamPoll(&pb.AccelStreamRequest{
@@ -746,7 +690,7 @@ func handleAccelWSCommand(conn *websocket.Conn, sub *wsSubscriber, data []byte,
 			ClientId: cmd.ClientID,
 		})
 		if err != nil {
-			writeAccelStreamStatus(conn, accelStreamAPIResponse{
+			writeInputStreamStatus(conn, accelStreamAPIResponse{
 				ClientID: cmd.ClientID,
 				Error:    err.Error(),
 			})
@@ -755,25 +699,12 @@ func handleAccelWSCommand(conn *websocket.Conn, sub *wsSubscriber, data []byte,
 		if ctl != nil {
 			ctl.Set(cmd.ClientID, resp.GetEnabled())
 		}
-		writeAccelStreamStatus(conn, accelStreamAPIResponse{
+		writeInputStreamStatus(conn, accelStreamAPIResponse{
 			Enabled:  resp.GetEnabled(),
 			ClientID: resp.GetClientId(),
 			Success:  resp.GetSuccess(),
 		})
 
-	case "set_tap_stream":
-		if cmd.Enable == nil {
-			writeTapStreamStatus(conn, TapStreamStatusMessage{
-				Type:  "tap_stream_status",
-				Error: "enable required",
-			})
-			return
-		}
-		writeTapStreamStatus(conn, hub.setTapStream(sub, *cmd.Enable, cmd.IntervalMs))
-
-	case "get_tap_stream":
-		writeTapStreamStatus(conn, hub.getTapStream(sub))
-
 	case "set_tap_notify":
 		if cmd.AllClients {
 			if cmd.Single == nil || cmd.DoubleTap == nil || cmd.Triple == nil {
@@ -827,11 +758,11 @@ func handleAccelWSCommand(conn *websocket.Conn, sub *wsSubscriber, data []byte,
 			tapCtl.Set(cmd.ClientID, resp.GetSingle(), resp.GetDoubleTap(), resp.GetTriple())
 		}
 		writeTapNotifyStatus(conn, tapNotifyAPIResponse{
-			ClientID: cmd.ClientID,
-			Success:  resp.GetSuccess(),
-			Single:   resp.GetSingle(),
+			ClientID:  cmd.ClientID,
+			Success:   resp.GetSuccess(),
+			Single:    resp.GetSingle(),
 			DoubleTap: resp.GetDoubleTap(),
-			Triple:   resp.GetTriple(),
+			Triple:    resp.GetTriple(),
 		})
 
 	case "set_led_ring":
@@ -860,7 +791,7 @@ func handleAccelWSCommand(conn *websocket.Conn, sub *wsSubscriber, data []byte,
 	default:
 		writeStreamStatus(conn, StreamStatusMessage{
 			Type: "stream_status",
-			Error: "unknown type (list_clients, set_stream, get_stream, set_accel_stream, get_accel_stream, set_tap_stream, get_tap_stream, set_tap_notify, get_tap_notify, set_led_ring, get_battery)",
+			Error: "unknown type (list_clients, set_stream, get_stream, set_input_stream, get_input_stream, set_tap_notify, get_tap_notify, set_led_ring, get_battery)",
 		})
 	}
 }
@@ -896,10 +827,11 @@ func mountExternalAPI(mux *http.ServeMux, portName string, defaultInterval time.
 			SerialPort:        portName,
 			WebSocket:         "/ws",
 			DefaultIntervalMs: defMs,
+			DefaultPreFetchMs: defaultPreFetchMs,
 			MinIntervalMs:     int(minAPIStreamInterval / time.Millisecond),
 			MaxIntervalMs:     int(maxAPIStreamInterval / time.Millisecond),
 			TapDisplayMinMs:   apiTapDisplayMinMs,
-			Description:       "WebSocket: set_accel_stream + set_stream for accel; set_tap_notify (slave S/D/T) then set_tap_stream for tap events (shown ≥2s)",
+			Description:       "WebSocket: set_input_stream + set_stream for input (accel + tap); set_tap_notify configures slave tap kinds",
 		})
 	})
 
@@ -915,7 +847,7 @@ func mountExternalAPI(mux *http.ServeMux, portName string, defaultInterval time.
 
 func runAPIServer(portName string, link *managedSerial, addr string, defaultInterval time.Duration, dash *wsHub, ctl *accelStreamCtl, tapCtl *tapNotifyCtl, stop <-chan struct{}) *http.Server {
 	hub := newAccelStreamHub(defaultInterval)
-	go runAccelStreamer(link, hub, dash, ctl, tapCtl, stop)
+	go runInputStreamer(link, hub, dash, ctl, tapCtl, stop)
 
 	mux := http.NewServeMux()
 	mountExternalAPI(mux, portName, defaultInterval, hub, link, dash, ctl, tapCtl)
@@ -924,7 +856,7 @@ func runAPIServer(portName string, link *managedSerial, addr string, defaultInte
 
 	srv := &http.Server{Addr: addr, Handler: mux}
 	go func() {
-		log.Printf("external API http://localhost%s  WebSocket ws://localhost%s/ws  (default stream interval %s, per-client via set_stream / set_tap_stream)",
+		log.Printf("external API http://localhost%s  WebSocket ws://localhost%s/ws  (default stream interval %s, per-client via set_stream)",
 			addr, addr, defaultInterval.String())
 		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
 			log.Printf("external API server: %v", err)

goTool/autotest/runner.go

@@ -347,6 +347,8 @@ func ledRingModeValue(mode string) (uint32, error) {
 		return 3, nil
 	case "find_me", "findme":
 		return 4, nil
+	case "battery_low", "batterylow":
+		return 6, nil
 	case "color", "solid", "fill":
 		return 5, nil
 	default:

goTool/autotest/runner_test.go

@@ -12,6 +12,7 @@ func TestLedRingModeValue(t *testing.T) {
 		{"digit", 2},
 		{"blink", 3},
 		{"find-me", 4},
+		{"battery-low", 6},
 	}
 	for _, tc := range tests {
 		got, err := ledRingModeValue(tc.mode)

goTool/client_api.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"time"
 
 	"google.golang.org/protobuf/proto"
 
@@ -410,16 +411,93 @@ func (s *serialPort) espnowUnicastTest(clientID, seq uint32) (*pb.EspNowUnicastT
 	return r, nil
 }
 
+// EchoPingResult is the host-side round-trip for ESP-NOW echo ping.
+type EchoPingResult struct {
+	Success     bool    `json:"success"`
+	ClientID    uint32  `json:"client_id"`
+	TimestampUs uint64  `json:"timestamp_us"`
+	RttMs       float64 `json:"rtt_ms"`     // goTool: full UART round-trip
+	EspRttUs    uint32  `json:"esp_rtt_us"` // master: µs delta ping send → pong recv
+}
+
+func (s *serialPort) echoPing(clientID uint32) (*EchoPingResult, error) {
+	t0 := time.Now()
+	timestampUs := uint64(t0.UnixMicro())
+	req := &pb.EspNowEchoPingRequest{
+		ClientId:    clientID,
+		TimestampUs: timestampUs,
+	}
+	msg := &pb.UartMessage{
+		Type: pb.MessageType_ESPNOW_ECHO_PING,
+		Payload: &pb.UartMessage_EspnowEchoPingRequest{
+			EspnowEchoPingRequest: req,
+		},
+	}
+	body, err := proto.Marshal(msg)
+	if err != nil {
+		return nil, fmt.Errorf("encode: %w", err)
+	}
+	payload := append([]byte{byte(pb.MessageType_ESPNOW_ECHO_PING)}, body...)
+	respPayload, err := s.exchangePayload(payload, "ESPNOW_ECHO_PING")
+	if err != nil {
+		return nil, err
+	}
+	rttMs := float64(time.Since(t0).Microseconds()) / 1000.0
+
+	var respMsg pb.UartMessage
+	if err := proto.Unmarshal(respPayload[1:], &respMsg); err != nil {
+		return nil, fmt.Errorf("decode: %w", err)
+	}
+	r := respMsg.GetEspnowEchoPingResponse()
+	if r == nil {
+		return nil, fmt.Errorf("missing espnow_echo_ping_response")
+	}
+	if !r.GetSuccess() {
+		return &EchoPingResult{
+			Success:  false,
+			ClientID: r.GetClientId(),
+			RttMs:    rttMs,
+		}, nil
+	}
+	if r.GetTimestampUs() != timestampUs {
+		return nil, fmt.Errorf("timestamp mismatch: sent %d got %d", timestampUs, r.GetTimestampUs())
+	}
+	return &EchoPingResult{
+		Success:     true,
+		ClientID:    r.GetClientId(),
+		TimestampUs: r.GetTimestampUs(),
+		RttMs:       rttMs,
+		EspRttUs:    r.GetEspRttUs(),
+	}, nil
+}
+
 func (m *managedSerial) FindMe(clientID uint32) error {
 	return m.withPort(func(sp *serialPort) error {
 		return runFindMeClient(sp, clientID)
 	})
 }
 
+func (m *managedSerial) SetLogLevel(write bool, level uint32) (*pb.SetLogLevelResponse, error) {
+	var resp *pb.SetLogLevelResponse
+	err := m.withPort(func(sp *serialPort) error {
+		var e error
+		resp, e = runSetLogLevelClient(sp, write, level)
+		return e
+	})
+	return resp, err
+}
+
 func (m *managedSerial) Restart(clientID uint32) error {
-	return m.withPort(func(sp *serialPort) error {
+	err := m.withPort(func(sp *serialPort) error {
 		return runRestartClient(sp, clientID)
 	})
+	if err != nil {
+		return err
+	}
+	if clientID == 0 {
+		m.recoverAfterMasterRestart()
+	}
+	return nil
 }
 
 func (s *serialPort) ledRingProgress(req *pb.LedRingProgressRequest) (*pb.LedRingProgressResponse, error) {
@@ -483,6 +561,20 @@ func (s *serialPort) EspnowUnicastTest(clientID, seq uint32) (*pb.EspNowUnicastT
 	return s.espnowUnicastTest(clientID, seq)
 }
 
+func (s *serialPort) EchoPing(clientID uint32) (*EchoPingResult, error) {
+	return s.echoPing(clientID)
+}
+
+func (m *managedSerial) EchoPing(clientID uint32) (*EchoPingResult, error) {
+	var result *EchoPingResult
+	err := m.withPort(func(sp *serialPort) error {
+		var e error
+		result, e = sp.echoPing(clientID)
+		return e
+	})
+	return result, err
+}
+
 func (s *serialPort) LedRing(req *pb.LedRingProgressRequest) (*pb.LedRingProgressResponse, error) {
 	return s.ledRingProgress(req)
 }

goTool/cmd_autotest.go

@@ -62,6 +62,8 @@ func runTest(portOverride string, baudOverride int, args []string) error {
 	if err != nil {
 		return fmt.Errorf("open %s: %w", port, err)
 	}
+	registerShutdown(func() { _ = sp.Close() })
+	enableShutdownOnInterrupt()
 	defer sp.Close()
 
 	if !*verbose {

goTool/cmd_echo_ping.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+)
+
+func runEchoPing(sp *serialPort, args []string) error {
+	fs := flag.NewFlagSet("echo-ping", flag.ExitOnError)
+	clientID := fs.Uint("client", 0, "slave client id from `clients`")
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+	if *clientID == 0 {
+		return fmt.Errorf("client id required (see `gotool clients`)")
+	}
+
+	r, err := sp.echoPing(uint32(*clientID))
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("echo ping: success=%v client_id=%d rtt_ms=%.3f esp_rtt_us=%d\n",
+		r.Success, r.ClientID, r.RttMs, r.EspRttUs)
+	return nil
+}

goTool/cmd_led_ring.go

@@ -9,7 +9,7 @@ import (
 
 func runLedRing(sp *serialPort, args []string) error {
 	fs := flag.NewFlagSet("led-ring", flag.ExitOnError)
-	mode := fs.String("mode", "progress", "clear, color, progress, digit, blink, or find-me")
+	mode := fs.String("mode", "progress", "clear, color, progress, digit, blink, find-me, or battery-low")
 	clientID := fs.Uint("client", 0, "0=master ring, >0=slave via ESP-NOW")
 	allClients := fs.Bool("all", false, "broadcast to all slaves")
 	slavesOnly := fs.Bool("slaves-only", false, "with -all: do not change master ring")

goTool/cmd_log_level.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+
+	"google.golang.org/protobuf/proto"
+	"powerpod/gotool/pb"
+)
+
+func runLogLevel(sp *serialPort, args []string) error {
+	fs := flag.NewFlagSet("log-level", flag.ExitOnError)
+	write := fs.Bool("set", false, "write log level (default: read)")
+	level := fs.Uint("level", 0, "esp_log_level_t 0–5 (with -set)")
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+	resp, err := sp.setLogLevel(*write, uint32(*level))
+	if err != nil {
+		return err
+	}
+	if !resp.GetSuccess() {
+		return fmt.Errorf("set_log_level rejected (level=%d)", resp.GetLevel())
+	}
+	fmt.Printf("log_level=%d success=%v\n", resp.GetLevel(), resp.GetSuccess())
+	return nil
+}
+
+func runSetLogLevelClient(sp *serialPort, write bool, level uint32) (*pb.SetLogLevelResponse, error) {
+	return sp.setLogLevel(write, level)
+}
+
+func (s *serialPort) setLogLevel(write bool, level uint32) (*pb.SetLogLevelResponse, error) {
+	msg := &pb.UartMessage{
+		Type: pb.MessageType_SET_LOG_LEVEL,
+		Payload: &pb.UartMessage_SetLogLevelRequest{
+			SetLogLevelRequest: &pb.SetLogLevelRequest{
+				Write: write,
+				Level: level,
+			},
+		},
+	}
+	body, err := proto.Marshal(msg)
+	if err != nil {
+		return nil, fmt.Errorf("encode: %w", err)
+	}
+	payload := append([]byte{byte(pb.MessageType_SET_LOG_LEVEL)}, body...)
+	respPayload, err := s.exchangePayload(payload, "SET_LOG_LEVEL")
+	if err != nil {
+		return nil, err
+	}
+	var respMsg pb.UartMessage
+	if err := proto.Unmarshal(respPayload[1:], &respMsg); err != nil {
+		return nil, fmt.Errorf("decode: %w", err)
+	}
+	r := respMsg.GetSetLogLevelResponse()
+	if r == nil {
+		return nil, fmt.Errorf("missing set_log_level_response")
+	}
+	return r, nil
+}

goTool/cmd_ota.go

@@ -16,8 +16,7 @@ func runOTA(sp *serialPort, args []string) error {
 
 	sp.mu.Lock()
 	defer sp.mu.Unlock()
-	m := &managedSerial{quiet: false, sp: sp}
-	return runOTAOnPortUnlocked(m, data, func(p OTAProgress) {
+	return runOTAOnPortUnlocked(sp, data, func(p OTAProgress) {
 		switch p.Phase {
 		case "preparing", "ready":
 			fmt.Println(p.Message)

goTool/cmd_serve.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"embed"
+	"errors"
 	"flag"
 	"fmt"
 	"io/fs"
@@ -34,21 +35,29 @@ func runServe(portName string, baud int, args []string) error {
 
 	link := newManagedSerial(portName, baud)
 	link.quiet = true
-	defer link.Close()
 
 	hub := newWSHub()
 	streamCtl := newAccelStreamCtl()
 	tapCtl := newTapNotifyCtl()
 	stop := make(chan struct{})
-	defer close(stop)
+
+	var dashSrv *http.Server
+	var apiSrv *http.Server
+	registerShutdown(func() {
+		close(stop)
+		shutdownHTTPServer(dashSrv)
+		shutdownAPIServer(apiSrv)
+		if err := link.Close(); err != nil {
+			log.Printf("UART close: %v", err)
+		}
+	})
+
 	go runPoller(link, portName, hub, streamCtl, tapCtl, *interval, stop)
 	go runBatteryPoller(link, hub, 5*time.Second, stop)
 	go runCacheStatusDashboardPoller(link, hub, *accelInterval, stop)
 
-	var apiSrv *http.Server
 	if *apiAddr != "" {
 		apiSrv = runAPIServer(portName, link, *apiAddr, *accelInterval, hub, streamCtl, tapCtl, stop)
-		defer shutdownAPIServer(apiSrv)
 	}
 
 	mux := http.NewServeMux()
@@ -81,5 +90,14 @@ func runServe(portName string, baud int, args []string) error {
 	if *apiAddr == "" {
 		log.Printf("external API disabled (-api-addr \"\")")
 	}
-	return http.ListenAndServe(*addr, mux)
+
+	dashSrv = &http.Server{Addr: *addr, Handler: mux}
+	go func() {
+		if err := dashSrv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			log.Printf("dashboard server: %v", err)
+		}
+	}()
+
+	waitForShutdown()
+	return nil
 }

goTool/dashboard.go

@@ -101,7 +101,7 @@ func (h *wsHub) setState(st DashboardState) {
 		return
 	}
 	for _, c := range conns {
-		_ = c.WriteMessage(websocket.TextMessage, data)
+		h.writeJSON(c, data)
 	}
 }
 
@@ -112,7 +112,7 @@ func (h *wsHub) register(c *websocket.Conn) {
 	h.mu.Unlock()
 
 	if data, err := json.Marshal(snap); err == nil {
-		_ = c.WriteMessage(websocket.TextMessage, data)
+		h.writeJSON(c, data)
 	}
 }
 
@@ -122,6 +122,30 @@ func (h *wsHub) unregister(c *websocket.Conn) {
 	h.mu.Unlock()
 }
 
+// writeJSON sends to one client; removes it on error or panic (closed connection).
+func (h *wsHub) writeJSON(c *websocket.Conn, data []byte) {
+	defer func() {
+		if recover() != nil {
+			h.unregister(c)
+		}
+	}()
+	if err := c.WriteMessage(websocket.TextMessage, data); err != nil {
+		h.unregister(c)
+	}
+}
+
+func (h *wsHub) broadcastJSON(data []byte) {
+	h.mu.RLock()
+	conns := make([]*websocket.Conn, 0, len(h.clients))
+	for c := range h.clients {
+		conns = append(conns, c)
+	}
+	h.mu.RUnlock()
+	for _, c := range conns {
+		h.writeJSON(c, data)
+	}
+}
+
 func applyAccelSamples(clients []ClientView, samples []*pb.AccelSample) []ClientView {
 	if len(samples) == 0 {
 		return clients
@@ -338,7 +362,7 @@ func (h *wsHub) patchClientAccelStream(clientID uint32, enabled bool) {
 		return
 	}
 	for _, c := range conns {
-		_ = c.WriteMessage(websocket.TextMessage, data)
+		h.writeJSON(c, data)
 	}
 }
 
@@ -397,7 +421,7 @@ func (h *wsHub) patchLiveStream(enabled bool) {
 		return
 	}
 	for _, c := range conns {
-		_ = c.WriteMessage(websocket.TextMessage, data)
+		h.writeJSON(c, data)
 	}
 }
 
@@ -430,7 +454,7 @@ func (h *wsHub) patchClientTapNotify(clientID uint32, single, doubleTap, triple
 		return
 	}
 	for _, c := range conns {
-		_ = c.WriteMessage(websocket.TextMessage, data)
+		h.writeJSON(c, data)
 	}
 }
 
@@ -455,7 +479,7 @@ func (h *wsHub) mergeAccel(samples []*pb.AccelSample) {
 		return
 	}
 	for _, c := range conns {
-		_ = c.WriteMessage(websocket.TextMessage, data)
+		h.writeJSON(c, data)
 	}
 }
 
@@ -479,25 +503,16 @@ func (h *wsHub) mergeTap(events []*pb.TapEvent) {
 		return
 	}
 	for _, c := range conns {
-		_ = c.WriteMessage(websocket.TextMessage, data)
+		h.writeJSON(c, data)
 	}
 }
 
 func (h *wsHub) broadcastRaw(v any) {
-	h.mu.RLock()
-	conns := make([]*websocket.Conn, 0, len(h.clients))
-	for c := range h.clients {
-		conns = append(conns, c)
-	}
-	h.mu.RUnlock()
-
 	data, err := json.Marshal(v)
 	if err != nil {
 		return
 	}
-	for _, c := range conns {
-		_ = c.WriteMessage(websocket.TextMessage, data)
-	}
+	h.broadcastJSON(data)
 }
 
 func pollDashboard(link *managedSerial, portName string, last *DashboardState, streamCtl *accelStreamCtl, tapCtl *tapNotifyCtl) DashboardState {
@@ -575,6 +590,9 @@ func pollDashboard(link *managedSerial, portName string, last *DashboardState, s
 
 func applyBatteryToState(link *managedSerial, st *DashboardState) {
 	bat, err := link.BatteryStatusPoll(&pb.BatteryStatusRequest{AllClients: true})
+	if errors.Is(err, errUARTBusy) {
+		return
+	}
 	if err != nil {
 		log.Printf("battery poll: %v", err)
 		return
@@ -602,7 +620,7 @@ func (h *wsHub) mergeBattery(samples []batterySampleJSON) {
 		return
 	}
 	for _, c := range conns {
-		_ = c.WriteMessage(websocket.TextMessage, data)
+		h.writeJSON(c, data)
 	}
 }
 
@@ -615,11 +633,11 @@ func runBatteryPoller(link *managedSerial, hub *wsHub, interval time.Duration, s
 		case <-stop:
 			return
 		case <-ticker.C:
-			if hub.clientCount() == 0 {
+			if !link.IsConnected() {
 				continue
 			}
 			bat, err := link.BatteryStatusPoll(&pb.BatteryStatusRequest{AllClients: true})
-			if err != nil {
+			if errors.Is(err, errUARTBusy) || err != nil {
 				continue
 			}
 			hub.mergeBattery(batterySamplesFromPB(bat.GetSamples()))

goTool/docs/API_REST.md

@@ -96,6 +96,7 @@ Body:
 | `digit` | `digit` 0–10 |
 | `blink` | `blink_ms`, `blink_count` |
 | `find-me` | Locate pod |
+| `battery-low` | First 4 LEDs red at ~10 % for 5 s (UV indicator test) |
 
 Use `client_id` (`0` = master) or `all_clients` (+ optional `slaves_only`) for broadcast.
 
@@ -216,6 +217,54 @@ Content-Type: application/json
 {"client_id": 16, "seq": 42}
 ```
 
+### Echo ping (ESP-NOW round-trip latency)
+
+```http
+POST /api/echo-ping
+Content-Type: application/json
+{"client_id": 16}
+```
+
+`client_id` must be a registered slave id (`> 0`). The host sends a microsecond timestamp; the master forwards it over ESP-NOW and the slave echoes it back unchanged.
+
+**Flow:** Host → UART → `cmd_espnow_echo_ping` → `ESPNOW_ECHO_PING` (with `master_time_us` from `esp_timer_get_time()`) → Slave → `ESPNOW_ECHO_PONG` → Master `recv_cb` → UART response.
+
+**Response fields:**
+
+| Field | Unit | Meaning |
+|-------|------|---------|
+| `success` | — | `true` if pong received within 500 ms |
+| `client_id` | — | Echo of request |
+| `timestamp_us` | µs (Unix) | Echoed host timestamp; must match request on success |
+| `rtt_ms` | ms | **Host-side** round-trip: goTool send → UART response (full chain incl. USB serial) |
+| `esp_rtt_us` | µs | **Master-side** ESP-NOW only: `esp_timer_get_time()` delta from ping send to pong recv |
+
+`esp_rtt_us` is the raw firmware value (microseconds, not converted). The web dashboard displays it converted to milliseconds for readability (`esp_rtt_us / 1000`, 3 decimal places). The success banner stays visible for at least 5 seconds.
+
+```json
+{
+  "success": true,
+  "client_id": 16,
+  "timestamp_us": 1717654321123456,
+  "rtt_ms": 49.729,
+  "esp_rtt_us": 18234
+}
+```
+
+On failure (`success: false`), `esp_rtt_us` is omitted; `rtt_ms` still reflects the host round-trip. HTTP 503 if UART exchange fails (e.g. timeout, client not in registry).
+
+**CLI:**
+
+```bash
+go run . -port /dev/ttyUSB0 echo-ping -client 16
+```
+
+Example output:
+
+```
+echo ping: success=true client_id=16 rtt_ms=49.729 esp_rtt_us=18234
+```
+
 ### Find me
 
 ```http
@@ -234,6 +283,39 @@ Content-Type: application/json
 {"client_id": 16}
 ```
 
+### Log level (master ESP-IDF console)
+
+Runtime get/set of the **global** log filter on the master (`esp_log_level_set("*", …)`). Output goes to **UART0** (USB debug, 115200), not the host protocol UART (GPIO 2/3, 921600).
+
+```http
+GET /api/log-level
+POST /api/log-level
+Content-Type: application/json
+{"write": true, "level": 3}
+```
+
+| `level` | Meaning |
+|---------|---------|
+| 0 | None (no log output) |
+| 1 | Error |
+| 2 | Warn |
+| 3 | Info |
+| 4 | Debug |
+| 5 | Verbose |
+
+```json
+{"success": true, "level": 3}
+```
+
+**CLI:**
+
+```bash
+go run . -port /dev/ttyUSB0 log-level
+go run . -port /dev/ttyUSB0 log-level -set -level 3
+```
+
+Dashboard: Master card → dropdown **ESP Log-Level** with **Lesen** / **Setzen**.
+
 ### OTA (master UART upload)
 
 ```http
@@ -280,5 +362,7 @@ Same as external API:
 | Einzelner Slave | `client_id: <id>` |
 | Alle Slaves deadzone | `all_clients` + `slaves_only` on POST |
 | Unicast test | `POST /api/unicast-test` |
+| Echo ping | `POST /api/echo-ping` (per-slave latency; UI shows Host ms + ESP ms) |
+| Master log level | `GET` / `POST /api/log-level` or CLI `log-level` |
 | Tap notify S/D/T | `PUT /api/clients/{id}/tap-notify` |
 | Tap receive (UI) | Live stream + tap notify; see WebSocket doc for external API |

goTool/docs/API_WEBSOCKET.md

@@ -1,62 +1,63 @@
 # WebSocket API
 
-`go run . -port /dev/ttyUSB0 serve` exposes two WebSocket endpoints. They share the same UART link but serve different purposes.
+External API: `ws://localhost:8081/ws` (default `-api-addr`, disable with empty string).
 
-| URL | Port (default) | Role |
-|-----|----------------|------|
-| `ws://localhost:8080/ws` | Dashboard (`-addr`) | Server → client only: full `DashboardState` JSON (~2 s poll + live-stream accel/tap) |
-| `ws://localhost:8081/ws` | External API (`-api-addr`) | Request/response commands + optional **accel** / **tap** push streams |
-
-Disable the external server with `-api-addr ""`.
-
-CLI overview and UART commands: [`../README.md`](../README.md). HTTP endpoints: [`API_REST.md`](API_REST.md).
+Start with `go run . -port /dev/ttyUSB0 serve`.
 
 ---
 
-## External API (`:8081/ws`)
+## Connection flow
 
-### Connection flow
+1. Connect → server sends `hello` (push off; defaults and command list).
+2. Send JSON commands → one reply per message (`*_status` or `client_list`).
+3. After `set_stream` with `enable: true`, server may push `input` messages without a prior command.
 
-1. Connect → server sends **`hello`** (receive off; lists available commands).
-2. Send JSON commands → server replies with a matching `*_status` or `client_list` message (one reply per command).
-3. After `set_stream` / `set_tap_stream` with `enable: true`, the server may send **`accel`** and/or **`tap`** messages **without** a prior command (push stream).
+Commands and pushes share one socket — always branch on `type`.
 
-Commands and stream pushes are multiplexed on one socket. While streaming, always parse `type` and branch (status vs sample vs error).
+On disconnect, `set_stream` state for that socket is dropped. Firmware settings (`set_input_stream`, `set_tap_notify`) stay on the master until changed.
 
-### Two layers (accel and tap)
+---
 
-| Layer | Commands | Effect |
-|-------|----------|--------|
-| **Firmware (ESP-NOW)** | `set_accel_stream`, `set_tap_notify` | Per `client_id`: slave sends accel or tap kinds to the master |
-| **This connection (host)** | `set_stream`, `set_tap_stream` | Whether **you** receive push JSON and at what rate (`interval_ms`, 1 ms … 10 s) |
+## Two layers (firmware vs host)
 
-- **Accel UART polling** runs only if at least one connection has `receive_accel: true` **and** at least one slave streams accel (`set_accel_stream` or dashboard).
-- **Tap UART polling** runs only if at least one connection has `receive_tap: true` (`set_tap_stream`). `set_tap_notify` alone does **not** poll.
+
+| Layer              | Commands                             | Effect                                                             |
+| ------------------ | ------------------------------------ | ------------------------------------------------------------------ |
+| Firmware (ESP-NOW) | `set_input_stream`, `set_tap_notify` | Per `client_id`: slave sends accel and/or tap events to the master |
+| This connection    | `set_stream`                         | Whether you receive push JSON on this socket                       |
+
+
+UART polling runs only when at least one connection has `receive_input: true` **and** at least one slave streams input or has tap notify enabled. `set_tap_notify` alone does not enable push — you still need `set_stream`.
+
+### Push timing (per connection)
+
+
+| Field         | Where                                  | Meaning                                                      |
+| ------------- | -------------------------------------- | ------------------------------------------------------------ |
+| `interval_ms` | `hello`, `set_stream`, `stream_status` | Minimum ms between `input` pushes on this socket (1 … 10000) |
+| `pre_fetch`   | `set_stream`, `stream_status`          | Ms before each push when the host starts the UART cache read |
+
+
+Global UART poll interval = minimum `interval_ms` among all connections with push enabled.
 
 Typical sequence:
 
 1. `list_clients` → slave IDs
-2. Per slave: `set_accel_stream` / `set_tap_notify` as needed
-3. `set_stream` and/or `set_tap_stream` with `"enable": true`
-4. Read push messages in a loop
-
-There is **no per-slave filter** on push messages: each `accel` contains all cached slaves; each `tap` contains all visible events. Filter by `client_id` in your app.
+2. Per slave: `set_input_stream` and/or `set_tap_notify`
+3. `set_stream` with `"enable": true`
+4. Read `input` messages; filter by `client_id` in your app (no per-slave filter on the wire)
 
 ---
 
-## Push stream messages
+## Push: `input`
 
-These are the samples you get after enabling receive. Interval is per WebSocket connection; the server UART poll uses the **minimum** `interval_ms` among all subscribers that want accel or tap.
+Combines latest accel cache and visible tap state for every slave slot on the master.
 
-### `accel` (type `"accel"`)
-
-Sent only when `set_stream` has `enable: true`, a slave streams accel, and the poll tick fires for this connection.
-
-**Success** — all slaves with a cache entry on the master (not only those with `valid: true`):
+**Success:**
 
 ```json
 {
-  "type": "accel",
+  "type": "input",
   "t": 1716900123456789012,
   "success": true,
   "clients": [
@@ -66,7 +67,9 @@ Sent only when `set_stream` has `enable: true`, a slave streams accel, and the p
       "x": 12,
       "y": -34,
       "z": 16384,
-      "age_ms": 8
+      "accel_age_ms": 8,
+      "tap_kind": "single",
+      "tap_age_ms": 3
     },
     {
       "client_id": 42,
@@ -76,96 +79,49 @@ Sent only when `set_stream` has `enable: true`, a slave streams accel, and the p
 }
 ```
 
-| Field | Meaning |
-|-------|---------|
-| `t` | Unix timestamp in **nanoseconds** when the host read the cache |
-| `success` | `true` if `CACHE_STATUS` succeeded |
-| `clients[]` | One entry per slave slot in the master cache |
-| `client_id` | ESP-NOW client id (same as `list_clients`) |
-| `valid` | `false` if no sample yet or stale; omit `x`/`y`/`z` when false |
-| `x`, `y`, `z` | Raw accelerometer LSB (BMA456, ±2 g scale on the pod) |
-| `age_ms` | Milliseconds since the master received this sample |
 
-**Failure** (e.g. UART busy):
+| Field          | Meaning                                                              |
+| -------------- | -------------------------------------------------------------------- |
+| `t`            | Unix timestamp in nanoseconds when the host read the cache           |
+| `success`      | `true` if `CACHE_STATUS` succeeded                                   |
+| `clients[]`    | One entry per slave slot (includes invalid/stale entries)            |
+| `client_id`    | Same id as in `list_clients`                                         |
+| `valid`        | `false` if no accel sample yet or stale; omit `x`/`y`/`z` when false |
+| `x`, `y`, `z`  | Raw accelerometer LSB (BMA456, ±2 g)                                 |
+| `accel_age_ms` | Ms since the master received this accel sample                       |
+| `tap_kind`     | `"single"`, `"double"`, or `"triple"`; omit when no recent tap       |
+| `tap_age_ms`   | Ms since tap in master cache; omit with `tap_kind`                   |
+
+
+Tap events stay visible for `tap_display_min_ms` (2000, in `hello`) after the API first saw them.
+
+**Failure** (no `clients` array):
 
 ```json
-{
-  "type": "accel",
-  "t": 1716900123456789012,
-  "success": false,
-  "error": "uart busy"
-}
-```
-
-No `clients` array on failure.
-
-### `tap` (type `"tap"`)
-
-Sent only when `set_tap_stream` has `enable: true` and there is at least one event to show.
-
-Events appear when the master cache reports a new tap. Each event stays in push payloads for **`tap_display_min_ms`** (2000 ms, also in `hello`) after the API first saw it, even if the hardware age grows.
-
-**Success**:
-
-```json
-{
-  "type": "tap",
-  "t": 1716900123456789012,
-  "success": true,
-  "events": [
-    {
-      "client_id": 16,
-      "valid": true,
-      "kind": "single",
-      "age_ms": 3,
-      "shown_at_ms": 1717000000123
-    }
-  ]
-}
-```
-
-| Field | Meaning |
-|-------|---------|
-| `t` | Unix timestamp in **nanoseconds** (poll time) |
-| `events[]` | All taps currently “on screen” for the API |
-| `client_id` | Slave that tapped |
-| `kind` | `"single"`, `"double"`, or `"triple"` |
-| `age_ms` | Age in the master cache when read |
-| `shown_at_ms` | Unix **milliseconds** when this host first included the event |
-
-If no events are visible, **no** `tap` message is sent on that tick (unlike accel, which can send empty `clients` only on success with cache data).
-
-**Failure**:
-
-```json
-{
-  "type": "tap",
-  "t": 1716900123456789012,
-  "success": false,
-  "error": "uart busy"
-}
+{"type":"input","t":1716900123456789012,"success":false,"error":"uart busy"}
 ```
 
 ---
 
-## Commands (request → response)
+## Commands
 
-Send one JSON object per message. Field `type` selects the command.
+One JSON object per message; field `type` selects the command.
 
-### `hello` (server → client, on connect)
+**Errors:** Replies use the matching response `type`. On failure: `success: false` (or omitted) and `"error": "…"`. Malformed JSON or unknown `type` → `stream_status` with `error`.
+
+### `hello` (server → client)
 
 ```json
 {
   "type": "hello",
   "serial_port": "/dev/ttyUSB0",
   "interval_ms": 16,
+  "pre_fetch_ms": 2,
   "tap_display_min_ms": 2000,
-  "note": "set_tap_notify configures slave S/D/T only; set_tap_stream enables tap polling/push",
   "commands": [
     "list_clients",
     "set_stream", "get_stream",
-    "set_accel_stream", "get_accel_stream",
-    "set_tap_stream", "get_tap_stream",
+    "set_input_stream", "get_input_stream",
     "set_tap_notify", "get_tap_notify",
     "set_led_ring", "get_battery"
   ]
@@ -186,12 +142,8 @@ Response `client_list`:
     {
       "id": 16,
       "mac": "aa:bb:cc:dd:ee:10",
-      "version": 1,
       "available": true,
-      "used": true,
-      "last_ping": 1234,
-      "last_success_ping": 1200,
-      "accel_stream": false,
+      "input_stream": false,
       "tap_notify_single": false,
       "tap_notify_double": false,
       "tap_notify_triple": false
@@ -200,149 +152,102 @@ Response `client_list`:
 }
 ```
 
-### `set_stream` / `get_stream` (receive accel on this connection)
+Also per client: `version`, `used`, `last_ping`, `last_success_ping`.
+
+### `set_stream` / `get_stream`
 
 ```json
-{"type":"set_stream","enable":true,"interval_ms":32}
+{"type":"set_stream","enable":true,"interval_ms":32,"pre_fetch":2}
 {"type":"get_stream"}
 ```
 
 Response `stream_status`:
 
 ```json
-{"type":"stream_status","receive_accel":true,"interval_ms":32,"success":true}
+{"type":"stream_status","receive_input":true,"interval_ms":32,"pre_fetch":2,"success":true}
 ```
 
-### `set_accel_stream` / `get_accel_stream` (firmware, per slave)
+### `set_input_stream` / `get_input_stream` (firmware)
 
 `client_id` required (> 0).
 
 ```json
-{"type":"set_accel_stream","client_id":16,"enable":true}
-{"type":"get_accel_stream","client_id":16}
+{"type":"set_input_stream","client_id":16,"enable":true}
+{"type":"get_input_stream","client_id":16}
 ```
 
-Response `accel_stream_status`:
+Response `input_stream_status`:
 
 ```json
-{"type":"accel_stream_status","client_id":16,"enabled":true,"success":true}
+{"type":"input_stream_status","client_id":16,"enabled":true,"success":true}
 ```
 
-### `set_tap_stream` / `get_tap_stream` (receive tap on this connection)
+### `set_tap_notify` / `get_tap_notify` (firmware)
 
-```json
-{"type":"set_tap_stream","enable":true,"interval_ms":16}
-{"type":"get_tap_stream"}
-```
-
-Response `tap_stream_status`:
-
-```json
-{"type":"tap_stream_status","receive_tap":true,"interval_ms":16,"success":true}
-```
-
-### `set_tap_notify` / `get_tap_notify` (firmware, per slave)
-
-Per client: `single`, `double_tap`, `triple` required on set.
+Set requires `single`, `double_tap`, `triple` per client, or `"all_clients": true` for broadcast.
 
 ```json
 {"type":"set_tap_notify","client_id":16,"single":true,"double_tap":false,"triple":false}
+{"type":"get_tap_notify","client_id":16}
 ```
 
-Broadcast: `"all_clients": true` with the three booleans.
-
 Response `tap_notify_status`:
 
 ```json
-{
-  "type": "tap_notify_status",
-  "client_id": 16,
-  "success": true,
-  "single": true,
-  "double_tap": false,
-  "triple": false
-}
+{"type":"tap_notify_status","client_id":16,"success":true,"single":true,"double_tap":false,"triple":false}
 ```
 
 ### `set_led_ring`
 
-Same JSON body as [`POST /api/led-ring`](API_REST.md#led-ring) with `"type":"set_led_ring"` added. Reply: `led_ring_status`.
+```json
+{"type":"set_led_ring","mode":"color","client_id":16,"r":255,"g":0,"b":0,"intensity":128}
+{"type":"set_led_ring","mode":"digit","client_id":0,"digit":3,"r":0,"g":255,"b":0}
+{"type":"set_led_ring","mode":"find-me","all_clients":true,"slaves_only":true}
+```
+
+
+| Request `mode` | Notes                       |
+| -------------- | --------------------------- |
+| `clear`        | Turn off                    |
+| `color`        | Full ring RGB + `intensity` |
+| `progress`     | `progress` 0–100            |
+| `digit`        | `digit` 0–10                |
+| `blink`        | `blink_ms`, `blink_count`   |
+| `find-me`      | Locate pod                  |
+| `battery-low`  | UV indicator (4 LEDs, 5 s)  |
+
+
+Target: `client_id` (`0` = master) or `all_clients` (+ optional `slaves_only`).
+
+Response `led_ring_status` — `mode` is numeric: 0=clear, 1=progress, 2=digit, 3=blink, 4=find-me, 5=color, 6=battery-low.
+
+```json
+{"type":"led_ring_status","success":true,"mode":5,"client_id":16,"slaves_updated":1}
+```
 
 ### `get_battery`
 
-Body: `{"type":"get_battery","all_clients":true}` or `"client_id":16`. Default if omitted: all clients.
+Slaves push battery every 30 s; this reads the master cache. Default: all clients.
 
