feat(#123): GPS refresh — self-telemetry stock-fw fallback (firmware-aware poll)

lib/connector/meshcore_connector.dart

@@ -19,6 +19,7 @@ import '../models/translation_support.dart';
 import '../helpers/reaction_helper.dart';
 import '../helpers/cyr2lat.dart';
 import '../helpers/smaz.dart';
+import '../helpers/cayenne_lpp.dart';
 import '../services/app_debug_log_service.dart';
 import '../services/ble_debug_log_service.dart';
 import '../services/linux_ble_error_classifier.dart';
@@ -2718,11 +2719,14 @@ class MeshCoreConnector extends ChangeNotifier {
     _batteryPollTimer = null;
   }
 
-  /// Poll the radio's GPS position every minute via the lightweight Offband
-  /// `0xC1` query — NOT `CMD_APP_START`, which re-inits the whole device
-  /// (re-walks channels, re-drains messages) and floods slow BLE links. (#140)
-  /// No-op if already running. Triggered when the radio reports `gps=1`; the
-  /// reply updates self-lat/lon via `_handleOffbandGps`. (#135)
+  /// Poll the radio's own GPS position every [_gpsLocationPollInterval] without
+  /// resetting the session (the old `CMD_APP_START` poll re-inited the device
+  /// and broke contact/channel sync on gps=1 radios — #110/#140). Mechanism is
+  /// firmware-aware: the Offband `0xC1` query where supported (#135, richer
+  /// state), else standard MeshCore self-telemetry (`CMD_SEND_TELEMETRY_REQ`
+  /// len==4 → `PUSH_CODE_TELEMETRY_RESPONSE`, decoded in [_handleSelfTelemetry])
+  /// as the stock-firmware fallback (#123). No-op if already running. Triggered
+  /// when the radio reports `gps=1`.
   void _startGpsLocationPolling() {
     if (_gpsLocationPollTimer != null) return;
     _gpsLocationPollTimer = Timer.periodic(_gpsLocationPollInterval, (timer) {
@@ -2731,7 +2735,19 @@ class MeshCoreConnector extends ChangeNotifier {
         _gpsLocationPollTimer = null;
         return;
       }
+      if (supportsOffbandGps) {
         unawaited(requestOffbandGps());
+      } else {
+        // Stock firmware (no 0xC1): non-destructive self-telemetry read. (#123)
+        unawaited(
+          sendFrame(buildSendTelemetryReq(null)).catchError((Object e) {
+            _appDebugLogService?.warn(
+              'GPS self-telemetry poll send failed: $e',
+              tag: 'GPS',
+            );
+          }),
+        );
+      }
     });
   }
 
@@ -2740,19 +2756,60 @@ class MeshCoreConnector extends ChangeNotifier {
     _gpsLocationPollTimer = null;
   }
 
-  /// Start or stop the 0xC1 GPS poll based on current state: only when the
-  /// radio reports `gps=1` AND the firmware advertises 0xC1 support. Called
-  /// from every input that can change either input (custom-var frames, the
-  /// enable toggle, and the device-info reply that delivers `offband_caps`) so
-  /// frame-arrival order doesn't matter. (#144)
+  /// Start or stop the GPS poll based on state: run whenever the radio reports
+  /// `gps=1` — the poll itself picks 0xC1 vs self-telemetry by firmware, so
+  /// stock-fw radios get the non-destructive self-telemetry refresh too (#123).
+  /// Called from every input that can change `gps` or `offband_caps` (custom-var
+  /// frames, the enable toggle, the device-info reply that delivers
+  /// `offband_caps`) so frame-arrival order doesn't matter. (#144)
   void _reconcileGpsPolling() {
-    if (supportsOffbandGps && _currentCustomVars?['gps'] == '1') {
+    if (_currentCustomVars?['gps'] == '1') {
       _startGpsLocationPolling();
     } else {
       _stopGpsLocationPolling();
     }
   }
 
+  /// Decode a self-telemetry reply
+  /// (`[0x8B][reserved][self-pubkey 6][CayenneLPP]`) and update the radio's own
+  /// position from its GPS — the non-destructive replacement for the APP_START
+  /// GPS poll (#110). Contact telemetry (a different pubkey) is ignored here;
+  /// the telemetry screen handles those.
+  void _handleSelfTelemetry(List<int> frame) {
+    final selfKey = _selfPublicKey;
+    if (selfKey == null || selfKey.length < 6) return;
+    if (frame.length < 8) return; // code + reserved + 6-byte pubkey prefix
+    if (!listEquals(frame.sublist(2, 8), selfKey.sublist(0, 6))) {
+      return; // not the self node — a contact telemetry reply
+    }
+    // Guard the parse: a malformed CayenneLPP payload from an external radio
+    // must not throw out of the RX dispatch and stall the receive loop. (#123)
+    try {
+      final gps = CayenneLpp.extractGps(
+        CayenneLpp.parseByChannel(Uint8List.fromList(frame.sublist(8))),
+      );
+      if (gps == null || !hasValidLocation(gps.latitude, gps.longitude)) {
+        _appDebugLogService?.info(
+          'Self-telemetry reply received, no valid GPS in payload',
+          tag: 'GPS',
+        );
+        return;
+      }
+      _appDebugLogService?.info(
+        'Self GPS via telemetry: ${gps.latitude}, ${gps.longitude}',
+        tag: 'GPS',
+      );
+      _selfLatitude = gps.latitude;
+      _selfLongitude = gps.longitude;
+      notifyListeners();
+    } catch (e) {
+      _appDebugLogService?.warn(
+        'Self-telemetry CayenneLPP parse failed: $e',
+        tag: 'GPS',
+      );
+    }
+  }
+
   void setPollingInterval(int i) {
     _pollingInterval = i.clamp(1, 60);
     if (isConnected) {
@@ -4112,6 +4169,9 @@ class MeshCoreConnector extends ChangeNotifier {
         _handleRxData(frame);
         _handleLogRxData(frame);
         break;
+      case pushCodeTelemetryResponse:
+        _handleSelfTelemetry(frame);
+        break;
       case respCodeChannelInfo:
         _handleChannelInfo(frame);
         break;

