Added ECHO cmd and fixed some timing issues

goTool/README.md

@@ -28,6 +28,7 @@ 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 |
@@ -113,8 +114,20 @@ 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
+```
+
+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

@@ -41,6 +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"`
 }
@@ -91,6 +104,13 @@ 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)
@@ -316,6 +336,30 @@ 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/client_api.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"time"
 
 	"google.golang.org/protobuf/proto"
 
@@ -410,6 +411,66 @@ 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)
@@ -490,6 +551,20 @@ 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_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/docs/API_REST.md

@@ -216,6 +216,54 @@ 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
@@ -280,5 +328,6 @@ 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) |
 | 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

@@ -5,6 +5,7 @@ External API: `ws://localhost:8081/ws` (default `-api-addr`, disable with empty
 Start with `go run . -port /dev/ttyUSB0 serve`.
 
 ---
+
 ## Connection flow
 
 1. Connect → server sends `hello` (push off; defaults and command list).
@@ -19,19 +20,23 @@ On disconnect, `set_stream` state for that socket is dropped. Firmware settings
 
 ## Two layers (firmware vs host)
 
-| Layer | Commands | Effect |
-|-------|----------|--------|
+
+| 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 |
+| 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 |
-|-------|-------|---------|
+
+| 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 |
+| `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.
 
@@ -74,17 +79,19 @@ Combines latest accel cache and visible tap state for every slave slot on the ma
 }
 ```
 
-| 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` |
+
+| 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.
 
@@ -198,14 +205,16 @@ Response `tap_notify_status`:
 {"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 |
+
+| 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                  |
+
 
 Target: `client_id` (`0` = master) or `all_clients` (+ optional `slaves_only`).
 
@@ -240,3 +249,4 @@ Response `battery_status`:
   ]
 }
 ```
+

goTool/main.go

@@ -19,6 +19,7 @@ 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")
@@ -52,7 +53,7 @@ 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", "ota", "ota-progress", "ota_progress":
 		if *portName == "" {
 			fmt.Fprintf(os.Stderr, "command %q requires -port\n\n", cmd)
 			usage()
@@ -78,6 +79,8 @@ 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":

goTool/pb/uart_messages.pb.go

@@ -46,6 +46,8 @@ 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
 )
 
 // Enum value maps for MessageType.
@@ -72,6 +74,7 @@ var (
 		26: "BATTERY_STATUS",
 		27: "TAP_NOTIFY",
 		29: "CACHE_STATUS",
+		30: "ESPNOW_ECHO_PING",
 	}
 	MessageType_value = map[string]int32{
 		"UNKNOWN":             0,
@@ -95,6 +98,7 @@ var (
 		"BATTERY_STATUS":      26,
 		"TAP_NOTIFY":          27,
 		"CACHE_STATUS":        29,
+		"ESPNOW_ECHO_PING":    30,
 	}
 )
 
@@ -211,6 +215,8 @@ type UartMessage struct {
 	//	*UartMessage_TapNotifyResponse
 	//	*UartMessage_CacheStatusRequest
 	//	*UartMessage_CacheStatusResponse
+	//	*UartMessage_EspnowEchoPingRequest
+	//	*UartMessage_EspnowEchoPingResponse
 	Payload       isUartMessage_Payload `protobuf_oneof:"payload"`
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
@@ -521,6 +527,24 @@ 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
+}
+
 type isUartMessage_Payload interface {
 	isUartMessage_Payload()
 }
@@ -641,6 +665,14 @@ 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"`
+}
+
 func (*UartMessage_AckPayload) isUartMessage_Payload() {}
 
 func (*UartMessage_EchoPayload) isUartMessage_Payload() {}
@@ -699,6 +731,10 @@ func (*UartMessage_CacheStatusRequest) isUartMessage_Payload() {}
 
 func (*UartMessage_CacheStatusResponse) isUartMessage_Payload() {}
 
+func (*UartMessage_EspnowEchoPingRequest) isUartMessage_Payload() {}
+
+func (*UartMessage_EspnowEchoPingResponse) isUartMessage_Payload() {}
+
 type Ack struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
 	unknownFields protoimpl.UnknownFields
@@ -2329,6 +2365,130 @@ 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.
 type LedRingProgressRequest struct {
@@ -2359,7 +2519,7 @@ 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 +2531,7 @@ 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 +2544,7 @@ 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 +2645,7 @@ 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 +2657,7 @@ 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 +2670,7 @@ 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 +2725,7 @@ 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 +2737,7 @@ 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 +2750,7 @@ 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 +2770,7 @@ 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 +2782,7 @@ 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 +2795,7 @@ 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 +2822,7 @@ 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 +2834,7 @@ 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 +2847,7 @@ 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 +2867,7 @@ 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 +2879,7 @@ 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 +2892,7 @@ 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 {
@@ -2759,7 +2919,7 @@ type OtaStartPayload struct {
 