-Reply: `battery_status` with `samples[]` (see REST doc).
-
----
-
-## Examples
-
-### Accel stream
-
-```python
-import asyncio, json, websockets
-
-async def main():
-    async with websockets.connect("ws://127.0.0.1:8081/ws") as ws:
-        print(await ws.recv())  # hello
-        await ws.send(json.dumps({"type": "list_clients"}))
-        clients = json.loads(await ws.recv())["clients"]
-        for c in clients:
-            if not c.get("available"):
-                continue
-            await ws.send(json.dumps({
-                "type": "set_accel_stream", "client_id": c["id"], "enable": True
-            }))
-            await ws.recv()  # accel_stream_status
-        await ws.send(json.dumps({"type": "set_stream", "enable": True, "interval_ms": 16}))
-        await ws.recv()  # stream_status
-        while True:
-            msg = json.loads(await ws.recv())
-            if msg.get("type") != "accel":
-                continue
-            if not msg.get("success"):
-                print("error:", msg.get("error"))
-                continue
-            for c in msg.get("clients", []):
-                if c.get("valid"):
-                    print(c["client_id"], c["x"], c["y"], c["z"], "age", c.get("age_ms"))
-
-asyncio.run(main())
+```json
+{"type":"get_battery","all_clients":true}
+{"type":"get_battery","client_id":16}
 ```
 
-### Tap stream
+Response `battery_status`:
 
-```python
-import asyncio, json, websockets
-
-async def main():
-    async with websockets.connect("ws://127.0.0.1:8081/ws") as ws:
-        print(await ws.recv())  # hello
-        await ws.send(json.dumps({
-            "type": "set_tap_notify", "client_id": 16,
-            "single": True, "double_tap": False, "triple": False
-        }))
-        await ws.recv()  # tap_notify_status
-        await ws.send(json.dumps({"type": "set_tap_stream", "enable": True, "interval_ms": 16}))
-        await ws.recv()  # tap_stream_status
-        while True:
-            msg = json.loads(await ws.recv())
-            if msg.get("type") == "tap" and msg.get("events"):
-                for e in msg["events"]:
-                    print(e["client_id"], e["kind"], "age", e.get("age_ms"))
-
-asyncio.run(main())
+```json
+{
+  "type": "battery_status",
+  "success": true,
+  "samples": [
+    {
+      "client_id": 16,
+      "lipo1": {"valid": true, "voltage_mv": 3850, "percent": 71},
+      "lipo2": {"valid": false},
+      "age_ms": 1200
+    }
+  ]
+}
 ```
 
----
-
-## Dashboard WebSocket (`:8080/ws`)
-
-Read-only from the browser’s perspective: the server pushes JSON whenever state changes. Clients do not send commands on this socket (messages are ignored).
-
-Payload shape: `DashboardState` — `updated_at`, `serial_port`, `uart_connected`, `live_stream`, `master`, `clients[]` (id, mac, accel, tap notify flags, battery, etc.). Accel/tap samples appear here when **Live stream** is enabled in the UI (`PUT /api/live-stream`).
-
-During OTA, additional messages with `"type":"ota_progress"` may appear on the same socket.
-
-Configure slaves via REST on `:8080` ([`API_REST.md`](API_REST.md)), not via this WebSocket.

goTool/led_ring_api.go

@@ -14,6 +14,7 @@ const (
 	ledRingModeBlink    = 3
 	ledRingModeFindMe   = 4
 	ledRingModeColor    = 5
+	ledRingModeBatteryLow = 6
 )
 
 type ledRingAPIRequest struct {
@@ -56,8 +57,10 @@ func ledRingModeFromString(s string) (uint32, error) {
 		return ledRingModeBlink, nil
 	case "find-me", "find_me", "findme":
 		return ledRingModeFindMe, nil
+	case "battery-low", "battery_low", "batterylow":
+		return ledRingModeBatteryLow, nil
 	default:
-		return 0, fmt.Errorf("unknown mode %q (clear, color, progress, digit, blink, find-me)", s)
+		return 0, fmt.Errorf("unknown mode %q (clear, color, progress, digit, blink, find-me, battery-low)", s)
 	}
 }
 

goTool/main.go

@@ -19,13 +19,15 @@ func usage() {
 	fmt.Fprintf(os.Stderr, "  tap-notify    get/set which tap kinds notify via ESP-NOW\n")
 	fmt.Fprintf(os.Stderr, "  cache-status  subscribed accel + tap cache (one UART round-trip)\n")
 	fmt.Fprintf(os.Stderr, "  unicast-test  send ESP-NOW unicast test to one slave\n")
+	fmt.Fprintf(os.Stderr, "  echo-ping     ESP-NOW timestamp echo round-trip to one slave\n")
 	fmt.Fprintf(os.Stderr, "  test          run automated scenario (see testdata/)\n")
 	fmt.Fprintf(os.Stderr, "  serve         web dashboard (Bootstrap + WebSocket)\n")
 	fmt.Fprintf(os.Stderr, "  ota           UART OTA upload (A/B partitions)\n")
 	fmt.Fprintf(os.Stderr, "  ota-progress  query per-slave ESP-NOW OTA progress on master\n")
 	fmt.Fprintf(os.Stderr, "  led-ring      set LED ring progress bar (0–100%%, rgb, intensity)\n")
 	fmt.Fprintf(os.Stderr, "  find-me       blink LED ring red/green/blue (3× each, full brightness)\n")
-	fmt.Fprintf(os.Stderr, "  restart       reboot master or slave (ESP-NOW)\n\n")
+	fmt.Fprintf(os.Stderr, "  restart       reboot master or slave (ESP-NOW)\n")
+	fmt.Fprintf(os.Stderr, "  log-level     get/set master ESP-IDF log level (global)\n\n")
 	flag.PrintDefaults()
 }
 
@@ -52,7 +54,7 @@ func main() {
 			os.Exit(2)
 		}
 		runErr = runServe(*portName, *baud, flag.Args()[1:])
-	case "version", "clients", "client-info", "deadzone", "accel-deadzone", "tap-notify", "tap_notify", "cache-status", "cache_status", "unicast-test", "unicast_test", "led-ring", "led_ring", "find-me", "find_me", "restart", "ota", "ota-progress", "ota_progress":
+	case "version", "clients", "client-info", "deadzone", "accel-deadzone", "tap-notify", "tap_notify", "cache-status", "cache_status", "unicast-test", "unicast_test", "echo-ping", "echo_ping", "led-ring", "led_ring", "find-me", "find_me", "restart", "log-level", "log_level", "ota", "ota-progress", "ota_progress":
 		if *portName == "" {
 			fmt.Fprintf(os.Stderr, "command %q requires -port\n\n", cmd)
 			usage()
@@ -62,6 +64,8 @@ func main() {
 		if err != nil {
 			log.Fatalf("open serial: %v", err)
 		}
+		registerShutdown(func() { _ = sp.Close() })
+		enableShutdownOnInterrupt()
 		defer sp.Close()
 		switch cmd {
 		case "version":
@@ -76,12 +80,16 @@ func main() {
 			runErr = runCacheStatus(sp)
 		case "unicast-test", "unicast_test":
 			runErr = runUnicastTest(sp, flag.Args()[1:])
+		case "echo-ping", "echo_ping":
+			runErr = runEchoPing(sp, flag.Args()[1:])
 		case "led-ring", "led_ring":
 			runErr = runLedRing(sp, flag.Args()[1:])
 		case "find-me", "find_me":
 			runErr = runFindMe(sp, flag.Args()[1:])
 		case "restart":
 			runErr = runRestart(sp, flag.Args()[1:])
+		case "log-level", "log_level":
+			runErr = runLogLevel(sp, flag.Args()[1:])
 		case "ota":
 			runErr = runOTA(sp, flag.Args()[1:])
 		case "ota-progress", "ota_progress":

goTool/ota_upload.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"fmt"
-	"log"
 	"time"
 
 	"google.golang.org/protobuf/proto"
@@ -21,6 +20,9 @@ const (
 	otaDistQueryInterval   = 500 * time.Millisecond
 	otaDistQueryTimeout    = 2 * time.Second
 	otaDistEmitMinInterval = 150 * time.Millisecond
+	// Pace host chunks so the master UART RX ring is not overrun (~20 frames/block).
+	otaHostChunkPace = 3 * time.Millisecond
+	otaBlockMaxRetries = 3
 )
 
 const (
@@ -69,16 +71,45 @@ const (
 )
 
 func runOTAUpload(m *managedSerial, firmware []byte, onProgress otaProgressFn) error {
+	push := func(phase, msg string) {
+		if onProgress == nil {
+			return
+		}
+		onProgress(OTAProgress{
+			Type: "ota_progress", Phase: phase, Step: otaStepMaster,
+			Percent: 0, Message: msg, MasterMessage: msg,
+		})
+	}
+	push("preparing", "UART wird vorbereitet…")
+
+	// Block until the UART is free, then hold m.mu for the entire upload so
+	// dashboard/API polling cannot interleave on the serial port.
 	m.mu.Lock()
-	defer m.mu.Unlock()
-	err := runOTAOnPortUnlocked(m, firmware, onProgress)
+	if m.otaActive {
+		m.mu.Unlock()
+		return errOTAInProgress
+	}
+	m.otaActive = true
+	if m.sp == nil {
+		if err := m.openLocked(); err != nil {
+			m.otaActive = false
+			m.mu.Unlock()
+			push("error", err.Error())
+			return err
+		}
+	}
+	sp := m.sp
+
+	err := runOTAOnPortUnlocked(sp, firmware, onProgress)
 	if err != nil {
 		m.invalidateLocked(err)
 	}
+	m.otaActive = false
+	m.mu.Unlock()
 	return err
 }
 
-func runOTAOnPortUnlocked(m *managedSerial, firmware []byte, onProgress otaProgressFn) error {
+func runOTAOnPortUnlocked(sp *serialPort, firmware []byte, onProgress otaProgressFn) error {
 	if len(firmware) == 0 {
 		return fmt.Errorf("empty firmware")
 	}
@@ -120,32 +151,31 @@ func runOTAOnPortUnlocked(m *managedSerial, firmware []byte, onProgress otaProgr
 		onProgress(p)
 	}
 
-	if m.sp == nil {
-		if err := m.openLocked(); err != nil {
-			notify("error", "", 0, err.Error())
-			return err
-		}
-	}
-
-	sp := m.sp
-	if err := sp.port.SetReadTimeout(otaPrepareTimeout); err != nil {
+	if err := sp.port.SetReadTimeout(readTimeout); err != nil {
 		notify("error", "", 0, err.Error())
 		return err
 	}
-	defer sp.port.SetReadTimeout(readTimeout)
 
 	notify("preparing", otaStepMaster, 0, fmt.Sprintf("Master: OTA start (%d bytes)…", imageSize))
 
+	flushSerialInput(sp)
+
 	if err := writeUartMessage(sp, &pb.UartMessage{
 		Type: pb.MessageType_OTA_START,
 		Payload: &pb.UartMessage_OtaStart{
 			OtaStart: &pb.OtaStartPayload{TotalSize: uint32(imageSize)},
 		},
-	}, false); err != nil {
+	}); err != nil {
 		notify("error", "", 0, err.Error())
 		return err
 	}
 
+	if err := sp.port.SetReadTimeout(otaPrepareTimeout); err != nil {
+		notify("error", "", 0, err.Error())
+		return err
+	}
+	defer func() { _ = sp.port.SetReadTimeout(readTimeout) }()
+
 	ready, err := waitOtaStatus(sp, otaStReady, otaPrepareTimeout, func(msg string) {
 		notify("preparing", otaStepMaster, 2, msg)
 	})
@@ -162,52 +192,83 @@ func runOTAOnPortUnlocked(m *managedSerial, firmware []byte, onProgress otaProgr
 
 	var seq uint32
 	for offset := 0; offset < imageSize; {
-		bytesInBlock := 0
-		for bytesInBlock < otaFlashBlockSize && offset < imageSize {
-			n := otaHostChunkSize
-			room := otaFlashBlockSize - bytesInBlock
-			if n > room {
-				n = room
-			}
-			if offset+n > imageSize {
-				n = imageSize - offset
-			}
-			chunk := firmware[offset : offset+n]
+		blockStart := offset
+		blockStartSeq := seq
 
-			if err := writeUartMessage(sp, &pb.UartMessage{
-				Type: pb.MessageType_OTA_PAYLOAD,
-				Payload: &pb.UartMessage_OtaPayload{
-					OtaPayload: &pb.OtaPayload{Seq: seq, Data: chunk},
-				},
-			}, false); err != nil {
-				notify("error", "", 0, err.Error())
-				return err
-			}
-			seq++
-			offset += n
-			bytesInBlock += n
+		sendBlock := func() (fullBlock bool, err error) {
+			bytesInBlock := 0
+			for bytesInBlock < otaFlashBlockSize && offset < imageSize {
+				n := otaHostChunkSize
+				room := otaFlashBlockSize - bytesInBlock
+				if n > room {
+					n = room
+				}
+				if offset+n > imageSize {
+					n = imageSize - offset
+				}
+				chunk := firmware[offset : offset+n]
 
-			pct := offset * 100 / imageSize
-			if pct > 99 {
-				pct = 99
+				if err := writeUartMessage(sp, &pb.UartMessage{
+					Type: pb.MessageType_OTA_PAYLOAD,
+					Payload: &pb.UartMessage_OtaPayload{
+						OtaPayload: &pb.OtaPayload{Seq: seq, Data: chunk},
+					},
+				}); err != nil {
+					return false, err
+				}
+				time.Sleep(otaHostChunkPace)
+				seq++
+				offset += n
+				bytesInBlock += n
+
+				pct := offset * 100 / imageSize
+				if pct > 99 {
+					pct = 99
+				}
+				notify("uploading", otaStepMaster, pct,
+					fmt.Sprintf("Master: %d / %d bytes", offset, imageSize))
 			}
-			notify("uploading", otaStepMaster, pct, fmt.Sprintf("Master: %d / %d bytes", offset, imageSize))
+			return bytesInBlock == otaFlashBlockSize, nil
 		}
 
-		if bytesInBlock == otaFlashBlockSize {
-			st, err := waitOtaStatus(sp, otaStBlockAck, otaDefaultTimeout, nil)
-			if err != nil {
-				notify("error", "", 0, err.Error())
-				return err
-			}
-			pct := offset * 100 / imageSize
-			if pct > 99 {
-				pct = 99
-			}
-			notify("uploading", otaStepMaster, pct,
-				fmt.Sprintf("Master: Block geschrieben (%d bytes)", st.GetBytesWritten()),
-				OTAProgress{Bytes: st.GetBytesWritten()})
+		fullBlock, err := sendBlock()
+		if err != nil {
+			notify("error", "", 0, err.Error())
+			return err
 		}
+
+		if !fullBlock {
+			continue
+		}
+
+		var st *pb.OtaStatusPayload
+		var ackErr error
+		for attempt := 0; attempt < otaBlockMaxRetries; attempt++ {
+			if attempt > 0 {
+				offset = blockStart
+				seq = blockStartSeq
+				if _, err := sendBlock(); err != nil {
+					notify("error", "", 0, err.Error())
+					return err
+				}
+			}
+			st, ackErr = waitOtaStatus(sp, otaStBlockAck, otaDefaultTimeout, nil)
+			if ackErr == nil {
+				break
+			}
+		}
+		if ackErr != nil {
+			notify("error", "", 0, ackErr.Error())
+			return ackErr
+		}
+
+		pct := offset * 100 / imageSize
+		if pct > 99 {
+			pct = 99
+		}
+		notify("uploading", otaStepMaster, pct,
+			fmt.Sprintf("Master: Block geschrieben (%d bytes)", st.GetBytesWritten()),
+			OTAProgress{Bytes: st.GetBytesWritten()})
 	}
 
 	masterPct = 100
@@ -219,7 +280,7 @@ func runOTAOnPortUnlocked(m *managedSerial, firmware []byte, onProgress otaProgr
 		Payload: &pb.UartMessage_OtaEnd{
 			OtaEnd: &pb.OtaEndPayload{},
 		},
-	}, false); err != nil {
+	}); err != nil {
 		notify("error", "", 0, err.Error())
 		return err
 	}
@@ -333,7 +394,7 @@ func queryOtaSlaveProgressLocked(sp *serialPort, clientID uint32,
 			},
 		},
 	}
-	if err := writeUartMessage(sp, req, false); err != nil {
+	if err := writeUartMessage(sp, req); err != nil {
 		return nil, err
 	}
 	if queryTimeout <= 0 {
@@ -389,7 +450,7 @@ func readUartMessageUntil(sp *serialPort, deadline time.Time, want pb.MessageTyp
 		if err := sp.port.SetReadTimeout(wait); err != nil {
 			return nil, err
 		}
-		payload, err := uartframe.ReadFrame(sp.port, nil)
+		payload, err := uartframe.ReadFrame(sp.port, nil, wait)
 		if err != nil {
 			return nil, err
 		}
@@ -487,14 +548,11 @@ func waitOtaComplete(sp *serialPort, timeout time.Duration,
 	}
 }
 
-func writeUartMessage(sp *serialPort, msg *pb.UartMessage, logFrame bool) error {
+func writeUartMessage(sp *serialPort, msg *pb.UartMessage) error {
 	frame, err := encodeUartMessage(msg)
 	if err != nil {
 		return err
 	}
-	if logFrame {
-		log.Printf("sending %s (%d frame bytes)", msg.Type, len(frame))
-	}
 	_, err = sp.port.Write(frame)
 	return err
 }
@@ -505,12 +563,24 @@ func waitOtaStatus(sp *serialPort, want uint32, timeout time.Duration, onPrepari
 		if time.Now().After(deadline) {
 			return nil, fmt.Errorf("timeout waiting for OTA status %d", want)
 		}
-		if err := sp.port.SetReadTimeout(time.Until(deadline)); err != nil {
+		readWait := time.Until(deadline)
+		if readWait > otaStatusPollTimeout {
+			readWait = otaStatusPollTimeout
+		}
+		if err := sp.port.SetReadTimeout(readWait); err != nil {
 			return nil, err
 		}
-		st, err := readOtaStatus(sp)
+		payload, err := uartframe.ReadFrame(sp.port, nil, readWait)
 		if err != nil {
-			return nil, err
+			continue
+		}
+		msg, err := decodeUartPayload(payload)
+		if err != nil || msg.GetType() != pb.MessageType_OTA_STATUS {
+			continue
+		}
+		st := msg.GetOtaStatus()
+		if st == nil {
+			continue
 		}
 		switch st.GetStatus() {
 		case want:
@@ -526,7 +596,7 @@ func waitOtaStatus(sp *serialPort, want uint32, timeout time.Duration, onPrepari
 }
 
 func readOtaStatus(sp *serialPort) (*pb.OtaStatusPayload, error) {
-	payload, err := uartframe.ReadFrame(sp.port, nil)
+	payload, err := uartframe.ReadFrame(sp.port, nil, readTimeout)
 	if err != nil {
 		return nil, fmt.Errorf("read response: %w", err)
 	}
@@ -553,6 +623,22 @@ func encodeUartMessage(msg *pb.UartMessage) ([]byte, error) {
 	return uartframe.EncodeFrame(payload)
 }
 
+// flushSerialInput drops stale RX bytes (not full frames — avoids ReadFrame blocking).
+func flushSerialInput(sp *serialPort) {
+	if sp == nil {
+		return
+	}
+	_ = sp.port.SetReadTimeout(10 * time.Millisecond)
+	buf := make([]byte, 256)
+	deadline := time.Now().Add(50 * time.Millisecond)
+	for time.Now().Before(deadline) {
+		n, err := sp.port.Read(buf)
+		if n == 0 || err != nil {
+			return
+		}
+	}
+}
+
 func decodeUartPayload(payload []byte) (*pb.UartMessage, error) {
 	if len(payload) == 0 {
 		return nil, fmt.Errorf("empty response")

goTool/pb/uart_messages.pb.go

@@ -46,6 +46,10 @@ const (
 	MessageType_TAP_NOTIFY          MessageType = 27
 	// * Combined cached accel + tap poll (one UART round-trip, ~16 ms cadence).
 	MessageType_CACHE_STATUS MessageType = 29
+	// * Host → master → slave → master: timestamp echo round-trip (latency test).
+	MessageType_ESPNOW_ECHO_PING MessageType = 30
+	// * Host → master: get/set ESP-IDF log level for tag "*" (global).
+	MessageType_SET_LOG_LEVEL MessageType = 31
 )
 
 // Enum value maps for MessageType.
@@ -72,6 +76,8 @@ var (
 		26: "BATTERY_STATUS",
 		27: "TAP_NOTIFY",
 		29: "CACHE_STATUS",
+		30: "ESPNOW_ECHO_PING",
+		31: "SET_LOG_LEVEL",
 	}
 	MessageType_value = map[string]int32{
 		"UNKNOWN":             0,
@@ -95,6 +101,8 @@ var (
 		"BATTERY_STATUS":      26,
 		"TAP_NOTIFY":          27,
 		"CACHE_STATUS":        29,
+		"ESPNOW_ECHO_PING":    30,
+		"SET_LOG_LEVEL":       31,
 	}
 )
 
@@ -211,6 +219,10 @@ type UartMessage struct {
 	//	*UartMessage_TapNotifyResponse
 	//	*UartMessage_CacheStatusRequest
 	//	*UartMessage_CacheStatusResponse
+	//	*UartMessage_EspnowEchoPingRequest
+	//	*UartMessage_EspnowEchoPingResponse
+	//	*UartMessage_SetLogLevelRequest
+	//	*UartMessage_SetLogLevelResponse
 	Payload       isUartMessage_Payload `protobuf_oneof:"payload"`
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
@@ -521,6 +533,42 @@ func (x *UartMessage) GetCacheStatusResponse() *CacheStatusResponse {
 	return nil
 }
 
+func (x *UartMessage) GetEspnowEchoPingRequest() *EspNowEchoPingRequest {
+	if x != nil {
+		if x, ok := x.Payload.(*UartMessage_EspnowEchoPingRequest); ok {
+			return x.EspnowEchoPingRequest
+		}
+	}
+	return nil
+}
+
+func (x *UartMessage) GetEspnowEchoPingResponse() *EspNowEchoPingResponse {
+	if x != nil {
+		if x, ok := x.Payload.(*UartMessage_EspnowEchoPingResponse); ok {
+			return x.EspnowEchoPingResponse
+		}
+	}
+	return nil
+}
+
+func (x *UartMessage) GetSetLogLevelRequest() *SetLogLevelRequest {
+	if x != nil {
+		if x, ok := x.Payload.(*UartMessage_SetLogLevelRequest); ok {
+			return x.SetLogLevelRequest
+		}
+	}
+	return nil
+}
+
+func (x *UartMessage) GetSetLogLevelResponse() *SetLogLevelResponse {
+	if x != nil {
+		if x, ok := x.Payload.(*UartMessage_SetLogLevelResponse); ok {
+			return x.SetLogLevelResponse
+		}
+	}
+	return nil
+}
+
 type isUartMessage_Payload interface {
 	isUartMessage_Payload()
 }
@@ -641,6 +689,22 @@ type UartMessage_CacheStatusResponse struct {
 	CacheStatusResponse *CacheStatusResponse `protobuf:"bytes,34,opt,name=cache_status_response,json=cacheStatusResponse,proto3,oneof"`
 }
 
+type UartMessage_EspnowEchoPingRequest struct {
+	EspnowEchoPingRequest *EspNowEchoPingRequest `protobuf:"bytes,35,opt,name=espnow_echo_ping_request,json=espnowEchoPingRequest,proto3,oneof"`
+}
+
+type UartMessage_EspnowEchoPingResponse struct {
+	EspnowEchoPingResponse *EspNowEchoPingResponse `protobuf:"bytes,36,opt,name=espnow_echo_ping_response,json=espnowEchoPingResponse,proto3,oneof"`
+}
+
+type UartMessage_SetLogLevelRequest struct {
+	SetLogLevelRequest *SetLogLevelRequest `protobuf:"bytes,37,opt,name=set_log_level_request,json=setLogLevelRequest,proto3,oneof"`
+}
+
+type UartMessage_SetLogLevelResponse struct {
+	SetLogLevelResponse *SetLogLevelResponse `protobuf:"bytes,38,opt,name=set_log_level_response,json=setLogLevelResponse,proto3,oneof"`
+}
+
 func (*UartMessage_AckPayload) isUartMessage_Payload() {}
 
 func (*UartMessage_EchoPayload) isUartMessage_Payload() {}
@@ -699,6 +763,14 @@ func (*UartMessage_CacheStatusRequest) isUartMessage_Payload() {}
 
 func (*UartMessage_CacheStatusResponse) isUartMessage_Payload() {}
 
+func (*UartMessage_EspnowEchoPingRequest) isUartMessage_Payload() {}
+
+func (*UartMessage_EspnowEchoPingResponse) isUartMessage_Payload() {}
+
+func (*UartMessage_SetLogLevelRequest) isUartMessage_Payload() {}
+
+func (*UartMessage_SetLogLevelResponse) isUartMessage_Payload() {}
+
 type Ack struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
 	unknownFields protoimpl.UnknownFields
@@ -2329,8 +2401,132 @@ func (x *EspNowUnicastTestResponse) GetSeq() uint32 {
 	return 0
 }
 
+// * Host → master: ESP-NOW echo ping to one slave (timestamp echoed back).
+type EspNowEchoPingRequest struct {
+	state    protoimpl.MessageState `protogen:"open.v1"`
+	ClientId uint32                 `protobuf:"varint,1,opt,name=client_id,json=clientId,proto3" json:"client_id,omitempty"`
+	// * Microseconds since Unix epoch (host clock).
+	TimestampUs   uint64 `protobuf:"varint,2,opt,name=timestamp_us,json=timestampUs,proto3" json:"timestamp_us,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *EspNowEchoPingRequest) Reset() {
+	*x = EspNowEchoPingRequest{}
+	mi := &file_uart_messages_proto_msgTypes[27]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *EspNowEchoPingRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*EspNowEchoPingRequest) ProtoMessage() {}
+
+func (x *EspNowEchoPingRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_uart_messages_proto_msgTypes[27]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use EspNowEchoPingRequest.ProtoReflect.Descriptor instead.
+func (*EspNowEchoPingRequest) Descriptor() ([]byte, []int) {
+	return file_uart_messages_proto_rawDescGZIP(), []int{27}
+}
+
+func (x *EspNowEchoPingRequest) GetClientId() uint32 {
+	if x != nil {
+		return x.ClientId
+	}
+	return 0
+}
+
+func (x *EspNowEchoPingRequest) GetTimestampUs() uint64 {
+	if x != nil {
+		return x.TimestampUs
+	}
+	return 0
+}
+
+type EspNowEchoPingResponse struct {
+	state    protoimpl.MessageState `protogen:"open.v1"`
+	Success  bool                   `protobuf:"varint,1,opt,name=success,proto3" json:"success,omitempty"`
+	ClientId uint32                 `protobuf:"varint,2,opt,name=client_id,json=clientId,proto3" json:"client_id,omitempty"`
+	// * Echoed host timestamp from goTool request.
+	TimestampUs uint64 `protobuf:"varint,3,opt,name=timestamp_us,json=timestampUs,proto3" json:"timestamp_us,omitempty"`
+	// * esp_timer_get_time() delta from ping send to pong recv (master→slave→master).
+	EspRttUs      uint32 `protobuf:"varint,4,opt,name=esp_rtt_us,json=espRttUs,proto3" json:"esp_rtt_us,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *EspNowEchoPingResponse) Reset() {
+	*x = EspNowEchoPingResponse{}
+	mi := &file_uart_messages_proto_msgTypes[28]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *EspNowEchoPingResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*EspNowEchoPingResponse) ProtoMessage() {}
+
+func (x *EspNowEchoPingResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_uart_messages_proto_msgTypes[28]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use EspNowEchoPingResponse.ProtoReflect.Descriptor instead.
+func (*EspNowEchoPingResponse) Descriptor() ([]byte, []int) {
+	return file_uart_messages_proto_rawDescGZIP(), []int{28}
+}
+
+func (x *EspNowEchoPingResponse) GetSuccess() bool {
+	if x != nil {
+		return x.Success
+	}
+	return false
+}
+
+func (x *EspNowEchoPingResponse) GetClientId() uint32 {
+	if x != nil {
+		return x.ClientId
+	}
+	return 0
+}
+
+func (x *EspNowEchoPingResponse) GetTimestampUs() uint64 {
+	if x != nil {
+		return x.TimestampUs
+	}
+	return 0
+}
+
+func (x *EspNowEchoPingResponse) GetEspRttUs() uint32 {
+	if x != nil {
+		return x.EspRttUs
+	}
+	return 0
+}
+
 // Host → master: LED ring on master (client_id=0) and/or slaves via ESP-NOW.
-// mode: 0=clear, 1=progress (0–100 %), 2=digit (0–10), 3=blink, 4=find-me, 5=all LEDs solid color.
+// mode: 0=clear, 1=progress (0–100 %), 2=digit (0–10), 3=blink, 4=find-me, 5=all LEDs solid color, 6=battery-low.
 type LedRingProgressRequest struct {
 	state protoimpl.MessageState `protogen:"open.v1"`
 	Mode  uint32                 `protobuf:"varint,1,opt,name=mode,proto3" json:"mode,omitempty"`
@@ -2359,7 +2555,7 @@ type LedRingProgressRequest struct {
 
 func (x *LedRingProgressRequest) Reset() {
 	*x = LedRingProgressRequest{}
-	mi := &file_uart_messages_proto_msgTypes[27]
+	mi := &file_uart_messages_proto_msgTypes[29]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2371,7 +2567,7 @@ func (x *LedRingProgressRequest) String() string {
 func (*LedRingProgressRequest) ProtoMessage() {}
 
 func (x *LedRingProgressRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[27]
+	mi := &file_uart_messages_proto_msgTypes[29]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2384,7 +2580,7 @@ func (x *LedRingProgressRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use LedRingProgressRequest.ProtoReflect.Descriptor instead.
 func (*LedRingProgressRequest) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{27}
+	return file_uart_messages_proto_rawDescGZIP(), []int{29}
 }
 
 func (x *LedRingProgressRequest) GetMode() uint32 {
@@ -2485,7 +2681,7 @@ type LedRingProgressResponse struct {
 
 func (x *LedRingProgressResponse) Reset() {
 	*x = LedRingProgressResponse{}
-	mi := &file_uart_messages_proto_msgTypes[28]
+	mi := &file_uart_messages_proto_msgTypes[30]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2497,7 +2693,7 @@ func (x *LedRingProgressResponse) String() string {
 func (*LedRingProgressResponse) ProtoMessage() {}
 
 func (x *LedRingProgressResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[28]
+	mi := &file_uart_messages_proto_msgTypes[30]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2510,7 +2706,7 @@ func (x *LedRingProgressResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use LedRingProgressResponse.ProtoReflect.Descriptor instead.
 func (*LedRingProgressResponse) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{28}
+	return file_uart_messages_proto_rawDescGZIP(), []int{30}
 }
 
 func (x *LedRingProgressResponse) GetSuccess() bool {
@@ -2565,7 +2761,7 @@ type EspNowFindMeRequest struct {
 
 func (x *EspNowFindMeRequest) Reset() {
 	*x = EspNowFindMeRequest{}
-	mi := &file_uart_messages_proto_msgTypes[29]
+	mi := &file_uart_messages_proto_msgTypes[31]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2577,7 +2773,7 @@ func (x *EspNowFindMeRequest) String() string {
 func (*EspNowFindMeRequest) ProtoMessage() {}
 
 func (x *EspNowFindMeRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[29]
+	mi := &file_uart_messages_proto_msgTypes[31]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2590,7 +2786,7 @@ func (x *EspNowFindMeRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use EspNowFindMeRequest.ProtoReflect.Descriptor instead.
 func (*EspNowFindMeRequest) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{29}
+	return file_uart_messages_proto_rawDescGZIP(), []int{31}
 }
 
 func (x *EspNowFindMeRequest) GetClientId() uint32 {
@@ -2610,7 +2806,7 @@ type EspNowFindMeResponse struct {
 
 func (x *EspNowFindMeResponse) Reset() {
 	*x = EspNowFindMeResponse{}
-	mi := &file_uart_messages_proto_msgTypes[30]
+	mi := &file_uart_messages_proto_msgTypes[32]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2622,7 +2818,7 @@ func (x *EspNowFindMeResponse) String() string {
 func (*EspNowFindMeResponse) ProtoMessage() {}
 
 func (x *EspNowFindMeResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[30]
+	mi := &file_uart_messages_proto_msgTypes[32]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2635,7 +2831,7 @@ func (x *EspNowFindMeResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use EspNowFindMeResponse.ProtoReflect.Descriptor instead.
 func (*EspNowFindMeResponse) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{30}
+	return file_uart_messages_proto_rawDescGZIP(), []int{32}
 }
 
 func (x *EspNowFindMeResponse) GetSuccess() bool {
@@ -2662,7 +2858,7 @@ type RestartRequest struct {
 
 func (x *RestartRequest) Reset() {
 	*x = RestartRequest{}
-	mi := &file_uart_messages_proto_msgTypes[31]
+	mi := &file_uart_messages_proto_msgTypes[33]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2674,7 +2870,7 @@ func (x *RestartRequest) String() string {
 func (*RestartRequest) ProtoMessage() {}
 
 func (x *RestartRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[31]
+	mi := &file_uart_messages_proto_msgTypes[33]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2687,7 +2883,7 @@ func (x *RestartRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use RestartRequest.ProtoReflect.Descriptor instead.
 func (*RestartRequest) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{31}
+	return file_uart_messages_proto_rawDescGZIP(), []int{33}
 }
 
 func (x *RestartRequest) GetClientId() uint32 {
@@ -2707,7 +2903,7 @@ type RestartResponse struct {
 
 func (x *RestartResponse) Reset() {
 	*x = RestartResponse{}
-	mi := &file_uart_messages_proto_msgTypes[32]
+	mi := &file_uart_messages_proto_msgTypes[34]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2719,7 +2915,7 @@ func (x *RestartResponse) String() string {
 func (*RestartResponse) ProtoMessage() {}
 
 func (x *RestartResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[32]
+	mi := &file_uart_messages_proto_msgTypes[34]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2732,7 +2928,7 @@ func (x *RestartResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use RestartResponse.ProtoReflect.Descriptor instead.
 func (*RestartResponse) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{32}
+	return file_uart_messages_proto_rawDescGZIP(), []int{34}
 }
 
 func (x *RestartResponse) GetSuccess() bool {
@@ -2749,6 +2945,112 @@ func (x *RestartResponse) GetClientId() uint32 {
 	return 0
 }
 
+// * Host → master: read/write global log level (esp_log_level_set("*", …)).
+type SetLogLevelRequest struct {
+	state protoimpl.MessageState `protogen:"open.v1"`
+	Write bool                   `protobuf:"varint,1,opt,name=write,proto3" json:"write,omitempty"`
+	// * esp_log_level_t: 0=NONE, 1=ERROR, 2=WARN, 3=INFO, 4=DEBUG, 5=VERBOSE
+	Level         uint32 `protobuf:"varint,2,opt,name=level,proto3" json:"level,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *SetLogLevelRequest) Reset() {
+	*x = SetLogLevelRequest{}
+	mi := &file_uart_messages_proto_msgTypes[35]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *SetLogLevelRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*SetLogLevelRequest) ProtoMessage() {}
+
+func (x *SetLogLevelRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_uart_messages_proto_msgTypes[35]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use SetLogLevelRequest.ProtoReflect.Descriptor instead.
+func (*SetLogLevelRequest) Descriptor() ([]byte, []int) {
+	return file_uart_messages_proto_rawDescGZIP(), []int{35}
+}
+
+func (x *SetLogLevelRequest) GetWrite() bool {
+	if x != nil {
+		return x.Write
+	}
+	return false
+}
+
+func (x *SetLogLevelRequest) GetLevel() uint32 {
+	if x != nil {
+		return x.Level
+	}
+	return 0
+}
+
+type SetLogLevelResponse struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	Success       bool                   `protobuf:"varint,1,opt,name=success,proto3" json:"success,omitempty"`
+	Level         uint32                 `protobuf:"varint,2,opt,name=level,proto3" json:"level,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *SetLogLevelResponse) Reset() {
+	*x = SetLogLevelResponse{}
+	mi := &file_uart_messages_proto_msgTypes[36]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *SetLogLevelResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*SetLogLevelResponse) ProtoMessage() {}
+
+func (x *SetLogLevelResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_uart_messages_proto_msgTypes[36]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use SetLogLevelResponse.ProtoReflect.Descriptor instead.
+func (*SetLogLevelResponse) Descriptor() ([]byte, []int) {
+	return file_uart_messages_proto_rawDescGZIP(), []int{36}
+}
+
+func (x *SetLogLevelResponse) GetSuccess() bool {
+	if x != nil {
+		return x.Success
+	}
+	return false
+}
+
+func (x *SetLogLevelResponse) GetLevel() uint32 {
+	if x != nil {
+		return x.Level
+	}
+	return 0
+}
+
 // Host → device: begin UART OTA (erase inactive OTA slot; device replies OTA_STATUS).
 type OtaStartPayload struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
@@ -2759,7 +3061,7 @@ type OtaStartPayload struct {
 
 func (x *OtaStartPayload) Reset() {
 	*x = OtaStartPayload{}
-	mi := &file_uart_messages_proto_msgTypes[33]
+	mi := &file_uart_messages_proto_msgTypes[37]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2771,7 +3073,7 @@ func (x *OtaStartPayload) String() string {
 func (*OtaStartPayload) ProtoMessage() {}
 
 func (x *OtaStartPayload) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[33]
+	mi := &file_uart_messages_proto_msgTypes[37]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2784,7 +3086,7 @@ func (x *OtaStartPayload) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use OtaStartPayload.ProtoReflect.Descriptor instead.
 func (*OtaStartPayload) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{33}
+	return file_uart_messages_proto_rawDescGZIP(), []int{37}
 }
 
 func (x *OtaStartPayload) GetTotalSize() uint32 {
@@ -2805,7 +3107,7 @@ type OtaPayload struct {
 
 func (x *OtaPayload) Reset() {
 	*x = OtaPayload{}
-	mi := &file_uart_messages_proto_msgTypes[34]
+	mi := &file_uart_messages_proto_msgTypes[38]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2817,7 +3119,7 @@ func (x *OtaPayload) String() string {
 func (*OtaPayload) ProtoMessage() {}
 
 func (x *OtaPayload) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[34]
+	mi := &file_uart_messages_proto_msgTypes[38]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2830,7 +3132,7 @@ func (x *OtaPayload) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use OtaPayload.ProtoReflect.Descriptor instead.
 func (*OtaPayload) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{34}
+	return file_uart_messages_proto_rawDescGZIP(), []int{38}
 }
 
 func (x *OtaPayload) GetSeq() uint32 {
@@ -2856,7 +3158,7 @@ type OtaEndPayload struct {
 
 func (x *OtaEndPayload) Reset() {
 	*x = OtaEndPayload{}
-	mi := &file_uart_messages_proto_msgTypes[35]
+	mi := &file_uart_messages_proto_msgTypes[39]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2868,7 +3170,7 @@ func (x *OtaEndPayload) String() string {
 func (*OtaEndPayload) ProtoMessage() {}
 
 func (x *OtaEndPayload) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[35]
+	mi := &file_uart_messages_proto_msgTypes[39]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2881,7 +3183,7 @@ func (x *OtaEndPayload) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use OtaEndPayload.ProtoReflect.Descriptor instead.
 func (*OtaEndPayload) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{35}
+	return file_uart_messages_proto_rawDescGZIP(), []int{39}
 }
 