lib/connector/meshcore_protocol.dart

@@ -1026,7 +1026,7 @@ Uint8List buildSendTelemetryReq(Uint8List? pubKey) {
     writer.writeBytes(Uint8List(3)); // reserved bytes
     writer.writeBytes(pubKey);
   } else {
-    writer.writeBytes(Uint8List(4)); // reserved bytes
+    writer.writeBytes(Uint8List(3)); // self: [cmd]+3 reserved => len==4 (#110)
   }
   return writer.toBytes();
 }

lib/helpers/cayenne_lpp.dart

@@ -4,6 +4,26 @@ import 'package:meshcore_open/utils/app_logger.dart';
 import '../connector/meshcore_protocol.dart';
 
 class CayenneLpp {
+  /// The first GPS fix in a parsed CayenneLPP set, or null if none carries one.
+  /// Self-telemetry returns the radio's own position on `TELEM_CHANNEL_SELF`,
+  /// so the first GPS reading is the device's own location (#110).
+  static ({double latitude, double longitude})? extractGps(
+    List<Map<String, dynamic>> parsed,
+  ) {
+    for (final entry in parsed) {
+      final values = entry['values'];
+      if (values is! Map) continue;
+      final gps = values['gps'];
+      if (gps is Map && gps['latitude'] is num && gps['longitude'] is num) {
+        return (
+          latitude: (gps['latitude'] as num).toDouble(),
+          longitude: (gps['longitude'] as num).toDouble(),
+        );
+      }
+    }
+    return null;
+  }
+
   static const int lppDigitalInput = 0; // 1 byte
   static const int lppDigitalOutput = 1; // 1 byte
   static const int lppAnalogInput = 2; // 2 bytes, 0.01 signed

test/connector/gps_self_telemetry_test.dart

@@ -0,0 +1,79 @@
+// Self-telemetry GPS read (#110). The client refreshes the radio's own
+// position via the self telemetry request (CMD_SEND_TELEMETRY_REQ, len==4)
+// instead of APP_START (which reset the session), then extracts GPS from the
+// CayenneLPP reply (firmware self-reply: [0x8B][reserved][self-pubkey 6][LPP]).
+
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meshcore_open/connector/meshcore_protocol.dart';
+import 'package:meshcore_open/helpers/cayenne_lpp.dart';
+
+void main() {
+  group('buildSendTelemetryReq(null) — the self request', () {
+    test(
+      'is CMD_SEND_TELEMETRY_REQ + 3 reserved = 4-byte frame (firmware len==4)',
+      () {
+        // Firmware MyMesh.cpp:2030 matches the self request on `len == 4` (total
+        // frame). 5 bytes ([39,0,0,0,0]) misses it and gets RESP_CODE_ERR (#110).
+        expect(buildSendTelemetryReq(null), [cmdSendTelemetryReq, 0, 0, 0]);
+      },
+    );
+  });
+
+  group('CayenneLpp.extractGps', () {
+    test('returns lat/lon from a parsed GPS reading', () {
+      final parsed = <Map<String, dynamic>>[
+        <String, dynamic>{
+          'channel': 1,
+          'values': <String, dynamic>{
+            'voltage': 4.1,
+            'gps': <String, dynamic>{
+              'latitude': 12.34,
+              'longitude': 56.78,
+              'altitude': 100.0,
+            },
+          },
+        },
+      ];
+      final gps = CayenneLpp.extractGps(parsed);
+      expect(gps, isNotNull);
+      expect(gps!.latitude, closeTo(12.34, 1e-9));
+      expect(gps.longitude, closeTo(56.78, 1e-9));
+    });
+
+    test('returns null when no channel carries GPS', () {
+      final parsed = <Map<String, dynamic>>[
+        <String, dynamic>{
+          'channel': 1,
+          'values': <String, dynamic>{'voltage': 4.1},
+        },
+      ];
+      expect(CayenneLpp.extractGps(parsed), isNull);
+    });
+
+    test('returns null for empty telemetry', () {
+      expect(CayenneLpp.extractGps(<Map<String, dynamic>>[]), isNull);
+    });
+  });
+
+  group('parseDeviceInfoStrings', () {
+    test('extracts build date, model, and firmware version', () {
+      final frame = Uint8List.fromList([
+        0x0d, 0x0e, 0xaf, 0x28, 0, 0, 0, 0, // header (code, ver, counts, rsvd)
+        ...'24-Jun-2026'.codeUnits, 0,
+        ...'RAK 3401'.codeUnits, 0,
+        ...'1.1.0-1.1.0'.codeUnits, 0,
+      ]);
+      expect(parseDeviceInfoStrings(frame), [
+        '24-Jun-2026',
+        'RAK 3401',
+        '1.1.0-1.1.0',
+      ]);
+    });
+
+    test('returns empty for a short frame', () {
+      expect(parseDeviceInfoStrings(Uint8List.fromList([0x0d, 0x0e])), isEmpty);
+    });
+  });
+}