 func (x *OtaStartPayload) Reset() {
 	*x = OtaStartPayload{}
-	mi := &file_uart_messages_proto_msgTypes[33]
+	mi := &file_uart_messages_proto_msgTypes[35]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2771,7 +2931,7 @@ 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[35]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2784,7 +2944,7 @@ 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{35}
 }
 
 func (x *OtaStartPayload) GetTotalSize() uint32 {
@@ -2805,7 +2965,7 @@ type OtaPayload struct {
 
 func (x *OtaPayload) Reset() {
 	*x = OtaPayload{}
-	mi := &file_uart_messages_proto_msgTypes[34]
+	mi := &file_uart_messages_proto_msgTypes[36]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2817,7 +2977,7 @@ 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[36]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2830,7 +2990,7 @@ 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{36}
 }
 
 func (x *OtaPayload) GetSeq() uint32 {
@@ -2856,7 +3016,7 @@ type OtaEndPayload struct {
 
 func (x *OtaEndPayload) Reset() {
 	*x = OtaEndPayload{}
-	mi := &file_uart_messages_proto_msgTypes[35]
+	mi := &file_uart_messages_proto_msgTypes[37]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2868,7 +3028,7 @@ 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[37]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2881,7 +3041,7 @@ 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{37}
 }
 
 // Device → host status (also used as ACK after each 4 KiB written).
@@ -2898,7 +3058,7 @@ type OtaStatusPayload struct {
 
 func (x *OtaStatusPayload) Reset() {
 	*x = OtaStatusPayload{}
-	mi := &file_uart_messages_proto_msgTypes[36]
+	mi := &file_uart_messages_proto_msgTypes[38]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2910,7 +3070,7 @@ 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[38]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2923,7 +3083,7 @@ 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{38}
 }
 
 func (x *OtaStatusPayload) GetStatus() uint32 {
@@ -2964,7 +3124,7 @@ type OtaSlaveProgressRequest struct {
 
 func (x *OtaSlaveProgressRequest) Reset() {
 	*x = OtaSlaveProgressRequest{}
-	mi := &file_uart_messages_proto_msgTypes[37]
+	mi := &file_uart_messages_proto_msgTypes[39]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -2976,7 +3136,7 @@ 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[39]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -2989,7 +3149,7 @@ 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{39}
 }
 
 func (x *OtaSlaveProgressRequest) GetClientId() uint32 {
@@ -3013,7 +3173,7 @@ type OtaSlaveProgressEntry struct {
 
 func (x *OtaSlaveProgressEntry) Reset() {
 	*x = OtaSlaveProgressEntry{}
-	mi := &file_uart_messages_proto_msgTypes[38]
+	mi := &file_uart_messages_proto_msgTypes[40]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -3025,7 +3185,7 @@ 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[40]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -3038,7 +3198,7 @@ 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{40}
 }
 
 func (x *OtaSlaveProgressEntry) GetClientId() uint32 {
@@ -3089,7 +3249,7 @@ type OtaSlaveProgressResponse struct {
 
 func (x *OtaSlaveProgressResponse) Reset() {
 	*x = OtaSlaveProgressResponse{}
-	mi := &file_uart_messages_proto_msgTypes[39]
+	mi := &file_uart_messages_proto_msgTypes[41]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -3101,7 +3261,7 @@ 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[41]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -3114,7 +3274,7 @@ 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{41}
 }
 