 // Device → host status (also used as ACK after each 4 KiB written).
@@ -2898,7 +3200,7 @@ type OtaStatusPayload struct {
 
 func (x *OtaStatusPayload) Reset() {
 	*x = OtaStatusPayload{}
-	mi := &file_uart_messages_proto_msgTypes[36]
+	mi := &file_uart_messages_proto_msgTypes[40]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2910,7 +3212,7 @@ func (x *OtaStatusPayload) String() string {
 func (*OtaStatusPayload) ProtoMessage() {}
 
 func (x *OtaStatusPayload) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[36]
+	mi := &file_uart_messages_proto_msgTypes[40]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2923,7 +3225,7 @@ func (x *OtaStatusPayload) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use OtaStatusPayload.ProtoReflect.Descriptor instead.
 func (*OtaStatusPayload) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{36}
+	return file_uart_messages_proto_rawDescGZIP(), []int{40}
 }
 
 func (x *OtaStatusPayload) GetStatus() uint32 {
@@ -2964,7 +3266,7 @@ type OtaSlaveProgressRequest struct {
 
 func (x *OtaSlaveProgressRequest) Reset() {
 	*x = OtaSlaveProgressRequest{}
-	mi := &file_uart_messages_proto_msgTypes[37]
+	mi := &file_uart_messages_proto_msgTypes[41]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2976,7 +3278,7 @@ func (x *OtaSlaveProgressRequest) String() string {
 func (*OtaSlaveProgressRequest) ProtoMessage() {}
 
 func (x *OtaSlaveProgressRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[37]
+	mi := &file_uart_messages_proto_msgTypes[41]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2989,7 +3291,7 @@ func (x *OtaSlaveProgressRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use OtaSlaveProgressRequest.ProtoReflect.Descriptor instead.
 func (*OtaSlaveProgressRequest) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{37}
+	return file_uart_messages_proto_rawDescGZIP(), []int{41}
 }
 
 func (x *OtaSlaveProgressRequest) GetClientId() uint32 {
@@ -3013,7 +3315,7 @@ type OtaSlaveProgressEntry struct {
 
 func (x *OtaSlaveProgressEntry) Reset() {
 	*x = OtaSlaveProgressEntry{}
-	mi := &file_uart_messages_proto_msgTypes[38]
+	mi := &file_uart_messages_proto_msgTypes[42]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -3025,7 +3327,7 @@ func (x *OtaSlaveProgressEntry) String() string {
 func (*OtaSlaveProgressEntry) ProtoMessage() {}
 
 func (x *OtaSlaveProgressEntry) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[38]
+	mi := &file_uart_messages_proto_msgTypes[42]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -3038,7 +3340,7 @@ func (x *OtaSlaveProgressEntry) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use OtaSlaveProgressEntry.ProtoReflect.Descriptor instead.
 func (*OtaSlaveProgressEntry) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{38}
+	return file_uart_messages_proto_rawDescGZIP(), []int{42}
 }
 
 func (x *OtaSlaveProgressEntry) GetClientId() uint32 {
@@ -3089,7 +3391,7 @@ type OtaSlaveProgressResponse struct {
 
 func (x *OtaSlaveProgressResponse) Reset() {
 	*x = OtaSlaveProgressResponse{}
-	mi := &file_uart_messages_proto_msgTypes[39]
+	mi := &file_uart_messages_proto_msgTypes[43]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -3101,7 +3403,7 @@ func (x *OtaSlaveProgressResponse) String() string {
 func (*OtaSlaveProgressResponse) ProtoMessage() {}
 
 func (x *OtaSlaveProgressResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_uart_messages_proto_msgTypes[39]
+	mi := &file_uart_messages_proto_msgTypes[43]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -3114,7 +3416,7 @@ func (x *OtaSlaveProgressResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use OtaSlaveProgressResponse.ProtoReflect.Descriptor instead.
 func (*OtaSlaveProgressResponse) Descriptor() ([]byte, []int) {
-	return file_uart_messages_proto_rawDescGZIP(), []int{39}
+	return file_uart_messages_proto_rawDescGZIP(), []int{43}
 }
 
 func (x *OtaSlaveProgressResponse) GetActive() bool {
@@ -3156,7 +3458,7 @@ var File_uart_messages_proto protoreflect.FileDescriptor
 
 const file_uart_messages_proto_rawDesc = "" +
 	"\n" +
-	"\x13uart_messages.proto\x12\x04alox\x1a\fnanopb.proto\"\xec\x11\n" +
+	"\x13uart_messages.proto\x12\x04alox\x1a\fnanopb.proto\"\xc0\x14\n" +
 	"\vUartMessage\x12%\n" +
 	"\x04type\x18\x01 \x01(\x0e2\x11.alox.MessageTypeR\x04type\x12,\n" +
 	"\vack_payload\x18\x02 \x01(\v2\t.alox.AckH\x00R\n" +
@@ -3191,7 +3493,11 @@ const file_uart_messages_proto_rawDesc = "" +
 	"\x12tap_notify_request\x18\x1d \x01(\v2\x16.alox.TapNotifyRequestH\x00R\x10tapNotifyRequest\x12I\n" +
 	"\x13tap_notify_response\x18\x1e \x01(\v2\x17.alox.TapNotifyResponseH\x00R\x11tapNotifyResponse\x12L\n" +
 	"\x14cache_status_request\x18! \x01(\v2\x18.alox.CacheStatusRequestH\x00R\x12cacheStatusRequest\x12O\n" +
-	"\x15cache_status_response\x18\" \x01(\v2\x19.alox.CacheStatusResponseH\x00R\x13cacheStatusResponseB\t\n" +
+	"\x15cache_status_response\x18\" \x01(\v2\x19.alox.CacheStatusResponseH\x00R\x13cacheStatusResponse\x12V\n" +
+	"\x18espnow_echo_ping_request\x18# \x01(\v2\x1b.alox.EspNowEchoPingRequestH\x00R\x15espnowEchoPingRequest\x12Y\n" +
+	"\x19espnow_echo_ping_response\x18$ \x01(\v2\x1c.alox.EspNowEchoPingResponseH\x00R\x16espnowEchoPingResponse\x12M\n" +
+	"\x15set_log_level_request\x18% \x01(\v2\x18.alox.SetLogLevelRequestH\x00R\x12setLogLevelRequest\x12P\n" +
+	"\x16set_log_level_response\x18& \x01(\v2\x19.alox.SetLogLevelResponseH\x00R\x13setLogLevelResponseB\t\n" +
 	"\apayload\"\x05\n" +
 	"\x03Ack\"!\n" +
 	"\vEchoPayload\x12\x12\n" +
@@ -3311,7 +3617,16 @@ const file_uart_messages_proto_rawDesc = "" +
 	"\x03seq\x18\x02 \x01(\rR\x03seq\"G\n" +
 	"\x19EspNowUnicastTestResponse\x12\x18\n" +
 	"\asuccess\x18\x01 \x01(\bR\asuccess\x12\x10\n" +
-	"\x03seq\x18\x02 \x01(\rR\x03seq\"\xc1\x02\n" +
+	"\x03seq\x18\x02 \x01(\rR\x03seq\"W\n" +
+	"\x15EspNowEchoPingRequest\x12\x1b\n" +
+	"\tclient_id\x18\x01 \x01(\rR\bclientId\x12!\n" +
+	"\ftimestamp_us\x18\x02 \x01(\x04R\vtimestampUs\"\x90\x01\n" +
+	"\x16EspNowEchoPingResponse\x12\x18\n" +
+	"\asuccess\x18\x01 \x01(\bR\asuccess\x12\x1b\n" +
+	"\tclient_id\x18\x02 \x01(\rR\bclientId\x12!\n" +
+	"\ftimestamp_us\x18\x03 \x01(\x04R\vtimestampUs\x12\x1c\n" +
+	"\n" +
+	"esp_rtt_us\x18\x04 \x01(\rR\bespRttUs\"\xc1\x02\n" +
 	"\x16LedRingProgressRequest\x12\x12\n" +
 	"\x04mode\x18\x01 \x01(\rR\x04mode\x12\x1a\n" +
 	"\bprogress\x18\x02 \x01(\rR\bprogress\x12\x14\n" +
@@ -3345,7 +3660,13 @@ const file_uart_messages_proto_rawDesc = "" +
 	"\tclient_id\x18\x01 \x01(\rR\bclientId\"H\n" +
 	"\x0fRestartResponse\x12\x18\n" +
 	"\asuccess\x18\x01 \x01(\bR\asuccess\x12\x1b\n" +
-	"\tclient_id\x18\x02 \x01(\rR\bclientId\"0\n" +
+	"\tclient_id\x18\x02 \x01(\rR\bclientId\"@\n" +
+	"\x12SetLogLevelRequest\x12\x14\n" +
+	"\x05write\x18\x01 \x01(\bR\x05write\x12\x14\n" +
+	"\x05level\x18\x02 \x01(\rR\x05level\"E\n" +
+	"\x13SetLogLevelResponse\x12\x18\n" +
+	"\asuccess\x18\x01 \x01(\bR\asuccess\x12\x14\n" +
+	"\x05level\x18\x02 \x01(\rR\x05level\"0\n" +
 	"\x0fOtaStartPayload\x12\x1d\n" +
 	"\n" +
 	"total_size\x18\x01 \x01(\rR\ttotalSize\":\n" +
@@ -3376,7 +3697,7 @@ const file_uart_messages_proto_rawDesc = "" +
 	"\x0faggregate_bytes\x18\x03 \x01(\rR\x0eaggregateBytes\x12\x1f\n" +
 	"\vslave_count\x18\x04 \x01(\rR\n" +
 	"slaveCount\x12:\n" +
-	"\x06slaves\x18\x05 \x03(\v2\x1b.alox.OtaSlaveProgressEntryB\x05\x92?\x02\x10\x10R\x06slaves*\xf1\x02\n" +
+	"\x06slaves\x18\x05 \x03(\v2\x1b.alox.OtaSlaveProgressEntryB\x05\x92?\x02\x10\x10R\x06slaves*\x9a\x03\n" +
 	"\vMessageType\x12\v\n" +
 	"\aUNKNOWN\x10\x00\x12\a\n" +
 	"\x03ACK\x10\x01\x12\b\n" +
@@ -3400,7 +3721,9 @@ const file_uart_messages_proto_rawDesc = "" +
 	"\x0eBATTERY_STATUS\x10\x1a\x12\x0e\n" +
 	"\n" +
 	"TAP_NOTIFY\x10\x1b\x12\x10\n" +
-	"\fCACHE_STATUS\x10\x1d\"\x04\b\x18\x10\x18\"\x04\b\x1c\x10\x1c*G\n" +
+	"\fCACHE_STATUS\x10\x1d\x12\x14\n" +
+	"\x10ESPNOW_ECHO_PING\x10\x1e\x12\x11\n" +
+	"\rSET_LOG_LEVEL\x10\x1f\"\x04\b\x18\x10\x18\"\x04\b\x1c\x10\x1c*G\n" +
 	"\aTapKind\x12\f\n" +
 	"\bTAP_NONE\x10\x00\x12\x0e\n" +
 	"\n" +
@@ -3423,7 +3746,7 @@ func file_uart_messages_proto_rawDescGZIP() []byte {
 }
 
 var file_uart_messages_proto_enumTypes = make([]protoimpl.EnumInfo, 2)
-var file_uart_messages_proto_msgTypes = make([]protoimpl.MessageInfo, 40)
+var file_uart_messages_proto_msgTypes = make([]protoimpl.MessageInfo, 44)
 var file_uart_messages_proto_goTypes = []any{
 	(MessageType)(0),                  // 0: alox.MessageType
 	(TapKind)(0),                      // 1: alox.TapKind
@@ -3454,19 +3777,23 @@ var file_uart_messages_proto_goTypes = []any{
 	(*CacheStatusResponse)(nil),       // 26: alox.CacheStatusResponse
 	(*EspNowUnicastTestRequest)(nil),  // 27: alox.EspNowUnicastTestRequest
 	(*EspNowUnicastTestResponse)(nil), // 28: alox.EspNowUnicastTestResponse
-	(*LedRingProgressRequest)(nil),    // 29: alox.LedRingProgressRequest
-	(*LedRingProgressResponse)(nil),   // 30: alox.LedRingProgressResponse
-	(*EspNowFindMeRequest)(nil),       // 31: alox.EspNowFindMeRequest
-	(*EspNowFindMeResponse)(nil),      // 32: alox.EspNowFindMeResponse
-	(*RestartRequest)(nil),            // 33: alox.RestartRequest
-	(*RestartResponse)(nil),           // 34: alox.RestartResponse
-	(*OtaStartPayload)(nil),           // 35: alox.OtaStartPayload
-	(*OtaPayload)(nil),                // 36: alox.OtaPayload
-	(*OtaEndPayload)(nil),             // 37: alox.OtaEndPayload
-	(*OtaStatusPayload)(nil),          // 38: alox.OtaStatusPayload
-	(*OtaSlaveProgressRequest)(nil),   // 39: alox.OtaSlaveProgressRequest
-	(*OtaSlaveProgressEntry)(nil),     // 40: alox.OtaSlaveProgressEntry
-	(*OtaSlaveProgressResponse)(nil),  // 41: alox.OtaSlaveProgressResponse
+	(*EspNowEchoPingRequest)(nil),     // 29: alox.EspNowEchoPingRequest
+	(*EspNowEchoPingResponse)(nil),    // 30: alox.EspNowEchoPingResponse
+	(*LedRingProgressRequest)(nil),    // 31: alox.LedRingProgressRequest
+	(*LedRingProgressResponse)(nil),   // 32: alox.LedRingProgressResponse
+	(*EspNowFindMeRequest)(nil),       // 33: alox.EspNowFindMeRequest
+	(*EspNowFindMeResponse)(nil),      // 34: alox.EspNowFindMeResponse
+	(*RestartRequest)(nil),            // 35: alox.RestartRequest
+	(*RestartResponse)(nil),           // 36: alox.RestartResponse
+	(*SetLogLevelRequest)(nil),        // 37: alox.SetLogLevelRequest
+	(*SetLogLevelResponse)(nil),       // 38: alox.SetLogLevelResponse
+	(*OtaStartPayload)(nil),           // 39: alox.OtaStartPayload
+	(*OtaPayload)(nil),                // 40: alox.OtaPayload
+	(*OtaEndPayload)(nil),             // 41: alox.OtaEndPayload
+	(*OtaStatusPayload)(nil),          // 42: alox.OtaStatusPayload
+	(*OtaSlaveProgressRequest)(nil),   // 43: alox.OtaSlaveProgressRequest
+	(*OtaSlaveProgressEntry)(nil),     // 44: alox.OtaSlaveProgressEntry
+	(*OtaSlaveProgressResponse)(nil),  // 45: alox.OtaSlaveProgressResponse
 }
 var file_uart_messages_proto_depIdxs = []int32{
 	0,  // 0: alox.UartMessage.type:type_name -> alox.MessageType
@@ -3475,22 +3802,22 @@ var file_uart_messages_proto_depIdxs = []int32{
 	5,  // 3: alox.UartMessage.version_response:type_name -> alox.VersionResponse
 	7,  // 4: alox.UartMessage.client_info_response:type_name -> alox.ClientInfoResponse
 	9,  // 5: alox.UartMessage.client_input_response:type_name -> alox.ClientInputResponse
-	35, // 6: alox.UartMessage.ota_start:type_name -> alox.OtaStartPayload
-	36, // 7: alox.UartMessage.ota_payload:type_name -> alox.OtaPayload
-	37, // 8: alox.UartMessage.ota_end:type_name -> alox.OtaEndPayload
-	38, // 9: alox.UartMessage.ota_status:type_name -> alox.OtaStatusPayload
+	39, // 6: alox.UartMessage.ota_start:type_name -> alox.OtaStartPayload
+	40, // 7: alox.UartMessage.ota_payload:type_name -> alox.OtaPayload
+	41, // 8: alox.UartMessage.ota_end:type_name -> alox.OtaEndPayload
+	42, // 9: alox.UartMessage.ota_status:type_name -> alox.OtaStatusPayload
 	10, // 10: alox.UartMessage.accel_deadzone_request:type_name -> alox.AccelDeadzoneRequest
 	11, // 11: alox.UartMessage.accel_deadzone_response:type_name -> alox.AccelDeadzoneResponse
 	27, // 12: alox.UartMessage.espnow_unicast_test_request:type_name -> alox.EspNowUnicastTestRequest
 	28, // 13: alox.UartMessage.espnow_unicast_test_response:type_name -> alox.EspNowUnicastTestResponse
-	39, // 14: alox.UartMessage.ota_slave_progress_request:type_name -> alox.OtaSlaveProgressRequest
-	41, // 15: alox.UartMessage.ota_slave_progress_response:type_name -> alox.OtaSlaveProgressResponse
-	29, // 16: alox.UartMessage.led_ring_progress_request:type_name -> alox.LedRingProgressRequest
-	30, // 17: alox.UartMessage.led_ring_progress_response:type_name -> alox.LedRingProgressResponse
-	31, // 18: alox.UartMessage.espnow_find_me_request:type_name -> alox.EspNowFindMeRequest
-	32, // 19: alox.UartMessage.espnow_find_me_response:type_name -> alox.EspNowFindMeResponse
-	33, // 20: alox.UartMessage.restart_request:type_name -> alox.RestartRequest
-	34, // 21: alox.UartMessage.restart_response:type_name -> alox.RestartResponse
+	43, // 14: alox.UartMessage.ota_slave_progress_request:type_name -> alox.OtaSlaveProgressRequest
+	45, // 15: alox.UartMessage.ota_slave_progress_response:type_name -> alox.OtaSlaveProgressResponse
+	31, // 16: alox.UartMessage.led_ring_progress_request:type_name -> alox.LedRingProgressRequest
+	32, // 17: alox.UartMessage.led_ring_progress_response:type_name -> alox.LedRingProgressResponse
+	33, // 18: alox.UartMessage.espnow_find_me_request:type_name -> alox.EspNowFindMeRequest
+	34, // 19: alox.UartMessage.espnow_find_me_response:type_name -> alox.EspNowFindMeResponse
+	35, // 20: alox.UartMessage.restart_request:type_name -> alox.RestartRequest
+	36, // 21: alox.UartMessage.restart_response:type_name -> alox.RestartResponse
 	12, // 22: alox.UartMessage.accel_stream_request:type_name -> alox.AccelStreamRequest
 	13, // 23: alox.UartMessage.accel_stream_response:type_name -> alox.AccelStreamResponse
 	14, // 24: alox.UartMessage.battery_status_request:type_name -> alox.BatteryStatusRequest
@@ -3499,22 +3826,26 @@ var file_uart_messages_proto_depIdxs = []int32{
 	20, // 27: alox.UartMessage.tap_notify_response:type_name -> alox.TapNotifyResponse
 	22, // 28: alox.UartMessage.cache_status_request:type_name -> alox.CacheStatusRequest
 	26, // 29: alox.UartMessage.cache_status_response:type_name -> alox.CacheStatusResponse
-	6,  // 30: alox.ClientInfoResponse.clients:type_name -> alox.ClientInfo
-	8,  // 31: alox.ClientInputResponse.clients:type_name -> alox.ClientInput
-	15, // 32: alox.BatterySample.lipo1:type_name -> alox.LipoReading
-	15, // 33: alox.BatterySample.lipo2:type_name -> alox.LipoReading
-	16, // 34: alox.BatteryStatusResponse.samples:type_name -> alox.BatterySample
-	1,  // 35: alox.TapEvent.kind:type_name -> alox.TapKind
-	1,  // 36: alox.CacheClientTap.kind:type_name -> alox.TapKind
-	23, // 37: alox.CacheClientStatus.accel:type_name -> alox.CacheClientAccel
-	24, // 38: alox.CacheClientStatus.tap:type_name -> alox.CacheClientTap
-	25, // 39: alox.CacheStatusResponse.clients:type_name -> alox.CacheClientStatus
-	40, // 40: alox.OtaSlaveProgressResponse.slaves:type_name -> alox.OtaSlaveProgressEntry
-	41, // [41:41] is the sub-list for method output_type
-	41, // [41:41] is the sub-list for method input_type
-	41, // [41:41] is the sub-list for extension type_name
-	41, // [41:41] is the sub-list for extension extendee
-	0,  // [0:41] is the sub-list for field type_name
+	29, // 30: alox.UartMessage.espnow_echo_ping_request:type_name -> alox.EspNowEchoPingRequest
+	30, // 31: alox.UartMessage.espnow_echo_ping_response:type_name -> alox.EspNowEchoPingResponse
+	37, // 32: alox.UartMessage.set_log_level_request:type_name -> alox.SetLogLevelRequest
+	38, // 33: alox.UartMessage.set_log_level_response:type_name -> alox.SetLogLevelResponse
+	6,  // 34: alox.ClientInfoResponse.clients:type_name -> alox.ClientInfo
+	8,  // 35: alox.ClientInputResponse.clients:type_name -> alox.ClientInput
+	15, // 36: alox.BatterySample.lipo1:type_name -> alox.LipoReading
+	15, // 37: alox.BatterySample.lipo2:type_name -> alox.LipoReading
+	16, // 38: alox.BatteryStatusResponse.samples:type_name -> alox.BatterySample
+	1,  // 39: alox.TapEvent.kind:type_name -> alox.TapKind
+	1,  // 40: alox.CacheClientTap.kind:type_name -> alox.TapKind
+	23, // 41: alox.CacheClientStatus.accel:type_name -> alox.CacheClientAccel
+	24, // 42: alox.CacheClientStatus.tap:type_name -> alox.CacheClientTap
+	25, // 43: alox.CacheStatusResponse.clients:type_name -> alox.CacheClientStatus
+	44, // 44: alox.OtaSlaveProgressResponse.slaves:type_name -> alox.OtaSlaveProgressEntry
+	45, // [45:45] is the sub-list for method output_type
+	45, // [45:45] is the sub-list for method input_type
+	45, // [45:45] is the sub-list for extension type_name
+	45, // [45:45] is the sub-list for extension extendee
+	0,  // [0:45] is the sub-list for field type_name
 }
 
 func init() { file_uart_messages_proto_init() }
@@ -3552,6 +3883,10 @@ func file_uart_messages_proto_init() {
 		(*UartMessage_TapNotifyResponse)(nil),
 		(*UartMessage_CacheStatusRequest)(nil),
 		(*UartMessage_CacheStatusResponse)(nil),
+		(*UartMessage_EspnowEchoPingRequest)(nil),
+		(*UartMessage_EspnowEchoPingResponse)(nil),
+		(*UartMessage_SetLogLevelRequest)(nil),
+		(*UartMessage_SetLogLevelResponse)(nil),
 	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
@@ -3559,7 +3894,7 @@ func file_uart_messages_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: unsafe.Slice(unsafe.StringData(file_uart_messages_proto_rawDesc), len(file_uart_messages_proto_rawDesc)),
 			NumEnums:      2,
-			NumMessages:   40,
+			NumMessages:   44,
 			NumExtensions: 0,
 			NumServices:   0,
 		},

goTool/serial_link.go

@@ -11,14 +11,18 @@ import (
 // errUARTBusy is returned when the port is held for OTA (poller should not treat as unplug).
 var errUARTBusy = errors.New("uart busy (OTA in progress)")
 
+// errOTAInProgress is returned when a second OTA upload is attempted while one is running.
+var errOTAInProgress = errors.New("OTA upload already in progress")
+
 // managedSerial keeps the UART open and reconnects after I/O failures or unplug.
 type managedSerial struct {
 	portName string
 	baud     int
 	quiet    bool
 
-	mu sync.Mutex
-	sp *serialPort
+	mu        sync.Mutex
+	sp        *serialPort
+	otaActive bool // UART held for firmware upload; poll/API must not interleave
 }
 
 func newManagedSerial(portName string, baud int) *managedSerial {
@@ -76,20 +80,17 @@ func (m *managedSerial) withPort(fn func(*serialPort) error) error {
 	return m.withPortLocked(false, fn)
 }
 
-// withPortPoll is like withPort but returns errUARTBusy instead of blocking during OTA.
+// withPortPoll is like withPort but returns errUARTBusy during OTA (no TryLock race).
 func (m *managedSerial) withPortPoll(fn func(*serialPort) error) error {
 	return m.withPortLocked(true, fn)
 }
 
-func (m *managedSerial) withPortLocked(try bool, fn func(*serialPort) error) error {
-	if try {
-		if !m.mu.TryLock() {
-			return errUARTBusy
-		}
-	} else {
-		m.mu.Lock()
-	}
+func (m *managedSerial) withPortLocked(poll bool, fn func(*serialPort) error) error {
+	m.mu.Lock()
 	defer m.mu.Unlock()
+	if m.otaActive {
+		return errUARTBusy
+	}
 
 	if m.sp == nil {
 		if err := m.openLocked(); err != nil {
@@ -104,6 +105,26 @@ func (m *managedSerial) withPortLocked(try bool, fn func(*serialPort) error) err
 	return err
 }
 
+func (m *managedSerial) recoverAfterMasterRestart() {
+	const bootWait = 6 * time.Second
+
+	m.mu.Lock()
+	m.closeLocked()
+	m.mu.Unlock()
+
+	log.Printf("UART: master restart — waiting %s for boot", bootWait)
+	time.Sleep(bootWait)
+
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if err := m.openLocked(); err != nil {
+		log.Printf("UART reconnect after master restart: %v", err)
+		return
+	}
+	flushSerialInput(m.sp)
+	log.Printf("UART %s ready after master restart", m.portName)
+}
+
 func (m *managedSerial) exchangePayload(payload []byte, cmdName string) ([]byte, error) {
 	return m.exchangePayloadVia(m.withPort, payload, cmdName)
 }

goTool/serialport.go

@@ -80,7 +80,7 @@ func (s *serialPort) exchangePayloadLocked(payload []byte, cmdName string, timeo
 	}
 	defer func() { _ = s.port.SetReadTimeout(readTimeout) }()
 
-	respPayload, err := uartframe.ReadFrame(s.port, nil)
+	respPayload, err := uartframe.ReadFrame(s.port, nil, timeout)
 	if err != nil {
 		return nil, fmt.Errorf("read response: %w", err)
 	}
@@ -113,7 +113,7 @@ func (s *serialPort) exchangeLocked(cmdID byte, cmdName string) ([]byte, error)
 		return nil, fmt.Errorf("write: %w", err)
 	}
 
-	payload, err := uartframe.ReadFrame(s.port, nil)
+	payload, err := uartframe.ReadFrame(s.port, nil, readTimeout)
 	if err != nil {
 		return nil, fmt.Errorf("read response: %w", err)
 	}

goTool/shutdown.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+	"time"
+)
+
+var (
+	shutdownMu   sync.Mutex
+	shutdownFns  []func()
+	hooksOnce    sync.Once
+	bgHandlerOnce sync.Once
+)
+
+// registerShutdown runs fn on SIGINT/SIGTERM (LIFO order).
+func registerShutdown(fn func()) {
+	shutdownMu.Lock()
+	shutdownFns = append(shutdownFns, fn)
+	shutdownMu.Unlock()
+}
+
+func runShutdownHooks() {
+	hooksOnce.Do(func() {
+		shutdownMu.Lock()
+		fns := shutdownFns
+		shutdownMu.Unlock()
+		for i := len(fns) - 1; i >= 0; i-- {
+			fns[i]()
+		}
+	})
+}
+
+// enableShutdownOnInterrupt listens for SIGINT/SIGTERM in the background and exits
+// after running shutdown hooks. Use for one-shot CLI commands (OTA, etc.).
+func enableShutdownOnInterrupt() {
+	bgHandlerOnce.Do(func() {
+		ch := make(chan os.Signal, 1)
+		signal.Notify(ch, os.Interrupt, syscall.SIGTERM)
+		go func() {
+			sig := <-ch
+			signal.Stop(ch)
+			log.Printf("received %v, shutting down…", sig)
+			runShutdownHooks()
+			os.Exit(0)
+		}()
+	})
+}
+
+// waitForShutdown blocks until SIGINT/SIGTERM, runs hooks, and returns.
+// Use for long-running servers (serve/dashboard).
+func waitForShutdown() {
+	ch := make(chan os.Signal, 1)
+	signal.Notify(ch, os.Interrupt, syscall.SIGTERM)
+	sig := <-ch
+	signal.Stop(ch)
+	log.Printf("received %v, shutting down…", sig)
+	runShutdownHooks()
+}
+
+func shutdownHTTPServer(srv *http.Server) {
+	if srv == nil {
+		return
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+	if err := srv.Shutdown(ctx); err != nil {
+		log.Printf("HTTP shutdown: %v", err)
+	}
+}

goTool/testdata/README.md

@@ -44,7 +44,7 @@ Ordered steps: UART commands, delays, or esptool reset.
 **unicast_test** — `input`: `slave` or `client_id`, `seq`  
 `expect`: `success`, `seq`
 
-**led_ring** — `input`: `mode` (`clear`, `progress`, `digit`, `blink`, `find_me`), `progress`, `digit`, `r`/`g`/`b`, `intensity`, `blink_ms`, `blink_count`  
+**led_ring** — `input`: `mode` (`clear`, `progress`, `digit`, `blink`, `find_me`, `battery_low`), `progress`, `digit`, `r`/`g`/`b`, `intensity`, `blink_ms`, `blink_count`  
 `expect`: `success`, `mode`, `progress`, `digit`
 
 **find_me** — `input`: `client` / `client_id` or `slave` (`0` = master ring)  

goTool/uart/frame.go

@@ -4,12 +4,14 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"time"
 )
 
 const (
 	StartMarker = 0xAA
 	StopMarker  = 0xCC
-	MaxPayload  = 252
+	// Must match main/uart.h MAX_PAYLOAD_SIZE (MAX_BUF_SIZE - 4).
+	MaxPayload = 248
 )
 
 var (
@@ -97,13 +99,22 @@ func (p *Parser) Feed(b byte) (payload []byte, ok bool, err error) {
 }
 
 // ReadFrame reads bytes from r until one full frame is parsed or an error occurs.
-func ReadFrame(r io.Reader, buf []byte) ([]byte, error) {
+// maxWait bounds total wait time; zero means no limit (serial read timeouts retry forever).
+func ReadFrame(r io.Reader, buf []byte, maxWait time.Duration) ([]byte, error) {
 	if buf == nil {
 		buf = make([]byte, 256)
 	}
 	parser := NewParser()
 
+	var deadline time.Time
+	if maxWait > 0 {
+		deadline = time.Now().Add(maxWait)
+	}
+
 	for {
+		if !deadline.IsZero() && !time.Now().Before(deadline) {
+			return nil, ErrTimeout
+		}
 		n, err := r.Read(buf)
 		if n > 0 {
 			for i := 0; i < n; i++ {

goTool/webui/index.html

@@ -219,6 +219,8 @@
                 <dd class="col-7" x-text="state.master.running_partition || '—'"></dd>
                 <dt class="col-5 text-muted">Deadzone</dt>
                 <dd class="col-7" x-text="state.master.deadzone != null ? state.master.deadzone + ' LSB' : '—'"></dd>
+                <dt class="col-5 text-muted">Log-Level</dt>
+                <dd class="col-7" x-text="formatLogLevel(masterLogLevel)"></dd>
                 <dt class="col-5 text-muted">LiPo 1</dt>
                 <dd class="col-7" x-text="formatLipo(state.master?.lipo1)"></dd>
                 <dt class="col-5 text-muted">LiPo 2</dt>
@@ -264,6 +266,31 @@
                   Restart
                 </button>
               </div>
+              <label class="form-label text-muted small mb-1 mt-3" for="master-log-level">
+                ESP Log-Level (global)
+              </label>
+              <div class="d-flex flex-wrap gap-2 align-items-end">
+                <select id="master-log-level" class="form-select form-select-sm config-input"
+                        x-model.number="masterLogLevel"
+                        :disabled="busy || !state.uart_connected">
+                  <option value="0">None (aus)</option>
+                  <option value="1">Error</option>
+                  <option value="2">Warn</option>
+                  <option value="3">Info</option>
+                  <option value="4">Debug</option>
+                  <option value="5">Verbose</option>
+                </select>
+                <button type="button" class="btn btn-outline-secondary btn-sm"
+                        @click="readMasterLogLevel()"
+                        :disabled="busy || !state.uart_connected">
+                  Lesen
+                </button>
+                <button type="button" class="btn btn-primary btn-sm"
+                        @click="setMasterLogLevel()"
+                        :disabled="busy || !state.uart_connected">
+                  Setzen
+                </button>
+              </div>
               <p class="text-muted small mt-2 mb-0" x-show="!state.uart_connected">
                 UART nicht verbunden — Eingabe gesperrt.
               </p>
@@ -403,6 +430,12 @@
                                   title="ESP-NOW Unicast-Test">
                             Test
                           </button>
+                          <button type="button" class="btn btn-outline-info btn-sm"
+                                  @click="echoPing(c.id)"
+                                  :disabled="busy || !state.uart_connected || !c.available"
+                                  title="ESP-NOW Timestamp-Echo (Round-Trip-Latenz)">
+                            Ping
+                          </button>
                           <button type="button" class="btn btn-outline-info btn-sm"
                                   @click="ledRing({ clientId: c.id })"
                                   :disabled="busy || !state.uart_connected || !c.available"
@@ -438,7 +471,7 @@
           <div class="card-body">
             <p class="text-muted small mb-3">
               Modi: <code>clear</code>, <code>color</code> (ganzer Ring), <code>progress</code> (0–100&nbsp;%),
-              <code>digit</code> (0–10), <code>blink</code>, <code>find-me</code>.
+              <code>digit</code> (0–10), <code>blink</code>, <code>find-me</code>, <code>battery-low</code>.
               Ziel: Master (<code>client_id=0</code>), ein Slave oder alle Slaves (Broadcast).
             </p>
             <div class="row g-3 align-items-end">
@@ -451,6 +484,7 @@
                   <option value="digit">Ziffer/Symbol</option>
                   <option value="blink">Blink</option>
                   <option value="find-me">Find me</option>
+                  <option value="battery-low">Battery low</option>
                 </select>
               </div>
               <div class="col-md-4">
@@ -621,6 +655,7 @@
         ws: null,
         wsConnected: false,
         masterDz: 100,
+        masterLogLevel: 0,
         allDz: 100,
         allTapSingle: false,
         allTapDouble: false,
@@ -640,6 +675,7 @@
         busy: false,
         configMsg: '',
         configMsgOk: false,
+        _flashTimer: null,
         led: {
           mode: 'color',
           r: 0,
@@ -734,21 +770,35 @@
         },
         applyBatterySamples(samples) {
           if (!samples?.length) return;
+          const master = { ...(this.state.master || {}) };
+          const clients = [...(this.state.clients || [])];
+          let masterChanged = false;
+          let clientsChanged = false;
           for (const s of samples) {
             if (s.client_id === 0) {
-              if (!this.state.master) this.state.master = {};
-              this.state.master.lipo1 = s.lipo1;
-              this.state.master.lipo2 = s.lipo2;
-              this.state.master.battery_age_ms = s.age_ms;
+              master.lipo1 = s.lipo1;
+              master.lipo2 = s.lipo2;
+              master.battery_age_ms = s.age_ms;
+              masterChanged = true;
               continue;
             }
-            const c = (this.state.clients || []).find((x) => x.id === s.client_id);
-            if (c) {
-              c.lipo1 = s.lipo1;
-              c.lipo2 = s.lipo2;
-              c.battery_age_ms = s.age_ms;
+            const idx = clients.findIndex((x) => x.id === s.client_id);
+            if (idx >= 0) {
+              clients[idx] = {
+                ...clients[idx],
+                lipo1: s.lipo1,
+                lipo2: s.lipo2,
+                battery_age_ms: s.age_ms,
+              };
+              clientsChanged = true;
             }
           }
+          if (!masterChanged && !clientsChanged) return;
+          this.state = {
+            ...this.state,
+            ...(masterChanged ? { master } : {}),
+            ...(clientsChanged ? { clients } : {}),
+          };
         },
         async refreshBattery() {
           if (!this.state?.uart_connected) return;
@@ -759,6 +809,11 @@
             if (data.samples?.length) this.applyBatterySamples(data.samples);
           } catch (_) {}
         },
+        formatLogLevel(level) {
+          const labels = ['None', 'Error', 'Warn', 'Info', 'Debug', 'Verbose'];
+          if (level == null || level < 0 || level > 5) return '—';
+          return `${labels[level]} (${level})`;
+        },
         formatMac(hex) {
           if (!hex || hex.length !== 12) return hex || '';
           return hex.match(/.{2}/g).join(':');
@@ -938,8 +993,21 @@
           return rows;
         },
         applyOTAProgress(p) {
-          this.ota.phase = p.phase || '';
-          this.ota.step = p.step || this.ota.step || '';
+          const prevPhase = this.ota.phase;
+          const prevStep = this.ota.step;
+          if (p.phase) {
+            // Ignore out-of-order master upload updates after distribution started.
+            if (!(p.phase === 'uploading' && prevPhase === 'distributing')) {
+              this.ota.phase = p.phase;
+            }
+          }
+          if (p.step) {
+            if (!(p.step === 'master' && (prevStep === 'slaves' || prevPhase === 'distributing'))) {
+              this.ota.step = p.step;
+            }
+          } else if (!this.ota.step) {
+            this.ota.step = '';
+          }
           this.ota.percent = p.percent ?? this.ota.percent;
           this.ota.message = p.message || '';
           if (p.image_size) this.ota.imageSize = p.image_size;
@@ -1018,10 +1086,14 @@
             this.busy = false;
           }
         },
-        flash(msg, ok) {
+        flash(msg, ok, durationMs = 5000) {
           this.configMsg = msg;
           this.configMsgOk = ok;
-          setTimeout(() => { this.configMsg = ''; }, 5000);
+          if (this._flashTimer) clearTimeout(this._flashTimer);
+          this._flashTimer = setTimeout(() => {
+            this.configMsg = '';
+            this._flashTimer = null;
+          }, durationMs);
         },
         async setDeadzone(clientId, deadzone, opts = {}) {
           if (deadzone == null || deadzone < 0) {
@@ -1080,6 +1152,44 @@
         async setMasterDeadzone() {
           await this.setDeadzone(0, this.masterDz);
         },
+        async readMasterLogLevel() {
+          this.busy = true;
+          try {
+            const r = await fetch('/api/log-level');
+            const data = await r.json();
+            if (!r.ok || !data.success) {
+              this.flash(data.error || 'Log-Level lesen fehlgeschlagen', false);
+              return;
+            }
+            this.masterLogLevel = data.level;
+            this.flash(`Master: Log-Level ${this.formatLogLevel(data.level)}`, true);
+          } catch (e) {
+            this.flash(String(e), false);
+          } finally {
+            this.busy = false;
+          }
+        },
+        async setMasterLogLevel() {
+          this.busy = true;
+          try {
+            const r = await fetch('/api/log-level', {
+              method: 'POST',
+              headers: { 'Content-Type': 'application/json' },
+              body: JSON.stringify({ write: true, level: this.masterLogLevel })
+            });
+            const data = await r.json();
+            if (!r.ok || !data.success) {
+              this.flash(data.error || 'Log-Level setzen fehlgeschlagen', false);
+              return;
+            }
+            this.masterLogLevel = data.level;
+            this.flash(`Master: Log-Level ${this.formatLogLevel(data.level)} gesetzt`, true);
+          } catch (e) {
+            this.flash(String(e), false);
+          } finally {
+            this.busy = false;
+          }
+        },
         patchLiveStream(enabled) {
           let clients = this.state.clients || [];
           if (!enabled) {
@@ -1245,6 +1355,43 @@
             this.busy = false;
           }
         },
+        formatMs(v) {
+          return v != null && Number.isFinite(Number(v)) ? Number(v).toFixed(3) : '—';
+        },
+        formatUsAsMs(us) {
+          return us != null && Number.isFinite(Number(us))
+            ? (Number(us) / 1000).toFixed(3)
+            : '—';
+        },
+        async echoPing(clientId) {
+          this.busy = true;
+          try {
+            const r = await fetch('/api/echo-ping', {
+              method: 'POST',
+              headers: { 'Content-Type': 'application/json' },
+              body: JSON.stringify({ client_id: clientId })
+            });
+            const data = await r.json();
+            if (!r.ok) {
+              this.flash(data.error || `Echo-Ping Slave ${clientId} fehlgeschlagen`, false);
+              return;
+            }
+            if (!data.success) {
+              this.flash(`Echo-Ping Slave ${clientId} fehlgeschlagen (${this.formatMs(data.rtt_ms)} ms)`, false);
+              return;
+            }
+            this.flash(
+              `Echo-Ping Slave ${clientId}: Host ${this.formatMs(data.rtt_ms)} ms, ` +
+              `ESP ${this.formatUsAsMs(data.esp_rtt_us)} ms`,
+              true,
+              5000
+            );
+          } catch (e) {
+            this.flash(String(e), false);
+          } finally {
+            this.busy = false;
+          }
+        },
         async restart(clientId = 0) {
           this.busy = true;
           try {

main/CMakeLists.txt

@@ -22,20 +22,27 @@ idf_component_register(
   "cmd/cmd_tap_notify.c"
   "cmd/cmd_cache_status.c"
   "cmd/cmd_espnow_unicast_test.c"
+  "cmd/cmd_espnow_echo_ping.c"
   "cmd/cmd_espnow_find_me.c"
   "cmd/cmd_restart.c"
   "pod_reboot.c"
   "cmd/cmd_led_ring.c"
   "cmd/cmd_battery.c"
+  "cmd/cmd_set_log_level.c"
   "cmd/cmd_ota.c"
   "cmd/cmd_ota_slave_progress.c"
   "ota_uart.c"
   "ota_espnow.c"
+  "ota_session.c"
   "client_registry.c"
   "esp_now_comm.c"
+  "esp_now_core.c"
+  "esp_now_master.c"
+  "esp_now_slave.c"
   "esp_now_proto.c"
   "bosch456.c"
   "board_input.c"
+  "battery_uv.c"
   "pod_settings.c"
   "proto/uart_messages.pb.c"
   "proto/esp_now_messages.pb.c"
@@ -57,7 +64,10 @@ idf_component_register(
   esp_driver_i2c
   esp_adc
   app_update
+  esp_timer
   bma456)
 
 target_compile_definitions(${COMPONENT_LIB}
                            PRIVATE "POWERPOD_GIT_HASH=\"${POWERPOD_GIT_HASH}\"")
+# Optional: disable software UV protection
+# target_compile_definitions(${COMPONENT_LIB} PRIVATE POWERPOD_BATTERY_UV_ENABLE=0)

main/README.md

@@ -2,6 +2,8 @@
 
 ESP32-S3 firmware for Powerpod nodes. Master and slave devices run the **same binary**; role and ESP-NOW network are selected at boot via DIP switches and an I2C IO expander.
 
