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>

goTool/README.md

@@ -33,7 +33,7 @@ go run . -port /dev/ttyUSB0 clients
 | `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 |

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/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/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.
 

goTool/docs/API_WEBSOCKET.md

@@ -214,11 +214,12 @@ Response `tap_notify_status`:
 | `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.
+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}

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/pb/uart_messages.pb.go

@@ -2526,7 +2526,7 @@ func (x *EspNowEchoPingResponse) GetEspRttUs() uint32 {
 }
 
 // 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"`

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/webui/index.html

@@ -471,7 +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">
@@ -484,6 +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">