 func (x *OtaSlaveProgressResponse) GetActive() bool {
@@ -3156,7 +3316,7 @@ 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\"\x9f\x13\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 +3351,9 @@ 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\x16espnowEchoPingResponseB\t\n" +
 	"\apayload\"\x05\n" +
 	"\x03Ack\"!\n" +
 	"\vEchoPayload\x12\x12\n" +
@@ -3311,7 +3473,16 @@ 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" +
@@ -3376,7 +3547,7 @@ 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*\x87\x03\n" +
 	"\vMessageType\x12\v\n" +
 	"\aUNKNOWN\x10\x00\x12\a\n" +
 	"\x03ACK\x10\x01\x12\b\n" +
@@ -3400,7 +3571,8 @@ 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\"\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 +3595,7 @@ 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, 42)
 var file_uart_messages_proto_goTypes = []any{
 	(MessageType)(0),                  // 0: alox.MessageType
 	(TapKind)(0),                      // 1: alox.TapKind
@@ -3454,19 +3626,21 @@ 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
+	(*OtaStartPayload)(nil),           // 37: alox.OtaStartPayload
+	(*OtaPayload)(nil),                // 38: alox.OtaPayload
+	(*OtaEndPayload)(nil),             // 39: alox.OtaEndPayload
+	(*OtaStatusPayload)(nil),          // 40: alox.OtaStatusPayload
+	(*OtaSlaveProgressRequest)(nil),   // 41: alox.OtaSlaveProgressRequest
+	(*OtaSlaveProgressEntry)(nil),     // 42: alox.OtaSlaveProgressEntry
+	(*OtaSlaveProgressResponse)(nil),  // 43: alox.OtaSlaveProgressResponse
 }
 var file_uart_messages_proto_depIdxs = []int32{
 	0,  // 0: alox.UartMessage.type:type_name -> alox.MessageType
@@ -3475,22 +3649,22 @@ 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
+	37, // 6: alox.UartMessage.ota_start:type_name -> alox.OtaStartPayload
+	38, // 7: alox.UartMessage.ota_payload:type_name -> alox.OtaPayload
+	39, // 8: alox.UartMessage.ota_end:type_name -> alox.OtaEndPayload
+	40, // 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
+	41, // 14: alox.UartMessage.ota_slave_progress_request:type_name -> alox.OtaSlaveProgressRequest
+	43, // 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 +3673,24 @@ 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
+	6,  // 32: alox.ClientInfoResponse.clients:type_name -> alox.ClientInfo
+	8,  // 33: alox.ClientInputResponse.clients:type_name -> alox.ClientInput
+	15, // 34: alox.BatterySample.lipo1:type_name -> alox.LipoReading
+	15, // 35: alox.BatterySample.lipo2:type_name -> alox.LipoReading
+	16, // 36: alox.BatteryStatusResponse.samples:type_name -> alox.BatterySample
+	1,  // 37: alox.TapEvent.kind:type_name -> alox.TapKind
+	1,  // 38: alox.CacheClientTap.kind:type_name -> alox.TapKind
+	23, // 39: alox.CacheClientStatus.accel:type_name -> alox.CacheClientAccel
+	24, // 40: alox.CacheClientStatus.tap:type_name -> alox.CacheClientTap
+	25, // 41: alox.CacheStatusResponse.clients:type_name -> alox.CacheClientStatus
+	42, // 42: alox.OtaSlaveProgressResponse.slaves:type_name -> alox.OtaSlaveProgressEntry
+	43, // [43:43] is the sub-list for method output_type
+	43, // [43:43] is the sub-list for method input_type
+	43, // [43:43] is the sub-list for extension type_name
+	43, // [43:43] is the sub-list for extension extendee
+	0,  // [0:43] is the sub-list for field type_name
 }
 
 func init() { file_uart_messages_proto_init() }
@@ -3552,6 +3728,8 @@ func file_uart_messages_proto_init() {
 		(*UartMessage_TapNotifyResponse)(nil),
 		(*UartMessage_CacheStatusRequest)(nil),
 		(*UartMessage_CacheStatusResponse)(nil),
+		(*UartMessage_EspnowEchoPingRequest)(nil),
+		(*UartMessage_EspnowEchoPingResponse)(nil),
 	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
@@ -3559,7 +3737,7 @@ 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:   42,
 			NumExtensions: 0,
 			NumServices:   0,
 		},

goTool/webui/index.html

@@ -403,6 +403,12 @@
                                   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"
@@ -640,6 +646,7 @@
         busy: false,
         configMsg: '',
         configMsgOk: false,
+        _flashTimer: null,
         led: {
           mode: 'color',
           r: 0,
@@ -1031,10 +1038,14 @@
             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) {
@@ -1258,6 +1269,43 @@
             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 {