+**Architektur & ESP-only Doku (ohne goTool):** [`../docs/ARCHITECTURE.md`](../docs/ARCHITECTURE.md) (Datenflüsse UART/Commands/ESP-NOW), [`../docs/DOCUMENTATION.md`](../docs/DOCUMENTATION.md) (vollständige Referenz).
+
 ## System overview
 
 ```
@@ -53,18 +55,20 @@ Pins (`powerpod.h`):
 | BMA456 INT | 10 |
 | Button (Taster) | 12 |
 | LiPo sense 1 (ADC) | 1 |
-| LiPo sense 2 (ADC) | 12 (skipped if same as button) |
+| LiPo sense 2 (ADC) | 11 |
 
 > **TODO:** GPIO assignments above are provisional; confirm pinning against the real board before release.
 
-Startup order:
+Startup order (normal path; UV energy-save skips I2C/BMA456/ESP-NOW/UART/button — see **Software UV protection**):
 
-1. Read DIP + IO expander → `app_config`
-2. **I2C bus** — IO expander `0x20`; optional **BMA456H** (`init_bma456`, same bus)
-3. `esp_now_comm_init(&app_config)` — WiFi + ESP-NOW
-4. `led_ring_init()`
-5. `board_input_init()` — button press logs, LiPo ADC logs every **10 s**
-6. **Master only:** command queue, UART, registered commands (e.g. VERSION)
+1. `pod_settings_init()` — NVS
+2. LiPo ADC init + optional UV boot check (`battery_uv.c`)
+3. Read DIP + IO expander → `app_config`
+4. **I2C bus** — IO expander `0x20`; optional **BMA456H** (`init_bma456`, same bus)
+5. `esp_now_comm_init(&app_config)` — WiFi + ESP-NOW
+6. `led_ring_init()`
+7. LiPo monitor task + button (`board_input.c`)
+8. **Master only:** command queue, UART, registered commands (e.g. VERSION)
 
 ## BMA456 accelerometer (`bosch456.c`)
 
@@ -176,7 +180,7 @@ Logging:
 
 ## Command handler
 
-Generic dispatch for host commands (UART today; `msg_post()` for in-firmware sources later).
+Generic dispatch for host commands over UART only.
 
 ```
 UART  →  generic_msg_t queue  →  vCmdDispatcherTask  →  registered handler
@@ -186,7 +190,8 @@ UART  →  generic_msg_t queue  →  vCmdDispatcherTask  →  registered handler
 |-----|-------------|
 | `init_cmdHandler(queue)` | Start dispatcher task (priority 5) |
 | `msg_register_handler(id, cb)` | Register callback; max 32 handlers |
-| `msg_post(id, data, len)` | Enqueue from firmware (e.g. future ESP-NOW → PC path) |
+
+During an OTA session (`ota_session_busy()`), the dispatcher rejects all UART commands except OTA_* and `OTA_SLAVE_PROGRESS` (see `ota_session.c`).
 
 ```c
 typedef void (*msg_callback_t)(const uint8_t *data, size_t len);
@@ -225,6 +230,8 @@ Host and master speak nanopb-encoded `UartMessage` inside UART frames (byte 0 =
 | 25 | `ACCEL_STREAM` | Implemented — enable/disable slave ESP-NOW accel stream to master |
 | 27 | `TAP_NOTIFY` | Implemented (`cmd/cmd_tap_notify.c`) — get/set which tap kinds notify via ESP-NOW |
 | 29 | `CACHE_STATUS` | Implemented (`cmd/cmd_cache_status.c`) — subscribed accel + tap cache (one UART round-trip) |
+| 30 | `ESPNOW_ECHO_PING` | Implemented (`cmd/cmd_espnow_echo_ping.c`) — ESP-NOW timestamp echo (latency test) |
+| 31 | `SET_LOG_LEVEL` | Implemented (`cmd/cmd_set_log_level.c`) — get/set global `esp_log_level_set("*", …)` on master |
 
 Regenerate C code:
 
@@ -387,6 +394,30 @@ go run . -port /dev/ttyUSB0 find-me
 go run . -port /dev/ttyUSB0 find-me -client 16
 ```
 
+### SET_LOG_LEVEL command
+
+Read or set the **global** ESP-IDF log filter on the master (`esp_log_level_set("*", level)`). Does not affect the host UART protocol (UART1); `esp_log_*` output goes to the **debug console UART0** (USB, 115200).
+
+**Request:** framed `31` (`0x1f`) + `set_log_level_request` (`write`, `level` 0–5).
+
+**Response:** `set_log_level_response` (`success`, `level`).
+
+| `level` | `esp_log_level_t` |
+|---------|-------------------|
+| 0 | NONE |
+| 1 | ERROR |
+| 2 | WARN |
+| 3 | INFO |
+| 4 | DEBUG |
+| 5 | VERBOSE |
+
+Boot default follows `CONFIG_LOG_DEFAULT_LEVEL` in `sdkconfig` (not persisted across reboot).
+
+```bash
+go run . -port /dev/ttyUSB0 log-level
+go run . -port /dev/ttyUSB0 log-level -set -level 0
+```
+
 ### RESTART command
 
 Reboot the master (`client_id=0`) or one slave via ESP-NOW (`client_id` = registry id). The device sends the UART response, then restarts after ~150 ms.
@@ -411,6 +442,19 @@ Read **cached** LiPo ADC values on the **master** (master local + one entry per
 # Host / goTool: all_clients returns master (id 0) + slaves from cache
 ```
 
+### Software UV protection (LiPo)
+
+When `POWERPOD_BATTERY_UV_ENABLE` is `1` (default in `powerpod.h`, disable via CMake), the firmware monitors ADC pin voltages on GPIO 1 and 11:
+
+| Condition | ADC threshold | Action |
+|-----------|---------------|--------|
+| Under-voltage | any valid channel < **2300 mV** (3.0 V pack) | NVS latch `uv_latch`, restart into energy-save mode |
+| Charged | all valid channels ≥ **3000 mV** (4.0 V pack) | Clear latch, restart into normal boot |
+
+**Energy-save boot:** LED mode `6` (first 4 LEDs red ~10 % for 5 s), then no WiFi/ESP-NOW, UART, I2C, BMA456, or button — only LiPo ADC polling every 30 s until charged.
+
+**Test LED pattern from host:** `led-ring -mode battery-low` (works even when UV feature is disabled).
+
 ### LED_RING command
 
 Control the 95-LED ring from the host. The firmware **does not** animate digits locally; only UART updates the display.
@@ -419,7 +463,7 @@ Control the 95-LED ring from the host. The firmware **does not** animate digits
 
 | Field | Meaning |
 |-------|---------|
-| `mode` | `0` = clear, `1` = progress, `2` = digit (0–10), `3` = blink, `4` = find-me, `5` = solid color (all LEDs) |
+| `mode` | `0` = clear, `1` = progress, `2` = digit (0–10), `3` = blink, `4` = find-me, `5` = solid color (all LEDs), `6` = battery-low (first 4 LEDs red ~10 % for 5 s) |
 | `progress` | 0–100 (% of ring lit, mode `1`) |
 | `digit` | 0–10 (mode `2`, segment maps in `led_ring.c`) |
 | `r`, `g`, `b` | Color 0–255 |
@@ -441,6 +485,7 @@ go run . -port /dev/ttyUSB0 led-ring -mode blink -g 255 -blink-count 2
 go run . -port /dev/ttyUSB0 find-me
 go run . -port /dev/ttyUSB0 find-me -client 16
 go run . -port /dev/ttyUSB0 led-ring -mode find-me
+go run . -port /dev/ttyUSB0 led-ring -mode battery-low -client 0
 go run . -port /dev/ttyUSB0 led-ring -mode color -r 255 -g 0 -b 0 -client 16
 go run . -port /dev/ttyUSB0 led-ring -mode digit -digit 5 -all
 ```
@@ -517,7 +562,10 @@ Target: ESP32-S3. Close serial monitor on the UART adapter port before running `
 | `powerpod.c` | `app_main`, DIP/network config, init order |
 | `powerpod.h` | Pin defines |
 | `app_config.h` | `app_config_t` |
-| `esp_now_comm.c/h` | WiFi, ESP-NOW, discover / slave info / OTA send |
+| `esp_now_comm.c/h` | ESP-NOW init and recv router |
+| `esp_now_core.c/h` | Shared WiFi, peer, send |
+| `esp_now_master.c/h` | Master discover, monitor, unicast |
+| `esp_now_slave.c/h` | Slave join, heartbeat, telemetry |
 | `ota_uart.c/h` | Shared 4 KiB OTA flash buffer (UART + ESP-NOW) |
 | `ota_espnow.c/h` | Master: distribute staged image to slaves |
 | `cmd/cmd_ota.c/h` | UART OTA command handlers (master only) |
@@ -531,10 +579,12 @@ Target: ESP32-S3. Close serial monitor on the UART adapter port before running `
 | `bosch456.c/h` | BMA456H I2C driver, accel poll, on-demand read, tap INT, deadzone filter |
 | `cmd/cmd_tap_notify.c` | UART `TAP_NOTIFY` — ESP-NOW tap notify config |
 | `cmd/cmd_cache_status.c` | UART `CACHE_STATUS` — subscribed accel + tap cache poll |
-| `board_input.c/h` | Taster GPIO12, LiPo ADC on GPIO1 / GPIO12 |
-| `pod_settings.c/h` | NVS persistence (accel deadzone, …) |
+| `board_input.c/h` | Taster GPIO12, LiPo ADC on GPIO1 / GPIO11 |
+| `battery_uv.c/h` | Software LiPo UV latch, energy-save boot (`POWERPOD_BATTERY_UV_ENABLE`) |
+| `pod_settings.c/h` | NVS persistence (accel deadzone, UV latch, …) |
 | `led_ring.c/h` | LED ring (digit display, progress bar) |
 | `cmd/cmd_led_ring.c` | UART `LED_RING` progress command |
+| `cmd/cmd_set_log_level.c` | UART `SET_LOG_LEVEL` — runtime ESP-IDF log level |
 | `proto/uart_messages.proto` | UART protocol schema |
 | `proto/esp_now_messages.proto` | ESP-NOW protocol schema |
 | `esp_now_proto.c/h` | Encode/decode `EspNowMessage` |

main/battery_uv.c

@@ -0,0 +1,130 @@
+#include "battery_uv.h"
+
+#if POWERPOD_BATTERY_UV_ENABLE
+
+#include "led_ring.h"
+#include "pod_reboot.h"
+#include "pod_settings.h"
+#include "esp_log.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+
+static const char *TAG = "[BATTERY_UV]";
+
+#define UV_DEBOUNCE_SAMPLES 2u
+#define UV_POLL_INTERVAL_MS 30000u
+
+static uint8_t s_uv_streak;
+static uint8_t s_charge_streak;
+
+bool battery_uv_is_latched(void) { return pod_settings_is_uv_latched(); }
+
+bool battery_uv_reading_is_under(const board_lipo_reading_t *reading) {
+  if (reading == NULL) {
+    return false;
+  }
+
+  if (reading->lipo1_valid && reading->lipo1_mv < BATTERY_UV_ADC_MV) {
+    return true;
+  }
+  if (reading->lipo2_valid && reading->lipo2_mv < BATTERY_UV_ADC_MV) {
+    return true;
+  }
+  return false;
+}
+
+bool battery_uv_reading_is_charged(const board_lipo_reading_t *reading) {
+  if (reading == NULL) {
+    return false;
+  }
+
+  bool any_valid = false;
+  if (reading->lipo1_valid) {
+    any_valid = true;
+    if (reading->lipo1_mv < BATTERY_CHARGE_ADC_MV) {
+      return false;
+    }
+  }
+  if (reading->lipo2_valid) {
+    any_valid = true;
+    if (reading->lipo2_mv < BATTERY_CHARGE_ADC_MV) {
+      return false;
+    }
+  }
+  return any_valid;
+}
+
+bool battery_uv_evaluate_boot(void) {
+  board_lipo_reading_t reading;
+  board_input_read_lipo(&reading);
+
+  if (pod_settings_is_uv_latched() && battery_uv_reading_is_charged(&reading)) {
+    ESP_LOGI(TAG, "charged — clearing UV latch");
+    pod_settings_clear_uv_latched();
+    return false;
+  }
+
+  if (pod_settings_is_uv_latched() || battery_uv_reading_is_under(&reading)) {
+    if (!pod_settings_is_uv_latched()) {
+      ESP_LOGW(TAG, "under-voltage at boot — latching UV");
+    } else {
+      ESP_LOGW(TAG, "UV latched — energy-save boot");
+    }
+    pod_settings_set_uv_latched(true);
+    return true;
+  }
+
+  return false;
+}
+
+void battery_uv_poll(const board_lipo_reading_t *reading) {
+  if (reading == NULL || pod_settings_is_uv_latched()) {
+    return;
+  }
+
+  if (battery_uv_reading_is_under(reading)) {
+    s_uv_streak++;
+    ESP_LOGW(TAG, "under-voltage sample %u/%u", (unsigned)s_uv_streak,
+             (unsigned)UV_DEBOUNCE_SAMPLES);
+    if (s_uv_streak >= UV_DEBOUNCE_SAMPLES) {
+      ESP_LOGW(TAG, "UV confirmed — latching and restarting");
+      pod_settings_set_uv_latched(true);
+      pod_schedule_restart();
+    }
+    return;
+  }
+
+  s_uv_streak = 0;
+}
+
+void battery_uv_run_mode(void) {
+  s_charge_streak = 0;
+  s_uv_streak = 0;
+
+  led_ring_init();
+  led_ring_show_battery_low();
+
+  ESP_LOGW(TAG, "energy-save mode — ADC poll every %u ms", UV_POLL_INTERVAL_MS);
+
+  while (1) {
+    board_lipo_reading_t reading;
+    board_input_read_lipo(&reading);
+
+    if (battery_uv_reading_is_charged(&reading)) {
+      s_charge_streak++;
+      ESP_LOGI(TAG, "charge sample %u/%u", (unsigned)s_charge_streak,
+               (unsigned)UV_DEBOUNCE_SAMPLES);
+      if (s_charge_streak >= UV_DEBOUNCE_SAMPLES) {
+        ESP_LOGI(TAG, "charged — clearing UV latch and restarting");
+        pod_settings_clear_uv_latched();
+        pod_schedule_restart();
+      }
+    } else {
+      s_charge_streak = 0;
+    }
+
+    vTaskDelay(pdMS_TO_TICKS(UV_POLL_INTERVAL_MS));
+  }
+}
+
+#endif

main/battery_uv.h

@@ -0,0 +1,51 @@
+#ifndef BATTERY_UV_H
+#define BATTERY_UV_H
+
+#include "board_input.h"
+#include "powerpod.h"
+#include <stdbool.h>
+
+#if POWERPOD_BATTERY_UV_ENABLE
+
+/** ADC pin voltage (mV) below which UV is triggered (3.0 V pack via 33k/10k divider). */
+#define BATTERY_UV_ADC_MV 2300u
+/** ADC pin voltage (mV) at which charging is detected (4.0 V pack, rounded). */
+#define BATTERY_CHARGE_ADC_MV 3000u
+
+bool battery_uv_is_latched(void);
+bool battery_uv_reading_is_under(const board_lipo_reading_t *reading);
+bool battery_uv_reading_is_charged(const board_lipo_reading_t *reading);
+
+/** true → enter UV energy-save path (does not return). */
+bool battery_uv_evaluate_boot(void);
+
+void battery_uv_poll(const board_lipo_reading_t *reading);
+
+/** Blocks: LED indicator, then minimal ADC polling until charged. */
+void battery_uv_run_mode(void);
+
+#else
+
+static inline bool battery_uv_is_latched(void) { return false; }
+
+static inline bool battery_uv_reading_is_under(const board_lipo_reading_t *reading) {
+  (void)reading;
+  return false;
+}
+
+static inline bool battery_uv_reading_is_charged(const board_lipo_reading_t *reading) {
+  (void)reading;
+  return false;
+}
+
+static inline bool battery_uv_evaluate_boot(void) { return false; }
+
+static inline void battery_uv_poll(const board_lipo_reading_t *reading) {
+  (void)reading;
+}
+
+static inline void battery_uv_run_mode(void) {}
+
+#endif
+
+#endif

main/board_input.c

@@ -1,6 +1,10 @@
 #include "board_input.h"
 #include "powerpod.h"
+#include "client_registry.h"
 #include "driver/gpio.h"
+#if POWERPOD_BATTERY_UV_ENABLE
+#include "battery_uv.h"
+#endif
 #include "esp_adc/adc_oneshot.h"
 #include "esp_log.h"
 #include "freertos/FreeRTOS.h"
@@ -18,34 +22,51 @@ static const char *TAG_LIPO = "[LIPO]";
 #define LIPO_ADC_MAX_RAW 4095
 
 static QueueHandle_t s_button_queue;
-static adc_oneshot_unit_handle_t s_adc;
-static bool s_lipo1_ok;
-static bool s_lipo2_ok;
-static adc_channel_t s_lipo1_ch;
-static adc_channel_t s_lipo2_ch;
 
-static esp_err_t adc_init_channel(int gpio, adc_channel_t *out_ch, bool *out_ok) {
-  adc_unit_t unit;
-  esp_err_t err = adc_oneshot_io_to_channel(gpio, &unit, out_ch);
+typedef struct {
+  adc_oneshot_unit_handle_t unit;
+  adc_channel_t ch;
+  bool ok;
+} lipo_adc_t;
+
+static lipo_adc_t s_lipo1;
+static lipo_adc_t s_lipo2;
+
+static esp_err_t adc_init_gpio(int gpio, lipo_adc_t *out) {
+  out->unit = NULL;
+  out->ok = false;
+
+  adc_unit_t unit_id;
+  esp_err_t err = adc_oneshot_io_to_channel(gpio, &unit_id, &out->ch);
   if (err != ESP_OK) {
     ESP_LOGW(TAG_LIPO, "GPIO%d not an ADC channel: %s", gpio, esp_err_to_name(err));
-    *out_ok = false;
     return err;
   }
-  if (unit != ADC_UNIT_1) {
-    ESP_LOGW(TAG_LIPO, "GPIO%d on ADC unit %d (expected ADC1)", gpio, (int)unit);
+
+  adc_oneshot_unit_init_cfg_t init_cfg = {
+      .unit_id = unit_id,
+  };
+  err = adc_oneshot_new_unit(&init_cfg, &out->unit);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG_LIPO, "ADC unit %d init GPIO%d failed: %s", (int)unit_id, gpio,
+             esp_err_to_name(err));
+    return err;
   }
+
   adc_oneshot_chan_cfg_t chan_cfg = {
       .atten = ADC_ATTEN_DB_12,
       .bitwidth = ADC_BITWIDTH_DEFAULT,
   };
-  err = adc_oneshot_config_channel(s_adc, *out_ch, &chan_cfg);
+  err = adc_oneshot_config_channel(out->unit, out->ch, &chan_cfg);
   if (err != ESP_OK) {
     ESP_LOGW(TAG_LIPO, "ADC config GPIO%d failed: %s", gpio, esp_err_to_name(err));
-    *out_ok = false;
+    adc_oneshot_del_unit(out->unit);
+    out->unit = NULL;
     return err;
   }
-  *out_ok = true;
+
+  out->ok = true;
+  ESP_LOGI(TAG_LIPO, "GPIO%d ready (ADC unit %d)", gpio, (int)unit_id);
   return ESP_OK;
 }
 
@@ -56,15 +77,15 @@ static uint32_t raw_to_mv(int raw) {
   return (uint32_t)((raw * LIPO_ADC_FULL_SCALE_MV) / LIPO_ADC_MAX_RAW);
 }
 
-static void sample_one_channel(adc_channel_t ch, bool ok, uint32_t *mv_out,
+static void sample_one_channel(const lipo_adc_t *adc, uint32_t *mv_out,
                                bool *valid_out) {
   *valid_out = false;
   *mv_out = 0;
-  if (!ok || s_adc == NULL) {
+  if (adc == NULL || !adc->ok || adc->unit == NULL) {
     return;
   }
   int raw = 0;
-  if (adc_oneshot_read(s_adc, ch, &raw) == ESP_OK) {
+  if (adc_oneshot_read(adc->unit, adc->ch, &raw) == ESP_OK) {
     *valid_out = true;
     *mv_out = raw_to_mv(raw);
   }
@@ -75,8 +96,8 @@ void board_input_read_lipo(board_lipo_reading_t *out) {
     return;
   }
   memset(out, 0, sizeof(*out));
-  sample_one_channel(s_lipo1_ch, s_lipo1_ok, &out->lipo1_mv, &out->lipo1_valid);
-  sample_one_channel(s_lipo2_ch, s_lipo2_ok, &out->lipo2_mv, &out->lipo2_valid);
+  sample_one_channel(&s_lipo1, &out->lipo1_mv, &out->lipo1_valid);
+  sample_one_channel(&s_lipo2, &out->lipo2_mv, &out->lipo2_valid);
 }
 
 static void lipo_monitor_task(void *param) {
@@ -87,6 +108,7 @@ static void lipo_monitor_task(void *param) {
   while (1) {
     board_lipo_reading_t reading;
     board_input_read_lipo(&reading);
+    client_registry_set_master_battery(&reading);
 
     ESP_LOGI(TAG_LIPO,
              "LIPO1 GPIO%d %s %lu mV  LIPO2 GPIO%d %s %lu mV",
@@ -95,6 +117,10 @@ static void lipo_monitor_task(void *param) {
              reading.lipo2_valid ? "ok" : "n/a",
              (unsigned long)reading.lipo2_mv);
 
+#if POWERPOD_BATTERY_UV_ENABLE
+    battery_uv_poll(&reading);
+#endif
+
     vTaskDelay(pdMS_TO_TICKS(LIPO_SAMPLE_INTERVAL_MS));
   }
 }
@@ -165,29 +191,30 @@ static esp_err_t init_button(void) {
   return ESP_OK;
 }
 
-static esp_err_t init_lipo_adc(void) {
-  adc_oneshot_unit_init_cfg_t init_cfg = {
-      .unit_id = ADC_UNIT_1,
-  };
-  esp_err_t err = adc_oneshot_new_unit(&init_cfg, &s_adc);
-  if (err != ESP_OK) {
-    ESP_LOGW(TAG_LIPO, "ADC init failed: %s", esp_err_to_name(err));
-    return err;
-  }
+static esp_err_t init_lipo_adc_hw(void) {
+  memset(&s_lipo1, 0, sizeof(s_lipo1));
+  memset(&s_lipo2, 0, sizeof(s_lipo2));
 
-  adc_init_channel(V_LIPO_1_GPIO, &s_lipo1_ch, &s_lipo1_ok);
+  adc_init_gpio(V_LIPO_1_GPIO, &s_lipo1);
 
   if (V_LIPO_2_GPIO == TASTER_GPIO) {
     ESP_LOGW(TAG_LIPO, "LIPO2 on GPIO%d skipped (button uses same pin)",
              V_LIPO_2_GPIO);
-    s_lipo2_ok = false;
   } else {
-    adc_init_channel(V_LIPO_2_GPIO, &s_lipo2_ch, &s_lipo2_ok);
+    adc_init_gpio(V_LIPO_2_GPIO, &s_lipo2);
   }
 
-  if (!s_lipo1_ok && !s_lipo2_ok) {
-    adc_oneshot_del_unit(s_adc);
-    s_adc = NULL;
+  if (!s_lipo1.ok && !s_lipo2.ok) {
+    return ESP_FAIL;
+  }
+
+  return ESP_OK;
+}
+
+esp_err_t board_input_init_adc_only(void) { return init_lipo_adc_hw(); }
+
+esp_err_t board_input_start_lipo_monitor(void) {
+  if (!s_lipo1.ok && !s_lipo2.ok) {
     return ESP_FAIL;
   }
 
@@ -198,16 +225,23 @@ static esp_err_t init_lipo_adc(void) {
   return ESP_OK;
 }
 
+esp_err_t board_input_init_button(void) { return init_button(); }
+
 esp_err_t board_input_init(void) {
-  esp_err_t err = init_button();
+  esp_err_t err = board_input_init_adc_only();
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG_LIPO, "ADC init failed: %s", esp_err_to_name(err));
+  } else {
+    err = board_input_start_lipo_monitor();
+    if (err != ESP_OK) {
+      ESP_LOGW(TAG_LIPO, "monitor task failed: %s", esp_err_to_name(err));
+    }
+  }
+
+  err = board_input_init_button();
   if (err != ESP_OK) {
     ESP_LOGW(TAG_BTN, "init failed: %s", esp_err_to_name(err));
   }
 
-  err = init_lipo_adc();
-  if (err != ESP_OK) {
-    ESP_LOGW(TAG_LIPO, "init failed: %s", esp_err_to_name(err));
-  }
-
   return ESP_OK;
 }

main/board_input.h

@@ -19,6 +19,15 @@ typedef struct {
  */
 esp_err_t board_input_init(void);
 
+/** LiPo ADC channels only (no button, no background task). */
+esp_err_t board_input_init_adc_only(void);
+
+/** Start 10 s LiPo monitor task (normal boot only). */
+esp_err_t board_input_start_lipo_monitor(void);
+
+/** Front-panel button debounce task. */
+esp_err_t board_input_init_button(void);
+
 /** On-demand ADC read of both LiPo sense inputs (if configured). */
 void board_input_read_lipo(board_lipo_reading_t *out);
 

main/bosch456.c

@@ -38,6 +38,7 @@ static volatile bool s_int_pending;
 static SemaphoreHandle_t s_accel_mutex;
 static bma456_tap_handler_t s_tap_handler;
 static void *s_tap_handler_ctx;
+static const bma456_tap_config_t s_tap_config = BMA456_TAP_CONFIG_DEFAULT;
 
 static esp_err_t check_bma4(const char *api_name, int8_t rslt);
 
@@ -263,19 +264,48 @@ static esp_err_t configure_tap_interrupt(void) {
   if (check_bma4("bma456h_tap_get_parameter", ret) != ESP_OK) {
     return ESP_FAIL;
   }
-  tap_settings.tap_sens_thres = 0;
+  tap_settings.tap_sens_thres = s_tap_config.tap_sens_thres;
+  tap_settings.max_gest_dur = s_tap_config.max_gest_dur;
+  tap_settings.tap_shock_dur = s_tap_config.tap_shock_dur;
+  tap_settings.quite_time_after_gest = s_tap_config.quite_time_after_gest;
+  tap_settings.wait_for_timeout = s_tap_config.wait_for_timeout;
+  tap_settings.axis_sel = s_tap_config.axis_sel;
   ret = bma456h_tap_set_parameter(&tap_settings, &s_bma456);
   if (check_bma4("bma456h_tap_set_parameter", ret) != ESP_OK) {
     return ESP_FAIL;
   }
 
-  ret = bma456h_feature_enable(
-      (BMA456H_SINGLE_TAP_EN | BMA456H_DOUBLE_TAP_EN | BMA456H_TRIPLE_TAP_EN),
-      BMA4_ENABLE, &s_bma456);
+  uint16_t tap_features = 0;
+  if (s_tap_config.enable_single) {
+    tap_features |= BMA456H_SINGLE_TAP_EN;
+  }
+  if (s_tap_config.enable_double) {
+    tap_features |= BMA456H_DOUBLE_TAP_EN;
+  }
+  if (s_tap_config.enable_triple) {
+    tap_features |= BMA456H_TRIPLE_TAP_EN;
+  }
+  if (tap_features == 0) {
+    ESP_LOGW(TAG, "tap config: no tap kinds enabled");
+    return ESP_ERR_INVALID_ARG;
+  }
+
+  ret = bma456h_feature_enable(tap_features, BMA4_ENABLE, &s_bma456);
   if (check_bma4("bma456h_feature_enable", ret) != ESP_OK) {
     return ESP_FAIL;
   }
 
+  ESP_LOGI(TAG,
+           "tap config sens=%u max_gest=%u shock=%u quiet=%u wait=%u axis=%u "
+           "(single=%d double=%d triple=%d)",
+           (unsigned)s_tap_config.tap_sens_thres,
+           (unsigned)s_tap_config.max_gest_dur,
+           (unsigned)s_tap_config.tap_shock_dur,
+           (unsigned)s_tap_config.quite_time_after_gest,
+           (unsigned)s_tap_config.wait_for_timeout,
+           (unsigned)s_tap_config.axis_sel, s_tap_config.enable_single,
+           s_tap_config.enable_double, s_tap_config.enable_triple);
+
   ret = bma456h_map_interrupt(int_line, BMA456H_TAP_OUT_INT, BMA4_ENABLE,
                               &s_bma456);
   if (check_bma4("bma456h_map_interrupt", ret) != ESP_OK) {

main/bosch456.h

@@ -10,6 +10,8 @@
 
 #include "driver/i2c_types.h"
 #include "esp_err.h"
+#include <stdbool.h>
+#include <stdint.h>
 
 /** 7-bit I2C address (SDO low). */
 #define BMA456_I2C_ADDR 0x18
@@ -20,6 +22,40 @@
 /** Software filter: log accel only when |axis - last| > deadzone (raw LSB). */
 #define BMA456_DEFAULT_ACCEL_DEADZONE 100u
 
+/**
+ * BMA456H multitap tuning (see BST-BMA456-AN000).
+ *
+ * Time fields use register units: value × 5 ms (e.g. 100 → 500 ms).
+ * tap_sens_thres: 0 = most sensitive … 15 = least (~78 mg per LSB).
+ * axis_sel: 0 = X, 1 = Y, 2 = Z.
+ * wait_for_timeout: 0 = report immediately, 1 = wait max_gest_dur for classification.
+ */
+typedef struct {
+  uint16_t tap_sens_thres;
+  uint16_t max_gest_dur;
+  uint16_t tap_shock_dur;
+  uint16_t quite_time_after_gest;
+  uint16_t wait_for_timeout;
+  uint16_t axis_sel;
+  bool enable_single;
+  bool enable_double;
+  bool enable_triple;
+} bma456_tap_config_t;
+
+/** Edit these values to tune tap detection, then rebuild. */
+#define BMA456_TAP_CONFIG_DEFAULT                                              \
+  {                                                                            \
+      .tap_sens_thres = 5,           /* sensitive; 0=max, Bosch default=9 */   \
+      .max_gest_dur = 100,             /* 500 ms window for double/triple */   \
+      .tap_shock_dur = 6,              /* 30 ms debounce after each impulse */ \
+      .quite_time_after_gest = 60,     /* 300 ms min gap between gestures */   \
+      .wait_for_timeout = 0,           /* 0 = faster single-tap response */    \
+      .axis_sel = 2,                   /* Z axis */                            \
+      .enable_single = true,                                                   \
+      .enable_double = true,                                                   \
+      .enable_triple = true,                                                   \
+  }
+
 /**
  * Probe and configure the sensor on bus_handle (100 kHz device).
  * On failure the device is removed and ESP_ERR_NOT_FOUND / ESP_FAIL is returned;

main/cmd/cmd_accel_stream.c

@@ -33,12 +33,20 @@ static void handle_accel_stream(const uint8_t *data, size_t len) {
   alox_UartMessage uart_msg;
   alox_AccelStreamRequest req = alox_AccelStreamRequest_init_zero;
 
-  if (uart_cmd_decode(data, len, &uart_msg) == ESP_OK) {
+  if (len > 0) {
+    if (uart_cmd_decode(data, len, &uart_msg) != ESP_OK) {
+      ESP_LOGW(TAG, "decode failed");
+      reply(false, 0, false, 0);
+      return;
+    }
     const alox_AccelStreamRequest *req_ptr = UART_CMD_REQ(
         &uart_msg, alox_UartMessage_accel_stream_request_tag, accel_stream_request);
-    if (req_ptr != NULL) {
-      req = *req_ptr;
+    if (req_ptr == NULL) {
+      ESP_LOGW(TAG, "missing accel_stream_request");
+      reply(false, 0, false, 0);
+      return;
     }
+    req = *req_ptr;
   }
 
   if (req.write) {

main/cmd/cmd_battery.c

@@ -33,18 +33,14 @@ static bool append_battery_sample(alox_BatteryStatusResponse *resp,
   return lipo1_valid || lipo2_valid;
 }
 
-static bool append_master_cached(alox_BatteryStatusResponse *resp) {
+static bool append_master_sample(alox_BatteryStatusResponse *resp) {
   board_lipo_reading_t reading;
-  uint32_t age_ms = 0;
 
-  if (!client_registry_get_master_battery(&reading, &age_ms)) {
-    board_input_read_lipo(&reading);
-    client_registry_set_master_battery(&reading);
-    age_ms = 0;
-  }
+  board_input_read_lipo(&reading);
+  client_registry_set_master_battery(&reading);
 
   return append_battery_sample(resp, 0, reading.lipo1_valid, reading.lipo1_mv,
-                               reading.lipo2_valid, reading.lipo2_mv, age_ms);
+                               reading.lipo2_valid, reading.lipo2_mv, 0);
 }
 
 static bool append_slave_cached(alox_BatteryStatusResponse *resp,
@@ -67,14 +63,28 @@ static void handle_battery_status(const uint8_t *data, size_t len) {
 
   if (len > 0) {
     alox_UartMessage uart_msg;
-    if (uart_cmd_decode(data, len, &uart_msg) == ESP_OK) {
-      const alox_BatteryStatusRequest *req_ptr = UART_CMD_REQ(
-          &uart_msg, alox_UartMessage_battery_status_request_tag,
-          battery_status_request);
-      if (req_ptr != NULL) {
-        req = *req_ptr;
-      }
+    if (uart_cmd_decode(data, len, &uart_msg) != ESP_OK) {
+      ESP_LOGW(TAG, "decode failed");
+      alox_UartMessage response;
+      uart_cmd_init_response(&response, alox_MessageType_BATTERY_STATUS,
+                             alox_UartMessage_battery_status_response_tag);
+      response.payload.battery_status_response.success = false;
+      uart_cmd_send(&response, TAG);
+      return;
     }
+    const alox_BatteryStatusRequest *req_ptr = UART_CMD_REQ(
+        &uart_msg, alox_UartMessage_battery_status_request_tag,
+        battery_status_request);
+    if (req_ptr == NULL) {
+      ESP_LOGW(TAG, "missing battery_status_request");
+      alox_UartMessage response;
+      uart_cmd_init_response(&response, alox_MessageType_BATTERY_STATUS,
+                             alox_UartMessage_battery_status_response_tag);
+      response.payload.battery_status_response.success = false;
+      uart_cmd_send(&response, TAG);
+      return;
+    }
+    req = *req_ptr;
   }
 
   alox_UartMessage response;
@@ -88,7 +98,7 @@ static void handle_battery_status(const uint8_t *data, size_t len) {
   bool any = false;
 
   if (req.all_clients) {
-    any |= append_master_cached(resp);
+    any |= append_master_sample(resp);
     for (size_t i = 0; i < client_registry_count(); i++) {
       const client_info_t *client = client_registry_at(i);
       if (client == NULL) {
@@ -99,7 +109,7 @@ static void handle_battery_status(const uint8_t *data, size_t len) {
     ESP_LOGI(TAG, "battery cache all_clients → %u samples",
              (unsigned)resp->samples_count);
   } else if (req.client_id == 0) {
-    any = append_master_cached(resp);
+    any = append_master_sample(resp);
     ESP_LOGI(TAG, "battery cache master");
   } else {
     const client_info_t *client = client_registry_find_by_id(req.client_id);

main/cmd/cmd_espnow_echo_ping.c

@@ -0,0 +1,70 @@
+#include "client_registry.h"
+#include "cmd_espnow_echo_ping.h"
+#include "esp_log.h"
+#include "esp_now_comm.h"
+#include "uart_cmd.h"
+
+static const char *TAG = "[ECHO_PING]";
+
+static void reply(bool success, uint32_t client_id, uint64_t timestamp_us,
+                  uint32_t esp_rtt_us) {
+  alox_UartMessage response;
+  uart_cmd_init_response(&response, alox_MessageType_ESPNOW_ECHO_PING,
+                         alox_UartMessage_espnow_echo_ping_response_tag);
+  response.payload.espnow_echo_ping_response.success = success;
+  response.payload.espnow_echo_ping_response.client_id = client_id;
+  response.payload.espnow_echo_ping_response.timestamp_us = timestamp_us;
+  response.payload.espnow_echo_ping_response.esp_rtt_us = esp_rtt_us;
+  uart_cmd_send(&response, TAG);
+}
+
+static void handle_espnow_echo_ping(const uint8_t *data, size_t len) {
+  alox_UartMessage uart_msg;
+
+  if (uart_cmd_decode(data, len, &uart_msg) != ESP_OK) {
+    ESP_LOGW(TAG, "decode failed");
+    reply(false, 0, 0, 0);
+    return;
+  }
+
+  const alox_EspNowEchoPingRequest *req = UART_CMD_REQ(
+      &uart_msg, alox_UartMessage_espnow_echo_ping_request_tag,
+      espnow_echo_ping_request);
+  if (req == NULL || req->client_id == 0) {
+    ESP_LOGW(TAG, "need client_id in request");
+    reply(false, 0, 0, 0);
+    return;
+  }
+
+  const client_info_t *client = client_registry_find_by_id(req->client_id);
+  if (client == NULL) {
+    ESP_LOGW(TAG, "client id %lu not in registry",
+             (unsigned long)req->client_id);
+    reply(false, req->client_id, 0, 0);
+    return;
+  }
+
+  ESP_LOGI(TAG, "UART request client_id=%lu host_ts=%llu",
+           (unsigned long)req->client_id,
+           (unsigned long long)req->timestamp_us);
+
+  esp_now_echo_ping_result_t ping_result = {0};
+  esp_err_t err =
+      esp_now_comm_echo_ping(client->mac, req->timestamp_us, &ping_result);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "echo ping to id=%lu failed: %s", (unsigned long)req->client_id,
+             esp_err_to_name(err));
+    reply(false, req->client_id, 0, 0);
+    return;
+  }
+
+  ESP_LOGI(TAG, "UART reply client_id=%lu host_ts=%llu esp_rtt_us=%lu",
+           (unsigned long)req->client_id,
+           (unsigned long long)ping_result.echoed_us,
+           (unsigned long)ping_result.esp_rtt_us);
+  reply(true, req->client_id, ping_result.echoed_us, ping_result.esp_rtt_us);
+}
+
+void cmd_espnow_echo_ping_register(void) {
+  uart_cmd_register(alox_MessageType_ESPNOW_ECHO_PING, handle_espnow_echo_ping);
+}

main/cmd/cmd_espnow_echo_ping.h

@@ -0,0 +1,6 @@
+#ifndef CMD_ESPNOW_ECHO_PING_H
+#define CMD_ESPNOW_ECHO_PING_H
+
+void cmd_espnow_echo_ping_register(void);
+
+#endif

main/cmd/cmd_handler.c

@@ -1,4 +1,5 @@
 #include "cmd_handler.h"
+#include "ota_session.h"
 #include "esp_err.h"
 #include "esp_log.h"
 #include "freertos/FreeRTOS.h"
@@ -56,6 +57,10 @@ static const char *message_type_name(uint16_t id) {
     return "TAP_NOTIFY";
   case alox_MessageType_CACHE_STATUS:
     return "CACHE_STATUS";
+  case alox_MessageType_ESPNOW_ECHO_PING:
+    return "ESPNOW_ECHO_PING";
+  case alox_MessageType_SET_LOG_LEVEL:
+    return "SET_LOG_LEVEL";
   default:
     return "UNKNOWN";
   }
@@ -88,33 +93,19 @@ esp_err_t msg_register_handler(uint16_t id, msg_callback_t cb) {
   return ESP_OK;
 }
 
-esp_err_t msg_post(uint16_t id, const uint8_t *data, size_t len) {
-  if (cmd_queue == NULL) {
-    return ESP_ERR_INVALID_STATE;
-  }
-
-  generic_msg_t msg = {.msg_id = id, .len = len, .payload = NULL};
-  if (len > 0) {
-    msg.payload = malloc(len);
-    if (msg.payload == NULL) {
-      return ESP_ERR_NO_MEM;
-    }
-    memcpy(msg.payload, data, len);
-  }
-
-  if (xQueueSend(cmd_queue, &msg, pdMS_TO_TICKS(100)) != pdPASS) {
-    free(msg.payload);
-    return ESP_ERR_TIMEOUT;
-  }
-  return ESP_OK;
-}
-
 void vCmdDispatcherTask(void *param) {
   (void)param;
   generic_msg_t msg;
 
   while (1) {
     if (xQueueReceive(cmd_queue, &msg, portMAX_DELAY) == pdPASS) {
+      if (!ota_session_uart_cmd_allowed(msg.msg_id)) {
+        ESP_LOGW(TAG, "reject %s (0x%02x) during OTA session",
+                 message_type_name(msg.msg_id), (unsigned)msg.msg_id);
+        free(msg.payload);
+        continue;
+      }
+
       bool handled = false;
       for (int i = 0; i < handler_count; i++) {
         if (handlers[i].msg_id == msg.msg_id) {

main/cmd/cmd_handler.h

@@ -21,6 +21,5 @@ void init_cmdHandler(QueueHandle_t queue);
 void vCmdDispatcherTask(void *param);
 
 esp_err_t msg_register_handler(uint16_t id, msg_callback_t cb);
-esp_err_t msg_post(uint16_t id, const uint8_t *data, size_t len);
 
 #endif

main/cmd/cmd_led_ring.c

@@ -13,6 +13,7 @@ static const char *TAG = "[LED_RING_CMD]";
 #define LED_RING_MODE_BLINK    3
 #define LED_RING_MODE_FIND_ME  4
 #define LED_RING_MODE_COLOR    5
+#define LED_RING_MODE_BATTERY_LOW 6
 
 static uint8_t clamp_u8(uint32_t v) {
   if (v > 255) {
@@ -90,6 +91,10 @@ bool cmd_led_ring_apply(const alox_LedRingProgressRequest *req) {
     led_ring_find_me();
     return true;
 
+  case LED_RING_MODE_BATTERY_LOW:
+    led_ring_show_battery_low();
+    return true;
+
   case LED_RING_MODE_BLINK:
     cmd.mode = LED_CMD_BLINK;
     cmd.r = r;

main/cmd/cmd_ota.c

@@ -81,8 +81,6 @@ static const ota_espnow_progress_cbs_t s_dist_progress = {
 static void ota_prepare_task(void *param) {
   uint32_t total_size = (uint32_t)(uintptr_t)param;
 
-  send_ota_status(OTA_UART_ST_PREPARING, 0);
-
   int slot = ota_uart_prepare(total_size);
   if (slot < 0) {
     send_ota_failed(1);
@@ -116,27 +114,32 @@ static void handle_ota_start(const uint8_t *data, size_t len) {
 
   const alox_OtaStartPayload *req_ptr =
       UART_CMD_REQ(&uart_msg, alox_UartMessage_ota_start_tag, ota_start);
-  if (req_ptr != NULL) {
-    req = *req_ptr;
+  if (req_ptr == NULL) {
+    ESP_LOGW(TAG, "OTA_START: missing ota_start payload");
+    send_ota_failed(3);
+    return;
   }
+  req = *req_ptr;
 
   if (req.total_size == 0) {
     ESP_LOGW(TAG, "OTA_START: total_size required");
-    send_ota_failed( 3);
+    send_ota_failed(3);
     return;
   }
 
   if (ota_uart_is_active()) {
     ESP_LOGW(TAG, "OTA_START while session active");
-    send_ota_failed( 4);
+    send_ota_failed(4);
     return;
   }
 
+  send_ota_status(OTA_UART_ST_PREPARING, 0);
+
   if (xTaskCreate(ota_prepare_task, "ota_prepare", OTA_PREPARE_STACK,
                   (void *)(uintptr_t)req.total_size, OTA_PREPARE_PRIO,
                   NULL) != pdPASS) {
     ESP_LOGE(TAG, "failed to create ota_prepare task");
-    send_ota_failed( 5);
+    send_ota_failed(5);
   }
 }
 
@@ -172,8 +175,18 @@ static void handle_ota_payload(const uint8_t *data, size_t len) {
     return;
   }
 
-  ota_feed_result_t r =
-      ota_uart_feed(req_ptr->data.bytes, req_ptr->data.size);
+  ota_feed_result_t r = ota_uart_feed_chunk(req_ptr->seq, req_ptr->data.bytes,
+                                            req_ptr->data.size);
+  if (r == OTA_FEED_SEQ_GAP) {
+    send_ota_failed(16);
+    return;
+  }
+  if (r == OTA_FEED_SEQ_DUP) {
+    if (ota_uart_block_ready_for_reack()) {
+      send_ota_status(OTA_UART_ST_BLOCK_ACK, 0);
+    }
+    return;
+  }
   if (r == OTA_FEED_ERROR) {
     send_ota_failed( 13);
     return;
@@ -186,15 +199,6 @@ static void handle_ota_payload(const uint8_t *data, size_t len) {
     led_ring_show_ota_progress(done, total, OTA_LED_UART_R, OTA_LED_UART_G,
                                OTA_LED_UART_B);
     send_ota_status(OTA_UART_ST_BLOCK_ACK, 0);
-    return;
-  }
-
-  if (r == OTA_FEED_OK) {
-    uint32_t total = ota_uart_total_size();
-    if (total > 0) {
-      led_ring_show_ota_progress(ota_uart_bytes_received(), total,
-                                 OTA_LED_UART_R, OTA_LED_UART_G, OTA_LED_UART_B);
-    }
   }
 }
 
@@ -293,31 +297,28 @@ static void handle_ota_end(const uint8_t *data, size_t len) {
   }
 }
 
-static void handle_ota_start_espnow(const uint8_t *data, size_t len) {
-  (void)data;
-  (void)len;
-
-  if (ota_uart_is_active()) {
-    send_ota_failed( 40);
-    return;
-  }
+static void ota_start_espnow_task(void *param) {
+  (void)param;
 
   const esp_partition_t *part = NULL;
   uint32_t image_size = 0;
   if (!ota_uart_get_staged_image(&part, &image_size)) {
-    send_ota_failed( 41);
+    send_ota_failed(41);
+    vTaskDelete(NULL);
     return;
   }
 
-  esp_err_t   err = ota_espnow_distribute(part, image_size, &s_dist_progress);
+  esp_err_t err = ota_espnow_distribute(part, image_size, &s_dist_progress);
   if (err != ESP_OK) {
-    send_ota_failed( 42);
+    send_ota_failed(42);
+    vTaskDelete(NULL);
     return;
   }
 
   err = ota_uart_apply_boot();
   if (err != ESP_OK) {
-    send_ota_failed( (uint32_t)err);
+    send_ota_failed((uint32_t)err);
+    vTaskDelete(NULL);
     return;
   }
 
@@ -329,6 +330,30 @@ static void handle_ota_start_espnow(const uint8_t *data, size_t len) {
   response.payload.ota_status.error = 0;
   uart_cmd_send(&response, TAG);
   led_ring_ota_success();
+  vTaskDelete(NULL);
+}
+
+static void handle_ota_start_espnow(const uint8_t *data, size_t len) {
+  (void)data;
+  (void)len;
+
+  if (ota_uart_is_active()) {
+    send_ota_failed(40);
+    return;
+  }
+
+  const esp_partition_t *part = NULL;
+  uint32_t image_size = 0;
+  if (!ota_uart_get_staged_image(&part, &image_size)) {
+    send_ota_failed(41);
+    return;
+  }
+
+  if (xTaskCreate(ota_start_espnow_task, "ota_espnow", OTA_DIST_STACK, NULL,
+                  OTA_DIST_PRIO, NULL) != pdPASS) {
+    ESP_LOGE(TAG, "failed to create ota_start_espnow task");
+    send_ota_failed(43);
+  }
 }
 
 void cmd_ota_register(void) {

main/cmd/cmd_ota_slave_progress.c

@@ -9,13 +9,29 @@ static void handle_ota_slave_progress(const uint8_t *data, size_t len) {
   alox_UartMessage uart_msg;
   uint32_t filter = 0;
 
-  if (uart_cmd_decode(data, len, &uart_msg) == ESP_OK) {
+  if (len > 0) {
+    if (uart_cmd_decode(data, len, &uart_msg) != ESP_OK) {
+      ESP_LOGW(TAG, "decode failed");
+      alox_UartMessage response;
+      uart_cmd_init_response(
+          &response, alox_MessageType_OTA_SLAVE_PROGRESS,
+          alox_UartMessage_ota_slave_progress_response_tag);
+      uart_cmd_send(&response, TAG);
+      return;
+    }
     const alox_OtaSlaveProgressRequest *req =
         UART_CMD_REQ(&uart_msg, alox_UartMessage_ota_slave_progress_request_tag,
                      ota_slave_progress_request);
-    if (req != NULL) {
-      filter = req->client_id;
+    if (req == NULL) {
+      ESP_LOGW(TAG, "missing ota_slave_progress_request");
+      alox_UartMessage response;
+      uart_cmd_init_response(
+          &response, alox_MessageType_OTA_SLAVE_PROGRESS,
+          alox_UartMessage_ota_slave_progress_response_tag);
+      uart_cmd_send(&response, TAG);
+      return;
     }
+    filter = req->client_id;
   }
 
   alox_UartMessage response;

main/cmd/cmd_set_log_level.c

@@ -0,0 +1,51 @@
+#include "cmd_set_log_level.h"
+#include "esp_log.h"
+#include "uart_cmd.h"
+
+static const char *TAG = "[LOG_LVL]";
+
+static bool valid_level(uint32_t level) { return level <= ESP_LOG_VERBOSE; }
+
+static void reply(uint32_t level, bool success) {
+  alox_UartMessage response;
+  uart_cmd_init_response(&response, alox_MessageType_SET_LOG_LEVEL,
+                         alox_UartMessage_set_log_level_response_tag);
+  response.payload.set_log_level_response.success = success;
+  response.payload.set_log_level_response.level = level;
+  uart_cmd_send(&response, TAG);
+}
+
+static void handle_set_log_level(const uint8_t *data, size_t len) {
+  alox_UartMessage uart_msg;
+  alox_SetLogLevelRequest req = alox_SetLogLevelRequest_init_zero;
+
+  if (uart_cmd_decode(data, len, &uart_msg) != ESP_OK) {
+    ESP_LOGW(TAG, "decode failed");
+    reply((uint32_t)esp_log_level_get("*"), false);
+    return;
+  }
+
+  const alox_SetLogLevelRequest *req_ptr = UART_CMD_REQ(
+      &uart_msg, alox_UartMessage_set_log_level_request_tag, set_log_level_request);
+  if (req_ptr != NULL) {
+    req = *req_ptr;
+  }
+
+  if (req.write) {
+    if (!valid_level(req.level)) {
+      ESP_LOGW(TAG, "invalid level %lu", (unsigned long)req.level);
+      reply((uint32_t)esp_log_level_get("*"), false);
+      return;
+    }
+    esp_log_level_set("*", (esp_log_level_t)req.level);
+    ESP_LOGI(TAG, "global log level set to %lu", (unsigned long)req.level);
+    reply(req.level, true);
+    return;
+  }
+
+  reply((uint32_t)esp_log_level_get("*"), true);
+}
+
+void cmd_set_log_level_register(void) {
+  uart_cmd_register(alox_MessageType_SET_LOG_LEVEL, handle_set_log_level);
+}

main/cmd/cmd_set_log_level.h

@@ -0,0 +1,6 @@
+#ifndef CMD_SET_LOG_LEVEL_H
+#define CMD_SET_LOG_LEVEL_H
+
+void cmd_set_log_level_register(void);
+
+#endif

main/cmd/cmd_tap_notify.c

@@ -39,12 +39,20 @@ static void handle_tap_notify(const uint8_t *data, size_t len) {
   alox_UartMessage uart_msg;
   alox_TapNotifyRequest req = alox_TapNotifyRequest_init_zero;
 
-  if (uart_cmd_decode(data, len, &uart_msg) == ESP_OK) {
+  if (len > 0) {
+    if (uart_cmd_decode(data, len, &uart_msg) != ESP_OK) {
+      ESP_LOGW(TAG, "decode failed");
+      reply(0, false, 0, false, false, false);
+      return;
+    }
     const alox_TapNotifyRequest *req_ptr = UART_CMD_REQ(
         &uart_msg, alox_UartMessage_tap_notify_request_tag, tap_notify_request);
-    if (req_ptr != NULL) {
-      req = *req_ptr;
+    if (req_ptr == NULL) {
+      ESP_LOGW(TAG, "missing tap_notify_request");
+      reply(0, false, 0, false, false, false);
+      return;
     }
+    req = *req_ptr;
   }
 
   if (req.write) {

main/esp_now_comm.h

@@ -26,6 +26,17 @@ esp_err_t esp_now_comm_send_accel_deadzone(const uint8_t mac[CLIENT_MAC_LEN],
 esp_err_t esp_now_comm_send_unicast_test(const uint8_t mac[CLIENT_MAC_LEN],
                                          uint32_t seq);
 
+/** Result of a master-side ESP-NOW echo ping round-trip. */
+typedef struct {
+  uint64_t echoed_us;
+  uint32_t esp_rtt_us;
+} esp_now_echo_ping_result_t;
+
+/** Master: ESP-NOW echo ping round-trip; fills result on success. */
+esp_err_t esp_now_comm_echo_ping(const uint8_t mac[CLIENT_MAC_LEN],
+                                 uint64_t timestamp_us,
+                                 esp_now_echo_ping_result_t *result);
+
 /** Master: trigger find-me LED sequence on one slave. */
 esp_err_t esp_now_comm_send_find_me(const uint8_t mac[CLIENT_MAC_LEN],
                                     uint32_t client_id);

main/esp_now_core.c

@@ -0,0 +1,282 @@
+#include "esp_now_core.h"
+#include "esp_now_proto.h"
+#include "esp_err.h"
+#include "esp_event.h"
+#include "esp_log.h"
+#include "esp_mac.h"
+#include "esp_netif.h"
+#include "esp_now.h"
+#include "esp_wifi.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/idf_additions.h"
+#include <stdio.h>
+#include <string.h>
+
+static const char *TAG = "[ESPNOW_CORE]";
+
+static const uint8_t ESPNOW_BCAST[ESP_NOW_ETH_ALEN] = {0xff, 0xff, 0xff,
+                                                       0xff, 0xff, 0xff};
+
+static app_config_t s_config;
+static uint8_t s_wifi_channel;
+static uint8_t s_own_mac[ESP_NOW_ETH_ALEN];
+static SemaphoreHandle_t s_send_done;
+static SemaphoreHandle_t s_send_lock;
+static bool s_send_cb_ready;
+static volatile esp_now_send_status_t s_last_send_status;
+static volatile bool s_last_send_ok;
+
+#define ESPNOW_SEND_DONE_TIMEOUT_MS 500u
+#define ESPNOW_SEND_MAX_ATTEMPTS 8u
+#define ESPNOW_SEND_RETRY_DELAY_MS 10u
+#define ESPNOW_NOMEM_RETRY_DELAY_MS 50u
+
+#define ESPNOW_RELIABLE_MAX_ATTEMPTS 24u
+#define ESPNOW_RELIABLE_NOMEM_DELAY_MS 50u
+
+static uint8_t network_to_channel(uint8_t network) {
+  if (network < 1 || network > 13) {
+    return 1;
+  }
+  return network;
+}
+
+static void espnow_send_done_cb(const esp_now_send_info_t *tx_info,
+                                esp_now_send_status_t status) {
+  (void)tx_info;
+  s_last_send_status = status;
+  s_last_send_ok = (status == ESP_NOW_SEND_SUCCESS);
+  if (s_send_done != NULL) {
+    xSemaphoreGive(s_send_done);
+  }
+}
+
+void esp_now_core_store_config(const app_config_t *config) {
+  if (config == NULL) {
+    return;
+  }
+  memset(&s_config, 0, sizeof(s_config));
+  memcpy(&s_config, config, sizeof(s_config));
+  s_wifi_channel = network_to_channel(config->network);
+}
+
+const app_config_t *esp_now_core_get_config(void) { return &s_config; }
+
+bool esp_now_core_is_master(void) { return s_config.master; }
+
+uint8_t esp_now_core_network(void) { return s_config.network; }
+
+uint8_t esp_now_core_wifi_channel(void) { return s_wifi_channel; }
+
+const uint8_t *esp_now_core_own_mac(void) { return s_own_mac; }
+
+uint32_t esp_now_core_now_ms(void) {
+  return (uint32_t)(xTaskGetTickCount() * portTICK_PERIOD_MS);
+}
+
+bool esp_now_core_mac_equal(const uint8_t *a, const uint8_t *b) {
+  return memcmp(a, b, ESP_NOW_ETH_ALEN) == 0;
+}
+
+void esp_now_core_mac_to_str(const uint8_t *mac, char *out, size_t out_len) {
+  snprintf(out, out_len, "%02x:%02x:%02x:%02x:%02x:%02x", mac[0], mac[1],
+           mac[2], mac[3], mac[4], mac[5]);
+}
+
+esp_err_t esp_now_core_ensure_peer(const uint8_t *mac) {
+  if (esp_now_is_peer_exist(mac)) {
+    return ESP_OK;
+  }
+
+  esp_now_peer_info_t peer = {0};
+  memcpy(peer.peer_addr, mac, ESP_NOW_ETH_ALEN);
+  peer.channel = s_wifi_channel;
+  peer.ifidx = WIFI_IF_STA;
+  peer.encrypt = false;
+
+  esp_err_t err = esp_now_add_peer(&peer);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "add peer failed: %s", esp_err_to_name(err));
+  }
+  return err;
+}
+
+esp_err_t esp_now_core_ensure_broadcast_peer(void) {
+  return esp_now_core_ensure_peer(ESPNOW_BCAST);
+}
+
+static esp_err_t send_with_backpressure(const uint8_t *dest_mac,
+                                        const alox_EspNowMessage *msg,
+                                        uint32_t max_attempts,
+                                        uint32_t nomem_delay_ms,
+                                        uint32_t retry_delay_ms,
+                                        bool quiet_retries) {
+  if (s_send_lock == NULL ||
+      xSemaphoreTake(s_send_lock, pdMS_TO_TICKS(5000)) != pdTRUE) {
+    return ESP_ERR_TIMEOUT;
+  }
+
+  uint8_t buf[ESPNOW_PB_MAX_SIZE];
+  size_t len = 0;
+  esp_err_t result = ESP_FAIL;
+
+  esp_err_t err = esp_now_proto_encode(msg, buf, sizeof(buf), &len);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "encode failed");
+    result = err;
+    goto out;
+  }
+
+  if (len > ESP_NOW_MAX_DATA_LEN) {
+    ESP_LOGW(TAG, "encoded len %u > ESP-NOW max %u", (unsigned)len,
+             (unsigned)ESP_NOW_MAX_DATA_LEN);
+    result = ESP_ERR_INVALID_SIZE;
+    goto out;
+  }
+
+  if (esp_now_core_ensure_peer(dest_mac) != ESP_OK) {
+    result = ESP_FAIL;
+    goto out;
+  }
+
+  for (uint32_t attempt = 0; attempt < max_attempts; attempt++) {
+    if (s_send_cb_ready && s_send_done != NULL) {
+      xSemaphoreTake(s_send_done, 0);
+    }
+    s_last_send_ok = false;
+
+    err = esp_now_send(dest_mac, buf, len);
+    if (err != ESP_OK) {
+      const bool last = (attempt + 1 >= max_attempts);
+      if (!quiet_retries || last) {
+        ESP_LOGW(TAG, "send type=%u failed (attempt %lu/%lu): %s",
+                 (unsigned)msg->type, (unsigned long)(attempt + 1),
+                 (unsigned long)max_attempts, esp_err_to_name(err));
+      }
+      vTaskDelay(pdMS_TO_TICKS(err == ESP_ERR_ESPNOW_NO_MEM ? nomem_delay_ms
+                                                             : retry_delay_ms));
+      continue;
+    }
+
+    if (s_send_cb_ready && s_send_done != NULL) {
+      if (xSemaphoreTake(s_send_done, pdMS_TO_TICKS(ESPNOW_SEND_DONE_TIMEOUT_MS)) !=
+          pdTRUE) {
+        const bool last = (attempt + 1 >= max_attempts);
+        if (!quiet_retries || last) {
+          ESP_LOGW(TAG, "send type=%u done timeout (attempt %lu/%lu)",
+                   (unsigned)msg->type, (unsigned long)(attempt + 1),
+                   (unsigned long)max_attempts);
+        }
+        vTaskDelay(pdMS_TO_TICKS(retry_delay_ms));
+        continue;
+      }
+      if (!s_last_send_ok) {
+        const bool last = (attempt + 1 >= max_attempts);
+        if (!quiet_retries || last) {
+          ESP_LOGW(TAG, "send type=%u peer status=%d (attempt %lu/%lu)",
+                   (unsigned)msg->type, (int)s_last_send_status,
+                   (unsigned long)(attempt + 1), (unsigned long)max_attempts);
+        }
+        vTaskDelay(pdMS_TO_TICKS(retry_delay_ms));
+        continue;
+      }
+    }
+    result = ESP_OK;
+    goto out;
+  }
+
+out:
+  xSemaphoreGive(s_send_lock);
+  return result;
+}
+
+esp_err_t esp_now_core_send_wait(const uint8_t *dest_mac,
+                                 const alox_EspNowMessage *msg) {
+  return send_with_backpressure(dest_mac, msg, ESPNOW_SEND_MAX_ATTEMPTS,
+                                ESPNOW_NOMEM_RETRY_DELAY_MS,
+                                ESPNOW_SEND_RETRY_DELAY_MS, false);
+}
+
+esp_err_t esp_now_core_send_reliable(const uint8_t *dest_mac,
+                                     const alox_EspNowMessage *msg) {
+  return send_with_backpressure(dest_mac, msg, ESPNOW_RELIABLE_MAX_ATTEMPTS,
+                                ESPNOW_RELIABLE_NOMEM_DELAY_MS,
+                                ESPNOW_SEND_RETRY_DELAY_MS, true);
+}
+
+esp_err_t esp_now_core_send_fast(const uint8_t *dest_mac,
+                                 const alox_EspNowMessage *msg) {
+  if (s_send_lock == NULL ||
+      xSemaphoreTake(s_send_lock, pdMS_TO_TICKS(5000)) != pdTRUE) {
+    return ESP_ERR_TIMEOUT;
+  }
+
+  uint8_t buf[ESPNOW_PB_MAX_SIZE];
+  size_t len = 0;
+
+  esp_err_t err = esp_now_proto_encode(msg, buf, sizeof(buf), &len);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "encode failed");
+    xSemaphoreGive(s_send_lock);
+    return err;
+  }
+
+  if (len > ESP_NOW_MAX_DATA_LEN) {
+    ESP_LOGW(TAG, "encoded len %u > ESP-NOW max %u", (unsigned)len,
+             (unsigned)ESP_NOW_MAX_DATA_LEN);
+    xSemaphoreGive(s_send_lock);
+    return ESP_ERR_INVALID_SIZE;
+  }
+
+  if (esp_now_core_ensure_peer(dest_mac) != ESP_OK) {
+    xSemaphoreGive(s_send_lock);
+    return ESP_FAIL;
+  }
+
+  err = esp_now_send(dest_mac, buf, len);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "send type=%u failed: %s", (unsigned)msg->type,
+             esp_err_to_name(err));
+  }
+  xSemaphoreGive(s_send_lock);
+  return err;
+}
+
+esp_err_t esp_now_core_send(const uint8_t *dest_mac,
+                            const alox_EspNowMessage *msg) {
+  return esp_now_core_send_wait(dest_mac, msg);
+}
+
+esp_err_t esp_now_core_init_radio(uint8_t channel) {
+  ESP_ERROR_CHECK(esp_netif_init());
+  ESP_ERROR_CHECK(esp_event_loop_create_default());
+
+  wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
+  ESP_ERROR_CHECK(esp_wifi_init(&cfg));
+
+  wifi_config_t wifi_config = {0};
+  wifi_config.sta.channel = channel;
+  wifi_config.sta.scan_method = WIFI_ALL_CHANNEL_SCAN;
+  wifi_config.sta.sort_method = WIFI_CONNECT_AP_BY_SIGNAL;
+
+  ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
+  ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wifi_config));
+  ESP_ERROR_CHECK(esp_wifi_start());
+  ESP_ERROR_CHECK(esp_wifi_set_ps(WIFI_PS_NONE));
+  ESP_ERROR_CHECK(esp_wifi_set_channel(channel, WIFI_SECOND_CHAN_NONE));
+
+  ESP_ERROR_CHECK(esp_read_mac(s_own_mac, ESP_MAC_WIFI_STA));
+  s_wifi_channel = channel;
+  return ESP_OK;
+}
+
+void esp_now_core_init_send_done(void) {
+  s_send_done = xSemaphoreCreateBinary();
+  s_send_lock = xSemaphoreCreateMutex();
+  if (s_send_done != NULL && s_send_lock != NULL &&
+      esp_now_register_send_cb(espnow_send_done_cb) == ESP_OK) {
+    s_send_cb_ready = true;
+  } else {
+    ESP_LOGW(TAG, "send-done callback unavailable (OTA may drop packets)");
+  }
+}

main/esp_now_core.h

@@ -0,0 +1,38 @@
+#ifndef ESP_NOW_CORE_H
+#define ESP_NOW_CORE_H
+
+#include "app_config.h"
+#include "esp_err.h"
+#include "esp_now_messages.pb.h"
+#include <stdbool.h>
+#include <stdint.h>
+
+void esp_now_core_store_config(const app_config_t *config);
+const app_config_t *esp_now_core_get_config(void);
+bool esp_now_core_is_master(void);
+uint8_t esp_now_core_network(void);
+uint8_t esp_now_core_wifi_channel(void);
+const uint8_t *esp_now_core_own_mac(void);
+
+uint32_t esp_now_core_now_ms(void);
+bool esp_now_core_mac_equal(const uint8_t *a, const uint8_t *b);
+void esp_now_core_mac_to_str(const uint8_t *mac, char *out, size_t out_len);
+
+esp_err_t esp_now_core_ensure_peer(const uint8_t *mac);
+esp_err_t esp_now_core_ensure_broadcast_peer(void);
+
+esp_err_t esp_now_core_send(const uint8_t *dest_mac,
+                            const alox_EspNowMessage *msg);
+/** Like send but does not wait for esp_now send-done (lower latency). */
+esp_err_t esp_now_core_send_fast(const uint8_t *dest_mac,
+                                 const alox_EspNowMessage *msg);
+esp_err_t esp_now_core_send_wait(const uint8_t *dest_mac,
+                                 const alox_EspNowMessage *msg);
+/** OTA payloads: wait for send-done with extra NO_MEM backoff (queue drain). */
+esp_err_t esp_now_core_send_reliable(const uint8_t *dest_mac,
+                                     const alox_EspNowMessage *msg);
+
+esp_err_t esp_now_core_init_radio(uint8_t channel);
+void esp_now_core_init_send_done(void);
+
+#endif

main/esp_now_master.c

@@ -0,0 +1,597 @@
+#include "esp_now_master.h"
+#include "client_registry.h"
+#include "esp_now_comm.h"
+#include "esp_now_core.h"
+#include "esp_now_proto.h"
+#include "board_input.h"
+#include "ota_espnow.h"
+#include "ota_session.h"
+#include "ota_uart.h"
+#include "esp_log.h"
+#include "esp_timer.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/idf_additions.h"
+#include <string.h>
+
+static const uint8_t ESPNOW_BCAST[ESP_NOW_ETH_ALEN] = {0xff, 0xff, 0xff,
+                                                       0xff, 0xff, 0xff};
+
+#define ESPNOW_DISCOVER_INTERVAL_MS 500
+#define ESPNOW_HEARTBEAT_INTERVAL_MS 1000
+#define ESPNOW_HEARTBEAT_MISS_COUNT 3
+#define ESPNOW_CLIENT_TIMEOUT_MS                                               \
+  (ESPNOW_HEARTBEAT_INTERVAL_MS * ESPNOW_HEARTBEAT_MISS_COUNT)
+#define ESPNOW_BATTERY_INTERVAL_MS 30000
+
+static const char *TAG = "[ESPNOW_M]";
+
+static esp_err_t send_accel_stream(const uint8_t *dest_mac, uint32_t client_id,
+                                   bool enable) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_SET_ACCEL_STREAM;
+  msg.which_payload = alox_EspNowMessage_accel_stream_tag;
+  msg.payload.accel_stream.enable = enable;
+  msg.payload.accel_stream.client_id = client_id;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+static esp_err_t send_accel_deadzone(const uint8_t *dest_mac, uint32_t client_id,
+                                     uint32_t deadzone) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_SET_ACCEL_DEADZONE;
+  msg.which_payload = alox_EspNowMessage_accel_deadzone_tag;
+  msg.payload.accel_deadzone.deadzone = deadzone;
+  msg.payload.accel_deadzone.client_id = client_id;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+static esp_err_t send_unicast_test(const uint8_t *dest_mac, uint32_t seq) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_UNICAST_TEST;
+  msg.which_payload = alox_EspNowMessage_unicast_test_tag;
+  msg.payload.unicast_test.seq = seq;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+#define ESPNOW_ECHO_PING_TIMEOUT_MS 500
+#define ECHO_PING_TAG "[ECHO_PING]"
+
+static SemaphoreHandle_t s_echo_pong_sem;
+static bool s_echo_waiting;
+static uint64_t s_echo_expect_ts;
+static uint32_t s_echo_esp_rtt_us;
+static uint8_t s_echo_expect_mac[ESP_NOW_ETH_ALEN];
+
+static esp_err_t echo_ping_init(void) {
+  if (s_echo_pong_sem != NULL) {
+    return ESP_OK;
+  }
+  s_echo_pong_sem = xSemaphoreCreateBinary();
+  if (s_echo_pong_sem == NULL) {
+    return ESP_ERR_NO_MEM;
+  }
+  return ESP_OK;
+}
+
+static esp_err_t send_echo_ping(const uint8_t *dest_mac, uint64_t host_timestamp_us,
+                                uint64_t master_time_us) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_ECHO_PING;
+  msg.which_payload = alox_EspNowMessage_echo_ping_tag;
+  msg.payload.echo_ping.host_timestamp_us = host_timestamp_us;
+  msg.payload.echo_ping.master_time_us = master_time_us;
+  char mac_str[18];
+  esp_now_core_mac_to_str(dest_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(ECHO_PING_TAG, "ESP-NOW PING send to %s host_ts=%llu master_time_us=%llu",
+           mac_str, (unsigned long long)host_timestamp_us,
+           (unsigned long long)master_time_us);
+  return esp_now_core_send_fast(dest_mac, &msg);
+}
+
+static void echo_ping_on_pong(const uint8_t mac[ESP_NOW_ETH_ALEN],
+                              const alox_EspNowEchoPong *pong) {
+  if (pong == NULL || !s_echo_waiting) {
+    return;
+  }
+  if (!esp_now_core_mac_equal(mac, s_echo_expect_mac)) {
+    return;
+  }
+  if (pong->host_timestamp_us != s_echo_expect_ts) {
+    return;
+  }
+  int64_t now_us = esp_timer_get_time();
+  s_echo_esp_rtt_us =
+      (uint32_t)(now_us - (int64_t)pong->master_time_us);
+  char mac_str[18];
+  esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(ECHO_PING_TAG,
+           "ESP-NOW PONG recv from %s host_ts=%llu master_time_us=%llu "
+           "recv_time_us=%lld esp_rtt_us=%lu",
+           mac_str, (unsigned long long)pong->host_timestamp_us,
+           (unsigned long long)pong->master_time_us, (long long)now_us,
+           (unsigned long)s_echo_esp_rtt_us);
+  xSemaphoreGive(s_echo_pong_sem);
+}
+
+static esp_err_t send_find_me(const uint8_t *dest_mac, uint32_t client_id) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_FIND_ME;
+  msg.which_payload = alox_EspNowMessage_find_me_tag;
+  msg.payload.find_me.client_id = client_id;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+static esp_err_t send_led_ring(const uint8_t *dest_mac, uint32_t client_id,
+                               const alox_LedRingProgressRequest *req) {
+  if (req == NULL) {
+    return ESP_ERR_INVALID_ARG;
+  }
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_LED_RING;
+  msg.which_payload = alox_EspNowMessage_led_ring_tag;
+  msg.payload.led_ring.client_id = client_id;
+  msg.payload.led_ring.mode = req->mode;
+  msg.payload.led_ring.progress = req->progress;
+  msg.payload.led_ring.digit = req->digit;
+  msg.payload.led_ring.r = req->r;
+  msg.payload.led_ring.g = req->g;
+  msg.payload.led_ring.b = req->b;
+  msg.payload.led_ring.intensity = req->intensity;
+  msg.payload.led_ring.blink_ms = req->blink_ms;
+  msg.payload.led_ring.blink_count = req->blink_count;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+static esp_err_t send_restart(const uint8_t *dest_mac, uint32_t client_id) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_RESTART;
+  msg.which_payload = alox_EspNowMessage_restart_tag;
+  msg.payload.restart.client_id = client_id;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+static esp_err_t send_tap_notify(const uint8_t *dest_mac, uint32_t client_id,
+                                 bool single, bool double_tap, bool triple) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_SET_TAP_NOTIFY;
+  msg.which_payload = alox_EspNowMessage_tap_notify_tag;
+  msg.payload.tap_notify.client_id = client_id;
+  msg.payload.tap_notify.single = single;
+  msg.payload.tap_notify.double_tap = double_tap;
+  msg.payload.tap_notify.triple = triple;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+static esp_err_t send_ota_start(const uint8_t *dest_mac, uint32_t total_size) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_OTA_START;
+  msg.which_payload = alox_EspNowMessage_ota_start_tag;
+  msg.payload.ota_start.total_size = total_size;
+  return esp_now_core_send_wait(dest_mac, &msg);
+}
+
+static esp_err_t send_ota_payload(const uint8_t *dest_mac, uint32_t seq,
+                                  const uint8_t *data, size_t len) {
+  if (data == NULL || len == 0 || len > OTA_UART_HOST_CHUNK_SIZE) {
+    return ESP_ERR_INVALID_ARG;
+  }
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_OTA_PAYLOAD;
+  msg.which_payload = alox_EspNowMessage_ota_payload_tag;
+  msg.payload.ota_payload.seq = seq;
+  msg.payload.ota_payload.data.size = len;
+  memcpy(msg.payload.ota_payload.data.bytes, data, len);
+  return esp_now_core_send_reliable(dest_mac, &msg);
+}
+
+static esp_err_t send_ota_end(const uint8_t *dest_mac) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_OTA_END;
+  msg.which_payload = alox_EspNowMessage_ota_end_tag;
+  return esp_now_core_send_wait(dest_mac, &msg);
+}
+
+esp_err_t esp_now_comm_send_ota_start(const uint8_t mac[CLIENT_MAC_LEN],
+                                      uint32_t total_size) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  return send_ota_start(mac, total_size);
+}
+
+esp_err_t esp_now_comm_send_ota_payload(const uint8_t mac[CLIENT_MAC_LEN],
+                                        uint32_t seq, const uint8_t *data,
+                                        size_t len) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  return send_ota_payload(mac, seq, data, len);
+}
+
+esp_err_t esp_now_comm_send_ota_end(const uint8_t mac[CLIENT_MAC_LEN]) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  return send_ota_end(mac);
+}
+
+esp_err_t esp_now_comm_send_restart(const uint8_t mac[CLIENT_MAC_LEN],
+                                    uint32_t client_id) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  char mac_str[18];
+  esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+  esp_err_t err = send_restart(mac, client_id);
+  if (err == ESP_OK) {
+    ESP_LOGI(TAG, "unicast RESTART to %s client_id=%lu", mac_str,
+             (unsigned long)client_id);
+  } else {
+    ESP_LOGW(TAG, "unicast RESTART to %s failed: %s", mac_str,
+             esp_err_to_name(err));
+  }
+  return err;
+}
+
+esp_err_t esp_now_comm_send_find_me(const uint8_t mac[CLIENT_MAC_LEN],
+                                    uint32_t client_id) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  char mac_str[18];
+  esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+  esp_err_t err = send_find_me(mac, client_id);
+  if (err == ESP_OK) {
+    ESP_LOGI(TAG, "unicast FIND_ME to %s client_id=%lu", mac_str,
+             (unsigned long)client_id);
+  } else {
+    ESP_LOGW(TAG, "unicast FIND_ME to %s failed: %s", mac_str,
+             esp_err_to_name(err));
+  }
+  return err;
+}
+
+esp_err_t esp_now_comm_send_led_ring(const uint8_t mac[CLIENT_MAC_LEN],
+                                     uint32_t client_id,
+                                     const alox_LedRingProgressRequest *req) {
+  if (mac == NULL || !esp_now_core_is_master() || req == NULL) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  char mac_str[18];
+  esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+  esp_err_t err = send_led_ring(mac, client_id, req);
+  if (err == ESP_OK) {
+    ESP_LOGI(TAG, "unicast LED_RING mode %lu to %s client_id=%lu",
+             (unsigned long)req->mode, mac_str, (unsigned long)client_id);
+  } else {
+    ESP_LOGW(TAG, "unicast LED_RING to %s failed: %s", mac_str,
+             esp_err_to_name(err));
+  }
+  return err;
+}
+
+esp_err_t esp_now_comm_send_unicast_test(const uint8_t mac[CLIENT_MAC_LEN],
+                                         uint32_t seq) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  char mac_str[18];
+  esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+  esp_err_t err = send_unicast_test(mac, seq);
+  if (err == ESP_OK) {
+    ESP_LOGI(TAG, "unicast TEST to %s seq=%lu", mac_str, (unsigned long)seq);
+  } else {
+    ESP_LOGW(TAG, "unicast TEST to %s failed: %s", mac_str, esp_err_to_name(err));
+  }
+  return err;
+}
+
+esp_err_t esp_now_comm_echo_ping(const uint8_t mac[CLIENT_MAC_LEN],
+                                 uint64_t timestamp_us,
+                                 esp_now_echo_ping_result_t *result) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  if (echo_ping_init() != ESP_OK) {
+    return ESP_ERR_NO_MEM;
+  }
+
+  xSemaphoreTake(s_echo_pong_sem, 0);
+  s_echo_waiting = true;
+  s_echo_expect_ts = timestamp_us;
+  s_echo_esp_rtt_us = 0;
+  memcpy(s_echo_expect_mac, mac, ESP_NOW_ETH_ALEN);
+
+  uint64_t master_time_us = (uint64_t)esp_timer_get_time();
+  esp_err_t err = send_echo_ping(mac, timestamp_us, master_time_us);
+  if (err != ESP_OK) {
+    s_echo_waiting = false;
+    return err;
+  }
+
+  if (xSemaphoreTake(s_echo_pong_sem,
+                     pdMS_TO_TICKS(ESPNOW_ECHO_PING_TIMEOUT_MS)) != pdTRUE) {
+    s_echo_waiting = false;
+    char mac_str[18];
+    esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+    ESP_LOGW(ECHO_PING_TAG,
+             "ESP-NOW PONG timeout to %s host_ts=%llu",
+             mac_str, (unsigned long long)timestamp_us);
+    return ESP_ERR_TIMEOUT;
+  }
+
+  s_echo_waiting = false;
+  if (result != NULL) {
+    result->echoed_us = timestamp_us;
+    result->esp_rtt_us = s_echo_esp_rtt_us;
+  }
+  return ESP_OK;
+}
+
+esp_err_t esp_now_comm_send_accel_stream(const uint8_t mac[CLIENT_MAC_LEN],
+                                         uint32_t client_id, bool enable) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  char mac_str[18];
+  esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+  esp_err_t err = send_accel_stream(mac, client_id, enable);
+  if (err == ESP_OK) {
+    ESP_LOGI(TAG, "unicast SET_ACCEL_STREAM to %s: %s client_id=%lu", mac_str,
+             enable ? "on" : "off", (unsigned long)client_id);
+  } else {
+    ESP_LOGW(TAG, "unicast SET_ACCEL_STREAM to %s failed: %s", mac_str,
+             esp_err_to_name(err));
+  }
+  return err;
+}
+
+esp_err_t esp_now_comm_send_tap_notify(const uint8_t mac[CLIENT_MAC_LEN],
+                                       uint32_t client_id, bool single,
+                                       bool double_tap, bool triple) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  char mac_str[18];
+  esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+  esp_err_t err =
+      send_tap_notify(mac, client_id, single, double_tap, triple);
+  if (err == ESP_OK) {
+    ESP_LOGI(TAG,
+             "unicast SET_TAP_NOTIFY to %s: single=%d double=%d triple=%d "
+             "client_id=%lu",
+             mac_str, single, double_tap, triple, (unsigned long)client_id);
+  } else {
+    ESP_LOGW(TAG, "unicast SET_TAP_NOTIFY to %s failed: %s", mac_str,
+             esp_err_to_name(err));
+  }
+  return err;
+}
+
+esp_err_t esp_now_comm_send_accel_deadzone(const uint8_t mac[CLIENT_MAC_LEN],
+                                           uint32_t client_id,
+                                           uint32_t deadzone) {
+  if (mac == NULL || !esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  char mac_str[18];
+  esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+  esp_err_t err = send_accel_deadzone(mac, client_id, deadzone);
+  if (err == ESP_OK) {
+    ESP_LOGI(TAG, "unicast SET_ACCEL_DEADZONE to %s: deadzone=%lu client_id=%lu",
+             mac_str, (unsigned long)deadzone, (unsigned long)client_id);
+  } else {
+    ESP_LOGW(TAG, "unicast SET_ACCEL_DEADZONE to %s failed: %s", mac_str,
+             esp_err_to_name(err));
+  }
+  return err;
+}
+
+static void handle_accel_sample(const uint8_t mac[CLIENT_MAC_LEN],
+                                const alox_EspNowAccelSample *sample) {
+  if (sample == NULL) {
+    return;
+  }
+  esp_err_t err = client_registry_update_accel(
+      mac, sample->slave_id, (int16_t)sample->x, (int16_t)sample->y,
+      (int16_t)sample->z);
+  if (err == ESP_ERR_NOT_FOUND) {
+    return;
+  }
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "accel sample id mismatch from %02x:…:%02x", mac[0], mac[5]);
+  }
+}
+
+static void handle_tap_event(const uint8_t mac[CLIENT_MAC_LEN],
+                             const alox_EspNowTapEvent *event) {
+  if (event == NULL) {
+    return;
+  }
+  esp_err_t err =
+      client_registry_update_tap(mac, event->slave_id, event->kind);
+  if (err == ESP_ERR_NOT_FOUND) {
+    return;
+  }
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "tap event id=%lu kind=%lu rejected from %02x:…:%02x",
+             (unsigned long)event->slave_id, (unsigned long)event->kind, mac[0],
+             mac[5]);
+  }
+}
+
+static void handle_battery_report(const uint8_t mac[CLIENT_MAC_LEN],
+                                  const alox_EspNowBatteryReport *report) {
+  if (report == NULL) {
+    return;
+  }
+  esp_err_t err = client_registry_update_battery(
+      mac, report->client_id, report->lipo1_valid, report->lipo1_mv,
+      report->lipo2_valid, report->lipo2_mv);
+  if (err == ESP_ERR_NOT_FOUND) {
+    ESP_LOGW(TAG, "battery report from unregistered slave id=%lu",
+             (unsigned long)report->client_id);
+    return;
+  }
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "battery report id=%lu rejected: %s",
+             (unsigned long)report->client_id, esp_err_to_name(err));
+    return;
+  }
+  ESP_LOGI(TAG, "battery cached id=%lu L1=%s %lu mV L2=%s %lu mV",
+           (unsigned long)report->client_id,
+           report->lipo1_valid ? "ok" : "n/a",
+           (unsigned long)report->lipo1_mv, report->lipo2_valid ? "ok" : "n/a",
+           (unsigned long)report->lipo2_mv);
+}
+
+static void handle_client_presence(const alox_EspNowSlavePresence *presence,
+                                   const uint8_t mac[CLIENT_MAC_LEN]) {
+  if (presence->network != esp_now_core_network()) {
+    return;
+  }
+
+  esp_now_core_ensure_peer(mac);
+
+  bool is_new = false;
+  bool reactivated = false;
+  esp_err_t err = client_registry_heartbeat(
+      mac, presence->slave_id, presence->version, presence->used, &is_new,
+      &reactivated);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "client registry full");
+    return;
+  }
+
+  char mac_str[18];
+  esp_now_core_mac_to_str(mac, mac_str, sizeof(mac_str));
+  if (is_new) {
+    ESP_LOGI(TAG, "client registered id=%lu mac=%s ver=%lu",
+             (unsigned long)presence->slave_id, mac_str,
+             (unsigned long)presence->version);
+  } else if (reactivated) {
+    ESP_LOGI(TAG, "client reconnected id=%lu mac=%s",
+             (unsigned long)presence->slave_id, mac_str);
+  }
+}
+
+void esp_now_master_on_recv(const esp_now_recv_info_t *info, const uint8_t *data,
+                            int len) {
+  if (info == NULL || data == NULL || len <= 0) {
+    return;
+  }
+
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  if (esp_now_proto_decode(data, (size_t)len, &msg) != ESP_OK) {
+    ESP_LOGW(TAG, "decode failed (%d bytes)", len);
+    return;
+  }
+
+  if (ota_espnow_distribution_active()) {
+    if (msg.which_payload == alox_EspNowMessage_ota_status_tag) {
+      esp_now_core_ensure_peer(info->src_addr);
+      ota_espnow_master_on_status(info->src_addr, &msg.payload.ota_status);
+    }
+    return;
+  }
+
+  if (msg.which_payload == alox_EspNowMessage_ota_status_tag) {
+    esp_now_core_ensure_peer(info->src_addr);
+    ota_espnow_master_on_status(info->src_addr, &msg.payload.ota_status);
+    return;
+  }
+
+  if (msg.which_payload == alox_EspNowMessage_accel_sample_tag) {
+    esp_now_core_ensure_peer(info->src_addr);
+    handle_accel_sample(info->src_addr, &msg.payload.accel_sample);
+    return;
+  }
+
+  if (msg.which_payload == alox_EspNowMessage_tap_event_tag) {
+    esp_now_core_ensure_peer(info->src_addr);
+    handle_tap_event(info->src_addr, &msg.payload.tap_event);
+    return;
+  }
+
+  if (msg.which_payload == alox_EspNowMessage_battery_report_tag) {
+    esp_now_core_ensure_peer(info->src_addr);
+    handle_battery_report(info->src_addr, &msg.payload.battery_report);
+    return;
+  }
+
+  if (msg.which_payload == alox_EspNowMessage_echo_pong_tag) {
+    esp_now_core_ensure_peer(info->src_addr);
+    echo_ping_on_pong(info->src_addr, &msg.payload.echo_pong);
+    return;
+  }
+
+  if (msg.type == alox_EspNowMessageType_ESPNOW_BATTERY_REPORT &&
+      msg.which_payload != alox_EspNowMessage_battery_report_tag) {
+    ESP_LOGW(TAG, "BATTERY_REPORT type but which=%u", msg.which_payload);
+  }
+
+  const alox_EspNowSlavePresence *presence = esp_now_proto_get_presence(&msg);
+  if (presence != NULL) {
+    esp_now_core_ensure_peer(info->src_addr);
+    handle_client_presence(presence, info->src_addr);
+  }
+}
+
+static void discover_task(void *param) {
+  (void)param;
+
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_DISCOVER;
+  msg.which_payload = alox_EspNowMessage_discover_tag;
+  msg.payload.discover.network = esp_now_core_network();
+
+  ESP_LOGI(TAG, "discover on network %u ch %u", (unsigned)esp_now_core_network(),
+           (unsigned)esp_now_core_wifi_channel());
+
+  while (1) {
+    msg.payload.discover.master_ota_pending = ota_session_busy();
+    if (!ota_espnow_distribution_active()) {
+      esp_now_core_send_fast(ESPNOW_BCAST, &msg);
+    }
+    vTaskDelay(pdMS_TO_TICKS(ESPNOW_DISCOVER_INTERVAL_MS));
+  }
+}
+
+static void monitor_task(void *param) {
+  (void)param;
+  uint32_t last_local_battery_ms = 0;
+
+  ESP_LOGI(TAG, "monitor (client timeout %u ms)",
+           (unsigned)ESPNOW_CLIENT_TIMEOUT_MS);
+
+  board_lipo_reading_t reading;
+  board_input_read_lipo(&reading);
+  client_registry_set_master_battery(&reading);
+  last_local_battery_ms = esp_now_core_now_ms();
+
+  while (1) {
+    vTaskDelay(pdMS_TO_TICKS(ESPNOW_HEARTBEAT_INTERVAL_MS));
+    client_registry_check_timeouts(ESPNOW_CLIENT_TIMEOUT_MS);
+
+    uint32_t t = esp_now_core_now_ms();
+    if (t - last_local_battery_ms >= ESPNOW_BATTERY_INTERVAL_MS) {
+      board_input_read_lipo(&reading);
+      client_registry_set_master_battery(&reading);
+      last_local_battery_ms = t;
+    }
+  }
+}
+
+esp_err_t esp_now_master_start(void) {
+  ESP_ERROR_CHECK(esp_now_core_ensure_broadcast_peer());
+
+  if (xTaskCreate(discover_task, "espnow_disc", 4096, NULL, 4, NULL) != pdPASS) {
+    ESP_LOGE(TAG, "failed to create discover task");
+    return ESP_FAIL;
+  }
+  if (xTaskCreate(monitor_task, "espnow_mon", 4096, NULL, 4, NULL) != pdPASS) {
+    ESP_LOGE(TAG, "failed to create monitor task");
+    return ESP_FAIL;
+  }
+  return ESP_OK;
+}

main/esp_now_master.h

@@ -0,0 +1,11 @@
+#ifndef ESP_NOW_MASTER_H
+#define ESP_NOW_MASTER_H
+
+#include "esp_err.h"
+#include "esp_now.h"
+
+esp_err_t esp_now_master_start(void);
+void esp_now_master_on_recv(const esp_now_recv_info_t *info, const uint8_t *data,
+                            int len);
+
+#endif

main/esp_now_slave.c

@@ -0,0 +1,646 @@
+#include "esp_now_slave.h"
+#include "bosch456.h"
+#include "cmd_led_ring.h"
+#include "esp_now_comm.h"
+#include "esp_now_core.h"
+#include "esp_now_proto.h"
+#include "board_input.h"
+#include "led_ring.h"
+#include "ota_espnow.h"
+#include "ota_uart.h"
+#include "pod_reboot.h"
+#include "pod_settings.h"
+#include "esp_log.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/idf_additions.h"
+#include <string.h>
+
+#ifndef POWERPOD_FW_VERSION
+#define POWERPOD_FW_VERSION 1u
+#endif
+
+#define ESPNOW_HEARTBEAT_INTERVAL_MS 1000
+#define SLAVE_MASTER_LOST_MS (ESPNOW_HEARTBEAT_INTERVAL_MS * 5)
+/** While master or slave OTA is in progress (discover may be sparse). */
+#define SLAVE_MASTER_OTA_GRACE_MS 300000u
+#define ESPNOW_ACCEL_INTERVAL_MS 16
+#define ESPNOW_BATTERY_INTERVAL_MS 30000
+#define SLAVE_BATTERY_AFTER_JOIN_MS 150
+
+static const char *TAG = "[ESPNOW_S]";
+
+static bool s_joined;
+static bool s_master_ota_grace;
+static bool s_accel_stream_enabled;
+static bool s_tap_notify_single;
+static bool s_tap_notify_double;
+static bool s_tap_notify_triple;
+static uint8_t s_master_mac[ESP_NOW_ETH_ALEN];
+static uint32_t s_last_discover_ms;
+
+typedef enum {
+  SLAVE_TX_SLAVE_INFO = 1,
+  SLAVE_TX_BATTERY,
+} slave_tx_op_t;
+
+static QueueHandle_t s_tx_queue;
+
+static bool from_joined_master(const uint8_t *master_mac) {
+  return s_joined && esp_now_core_mac_equal(master_mac, s_master_mac);
+}
+
+static void fill_presence(alox_EspNowSlavePresence *presence) {
+  const uint8_t *own = esp_now_core_own_mac();
+  presence->network = esp_now_core_network();
+  presence->version = POWERPOD_FW_VERSION;
+  presence->slave_id = own[5];
+  presence->available = true;
+  presence->used = false;
+  esp_now_proto_setup_presence_encode(presence, own);
+}
+
+static void send_presence(const uint8_t *dest_mac, alox_EspNowMessageType type) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  alox_EspNowSlavePresence *presence = NULL;
+
+  msg.type = type;
+  if (type == alox_EspNowMessageType_ESPNOW_SLAVE_INFO) {
+    msg.which_payload = alox_EspNowMessage_slave_info_tag;
+    presence = &msg.payload.slave_info;
+  } else {
+    msg.which_payload = alox_EspNowMessage_heartbeat_tag;
+    presence = &msg.payload.heartbeat;
+  }
+  fill_presence(presence);
+  esp_now_core_send(dest_mac, &msg);
+}
+
+static esp_err_t send_accel_sample(const uint8_t *dest_mac, uint32_t slave_id,
+                                   int16_t x, int16_t y, int16_t z) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_ACCEL_SAMPLE;
+  msg.which_payload = alox_EspNowMessage_accel_sample_tag;
+  msg.payload.accel_sample.slave_id = slave_id;
+  msg.payload.accel_sample.x = x;
+  msg.payload.accel_sample.y = y;
+  msg.payload.accel_sample.z = z;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+static esp_err_t send_tap_event(const uint8_t *dest_mac, uint32_t slave_id,
+                                uint32_t kind) {
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_TAP_EVENT;
+  msg.which_payload = alox_EspNowMessage_tap_event_tag;
+  msg.payload.tap_event.slave_id = slave_id;
+  msg.payload.tap_event.kind = kind;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+static esp_err_t send_battery_report(const uint8_t *dest_mac,
+                                     const alox_EspNowBatteryReport *report) {
+  if (report == NULL) {
+    return ESP_ERR_INVALID_ARG;
+  }
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_BATTERY_REPORT;
+  msg.which_payload = alox_EspNowMessage_battery_report_tag;
+  msg.payload.battery_report = *report;
+  return esp_now_core_send(dest_mac, &msg);
+}
+
+static uint32_t slave_master_lost_ms(void) {
+  if (ota_uart_is_active() || s_master_ota_grace) {
+    return SLAVE_MASTER_OTA_GRACE_MS;
+  }
+  return SLAVE_MASTER_LOST_MS;
+}
+
+static void touch_master_presence(uint32_t now) { s_last_discover_ms = now; }
+
+static void reset_join(void) {
+  s_joined = false;
+  s_master_ota_grace = false;
+  s_accel_stream_enabled = false;
+  memset(s_master_mac, 0, sizeof(s_master_mac));
+  s_last_discover_ms = 0;
+  if (s_tx_queue != NULL) {
+    xQueueReset(s_tx_queue);
+  }
+}
+
+static void queue_tx(slave_tx_op_t op) {
+  if (s_tx_queue == NULL) {
+    return;
+  }
+  if (xQueueSend(s_tx_queue, &op, 0) != pdTRUE) {
+    ESP_LOGW(TAG, "tx queue full (op=%d)", (int)op);
+  }
+}
+
+static void send_battery_to_master(void) {
+  if (!s_joined) {
+    return;
+  }
+
+  board_lipo_reading_t reading;
+  board_input_read_lipo(&reading);
+
+  alox_EspNowBatteryReport report = alox_EspNowBatteryReport_init_zero;
+  report.client_id = esp_now_core_own_mac()[5];
+  report.lipo1_valid = reading.lipo1_valid;
+  report.lipo2_valid = reading.lipo2_valid;
+  report.lipo1_mv = reading.lipo1_mv;
+  report.lipo2_mv = reading.lipo2_mv;
+
+  esp_err_t err = send_battery_report(s_master_mac, &report);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "battery report send failed id=%lu: %s",
+             (unsigned long)report.client_id, esp_err_to_name(err));
+  } else {
+    ESP_LOGI(TAG, "battery report sent id=%lu L1=%s %lu mV L2=%s %lu mV",
+             (unsigned long)report.client_id,
+             report.lipo1_valid ? "ok" : "n/a",
+             (unsigned long)report.lipo1_mv,
+             report.lipo2_valid ? "ok" : "n/a",
+             (unsigned long)report.lipo2_mv);
+  }
+}
+
+esp_err_t esp_now_comm_send_ota_status(const uint8_t master_mac[CLIENT_MAC_LEN],
+                                       uint32_t status, uint32_t bytes_written,
+                                       uint32_t error) {
+  if (master_mac == NULL || esp_now_core_is_master()) {
+    return ESP_ERR_INVALID_STATE;
+  }
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_OTA_STATUS;
+  msg.which_payload = alox_EspNowMessage_ota_status_tag;
+  msg.payload.ota_status.status = status;
+  msg.payload.ota_status.bytes_written = bytes_written;
+  msg.payload.ota_status.error = error;
+  return esp_now_core_send_wait(master_mac, &msg);
+}
+
+bool esp_now_comm_get_master_mac(uint8_t mac_out[CLIENT_MAC_LEN]) {
+  return esp_now_slave_get_master_mac(mac_out);
+}
+
+bool esp_now_slave_get_master_mac(uint8_t mac_out[CLIENT_MAC_LEN]) {
+  if (mac_out == NULL || !s_joined) {
+    return false;
+  }
+  memcpy(mac_out, s_master_mac, CLIENT_MAC_LEN);
+  return true;
+}
+
+static void tx_task(void *param) {
+  (void)param;
+  slave_tx_op_t op;
+
+  ESP_LOGI(TAG, "deferred tx task ready");
+
+  while (1) {
+    if (xQueueReceive(s_tx_queue, &op, portMAX_DELAY) != pdTRUE) {
+      continue;
+    }
+    if (!s_joined) {
+      continue;
+    }
+    switch (op) {
+    case SLAVE_TX_SLAVE_INFO:
+      send_presence(s_master_mac, alox_EspNowMessageType_ESPNOW_SLAVE_INFO);
+      break;
+    case SLAVE_TX_BATTERY:
+      vTaskDelay(pdMS_TO_TICKS(SLAVE_BATTERY_AFTER_JOIN_MS));
+      send_battery_to_master();
+      break;
+    default:
+      break;
+    }
+  }
+}
+
+static void handle_unicast_test(const uint8_t *master_mac,
+                                const alox_EspNowUnicastTest *test) {
+  char mac_str[18];
+  esp_now_core_mac_to_str(master_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(TAG, "UNICAST TEST OK from master %s seq=%lu (joined=%d)", mac_str,
+           (unsigned long)test->seq, (int)s_joined);
+}
+
+static void handle_echo_ping(const uint8_t *master_mac,
+                             const alox_EspNowEchoPing *ping) {
+  if (ping == NULL || !s_joined ||
+      !esp_now_core_mac_equal(master_mac, s_master_mac)) {
+    return;
+  }
+
+  char mac_str[18];
+  esp_now_core_mac_to_str(master_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(TAG, "ESP-NOW PING recv from %s host_ts=%llu master_time_us=%llu",
+           mac_str, (unsigned long long)ping->host_timestamp_us,
+           (unsigned long long)ping->master_time_us);
+
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  msg.type = alox_EspNowMessageType_ESPNOW_ECHO_PONG;
+  msg.which_payload = alox_EspNowMessage_echo_pong_tag;
+  msg.payload.echo_pong.host_timestamp_us = ping->host_timestamp_us;
+  msg.payload.echo_pong.master_time_us = ping->master_time_us;
+
+  esp_err_t err = esp_now_core_send_fast(s_master_mac, &msg);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "ECHO PONG send failed: %s", esp_err_to_name(err));
+    return;
+  }
+
+  ESP_LOGI(TAG, "ESP-NOW PONG send to %s host_ts=%llu master_time_us=%llu",
+           mac_str, (unsigned long long)ping->host_timestamp_us,
+           (unsigned long long)ping->master_time_us);
+}
+
+static void handle_restart(const uint8_t *master_mac,
+                           const alox_EspNowRestart *req) {
+  const uint8_t *own = esp_now_core_own_mac();
+  uint32_t my_id = own[5];
+
+  if (req->client_id != 0 && req->client_id != my_id) {
+    return;
+  }
+  if (s_joined && !esp_now_core_mac_equal(master_mac, s_master_mac)) {
+    return;
+  }
+
+  char mac_str[18];
+  esp_now_core_mac_to_str(master_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(TAG, "RESTART from master %s (id=%lu)", mac_str, (unsigned long)my_id);
+  pod_schedule_restart();
+}
+
+static void handle_battery_query(const uint8_t *master_mac,
+                                 const alox_EspNowBatteryQuery *query) {
+  uint32_t my_id = esp_now_core_own_mac()[5];
+  if (query->client_id != 0 && query->client_id != my_id) {
+    return;
+  }
+  if (s_joined && !esp_now_core_mac_equal(master_mac, s_master_mac)) {
+    return;
+  }
+  send_battery_to_master();
+}
+
+static void handle_led_ring(const uint8_t *master_mac,
+                            const alox_EspNowLedRing *msg) {
+  uint32_t my_id = esp_now_core_own_mac()[5];
+  if (msg->client_id != 0 && msg->client_id != my_id) {
+    return;
+  }
+  if (s_joined && !esp_now_core_mac_equal(master_mac, s_master_mac)) {
+    return;
+  }
+
+  alox_LedRingProgressRequest req = alox_LedRingProgressRequest_init_zero;
+  req.mode = msg->mode;
+  req.progress = msg->progress;
+  req.digit = msg->digit;
+  req.r = msg->r;
+  req.g = msg->g;
+  req.b = msg->b;
+  req.intensity = msg->intensity;
+  req.blink_ms = msg->blink_ms;
+  req.blink_count = msg->blink_count;
+
+  char mac_str[18];
+  esp_now_core_mac_to_str(master_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(TAG, "LED_RING mode %lu from master %s (id=%lu)",
+           (unsigned long)req.mode, mac_str, (unsigned long)my_id);
+  cmd_led_ring_apply(&req);
+}
+
+static void handle_find_me(const uint8_t *master_mac, const alox_EspNowFindMe *req) {
+  uint32_t my_id = esp_now_core_own_mac()[5];
+  if (req->client_id != 0 && req->client_id != my_id) {
+    return;
+  }
+  if (s_joined && !esp_now_core_mac_equal(master_mac, s_master_mac)) {
+    return;
+  }
+  char mac_str[18];
+  esp_now_core_mac_to_str(master_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(TAG, "FIND_ME from master %s (id=%lu)", mac_str, (unsigned long)my_id);
+  led_ring_find_me();
+}
+
+static void handle_accel_stream(const uint8_t *master_mac,
+                                const alox_EspNowAccelStream *cfg) {
+  uint32_t my_id = esp_now_core_own_mac()[5];
+  if (cfg->client_id != 0 && cfg->client_id != my_id) {
+    return;
+  }
+  if (s_joined && !esp_now_core_mac_equal(master_mac, s_master_mac)) {
+    return;
+  }
+  s_accel_stream_enabled = cfg->enable;
+  char mac_str[18];
+  esp_now_core_mac_to_str(master_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(TAG, "accel stream %s from master %s (id=%lu)",
+           cfg->enable ? "on" : "off", mac_str, (unsigned long)my_id);
+}
+
+static void handle_tap_notify(const uint8_t *master_mac,
+                              const alox_EspNowTapNotify *cfg) {
+  uint32_t my_id = esp_now_core_own_mac()[5];
+  if (cfg->client_id != 0 && cfg->client_id != my_id) {
+    return;
+  }
+  if (s_joined && !esp_now_core_mac_equal(master_mac, s_master_mac)) {
+    return;
+  }
+  s_tap_notify_single = cfg->single;
+  s_tap_notify_double = cfg->double_tap;
+  s_tap_notify_triple = cfg->triple;
+  char mac_str[18];
+  esp_now_core_mac_to_str(master_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(TAG,
+           "tap notify single=%d double=%d triple=%d from master %s (id=%lu)",
+           cfg->single, cfg->double_tap, cfg->triple, mac_str,
+           (unsigned long)my_id);
+}
+
+static void handle_accel_deadzone(const uint8_t *master_mac,
+                                  const alox_EspNowAccelDeadzone *cfg) {
+  uint32_t my_id = esp_now_core_own_mac()[5];
+  if (cfg->client_id != 0 && cfg->client_id != my_id) {
+    return;
+  }
+  if (s_joined && !esp_now_core_mac_equal(master_mac, s_master_mac)) {
+    return;
+  }
+  char mac_str[18];
+  esp_now_core_mac_to_str(master_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(TAG,
+           "accel deadzone from master %s: %lu LSB id=%lu (sensor %s)", mac_str,
+           (unsigned long)cfg->deadzone, (unsigned long)my_id,
+           bma456_is_ready() ? "ok" : "not installed");
+  bma456_set_accel_deadzone(cfg->deadzone);
+  if (pod_settings_save_accel_deadzone(cfg->deadzone) != ESP_OK) {
+    ESP_LOGW(TAG, "deadzone %lu applied but not saved to NVS",
+             (unsigned long)cfg->deadzone);
+  }
+}
+
+static void handle_discover(const uint8_t *sender_mac,
+                            const alox_EspNowDiscover *discover) {
+  if (discover->network != esp_now_core_network()) {
+    return;
+  }
+
+  uint32_t now = esp_now_core_now_ms();
+
+  if (s_joined) {
+    if (!esp_now_core_mac_equal(sender_mac, s_master_mac)) {
+      return;
+    }
+    s_master_ota_grace = discover->master_ota_pending;
+    if ((now - s_last_discover_ms) <= slave_master_lost_ms()) {
+      touch_master_presence(now);
+      return;
+    }
+    if (ota_uart_is_active()) {
+      touch_master_presence(now);
+      return;
+    }
+    ESP_LOGW(TAG, "master lost, rejoining");
+    reset_join();
+  }
+
+  memcpy(s_master_mac, sender_mac, ESP_NOW_ETH_ALEN);
+  s_joined = true;
+  s_master_ota_grace = discover->master_ota_pending;
+  touch_master_presence(now);
+  esp_now_core_ensure_peer(sender_mac);
+
+  char mac_str[18];
+  esp_now_core_mac_to_str(sender_mac, mac_str, sizeof(mac_str));
+  ESP_LOGI(TAG, "joined network %u, master %s", (unsigned)discover->network,
+           mac_str);
+
+  queue_tx(SLAVE_TX_SLAVE_INFO);
+  queue_tx(SLAVE_TX_BATTERY);
+}
+
+static void check_master_timeout(void) {
+  if (!s_joined || s_last_discover_ms == 0) {
+    return;
+  }
+  if (ota_uart_is_active()) {
+    return;
+  }
+  uint32_t now = esp_now_core_now_ms();
+  uint32_t limit = slave_master_lost_ms();
+  if ((now - s_last_discover_ms) > limit) {
+    ESP_LOGW(TAG, "no master discover for %u ms (limit %u), reconnecting",
+             (unsigned)(now - s_last_discover_ms), (unsigned)limit);
+    reset_join();
+  }
+}
+
+static void accel_stream_task(void *param) {
+  (void)param;
+  const uint8_t *own = esp_now_core_own_mac();
+
+  ESP_LOGI(TAG, "accel stream task (interval %u ms)",
+           (unsigned)ESPNOW_ACCEL_INTERVAL_MS);
+
+  while (1) {
+    vTaskDelay(pdMS_TO_TICKS(ESPNOW_ACCEL_INTERVAL_MS));
+    if (!s_joined || !s_accel_stream_enabled || !bma456_is_ready()) {
+      continue;
+    }
+    int16_t x = 0;
+    int16_t y = 0;
+    int16_t z = 0;
+    if (bma456_read_accel(&x, &y, &z) != ESP_OK) {
+      continue;
+    }
+    (void)send_accel_sample(s_master_mac, own[5], x, y, z);
+  }
+}
+
+static void on_bma456_tap(bma456_tap_kind_t kind, void *ctx) {
+  (void)ctx;
+  if (!s_joined) {
+    return;
+  }
+  bool enabled = false;
+  switch (kind) {
+  case BMA456_TAP_SINGLE:
+    enabled = s_tap_notify_single;
+    break;
+  case BMA456_TAP_DOUBLE:
+    enabled = s_tap_notify_double;
+    break;
+  case BMA456_TAP_TRIPLE:
+    enabled = s_tap_notify_triple;
+    break;
+  default:
+    return;
+  }
+  if (!enabled) {
+    return;
+  }
+  (void)send_tap_event(s_master_mac, esp_now_core_own_mac()[5], (uint32_t)kind);
+}
+
+static void heartbeat_task(void *param) {
+  (void)param;
+  uint32_t last_battery_ms = 0;
+
+  ESP_LOGI(TAG, "heartbeat task (interval %u ms)",
+           (unsigned)ESPNOW_HEARTBEAT_INTERVAL_MS);
+
+  while (1) {
+    vTaskDelay(pdMS_TO_TICKS(ESPNOW_HEARTBEAT_INTERVAL_MS));
+    check_master_timeout();
+    if (!s_joined) {
+      last_battery_ms = 0;
+      continue;
+    }
+    send_presence(s_master_mac, alox_EspNowMessageType_ESPNOW_HEARTBEAT);
+    uint32_t now = esp_now_core_now_ms();
+    if (last_battery_ms == 0 ||
+        (now - last_battery_ms) >= ESPNOW_BATTERY_INTERVAL_MS) {
+      send_battery_to_master();
+      last_battery_ms = now;
+    }
+  }
+}
+
+void esp_now_slave_on_recv(const esp_now_recv_info_t *info, const uint8_t *data,
+                           int len) {
+  if (info == NULL || data == NULL || len <= 0) {
+    return;
+  }
+
+  alox_EspNowMessage msg = alox_EspNowMessage_init_zero;
+  if (esp_now_proto_decode(data, (size_t)len, &msg) != ESP_OK) {
+    ESP_LOGW(TAG, "decode failed (%d bytes)", len);
+    return;
+  }
+
+  if (from_joined_master(info->src_addr)) {
+    esp_now_core_ensure_peer(info->src_addr);
+  }
+
+  if (ota_uart_is_active()) {
+    switch (msg.which_payload) {
+    case alox_EspNowMessage_discover_tag:
+      handle_discover(info->src_addr, &msg.payload.discover);
+      break;
+    case alox_EspNowMessage_ota_start_tag:
+    case alox_EspNowMessage_ota_payload_tag:
+    case alox_EspNowMessage_ota_end_tag:
+      if (!from_joined_master(info->src_addr)) {
+        break;
+      }
+      touch_master_presence(esp_now_core_now_ms());
+      if (msg.which_payload == alox_EspNowMessage_ota_start_tag) {
+        ota_espnow_slave_on_start(info->src_addr, &msg.payload.ota_start);
+      } else if (msg.which_payload == alox_EspNowMessage_ota_payload_tag) {
+        ota_espnow_slave_on_payload(info->src_addr, &msg.payload.ota_payload);
+      } else {
+        ota_espnow_slave_on_end(info->src_addr);
+      }
+      break;
+    default:
+      break;
+    }
+    return;
+  }
+
+  switch (msg.which_payload) {
+  case alox_EspNowMessage_discover_tag:
+    handle_discover(info->src_addr, &msg.payload.discover);
+    break;
+  case alox_EspNowMessage_unicast_test_tag:
+    if (from_joined_master(info->src_addr)) {
+      handle_unicast_test(info->src_addr, &msg.payload.unicast_test);
+    }
+    break;
+  case alox_EspNowMessage_echo_ping_tag:
+    if (from_joined_master(info->src_addr)) {
+      handle_echo_ping(info->src_addr, &msg.payload.echo_ping);
+    }
+    break;
+  case alox_EspNowMessage_accel_deadzone_tag:
+    if (from_joined_master(info->src_addr)) {
+      handle_accel_deadzone(info->src_addr, &msg.payload.accel_deadzone);
+    }
+    break;
+  case alox_EspNowMessage_accel_stream_tag:
+    if (from_joined_master(info->src_addr)) {
+      handle_accel_stream(info->src_addr, &msg.payload.accel_stream);
+    }
+    break;
+  case alox_EspNowMessage_tap_notify_tag:
+    if (from_joined_master(info->src_addr)) {
+      handle_tap_notify(info->src_addr, &msg.payload.tap_notify);
+    }
+    break;
+  case alox_EspNowMessage_battery_query_tag:
+    if (from_joined_master(info->src_addr)) {
+      handle_battery_query(info->src_addr, &msg.payload.battery_query);
+    }
+    break;
+  case alox_EspNowMessage_led_ring_tag:
+    if (from_joined_master(info->src_addr)) {
+      handle_led_ring(info->src_addr, &msg.payload.led_ring);
+    }
+    break;
+  case alox_EspNowMessage_find_me_tag:
+    if (from_joined_master(info->src_addr)) {
+      handle_find_me(info->src_addr, &msg.payload.find_me);
+    }
+    break;
+  case alox_EspNowMessage_restart_tag:
+    if (from_joined_master(info->src_addr)) {
+      handle_restart(info->src_addr, &msg.payload.restart);
+    }
+    break;
+  case alox_EspNowMessage_ota_start_tag:
+    if (from_joined_master(info->src_addr)) {
+      ota_espnow_slave_on_start(info->src_addr, &msg.payload.ota_start);
+    }
+    break;
+  default:
+    ESP_LOGW(TAG, "unhandled which=%u type=%u", msg.which_payload,
+             (unsigned)msg.type);
+    break;
+  }
+}
+
+esp_err_t esp_now_slave_start(void) {
+  reset_join();
+
+  s_tx_queue = xQueueCreate(4, sizeof(slave_tx_op_t));
+  if (s_tx_queue == NULL) {
+    ESP_LOGE(TAG, "failed to create tx queue");
+    return ESP_ERR_NO_MEM;
+  }
+  if (xTaskCreate(tx_task, "espnow_stx", 4096, NULL, 5, NULL) != pdPASS) {
+    ESP_LOGE(TAG, "failed to create tx task");
+    return ESP_FAIL;
+  }
+  if (xTaskCreate(heartbeat_task, "espnow_hb", 4096, NULL, 4, NULL) != pdPASS) {
+    ESP_LOGE(TAG, "failed to create heartbeat task");
+    return ESP_FAIL;
+  }
+  if (xTaskCreate(accel_stream_task, "espnow_accel", 4096, NULL, 5, NULL) !=
+      pdPASS) {
+    ESP_LOGE(TAG, "failed to create accel stream task");
+    return ESP_FAIL;
+  }
+  ota_espnow_slave_init();
+  bma456_set_tap_handler(on_bma456_tap, NULL);
+  return ESP_OK;
+}

main/esp_now_slave.h

@@ -0,0 +1,14 @@
+#ifndef ESP_NOW_SLAVE_H
+#define ESP_NOW_SLAVE_H
+
+#include "client_registry.h"
+#include "esp_err.h"
+#include "esp_now.h"
+
+esp_err_t esp_now_slave_start(void);
+void esp_now_slave_on_recv(const esp_now_recv_info_t *info, const uint8_t *data,
+                           int len);
+
+bool esp_now_slave_get_master_mac(uint8_t mac_out[CLIENT_MAC_LEN]);
+
+#endif

main/led_ring.c

@@ -5,6 +5,7 @@
 #include "esp_log.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
+#include "freertos/semphr.h"
 #include "led_strip.h"
 #include <stdint.h>
 
@@ -23,8 +24,12 @@ static led_strip_handle_t led_ring;
 #define LED_RING_FIND_ME_ON_MS 300
 #define LED_RING_FIND_ME_OFF_MS 150
 #define LED_RING_FIND_ME_BLINKS_PER_COLOR 3
+#define LED_RING_BATTERY_LOW_R 255
+#define LED_RING_BATTERY_LOW_G 0
+#define LED_RING_BATTERY_LOW_B 0
 
 static QueueHandle_t led_queue;
+static SemaphoreHandle_t s_battery_low_done;
 
 // Led Matrix Maps
 const uint8_t d0[] = {46, 47, 60, 61, 62, 75, 78, 79,
@@ -145,6 +150,22 @@ void vTaskLedRing(void *pvParameters) {
           }
         }
         continue;
+      } else if (cmd.mode == LED_CMD_BATTERY_LOW) {
+        uint8_t r = LED_RING_BATTERY_LOW_R;
+        uint8_t g = LED_RING_BATTERY_LOW_G;
+        uint8_t b = LED_RING_BATTERY_LOW_B;
+        led_ring_scale_rgb(&r, &g, &b, LED_RING_BATTERY_LOW_INTENSITY);
+        for (uint32_t i = 0; i < LED_RING_BATTERY_LOW_LEDS; i++) {
+          led_strip_set_pixel(led_ring, i, r, g, b);
+        }
+        led_strip_refresh(led_ring);
+        vTaskDelay(pdMS_TO_TICKS(LED_RING_BATTERY_LOW_HOLD_MS));
+        led_strip_clear(led_ring);
+        led_strip_refresh(led_ring);
+        if (s_battery_low_done != NULL) {
+          xSemaphoreGive(s_battery_low_done);
+        }
+        continue;
       }
       led_strip_refresh(led_ring);
     }
@@ -153,12 +174,13 @@ void vTaskLedRing(void *pvParameters) {
 
 void led_ring_init(void) {
   led_queue = xQueueCreate(10, sizeof(led_command_t));
+  s_battery_low_done = xSemaphoreCreateBinary();
   xTaskCreate(vTaskLedRing, "led_task", 4096, NULL, 5, NULL);
 }
 
 void led_ring_send_command(led_command_t *cmd) {
   if (led_queue != NULL) {
-    xQueueSend(led_queue, cmd, portMAX_DELAY);
+    (void)xQueueSend(led_queue, cmd, 0);
   }
 }
 
@@ -224,3 +246,13 @@ void led_ring_find_me(void) {
   led_command_t cmd = {.mode = LED_CMD_FIND_ME};
   led_ring_send_command(&cmd);
 }
+
+void led_ring_show_battery_low(void) {
+  if (led_queue == NULL || s_battery_low_done == NULL) {
+    return;
+  }
+  (void)xSemaphoreTake(s_battery_low_done, 0);
+  led_command_t cmd = {.mode = LED_CMD_BATTERY_LOW};
+  led_ring_send_command(&cmd);
+  (void)xSemaphoreTake(s_battery_low_done, portMAX_DELAY);
+}

main/led_ring.h

@@ -7,6 +7,10 @@
 #define LED_RING_DEFAULT_INTENSITY 13
 /** Full brightness for find-me and similar alerts. */
 #define LED_RING_FULL_INTENSITY 255
+/** ~10 % brightness for battery-low indicator. */
+#define LED_RING_BATTERY_LOW_INTENSITY 26
+#define LED_RING_BATTERY_LOW_LEDS 4
+#define LED_RING_BATTERY_LOW_HOLD_MS 5000
 
 typedef enum {
   LED_CMD_CLEAR,
@@ -14,7 +18,8 @@ typedef enum {
   LED_CMD_SET_COLOR,
   LED_CMD_PROGRESS,
   LED_CMD_BLINK,
-  LED_CMD_FIND_ME
+  LED_CMD_FIND_ME,
+  LED_CMD_BATTERY_LOW
 } led_mode_t;
 
 typedef struct {
@@ -45,4 +50,7 @@ void led_ring_ota_failed(void);
 /** Red / green / blue: 3 blinks each at full intensity. */
 void led_ring_find_me(void);
 
+/** First 4 LEDs red at ~10 % for 5 s, then off (blocking in LED task). */
+void led_ring_show_battery_low(void);
+
 #endif

main/ota_espnow.c

@@ -18,9 +18,9 @@ static const char *TAG = "[OTA_ESPNOW]";
 #define OTA_ESPNOW_PREPARE_PRIO 5
 
 #define OTA_PREPARE_TIMEOUT_MS 120000u
-#define OTA_BLOCK_TIMEOUT_MS 30000u
+#define OTA_BLOCK_TIMEOUT_PER_SLAVE_MS 2000u
+#define OTA_BLOCK_MAX_RETRIES 2u
 #define OTA_END_TIMEOUT_MS 60000u
-#define OTA_PAYLOAD_DELAY_MS 3
 
 #define OTA_ST_PREPARING 1u
 #define OTA_ST_READY 2u
@@ -35,7 +35,29 @@ static const char *TAG = "[OTA_ESPNOW]";
 
 #define OTA_MAX_TARGETS CLIENT_REGISTRY_MAX
 
+/** ~21 payloads per 4 KiB block; headroom for bursts + status/end. */
+#define OTA_SLAVE_WORK_QUEUE_LEN 32
+#define OTA_SLAVE_WORK_STACK 8192
+#define OTA_SLAVE_WORK_PRIO 5
+
+typedef enum {
+  OTA_SLAVE_WORK_STATUS = 1,
+  OTA_SLAVE_WORK_PAYLOAD,
+  OTA_SLAVE_WORK_END,
+} ota_slave_work_op_t;
+
+typedef struct {
+  ota_slave_work_op_t op;
+  uint8_t master_mac[6];
+  uint32_t status;
+  uint32_t bytes_written;
+  uint32_t error;
+  alox_EspNowOtaPayload payload;
+} ota_slave_work_t;
+
 static EventGroupHandle_t s_eg;
+static QueueHandle_t s_slave_work_queue;
+static bool s_distribution_active;
 
 typedef struct {
   uint8_t count;
@@ -152,11 +174,204 @@ static bool wait_target_bits(uint32_t want_bits, uint32_t timeout_ms) {
   return (got & want_bits) == want_bits;
 }
 
+static uint32_t block_ack_timeout_ms(void) {
+  if (s_dist.count == 0) {
+    return OTA_BLOCK_TIMEOUT_PER_SLAVE_MS;
+  }
+  return (uint32_t)s_dist.count * OTA_BLOCK_TIMEOUT_PER_SLAVE_MS;
+}
+
+static void log_missing_block_acks(uint32_t expected_bytes) {
+  if (s_eg == NULL || s_dist.count == 0) {
+    return;
+  }
+  EventBits_t bits = xEventGroupGetBits(s_eg);
+  for (uint8_t i = 0; i < s_dist.count; i++) {
+    uint32_t bit = (1u << (unsigned)i);
+    if (bits & bit) {
+      continue;
+    }
+    const ota_prog_entry_t *e = &s_prog.entries[i];
+    ESP_LOGE(TAG,
+             "slave %lu missing block ack @%lu (last status=%lu bytes=%lu err=%lu)",
+             (unsigned long)s_dist.id[i], (unsigned long)expected_bytes,
+             (unsigned long)e->status, (unsigned long)e->bytes_written,
+             (unsigned long)e->error);
+  }
+}
+
+static esp_err_t send_block_payloads(const uint8_t *block_buf, uint32_t block_len,
+                                     uint32_t *seq_io) {
+  uint32_t sent = 0;
+  while (sent < block_len) {
+    uint32_t chunk = block_len - sent;
+    if (chunk > OTA_UART_HOST_CHUNK_SIZE) {
+      chunk = OTA_UART_HOST_CHUNK_SIZE;
+    }
+
+    for (uint8_t i = 0; i < s_dist.count; i++) {
+      esp_err_t err = esp_now_comm_send_ota_payload(s_dist.mac[i], *seq_io,
+                                                    block_buf + sent, chunk);
+      if (err != ESP_OK) {
+        return err;
+      }
+    }
+    (*seq_io)++;
+    sent += chunk;
+  }
+  return ESP_OK;
+}
+
+bool ota_espnow_distribution_active(void) { return s_distribution_active; }
+
 static void send_slave_status(const uint8_t master_mac[6], uint32_t status,
                               uint32_t bytes_written, uint32_t error) {
   esp_now_comm_send_ota_status(master_mac, status, bytes_written, error);
 }
 
+static bool queue_slave_work(const ota_slave_work_t *work) {
+  if (work == NULL || s_slave_work_queue == NULL) {
+    return false;
+  }
+  if (xQueueSend(s_slave_work_queue, work, 0) != pdTRUE) {
+    ESP_LOGW(TAG, "slave OTA work queue full (op=%d)", (int)work->op);
+    return false;
+  }
+  return true;
+}
+
+static void queue_slave_status(const uint8_t master_mac[6], uint32_t status,
+                               uint32_t bytes_written, uint32_t error) {
+  ota_slave_work_t work = {
+      .op = OTA_SLAVE_WORK_STATUS,
+      .status = status,
+      .bytes_written = bytes_written,
+      .error = error,
+  };
+  memcpy(work.master_mac, master_mac, 6);
+  (void)queue_slave_work(&work);
+}
+
+static void process_slave_payload(const uint8_t master_mac[6],
+                                  const alox_EspNowOtaPayload *payload) {
+  if (payload == NULL || payload->data.size == 0) {
+    send_slave_status(master_mac, OTA_ST_FAILED, 0, 11);
+    return;
+  }
+
+  if (!ota_uart_is_active()) {
+    ESP_LOGW(TAG, "OTA_PAYLOAD seq=%lu but no active session",
+             (unsigned long)payload->seq);
+    send_slave_status(master_mac, OTA_ST_FAILED, 0, 12);
+    return;
+  }
+
+  if (payload->seq == 0) {
+    ESP_LOGI(TAG, "ESP-NOW OTA payloads started");
+  }
+
+  ota_feed_result_t r = ota_uart_feed_chunk(payload->seq, payload->data.bytes,
+                                            payload->data.size);
+  if (r == OTA_FEED_SEQ_GAP) {
+    led_ring_ota_failed();
+    send_slave_status(master_mac, OTA_ST_FAILED, ota_uart_bytes_written(), 16);
+    return;
+  }
+  if (r == OTA_FEED_SEQ_DUP) {
+    if (ota_uart_block_ready_for_reack()) {
+      send_slave_status(master_mac, OTA_ST_BLOCK_ACK, ota_uart_bytes_written(),
+                        0);
+    }
+    return;
+  }
+  if (r == OTA_FEED_ERROR) {
+    led_ring_ota_failed();
+    send_slave_status(master_mac, OTA_ST_FAILED, ota_uart_bytes_written(), 13);
+    return;
+  }
+  if (r == OTA_FEED_BLOCK_WRITTEN) {
+    uint32_t written = ota_uart_bytes_written();
+    uint32_t total = ota_uart_total_size();
+    ESP_LOGI(TAG, "block written %lu bytes -> ack master", (unsigned long)written);
+    led_ring_show_ota_progress(written, total, OTA_LED_ESPNOW_RX_R, OTA_LED_ESPNOW_RX_G,
+                               OTA_LED_ESPNOW_RX_B);
+    send_slave_status(master_mac, OTA_ST_BLOCK_ACK, written, 0);
+    return;
+  }
+
+  if (r == OTA_FEED_OK) {
+    uint32_t total = ota_uart_total_size();
+    if (total > 0) {
+      led_ring_show_ota_progress(ota_uart_bytes_received(), total,
+                                 OTA_LED_ESPNOW_RX_R, OTA_LED_ESPNOW_RX_G,
+                                 OTA_LED_ESPNOW_RX_B);
+    }
+  }
+}
+
+static void process_slave_end(const uint8_t master_mac[6]) {
+  ESP_LOGI(TAG, "ESP-NOW OTA_END");
+  if (!ota_uart_is_active()) {
+    send_slave_status(master_mac, OTA_ST_FAILED, 0, 20);
+    return;
+  }
+
+  uint32_t written = ota_uart_bytes_written();
+  bool success = false;
+  esp_err_t err = ota_uart_finish(true, &success);
+  if (err != ESP_OK || !success) {
+    led_ring_ota_failed();
+    send_slave_status(master_mac, OTA_ST_FAILED, written, (uint32_t)err);
+    return;
+  }
+
+  send_slave_status(master_mac, OTA_ST_SUCCESS, written, 0);
+  led_ring_ota_success();
+  ESP_LOGI(TAG, "slave OTA success (%lu bytes), reboot to run",
+           (unsigned long)written);
+}
+
+static void ota_slave_work_task(void *param) {
+  (void)param;
+  ota_slave_work_t work;
+
+  while (1) {
+    if (xQueueReceive(s_slave_work_queue, &work, portMAX_DELAY) != pdTRUE) {
+      continue;
+    }
+
+    switch (work.op) {
+    case OTA_SLAVE_WORK_STATUS:
+      send_slave_status(work.master_mac, work.status, work.bytes_written,
+                        work.error);
+      break;
+    case OTA_SLAVE_WORK_PAYLOAD:
+      process_slave_payload(work.master_mac, &work.payload);
+      break;
+    case OTA_SLAVE_WORK_END:
+      process_slave_end(work.master_mac);
+      break;
+    default:
+      break;
+    }
+  }
+}
+
+void ota_espnow_slave_init(void) {
+  if (s_slave_work_queue != NULL) {
+    return;
+  }
+  s_slave_work_queue = xQueueCreate(OTA_SLAVE_WORK_QUEUE_LEN, sizeof(ota_slave_work_t));
+  if (s_slave_work_queue == NULL) {
+    ESP_LOGE(TAG, "failed to create slave OTA work queue");
+    return;
+  }
+  if (xTaskCreate(ota_slave_work_task, "ota_slave_wrk", OTA_SLAVE_WORK_STACK, NULL,
+                  OTA_SLAVE_WORK_PRIO, NULL) != pdPASS) {
+    ESP_LOGE(TAG, "failed to create slave OTA work task");
+  }
+}
+
 static void ota_slave_prepare_task(void *param) {
   uint32_t total_size = (uint32_t)(uintptr_t)param;
   uint8_t master_mac[6];
@@ -190,82 +405,37 @@ void ota_espnow_slave_on_start(const uint8_t master_mac[6],
   ESP_LOGI(TAG, "ESP-NOW OTA_START (%lu bytes)", (unsigned long)start->total_size);
 
   if (ota_uart_is_active()) {
-    send_slave_status(master_mac, OTA_ST_FAILED, 0, 4);
+    queue_slave_status(master_mac, OTA_ST_FAILED, 0, 4);
     return;
   }
 
   if (xTaskCreate(ota_slave_prepare_task, "ota_esp_prep", OTA_ESPNOW_PREPARE_STACK,
                   (void *)(uintptr_t)start->total_size, OTA_ESPNOW_PREPARE_PRIO,
                   NULL) != pdPASS) {
-    send_slave_status(master_mac, OTA_ST_FAILED, 0, 5);
+    queue_slave_status(master_mac, OTA_ST_FAILED, 0, 5);
   }
 }
 
 void ota_espnow_slave_on_payload(const uint8_t master_mac[6],
                                  const alox_EspNowOtaPayload *payload) {
-  if (payload == NULL || payload->data.size == 0) {
-    send_slave_status(master_mac, OTA_ST_FAILED, 0, 11);
+  if (payload == NULL) {
+    queue_slave_status(master_mac, OTA_ST_FAILED, 0, 11);
     return;
   }
 
-  if (!ota_uart_is_active()) {
-    ESP_LOGW(TAG, "OTA_PAYLOAD seq=%lu but no active session",
-             (unsigned long)payload->seq);
-    send_slave_status(master_mac, OTA_ST_FAILED, 0, 12);
-    return;
-  }
-
-  if (payload->seq == 0) {
-    ESP_LOGI(TAG, "ESP-NOW OTA payloads started");
-  }
-
-  ota_feed_result_t r =
-      ota_uart_feed(payload->data.bytes, payload->data.size);
-  if (r == OTA_FEED_ERROR) {
-    led_ring_ota_failed();
-    send_slave_status(master_mac, OTA_ST_FAILED, ota_uart_bytes_written(), 13);
-    return;
-  }
-  if (r == OTA_FEED_BLOCK_WRITTEN) {
-    uint32_t written = ota_uart_bytes_written();
-    uint32_t total = ota_uart_total_size();
-    ESP_LOGI(TAG, "block written %lu bytes -> ack master", (unsigned long)written);
-    led_ring_show_ota_progress(written, total, OTA_LED_ESPNOW_RX_R, OTA_LED_ESPNOW_RX_G,
-                               OTA_LED_ESPNOW_RX_B);
-    send_slave_status(master_mac, OTA_ST_BLOCK_ACK, written, 0);
-    return;
-  }
-
-  if (r == OTA_FEED_OK) {
-    uint32_t total = ota_uart_total_size();
-    if (total > 0) {
-      led_ring_show_ota_progress(ota_uart_bytes_received(), total,
-                                 OTA_LED_ESPNOW_RX_R, OTA_LED_ESPNOW_RX_G,
-                                 OTA_LED_ESPNOW_RX_B);
-    }
+  ota_slave_work_t work = {.op = OTA_SLAVE_WORK_PAYLOAD, .payload = *payload};
+  memcpy(work.master_mac, master_mac, 6);
+  if (!queue_slave_work(&work)) {
+    queue_slave_status(master_mac, OTA_ST_FAILED, 0, 14);
   }
 }
 
 void ota_espnow_slave_on_end(const uint8_t master_mac[6]) {
-  ESP_LOGI(TAG, "ESP-NOW OTA_END");
-  if (!ota_uart_is_active()) {
-    send_slave_status(master_mac, OTA_ST_FAILED, 0, 20);
-    return;
+  ota_slave_work_t work = {.op = OTA_SLAVE_WORK_END};
+  memcpy(work.master_mac, master_mac, 6);
+  if (!queue_slave_work(&work)) {
+    queue_slave_status(master_mac, OTA_ST_FAILED, 0, 15);
   }
-
-  uint32_t written = ota_uart_bytes_written();
-  bool success = false;
-  esp_err_t err = ota_uart_finish(true, &success);
-  if (err != ESP_OK || !success) {
-    led_ring_ota_failed();
-    send_slave_status(master_mac, OTA_ST_FAILED, written, (uint32_t)err);
-    return;
-  }
-
-  send_slave_status(master_mac, OTA_ST_SUCCESS, written, 0);
-  led_ring_ota_success();
-  ESP_LOGI(TAG, "slave OTA success (%lu bytes), reboot to run",
-           (unsigned long)written);
 }
 
 void ota_espnow_master_on_status(const uint8_t slave_mac[6],
@@ -342,6 +512,8 @@ static esp_err_t distribute_image(const esp_partition_t *partition,
     }
   }
 
+  s_distribution_active = true;
+
   memset(&s_dist.progress, 0, sizeof(s_dist.progress));
   if (progress != NULL) {
     s_dist.progress = *progress;
@@ -362,6 +534,7 @@ static esp_err_t distribute_image(const esp_partition_t *partition,
       ESP_LOGW(TAG, "OTA_START to slave %lu failed",
                (unsigned long)s_dist.id[i]);
       prog_end();
+      s_distribution_active = false;
       return err;
     }
   }
@@ -369,6 +542,7 @@ static esp_err_t distribute_image(const esp_partition_t *partition,
   if (!wait_target_bits(target_mask, OTA_PREPARE_TIMEOUT_MS)) {
     ESP_LOGE(TAG, "timeout waiting for slave OTA ready");
     prog_end();
+    s_distribution_active = false;
     return ESP_ERR_TIMEOUT;
   }
 
@@ -392,38 +566,77 @@ static esp_err_t distribute_image(const esp_partition_t *partition,
       ESP_LOGE(TAG, "partition read @%lu failed: %s", (unsigned long)offset,
                esp_err_to_name(err));
       prog_end();
+      s_distribution_active = false;
       return err;
     }
 
-    uint32_t sent = 0;
-    while (sent < block_len) {
-      uint32_t chunk = block_len - sent;
-      if (chunk > OTA_UART_HOST_CHUNK_SIZE) {
-        chunk = OTA_UART_HOST_CHUNK_SIZE;
-      }
-
-      for (uint8_t i = 0; i < s_dist.count; i++) {
-        err = esp_now_comm_send_ota_payload(s_dist.mac[i], seq,
-                                            block_buf + sent, chunk);
-        if (err != ESP_OK) {
-          prog_end();
-          return err;
-        }
-      }
-      seq++;
-      sent += chunk;
-      vTaskDelay(pdMS_TO_TICKS(OTA_PAYLOAD_DELAY_MS));
-    }
-
     const bool full_block = (block_len >= OTA_UART_FLASH_BLOCK_SIZE);
     s_dist.expected_bytes = offset + block_len;
+    const uint32_t block_start_seq = seq;
 
     if (full_block) {
       xEventGroupClearBits(s_eg, target_mask);
-      if (!wait_target_bits(target_mask, OTA_BLOCK_TIMEOUT_MS)) {
-        ESP_LOGE(TAG, "timeout block ack @%lu bytes",
-                 (unsigned long)s_dist.expected_bytes);
+    }
+
+    bool block_sent = false;
+    for (uint32_t send_attempt = 0; send_attempt <= OTA_BLOCK_MAX_RETRIES;
+         send_attempt++) {
+      if (send_attempt > 0) {
+        seq = block_start_seq;
+        if (full_block) {
+          xEventGroupClearBits(s_eg, target_mask);
+        }
+        ESP_LOGW(TAG, "block send failed @%lu — resend %lu/%lu",
+                 (unsigned long)s_dist.expected_bytes,
+                 (unsigned long)send_attempt,
+                 (unsigned long)OTA_BLOCK_MAX_RETRIES);
+      }
+      err = send_block_payloads(block_buf, block_len, &seq);
+      if (err == ESP_OK) {
+        block_sent = true;
+        break;
+      }
+    }
+    if (!block_sent) {
+      ESP_LOGE(TAG, "block send failed @%lu after %lu retries",
+               (unsigned long)s_dist.expected_bytes,
+               (unsigned long)OTA_BLOCK_MAX_RETRIES);
+      prog_end();
+      s_distribution_active = false;
+      return err;
+    }
+
+    if (full_block) {
+      const uint32_t ack_timeout = block_ack_timeout_ms();
+      bool acked = false;
+      for (uint32_t attempt = 0; attempt <= OTA_BLOCK_MAX_RETRIES; attempt++) {
+        if (wait_target_bits(target_mask, ack_timeout)) {
+          acked = true;
+          break;
+        }
+        log_missing_block_acks(s_dist.expected_bytes);
+        if (attempt >= OTA_BLOCK_MAX_RETRIES) {
+          break;
+        }
+        ESP_LOGW(TAG, "block ack timeout @%lu — resend %lu/%lu",
+                 (unsigned long)s_dist.expected_bytes,
+                 (unsigned long)(attempt + 1),
+                 (unsigned long)OTA_BLOCK_MAX_RETRIES);
+        xEventGroupClearBits(s_eg, target_mask);
+        seq = block_start_seq;
+        err = send_block_payloads(block_buf, block_len, &seq);
+        if (err != ESP_OK) {
+          prog_end();
+          s_distribution_active = false;
+          return err;
+        }
+      }
+      if (!acked) {
+        ESP_LOGE(TAG, "timeout block ack @%lu bytes after %lu retries",
+                 (unsigned long)s_dist.expected_bytes,
+                 (unsigned long)OTA_BLOCK_MAX_RETRIES);
         prog_end();
+        s_distribution_active = false;
         return ESP_ERR_TIMEOUT;
       }
       ESP_LOGI(TAG, "block ack @%lu/%lu (%lu%%)",
@@ -445,6 +658,7 @@ static esp_err_t distribute_image(const esp_partition_t *partition,
     err = esp_now_comm_send_ota_end(s_dist.mac[i]);
     if (err != ESP_OK) {
       prog_end();
+      s_distribution_active = false;
       return err;
     }
   }
@@ -452,11 +666,13 @@ static esp_err_t distribute_image(const esp_partition_t *partition,
   if (!wait_target_bits(target_mask, OTA_END_TIMEOUT_MS)) {
     ESP_LOGE(TAG, "timeout waiting for slave OTA success");
     prog_end();
+    s_distribution_active = false;
     return ESP_ERR_TIMEOUT;
   }
 
   prog_set_aggregate(size);
   prog_end();
+  s_distribution_active = false;
   ESP_LOGI(TAG, "ESP-NOW OTA complete for %u slave(s)", (unsigned)s_dist.count);
   return ESP_OK;
 }

main/ota_espnow.h

@@ -37,4 +37,10 @@ void ota_espnow_slave_on_end(const uint8_t master_mac[6]);
 void ota_espnow_progress_query(uint32_t filter_client_id,
                                alox_OtaSlaveProgressResponse *out);
 
+/** True while master is pushing a staged image to slaves. */
+bool ota_espnow_distribution_active(void);
+
+/** Slave: work queue for OTA (no esp_now_send from recv callback). */
+void ota_espnow_slave_init(void);
+
 #endif

main/ota_session.c

@@ -0,0 +1,25 @@
+#include "ota_session.h"
+#include "ota_espnow.h"
+#include "ota_uart.h"
+#include "uart_messages.pb.h"
+
+bool ota_session_busy(void) {
+  return ota_uart_is_active() || ota_espnow_distribution_active();
+}
+
+bool ota_session_uart_cmd_allowed(uint16_t msg_id) {
+  if (!ota_session_busy()) {
+    return true;
+  }
+
+  switch ((alox_MessageType)msg_id) {
+  case alox_MessageType_OTA_START:
+  case alox_MessageType_OTA_PAYLOAD:
+  case alox_MessageType_OTA_END:
+  case alox_MessageType_OTA_START_ESPNOW:
+  case alox_MessageType_OTA_SLAVE_PROGRESS:
+    return true;
+  default:
+    return false;
+  }
+}

main/ota_session.h

@@ -0,0 +1,13 @@
+#ifndef OTA_SESSION_H
+#define OTA_SESSION_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+/** UART upload or ESP-NOW slave distribution in progress. */
+bool ota_session_busy(void);
+
+/** During OTA only UART OTA-related commands are accepted on the master. */
+bool ota_session_uart_cmd_allowed(uint16_t msg_id);
+
+#endif

main/ota_uart.c

@@ -12,6 +12,7 @@ typedef struct {
   uint32_t total_size;
   uint32_t received;
   uint32_t written;
+  uint32_t expected_seq;
   int target_slot;
   uint8_t block_buf[OTA_UART_FLASH_BLOCK_SIZE];
   size_t block_len;
@@ -112,10 +113,30 @@ int ota_uart_prepare(uint32_t total_size) {
   return s_ota.target_slot;
 }
 
-ota_feed_result_t ota_uart_feed(const uint8_t *data, size_t len) {
+bool ota_uart_block_ready_for_reack(void) {
+  if (!s_ota.active) {
+    return false;
+  }
+  return s_ota.written > 0 &&
+         (s_ota.written % OTA_UART_FLASH_BLOCK_SIZE) == 0 &&
+         s_ota.block_len == 0;
+}
+
+ota_feed_result_t ota_uart_feed_chunk(uint32_t seq, const uint8_t *data,
+                                      size_t len) {
   if (!s_ota.active || data == NULL || len == 0) {
     return OTA_FEED_ERROR;
   }
+  if (seq < s_ota.expected_seq) {
+    return OTA_FEED_SEQ_DUP;
+  }
+  if (seq > s_ota.expected_seq) {
+    ESP_LOGW(TAG, "seq gap: got %lu expected %lu", (unsigned long)seq,
+             (unsigned long)s_ota.expected_seq);
+    return OTA_FEED_SEQ_GAP;
+  }
+  s_ota.expected_seq++;
+
   if (len > OTA_UART_HOST_CHUNK_SIZE) {
     ESP_LOGW(TAG, "chunk %u > %u, truncating", (unsigned)len,
              OTA_UART_HOST_CHUNK_SIZE);
@@ -200,6 +221,13 @@ esp_err_t ota_uart_finish(bool set_boot, bool *success_out) {
     return err;
   }
 
+  if (s_ota.total_size > 0 && s_ota.received != s_ota.total_size) {
+    ESP_LOGE(TAG, "size mismatch: received=%lu expected=%lu",
+             (unsigned long)s_ota.received, (unsigned long)s_ota.total_size);
+    ota_uart_abort();
+    return ESP_ERR_INVALID_SIZE;
+  }
+
   err = esp_ota_end(s_ota.handle);
   if (err != ESP_OK) {
     ESP_LOGE(TAG, "esp_ota_end failed: %s", esp_err_to_name(err));

main/ota_uart.h

@@ -28,6 +28,8 @@ typedef enum {
 typedef enum {
   OTA_FEED_OK = 0,
   OTA_FEED_BLOCK_WRITTEN,
+  OTA_FEED_SEQ_DUP,
+  OTA_FEED_SEQ_GAP,
   OTA_FEED_ERROR,
 } ota_feed_result_t;
 
@@ -41,8 +43,14 @@ int ota_uart_prepare(uint32_t total_size);
 
 void ota_uart_abort(void);
 
-/** Append up to 200 bytes; flushes 4 KiB blocks to flash when full. */
-ota_feed_result_t ota_uart_feed(const uint8_t *data, size_t len);
+/**
+ * Append up to 200 bytes with strict seq checking (0, 1, 2, …).
+ * Duplicates (seq < expected) return OTA_FEED_SEQ_DUP; gaps return OTA_FEED_SEQ_GAP.
+ */
+ota_feed_result_t ota_uart_feed_chunk(uint32_t seq, const uint8_t *data, size_t len);
+
+/** True when a full 4 KiB block is in flash (used to re-ACK host block retries). */
+bool ota_uart_block_ready_for_reack(void);
 
 uint32_t ota_uart_bytes_written(void);
 

main/pod_settings.c

@@ -7,6 +7,7 @@
 static const char *TAG = "[SETTINGS]";
 static const char *NS = "powerpod";
 static const char *KEY_ACCEL_DZ = "accel_dz";
+static const char *KEY_UV_LATCH = "uv_latch";
 
 #define ACCEL_DEADZONE_MAX 4095u
 
@@ -108,3 +109,53 @@ void pod_settings_apply_accel_deadzone(void) {
     bma456_set_accel_deadzone(deadzone);
   }
 }
+
+bool pod_settings_is_uv_latched(void) {
+  if (!s_nvs_ready) {
+    return false;
+  }
+
+  nvs_handle_t handle;
+  esp_err_t err = nvs_open(NS, NVS_READONLY, &handle);
+  if (err != ESP_OK) {
+    return false;
+  }
+
+  uint8_t value = 0;
+  err = nvs_get_u8(handle, KEY_UV_LATCH, &value);
+  nvs_close(handle);
+
+  return err == ESP_OK && value != 0;
+}
+
+esp_err_t pod_settings_set_uv_latched(bool latched) {
+  esp_err_t err = ensure_nvs();
+  if (err != ESP_OK) {
+    return err;
+  }
+
+  nvs_handle_t handle;
+  err = nvs_open(NS, NVS_READWRITE, &handle);
+  if (err != ESP_OK) {
+    ESP_LOGE(TAG, "nvs_open failed: %s", esp_err_to_name(err));
+    return err;
+  }
+
+  err = nvs_set_u8(handle, KEY_UV_LATCH, latched ? 1u : 0u);
+  if (err == ESP_OK) {
+    err = nvs_commit(handle);
+  }
+  nvs_close(handle);
+
+  if (err != ESP_OK) {
+    ESP_LOGE(TAG, "save uv_latch failed: %s", esp_err_to_name(err));
+    return err;
+  }
+
+  ESP_LOGI(TAG, "UV latch %s", latched ? "set" : "cleared");
+  return ESP_OK;
+}
+
+esp_err_t pod_settings_clear_uv_latched(void) {
+  return pod_settings_set_uv_latched(false);
+}

main/pod_settings.h

@@ -2,6 +2,7 @@
 #define POD_SETTINGS_H
 
 #include "esp_err.h"
+#include <stdbool.h>
 #include <stdint.h>
 
 /** Initialize NVS (idempotent) and log stored settings. Call once early in app_main. */
@@ -16,4 +17,9 @@ uint32_t pod_settings_load_accel_deadzone(void);
 /** Apply NVS deadzone to BMA456 when the sensor is present. */
 void pod_settings_apply_accel_deadzone(void);
 
+/** LiPo under-voltage latch persisted across reboot (software UV protection). */
+bool pod_settings_is_uv_latched(void);
+esp_err_t pod_settings_set_uv_latched(bool latched);
+esp_err_t pod_settings_clear_uv_latched(void);
+
 #endif

main/powerpod.c

@@ -5,6 +5,7 @@
 #include "cmd_tap_notify.h"
 #include "cmd_cache_status.h"
 #include "cmd_espnow_unicast_test.h"
+#include "cmd_espnow_echo_ping.h"
 #include "cmd_espnow_find_me.h"
 #include "cmd_restart.h"
 #include "cmd_client_info.h"
@@ -13,6 +14,7 @@
 #include "cmd_ota_slave_progress.h"
 #include "cmd_led_ring.h"
 #include "cmd_battery.h"
+#include "cmd_set_log_level.h"
 #include "esp_now_comm.h"
 #include "powerpod.h"
 #include "driver/gpio.h"
@@ -29,6 +31,7 @@
 #include "led_ring.h"
 #include "pod_settings.h"
 #include "uart.h"
+#include "battery_uv.h"
 #include <stdint.h>
 
 enum MASTER_STATES {
@@ -76,6 +79,16 @@ void app_main(void) {
     ESP_LOGW(TAG, "settings NVS init failed; using defaults");
   }
 
+  if (board_input_init_adc_only() != ESP_OK) {
+    ESP_LOGW(TAG, "LiPo ADC init failed");
+  }
+
+#if POWERPOD_BATTERY_UV_ENABLE
+  if (battery_uv_evaluate_boot()) {
+    battery_uv_run_mode();
+  }
+#endif
+
   // Get Master Mode Pin
   gpio_reset_pin(DIP_MASTER);
   gpio_set_direction(DIP_MASTER, GPIO_MODE_INPUT);
@@ -165,7 +178,8 @@ void app_main(void) {
   ESP_LOGI(TAG, "Running Partition: %s (OTA slot %d)",
            app_config.running_partition, ota_slot);
 
-  board_input_init();
+  board_input_start_lipo_monitor();
+  board_input_init_button();
 
   err = esp_now_comm_init(&app_config);
   if (err != ESP_OK) {
@@ -185,12 +199,14 @@ void app_main(void) {
     cmd_tap_notify_register();
     cmd_cache_status_register();
     cmd_espnow_unicast_test_register();
+    cmd_espnow_echo_ping_register();
     cmd_espnow_find_me_register();
     cmd_restart_register();
     cmd_led_ring_register();
     cmd_battery_register();
     cmd_ota_register();
     cmd_ota_slave_progress_register();
+    cmd_set_log_level_register();
   }
 
   ESP_LOGI(TAG, "LED ring: UART LED_RING commands only (no local demo loop)");

main/powerpod.h

@@ -1,6 +1,11 @@
 #ifndef POWERPOD_H
 #define POWERPOD_H
 
+/** 1 = software LiPo UV latch + energy-save mode; 0 = disabled (LED mode 6 still works). */
+#ifndef POWERPOD_BATTERY_UV_ENABLE
+#define POWERPOD_BATTERY_UV_ENABLE 0
+#endif
+
 #define DIP_MASTER 4
 #define I2C_SCL 5
 #define I2C_SDA 6
@@ -11,9 +16,8 @@
 /** Front-panel button (active low, internal pull-up). */
 #define TASTER_GPIO 12
 
-/** LiPo voltage sense inputs (ADC1-capable GPIOs). */
+/** LiPo voltage sense inputs (ADC-capable GPIOs; GPIO11 = ADC2 on ESP32-S3). */
 #define V_LIPO_1_GPIO 1
-/** Shares GPIO with TASTER on current bench wiring; second ADC is skipped in board_input.c. */
-#define V_LIPO_2_GPIO 12
+#define V_LIPO_2_GPIO 11
 
 #endif

main/proto/esp_now_messages.pb.c

@@ -9,6 +9,12 @@
 PB_BIND(alox_EspNowUnicastTest, alox_EspNowUnicastTest, AUTO)
 
 
+PB_BIND(alox_EspNowEchoPing, alox_EspNowEchoPing, AUTO)
+
+
+PB_BIND(alox_EspNowEchoPong, alox_EspNowEchoPong, AUTO)
+
+
 PB_BIND(alox_EspNowFindMe, alox_EspNowFindMe, AUTO)
 
 

main/proto/esp_now_messages.pb.h

@@ -29,7 +29,9 @@ typedef enum _alox_EspNowMessageType {
     alox_EspNowMessageType_ESPNOW_BATTERY_QUERY = 15,
     alox_EspNowMessageType_ESPNOW_BATTERY_REPORT = 16,
     alox_EspNowMessageType_ESPNOW_SET_TAP_NOTIFY = 17,
-    alox_EspNowMessageType_ESPNOW_TAP_EVENT = 18
+    alox_EspNowMessageType_ESPNOW_TAP_EVENT = 18,
+    alox_EspNowMessageType_ESPNOW_ECHO_PING = 19,
+    alox_EspNowMessageType_ESPNOW_ECHO_PONG = 20
 } alox_EspNowMessageType;
 
 /* Struct definitions */
@@ -37,6 +39,19 @@ typedef struct _alox_EspNowUnicastTest {
     uint32_t seq;
 } alox_EspNowUnicastTest;
 
+/* * Master → slave: echo ping (host ts + master monotonic time for RTT). */
+typedef struct _alox_EspNowEchoPing {
+    uint64_t host_timestamp_us;
+    /* * esp_timer_get_time() (µs since boot) when master forwarded this message. */
+    uint64_t master_time_us;
+} alox_EspNowEchoPing;
+
+/* * Slave → master: echo ping payload unchanged. */
+typedef struct _alox_EspNowEchoPong {
+    uint64_t host_timestamp_us;
+    uint64_t master_time_us;
+} alox_EspNowEchoPong;
+
 /* * Master → slave: locate pod (LED ring R/G/B ×3 @ full brightness). */
 typedef struct _alox_EspNowFindMe {
     /* * 0 = any slave; otherwise only slave_id must match */
@@ -50,6 +65,8 @@ typedef struct _alox_EspNowRestart {
 
 typedef struct _alox_EspNowDiscover {
     uint32_t network;
+    /* * Master is in an OTA session (UART upload or ESP-NOW distribution). */
+    bool master_ota_pending;
 } alox_EspNowDiscover;
 
 typedef struct _alox_EspNowSlavePresence {
@@ -169,6 +186,8 @@ typedef struct _alox_EspNowMessage {
         alox_EspNowBatteryReport battery_report;
         alox_EspNowTapNotify tap_notify;
         alox_EspNowTapEvent tap_event;
+        alox_EspNowEchoPing echo_ping;
+        alox_EspNowEchoPong echo_pong;
     } payload;
 } alox_EspNowMessage;
 
@@ -179,8 +198,10 @@ extern "C" {
 
 /* Helper constants for enums */
 #define _alox_EspNowMessageType_MIN alox_EspNowMessageType_ESPNOW_UNKNOWN
-#define _alox_EspNowMessageType_MAX alox_EspNowMessageType_ESPNOW_TAP_EVENT
-#define _alox_EspNowMessageType_ARRAYSIZE ((alox_EspNowMessageType)(alox_EspNowMessageType_ESPNOW_TAP_EVENT+1))
+#define _alox_EspNowMessageType_MAX alox_EspNowMessageType_ESPNOW_ECHO_PONG
+#define _alox_EspNowMessageType_ARRAYSIZE ((alox_EspNowMessageType)(alox_EspNowMessageType_ESPNOW_ECHO_PONG+1))
+
+
 
 
 
@@ -204,9 +225,11 @@ extern "C" {
 
 /* Initializer values for message structs */
 #define alox_EspNowUnicastTest_init_default      {0}
+#define alox_EspNowEchoPing_init_default         {0, 0}
+#define alox_EspNowEchoPong_init_default         {0, 0}
 #define alox_EspNowFindMe_init_default           {0}
 #define alox_EspNowRestart_init_default          {0}
-#define alox_EspNowDiscover_init_default         {0}
+#define alox_EspNowDiscover_init_default         {0, 0}
 #define alox_EspNowSlavePresence_init_default    {0, {{NULL}, NULL}, 0, 0, 0, 0}
 #define alox_EspNowAccelDeadzone_init_default    {0, 0}
 #define alox_EspNowAccelStream_init_default      {0, 0}
@@ -222,9 +245,11 @@ extern "C" {
 #define alox_EspNowOtaStatus_init_default        {0, 0, 0}
 #define alox_EspNowMessage_init_default          {_alox_EspNowMessageType_MIN, 0, {alox_EspNowDiscover_init_default}}
 #define alox_EspNowUnicastTest_init_zero         {0}
+#define alox_EspNowEchoPing_init_zero            {0, 0}
+#define alox_EspNowEchoPong_init_zero            {0, 0}
 #define alox_EspNowFindMe_init_zero              {0}
 #define alox_EspNowRestart_init_zero             {0}
-#define alox_EspNowDiscover_init_zero            {0}
+#define alox_EspNowDiscover_init_zero            {0, 0}
 #define alox_EspNowSlavePresence_init_zero       {0, {{NULL}, NULL}, 0, 0, 0, 0}
 #define alox_EspNowAccelDeadzone_init_zero       {0, 0}
 #define alox_EspNowAccelStream_init_zero         {0, 0}
@@ -242,9 +267,14 @@ extern "C" {
 
 /* Field tags (for use in manual encoding/decoding) */
 #define alox_EspNowUnicastTest_seq_tag           1
+#define alox_EspNowEchoPing_host_timestamp_us_tag 1
+#define alox_EspNowEchoPing_master_time_us_tag   2
+#define alox_EspNowEchoPong_host_timestamp_us_tag 1
+#define alox_EspNowEchoPong_master_time_us_tag   2
 #define alox_EspNowFindMe_client_id_tag          1
 #define alox_EspNowRestart_client_id_tag         1
 #define alox_EspNowDiscover_network_tag          1
+#define alox_EspNowDiscover_master_ota_pending_tag 2
 #define alox_EspNowSlavePresence_network_tag     1
 #define alox_EspNowSlavePresence_mac_tag         2
 #define alox_EspNowSlavePresence_version_tag     3
@@ -306,6 +336,8 @@ extern "C" {
 #define alox_EspNowMessage_battery_report_tag    17
 #define alox_EspNowMessage_tap_notify_tag        18
 #define alox_EspNowMessage_tap_event_tag         19
+#define alox_EspNowMessage_echo_ping_tag         20
+#define alox_EspNowMessage_echo_pong_tag         21
 
 /* Struct field encoding specification for nanopb */
 #define alox_EspNowUnicastTest_FIELDLIST(X, a) \
@@ -313,6 +345,18 @@ X(a, STATIC,   SINGULAR, UINT32,   seq,               1)
 #define alox_EspNowUnicastTest_CALLBACK NULL
 #define alox_EspNowUnicastTest_DEFAULT NULL
 
+#define alox_EspNowEchoPing_FIELDLIST(X, a) \
+X(a, STATIC,   SINGULAR, UINT64,   host_timestamp_us,   1) \
+X(a, STATIC,   SINGULAR, UINT64,   master_time_us,    2)
+#define alox_EspNowEchoPing_CALLBACK NULL
+#define alox_EspNowEchoPing_DEFAULT NULL
+
+#define alox_EspNowEchoPong_FIELDLIST(X, a) \
+X(a, STATIC,   SINGULAR, UINT64,   host_timestamp_us,   1) \
+X(a, STATIC,   SINGULAR, UINT64,   master_time_us,    2)
+#define alox_EspNowEchoPong_CALLBACK NULL
+#define alox_EspNowEchoPong_DEFAULT NULL
+
 #define alox_EspNowFindMe_FIELDLIST(X, a) \
 X(a, STATIC,   SINGULAR, UINT32,   client_id,         1)
 #define alox_EspNowFindMe_CALLBACK NULL
@@ -324,7 +368,8 @@ X(a, STATIC,   SINGULAR, UINT32,   client_id,         1)
 #define alox_EspNowRestart_DEFAULT NULL
 
 #define alox_EspNowDiscover_FIELDLIST(X, a) \
-X(a, STATIC,   SINGULAR, UINT32,   network,           1)
+X(a, STATIC,   SINGULAR, UINT32,   network,           1) \
+X(a, STATIC,   SINGULAR, BOOL,     master_ota_pending,   2)
 #define alox_EspNowDiscover_CALLBACK NULL
 #define alox_EspNowDiscover_DEFAULT NULL
 
@@ -442,7 +487,9 @@ X(a, STATIC,   ONEOF,    MESSAGE,  (payload,led_ring,payload.led_ring),  15) \
 X(a, STATIC,   ONEOF,    MESSAGE,  (payload,battery_query,payload.battery_query),  16) \
 X(a, STATIC,   ONEOF,    MESSAGE,  (payload,battery_report,payload.battery_report),  17) \
 X(a, STATIC,   ONEOF,    MESSAGE,  (payload,tap_notify,payload.tap_notify),  18) \
-X(a, STATIC,   ONEOF,    MESSAGE,  (payload,tap_event,payload.tap_event),  19)
+X(a, STATIC,   ONEOF,    MESSAGE,  (payload,tap_event,payload.tap_event),  19) \
+X(a, STATIC,   ONEOF,    MESSAGE,  (payload,echo_ping,payload.echo_ping),  20) \
+X(a, STATIC,   ONEOF,    MESSAGE,  (payload,echo_pong,payload.echo_pong),  21)
 #define alox_EspNowMessage_CALLBACK NULL
 #define alox_EspNowMessage_DEFAULT NULL
 #define alox_EspNowMessage_payload_discover_MSGTYPE alox_EspNowDiscover
@@ -463,8 +510,12 @@ X(a, STATIC,   ONEOF,    MESSAGE,  (payload,tap_event,payload.tap_event),  19)
 #define alox_EspNowMessage_payload_battery_report_MSGTYPE alox_EspNowBatteryReport
 #define alox_EspNowMessage_payload_tap_notify_MSGTYPE alox_EspNowTapNotify
 #define alox_EspNowMessage_payload_tap_event_MSGTYPE alox_EspNowTapEvent
+#define alox_EspNowMessage_payload_echo_ping_MSGTYPE alox_EspNowEchoPing
+#define alox_EspNowMessage_payload_echo_pong_MSGTYPE alox_EspNowEchoPong
 
 extern const pb_msgdesc_t alox_EspNowUnicastTest_msg;
+extern const pb_msgdesc_t alox_EspNowEchoPing_msg;
+extern const pb_msgdesc_t alox_EspNowEchoPong_msg;
 extern const pb_msgdesc_t alox_EspNowFindMe_msg;
 extern const pb_msgdesc_t alox_EspNowRestart_msg;
 extern const pb_msgdesc_t alox_EspNowDiscover_msg;
@@ -485,6 +536,8 @@ extern const pb_msgdesc_t alox_EspNowMessage_msg;
 
 /* Defines for backwards compatibility with code written before nanopb-0.4.0 */
 #define alox_EspNowUnicastTest_fields &alox_EspNowUnicastTest_msg
+#define alox_EspNowEchoPing_fields &alox_EspNowEchoPing_msg
+#define alox_EspNowEchoPong_fields &alox_EspNowEchoPong_msg
 #define alox_EspNowFindMe_fields &alox_EspNowFindMe_msg
 #define alox_EspNowRestart_fields &alox_EspNowRestart_msg
 #define alox_EspNowDiscover_fields &alox_EspNowDiscover_msg
@@ -512,7 +565,9 @@ extern const pb_msgdesc_t alox_EspNowMessage_msg;
 #define alox_EspNowAccelStream_size              8
 #define alox_EspNowBatteryQuery_size             6
 #define alox_EspNowBatteryReport_size            22
-#define alox_EspNowDiscover_size                 6
+#define alox_EspNowDiscover_size                 8
+#define alox_EspNowEchoPing_size                 22
+#define alox_EspNowEchoPong_size                 22
 #define alox_EspNowFindMe_size                   6
 #define alox_EspNowLedRing_size                  60
 #define alox_EspNowOtaEnd_size                   0

main/proto/esp_now_messages.proto

@@ -24,12 +24,27 @@ enum EspNowMessageType {
   ESPNOW_BATTERY_REPORT = 16;
   ESPNOW_SET_TAP_NOTIFY = 17;
   ESPNOW_TAP_EVENT = 18;
+  ESPNOW_ECHO_PING = 19;
+  ESPNOW_ECHO_PONG = 20;
 }
 
 message EspNowUnicastTest {
   uint32 seq = 1;
 }
 
+/** Master → slave: echo ping (host ts + master monotonic time for RTT). */
+message EspNowEchoPing {
+  uint64 host_timestamp_us = 1;
+  /** esp_timer_get_time() (µs since boot) when master forwarded this message. */
+  uint64 master_time_us = 2;
+}
+
+/** Slave → master: echo ping payload unchanged. */
+message EspNowEchoPong {
+  uint64 host_timestamp_us = 1;
+  uint64 master_time_us = 2;
+}
+
 /** Master → slave: locate pod (LED ring R/G/B ×3 @ full brightness). */
 message EspNowFindMe {
   /** 0 = any slave; otherwise only slave_id must match */
@@ -43,6 +58,8 @@ message EspNowRestart {
 
 message EspNowDiscover {
   uint32 network = 1;
+  /** Master is in an OTA session (UART upload or ESP-NOW distribution). */
+  bool master_ota_pending = 2;
 }
 
 message EspNowSlavePresence {
@@ -158,5 +175,7 @@ message EspNowMessage {
     EspNowBatteryReport battery_report = 17;
     EspNowTapNotify tap_notify = 18;
     EspNowTapEvent tap_event = 19;
+    EspNowEchoPing echo_ping = 20;
+    EspNowEchoPong echo_pong = 21;
   }
 }

main/proto/uart_messages.pb.c

@@ -87,6 +87,12 @@ PB_BIND(alox_EspNowUnicastTestRequest, alox_EspNowUnicastTestRequest, AUTO)
 PB_BIND(alox_EspNowUnicastTestResponse, alox_EspNowUnicastTestResponse, AUTO)
 
 
+PB_BIND(alox_EspNowEchoPingRequest, alox_EspNowEchoPingRequest, AUTO)
+
+
+PB_BIND(alox_EspNowEchoPingResponse, alox_EspNowEchoPingResponse, AUTO)
+
+
 PB_BIND(alox_LedRingProgressRequest, alox_LedRingProgressRequest, AUTO)
 
 
@@ -105,6 +111,12 @@ PB_BIND(alox_RestartRequest, alox_RestartRequest, AUTO)
 PB_BIND(alox_RestartResponse, alox_RestartResponse, AUTO)
 
 
+PB_BIND(alox_SetLogLevelRequest, alox_SetLogLevelRequest, AUTO)
+
+
+PB_BIND(alox_SetLogLevelResponse, alox_SetLogLevelResponse, AUTO)
+
+
 PB_BIND(alox_OtaStartPayload, alox_OtaStartPayload, AUTO)
 
 

main/proto/uart_messages.pb.h

@@ -32,7 +32,11 @@ typedef enum _alox_MessageType {
     alox_MessageType_BATTERY_STATUS = 26,
     alox_MessageType_TAP_NOTIFY = 27,
     /* * Combined cached accel + tap poll (one UART round-trip, ~16 ms cadence). */
-    alox_MessageType_CACHE_STATUS = 29
+    alox_MessageType_CACHE_STATUS = 29,
+    /* * Host → master → slave → master: timestamp echo round-trip (latency test). */
+    alox_MessageType_ESPNOW_ECHO_PING = 30,
+    /* * Host → master: get/set ESP-IDF log level for tag "*" (global). */
+    alox_MessageType_SET_LOG_LEVEL = 31
 } alox_MessageType;
 
 typedef enum _alox_TapKind {
@@ -235,8 +239,24 @@ typedef struct _alox_EspNowUnicastTestResponse {
     uint32_t seq;
 } alox_EspNowUnicastTestResponse;
 
+/* * Host → master: ESP-NOW echo ping to one slave (timestamp echoed back). */
+typedef struct _alox_EspNowEchoPingRequest {
+    uint32_t client_id;
+    /* * Microseconds since Unix epoch (host clock). */
+    uint64_t timestamp_us;
+} alox_EspNowEchoPingRequest;
+
+typedef struct _alox_EspNowEchoPingResponse {
+    bool success;
+    uint32_t client_id;
+    /* * Echoed host timestamp from goTool request. */
+    uint64_t timestamp_us;
+    /* * esp_timer_get_time() delta from ping send to pong recv (master→slave→master). */
+    uint32_t esp_rtt_us;
+} alox_EspNowEchoPingResponse;
+
 /* Host → master: LED ring on master (client_id=0) and/or slaves via ESP-NOW.
- mode: 0=clear, 1=progress (0–100 %), 2=digit (0–10), 3=blink, 4=find-me, 5=all LEDs solid color. */
+ mode: 0=clear, 1=progress (0–100 %), 2=digit (0–10), 3=blink, 4=find-me, 5=all LEDs solid color, 6=battery-low. */
 typedef struct _alox_LedRingProgressRequest {
     uint32_t mode;
     /* * 0–100: fraction of ring LEDs to light (mode=progress) */
@@ -289,6 +309,18 @@ typedef struct _alox_RestartResponse {
     uint32_t client_id;
 } alox_RestartResponse;
 
+/* * Host → master: read/write global log level (esp_log_level_set("*", …)). */
+typedef struct _alox_SetLogLevelRequest {
+    bool write;
+    /* * esp_log_level_t: 0=NONE, 1=ERROR, 2=WARN, 3=INFO, 4=DEBUG, 5=VERBOSE */
+    uint32_t level;
+} alox_SetLogLevelRequest;
+
+typedef struct _alox_SetLogLevelResponse {
+    bool success;
+    uint32_t level;
+} alox_SetLogLevelResponse;
+
 /* Host → device: begin UART OTA (erase inactive OTA slot; device replies OTA_STATUS). */
 typedef struct _alox_OtaStartPayload {
     uint32_t total_size;
@@ -371,6 +403,10 @@ typedef struct _alox_UartMessage {
         alox_TapNotifyResponse tap_notify_response;
         alox_CacheStatusRequest cache_status_request;
         alox_CacheStatusResponse cache_status_response;
+        alox_EspNowEchoPingRequest espnow_echo_ping_request;
+        alox_EspNowEchoPingResponse espnow_echo_ping_response;
+        alox_SetLogLevelRequest set_log_level_request;
+        alox_SetLogLevelResponse set_log_level_response;
     } payload;
 } alox_UartMessage;
 
@@ -381,8 +417,8 @@ extern "C" {
 
 /* Helper constants for enums */
 #define _alox_MessageType_MIN alox_MessageType_UNKNOWN
-#define _alox_MessageType_MAX alox_MessageType_CACHE_STATUS
-#define _alox_MessageType_ARRAYSIZE ((alox_MessageType)(alox_MessageType_CACHE_STATUS+1))
+#define _alox_MessageType_MAX alox_MessageType_SET_LOG_LEVEL
+#define _alox_MessageType_ARRAYSIZE ((alox_MessageType)(alox_MessageType_SET_LOG_LEVEL+1))
 
 #define _alox_TapKind_MIN alox_TapKind_TAP_NONE
 #define _alox_TapKind_MAX alox_TapKind_TAP_TRIPLE
@@ -429,6 +465,10 @@ extern "C" {
 
 
 
+
+
+
+
 
 
 
@@ -460,12 +500,16 @@ extern "C" {
 #define alox_CacheStatusResponse_init_default    {0, {alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default, alox_CacheClientStatus_init_default}}
 #define alox_EspNowUnicastTestRequest_init_default {0, 0}
 #define alox_EspNowUnicastTestResponse_init_default {0, 0}
+#define alox_EspNowEchoPingRequest_init_default  {0, 0}
+#define alox_EspNowEchoPingResponse_init_default {0, 0, 0, 0}
 #define alox_LedRingProgressRequest_init_default {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
 #define alox_LedRingProgressResponse_init_default {0, 0, 0, 0, 0, 0}
 #define alox_EspNowFindMeRequest_init_default    {0}
 #define alox_EspNowFindMeResponse_init_default   {0, 0}
 #define alox_RestartRequest_init_default         {0}
 #define alox_RestartResponse_init_default        {0, 0}
+#define alox_SetLogLevelRequest_init_default     {0, 0}
+#define alox_SetLogLevelResponse_init_default    {0, 0}
 #define alox_OtaStartPayload_init_default        {0}
 #define alox_OtaPayload_init_default             {0, {0, {0}}}
 #define alox_OtaEndPayload_init_default          {0}
@@ -500,12 +544,16 @@ extern "C" {
 #define alox_CacheStatusResponse_init_zero       {0, {alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero, alox_CacheClientStatus_init_zero}}
 #define alox_EspNowUnicastTestRequest_init_zero  {0, 0}
 #define alox_EspNowUnicastTestResponse_init_zero {0, 0}
+#define alox_EspNowEchoPingRequest_init_zero     {0, 0}
+#define alox_EspNowEchoPingResponse_init_zero    {0, 0, 0, 0}
 #define alox_LedRingProgressRequest_init_zero    {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
 #define alox_LedRingProgressResponse_init_zero   {0, 0, 0, 0, 0, 0}
 #define alox_EspNowFindMeRequest_init_zero       {0}
 #define alox_EspNowFindMeResponse_init_zero      {0, 0}
 #define alox_RestartRequest_init_zero            {0}
 #define alox_RestartResponse_init_zero           {0, 0}
+#define alox_SetLogLevelRequest_init_zero        {0, 0}
+#define alox_SetLogLevelResponse_init_zero       {0, 0}
 #define alox_OtaStartPayload_init_zero           {0}
 #define alox_OtaPayload_init_zero                {0, {0, {0}}}
 #define alox_OtaEndPayload_init_zero             {0}
@@ -599,6 +647,12 @@ extern "C" {
 #define alox_EspNowUnicastTestRequest_seq_tag    2
 #define alox_EspNowUnicastTestResponse_success_tag 1
 #define alox_EspNowUnicastTestResponse_seq_tag   2
+#define alox_EspNowEchoPingRequest_client_id_tag 1
+#define alox_EspNowEchoPingRequest_timestamp_us_tag 2
+#define alox_EspNowEchoPingResponse_success_tag  1
+#define alox_EspNowEchoPingResponse_client_id_tag 2
+#define alox_EspNowEchoPingResponse_timestamp_us_tag 3
+#define alox_EspNowEchoPingResponse_esp_rtt_us_tag 4
 #define alox_LedRingProgressRequest_mode_tag     1
 #define alox_LedRingProgressRequest_progress_tag 2
 #define alox_LedRingProgressRequest_digit_tag    3
@@ -623,6 +677,10 @@ extern "C" {
 #define alox_RestartRequest_client_id_tag        1
 #define alox_RestartResponse_success_tag         1
 #define alox_RestartResponse_client_id_tag       2
+#define alox_SetLogLevelRequest_write_tag        1
+#define alox_SetLogLevelRequest_level_tag        2
+#define alox_SetLogLevelResponse_success_tag     1
+#define alox_SetLogLevelResponse_level_tag       2
 #define alox_OtaStartPayload_total_size_tag      1
 #define alox_OtaPayload_seq_tag                  1
 #define alox_OtaPayload_data_tag                 2
@@ -671,6 +729,10 @@ extern "C" {
 #define alox_UartMessage_tap_notify_response_tag 30
 #define alox_UartMessage_cache_status_request_tag 33
 #define alox_UartMessage_cache_status_response_tag 34
+#define alox_UartMessage_espnow_echo_ping_request_tag 35
+#define alox_UartMessage_espnow_echo_ping_response_tag 36
+#define alox_UartMessage_set_log_level_request_tag 37
+#define alox_UartMessage_set_log_level_response_tag 38
 
 /* Struct field encoding specification for nanopb */
 #define alox_UartMessage_FIELDLIST(X, a) \
@@ -703,7 +765,11 @@ X(a, STATIC,   ONEOF,    MESSAGE,  (payload,battery_status_response,payload.batt
 X(a, STATIC,   ONEOF,    MESSAGE,  (payload,tap_notify_request,payload.tap_notify_request),  29) \
 X(a, STATIC,   ONEOF,    MESSAGE,  (payload,tap_notify_response,payload.tap_notify_response),  30) \
 X(a, STATIC,   ONEOF,    MESSAGE,  (payload,cache_status_request,payload.cache_status_request),  33) \
-X(a, STATIC,   ONEOF,    MESSAGE,  (payload,cache_status_response,payload.cache_status_response),  34)
+X(a, STATIC,   ONEOF,    MESSAGE,  (payload,cache_status_response,payload.cache_status_response),  34) \
+X(a, STATIC,   ONEOF,    MESSAGE,  (payload,espnow_echo_ping_request,payload.espnow_echo_ping_request),  35) \
+X(a, STATIC,   ONEOF,    MESSAGE,  (payload,espnow_echo_ping_response,payload.espnow_echo_ping_response),  36) \
+X(a, STATIC,   ONEOF,    MESSAGE,  (payload,set_log_level_request,payload.set_log_level_request),  37) \
+X(a, STATIC,   ONEOF,    MESSAGE,  (payload,set_log_level_response,payload.set_log_level_response),  38)
 #define alox_UartMessage_CALLBACK NULL
 #define alox_UartMessage_DEFAULT NULL
 #define alox_UartMessage_payload_ack_payload_MSGTYPE alox_Ack
@@ -735,6 +801,10 @@ X(a, STATIC,   ONEOF,    MESSAGE,  (payload,cache_status_response,payload.cache_
 #define alox_UartMessage_payload_tap_notify_response_MSGTYPE alox_TapNotifyResponse
 #define alox_UartMessage_payload_cache_status_request_MSGTYPE alox_CacheStatusRequest
 #define alox_UartMessage_payload_cache_status_response_MSGTYPE alox_CacheStatusResponse
+#define alox_UartMessage_payload_espnow_echo_ping_request_MSGTYPE alox_EspNowEchoPingRequest
+#define alox_UartMessage_payload_espnow_echo_ping_response_MSGTYPE alox_EspNowEchoPingResponse
+#define alox_UartMessage_payload_set_log_level_request_MSGTYPE alox_SetLogLevelRequest
+#define alox_UartMessage_payload_set_log_level_response_MSGTYPE alox_SetLogLevelResponse
 
 #define alox_Ack_FIELDLIST(X, a) \
 
@@ -934,6 +1004,20 @@ X(a, STATIC,   SINGULAR, UINT32,   seq,               2)
 #define alox_EspNowUnicastTestResponse_CALLBACK NULL
 #define alox_EspNowUnicastTestResponse_DEFAULT NULL
 
+#define alox_EspNowEchoPingRequest_FIELDLIST(X, a) \
+X(a, STATIC,   SINGULAR, UINT32,   client_id,         1) \
+X(a, STATIC,   SINGULAR, UINT64,   timestamp_us,      2)
+#define alox_EspNowEchoPingRequest_CALLBACK NULL
+#define alox_EspNowEchoPingRequest_DEFAULT NULL
+
+#define alox_EspNowEchoPingResponse_FIELDLIST(X, a) \
+X(a, STATIC,   SINGULAR, BOOL,     success,           1) \
+X(a, STATIC,   SINGULAR, UINT32,   client_id,         2) \
+X(a, STATIC,   SINGULAR, UINT64,   timestamp_us,      3) \
+X(a, STATIC,   SINGULAR, UINT32,   esp_rtt_us,        4)
+#define alox_EspNowEchoPingResponse_CALLBACK NULL
+#define alox_EspNowEchoPingResponse_DEFAULT NULL
+
 #define alox_LedRingProgressRequest_FIELDLIST(X, a) \
 X(a, STATIC,   SINGULAR, UINT32,   mode,              1) \
 X(a, STATIC,   SINGULAR, UINT32,   progress,          2) \
@@ -982,6 +1066,18 @@ X(a, STATIC,   SINGULAR, UINT32,   client_id,         2)
 #define alox_RestartResponse_CALLBACK NULL
 #define alox_RestartResponse_DEFAULT NULL
 
+#define alox_SetLogLevelRequest_FIELDLIST(X, a) \
+X(a, STATIC,   SINGULAR, BOOL,     write,             1) \
+X(a, STATIC,   SINGULAR, UINT32,   level,             2)
+#define alox_SetLogLevelRequest_CALLBACK NULL
+#define alox_SetLogLevelRequest_DEFAULT NULL
+
+#define alox_SetLogLevelResponse_FIELDLIST(X, a) \
+X(a, STATIC,   SINGULAR, BOOL,     success,           1) \
+X(a, STATIC,   SINGULAR, UINT32,   level,             2)
+#define alox_SetLogLevelResponse_CALLBACK NULL
+#define alox_SetLogLevelResponse_DEFAULT NULL
+
 #define alox_OtaStartPayload_FIELDLIST(X, a) \
 X(a, STATIC,   SINGULAR, UINT32,   total_size,        1)
 #define alox_OtaStartPayload_CALLBACK NULL
@@ -1057,12 +1153,16 @@ extern const pb_msgdesc_t alox_CacheClientStatus_msg;
 extern const pb_msgdesc_t alox_CacheStatusResponse_msg;
 extern const pb_msgdesc_t alox_EspNowUnicastTestRequest_msg;
 extern const pb_msgdesc_t alox_EspNowUnicastTestResponse_msg;
+extern const pb_msgdesc_t alox_EspNowEchoPingRequest_msg;
+extern const pb_msgdesc_t alox_EspNowEchoPingResponse_msg;
 extern const pb_msgdesc_t alox_LedRingProgressRequest_msg;
 extern const pb_msgdesc_t alox_LedRingProgressResponse_msg;
 extern const pb_msgdesc_t alox_EspNowFindMeRequest_msg;
 extern const pb_msgdesc_t alox_EspNowFindMeResponse_msg;
 extern const pb_msgdesc_t alox_RestartRequest_msg;
 extern const pb_msgdesc_t alox_RestartResponse_msg;
+extern const pb_msgdesc_t alox_SetLogLevelRequest_msg;
+extern const pb_msgdesc_t alox_SetLogLevelResponse_msg;
 extern const pb_msgdesc_t alox_OtaStartPayload_msg;
 extern const pb_msgdesc_t alox_OtaPayload_msg;
 extern const pb_msgdesc_t alox_OtaEndPayload_msg;
@@ -1099,12 +1199,16 @@ extern const pb_msgdesc_t alox_OtaSlaveProgressResponse_msg;
 #define alox_CacheStatusResponse_fields &alox_CacheStatusResponse_msg
 #define alox_EspNowUnicastTestRequest_fields &alox_EspNowUnicastTestRequest_msg
 #define alox_EspNowUnicastTestResponse_fields &alox_EspNowUnicastTestResponse_msg
+#define alox_EspNowEchoPingRequest_fields &alox_EspNowEchoPingRequest_msg
+#define alox_EspNowEchoPingResponse_fields &alox_EspNowEchoPingResponse_msg
 #define alox_LedRingProgressRequest_fields &alox_LedRingProgressRequest_msg
 #define alox_LedRingProgressResponse_fields &alox_LedRingProgressResponse_msg
 #define alox_EspNowFindMeRequest_fields &alox_EspNowFindMeRequest_msg
 #define alox_EspNowFindMeResponse_fields &alox_EspNowFindMeResponse_msg
 #define alox_RestartRequest_fields &alox_RestartRequest_msg
 #define alox_RestartResponse_fields &alox_RestartResponse_msg
+#define alox_SetLogLevelRequest_fields &alox_SetLogLevelRequest_msg
+#define alox_SetLogLevelResponse_fields &alox_SetLogLevelResponse_msg
 #define alox_OtaStartPayload_fields &alox_OtaStartPayload_msg
 #define alox_OtaPayload_fields &alox_OtaPayload_msg
 #define alox_OtaEndPayload_fields &alox_OtaEndPayload_msg
@@ -1136,6 +1240,8 @@ extern const pb_msgdesc_t alox_OtaSlaveProgressResponse_msg;
 #define alox_CacheStatusRequest_size             0
 #define alox_CacheStatusResponse_size            736
 #define alox_ClientInput_size                    22
+#define alox_EspNowEchoPingRequest_size          17
+#define alox_EspNowEchoPingResponse_size         25
 #define alox_EspNowFindMeRequest_size            6
 #define alox_EspNowFindMeResponse_size           8
 #define alox_EspNowUnicastTestRequest_size       12
@@ -1152,6 +1258,8 @@ extern const pb_msgdesc_t alox_OtaSlaveProgressResponse_msg;
 #define alox_OtaStatusPayload_size               24
 #define alox_RestartRequest_size                 6
 #define alox_RestartResponse_size                8
+#define alox_SetLogLevelRequest_size             8
+#define alox_SetLogLevelResponse_size            8
 #define alox_TapEvent_size                       16
 #define alox_TapNotifyRequest_size               16
 #define alox_TapNotifyResponse_size              20

main/proto/uart_messages.proto

@@ -29,6 +29,10 @@ enum MessageType {
   reserved 28;
   /** Combined cached accel + tap poll (one UART round-trip, ~16 ms cadence). */
   CACHE_STATUS = 29;
+  /** Host → master → slave → master: timestamp echo round-trip (latency test). */
+  ESPNOW_ECHO_PING = 30;
+  /** Host → master: get/set ESP-IDF log level for tag "*" (global). */
+  SET_LOG_LEVEL = 31;
 }
 
 message UartMessage {
@@ -63,6 +67,10 @@ message UartMessage {
     TapNotifyResponse tap_notify_response = 30;
     CacheStatusRequest cache_status_request = 33;
     CacheStatusResponse cache_status_response = 34;
+    EspNowEchoPingRequest espnow_echo_ping_request = 35;
+    EspNowEchoPingResponse espnow_echo_ping_response = 36;
+    SetLogLevelRequest set_log_level_request = 37;
+    SetLogLevelResponse set_log_level_response = 38;
   }
 }
 
@@ -255,8 +263,24 @@ message EspNowUnicastTestResponse {
   uint32 seq = 2;
 }
 
+/** Host → master: ESP-NOW echo ping to one slave (timestamp echoed back). */
+message EspNowEchoPingRequest {
+  uint32 client_id = 1;
+  /** Microseconds since Unix epoch (host clock). */
+  uint64 timestamp_us = 2;
+}
+
+message EspNowEchoPingResponse {
+  bool success = 1;
+  uint32 client_id = 2;
+  /** Echoed host timestamp from goTool request. */
+  uint64 timestamp_us = 3;
+  /** esp_timer_get_time() delta from ping send to pong recv (master→slave→master). */
+  uint32 esp_rtt_us = 4;
+}
+
 // Host → master: LED ring on master (client_id=0) and/or slaves via ESP-NOW.
-// mode: 0=clear, 1=progress (0–100 %), 2=digit (0–10), 3=blink, 4=find-me, 5=all LEDs solid color.
+// mode: 0=clear, 1=progress (0–100 %), 2=digit (0–10), 3=blink, 4=find-me, 5=all LEDs solid color, 6=battery-low.
 message LedRingProgressRequest {
   uint32 mode = 1;
   /** 0–100: fraction of ring LEDs to light (mode=progress) */
@@ -309,6 +333,18 @@ message RestartResponse {
   uint32 client_id = 2;
 }
 
+/** Host → master: read/write global log level (esp_log_level_set("*", …)). */
+message SetLogLevelRequest {
+  bool write = 1;
+  /** esp_log_level_t: 0=NONE, 1=ERROR, 2=WARN, 3=INFO, 4=DEBUG, 5=VERBOSE */
+  uint32 level = 2;
+}
+
+message SetLogLevelResponse {
+  bool success = 1;
+  uint32 level = 2;
+}
+
 // Host → device: begin UART OTA (erase inactive OTA slot; device replies OTA_STATUS).
 message OtaStartPayload {
   uint32 total_size = 1;

main/uart.c

@@ -52,7 +52,8 @@ void init_uart(QueueHandle_t cmd_queue) {
       .flow_ctrl = UART_HW_FLOWCTRL_DISABLE,
   };
 
-  err = uart_driver_install(UART_NUM, UART_BUF_SIZE * 2, UART_BUF_SIZE, 0, NULL, 0);
+  err = uart_driver_install(UART_NUM, UART_DRIVER_RX_BUF_SIZE,
+                            UART_DRIVER_TX_BUF_SIZE, 0, NULL, 0);
   if (err != ESP_OK) {
     ESP_LOGE(TAG, "uart_driver_install failed: %s", esp_err_to_name(err));
     return;

main/uart.h

@@ -16,7 +16,10 @@
 #define UART_RXD_PIN 3
 
 
-#define UART_BUF_SIZE 2048
+#define UART_BUF_SIZE 4096
+/** Driver RX ring — must hold a full OTA block burst (~20 × ~215 B frames). */
+#define UART_DRIVER_RX_BUF_SIZE 16384
+#define UART_DRIVER_TX_BUF_SIZE 4096
 #define START_MARKER 0xAA
 #define STOP_MARKER 0xCC
 #define MAX_BUF_SIZE 252