Merge pull request #34 from dz0ny/feat/channel-datagrams

feat: Add channel datagrams #1928

lib/providers/app_provider.dart

@@ -2,7 +2,8 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:math' as math;
 import 'package:flutter/foundation.dart';
-import 'package:meshcore_client/meshcore_client.dart' show BufferReader;
+import 'package:meshcore_client/meshcore_client.dart'
+    show BufferReader, MeshCoreConstants;
 import 'package:shared_preferences/shared_preferences.dart';
 import 'connection_provider.dart';
 import 'contacts_provider.dart';
@@ -211,6 +212,8 @@ class AppProvider with ChangeNotifier {
   static const int _maxPacketRetryAttempts = 4;
   final Map<String, String> _voiceSessionSenderKey6 = {};
   final Map<String, String> _imageSessionSenderKey6 = {};
+  final Map<String, Map<int, VoicePacket>> _pendingChannelVoicePackets = {};
+  final Map<String, Map<int, ImagePacket>> _pendingChannelImageFragments = {};
   final Map<String, Timer> _voiceMissingRetryTimers = {};
   final Map<String, int> _voiceMissingRetryAttempts = {};
   final Map<String, Timer> _imageMissingRetryTimers = {};
@@ -1315,6 +1318,7 @@ class AppProvider with ChangeNotifier {
               .toLowerCase();
         }
         voiceProvider.registerEnvelope(voiceEnvelope);
+        _replayPendingChannelVoicePackets(voiceEnvelope.sessionId);
         enrichedMessage = enrichedMessage.copyWith(
           isVoice: true,
           voiceId: voiceEnvelope.sessionId,
@@ -1352,6 +1356,7 @@ class AppProvider with ChangeNotifier {
               .toLowerCase();
         }
         imageProvider.registerEnvelope(imageEnvelope);
+        _replayPendingChannelImageFragments(imageEnvelope.sessionId);
         messagesProvider.addMessage(
           enrichedMessage,
           contactLookup: (name) {
@@ -1469,15 +1474,7 @@ class AppProvider with ChangeNotifier {
         return;
       }
 
-      final fastGpsPacket = FastGpsPacket.tryParseBinary(payload);
+      if (_handleFastGpsPayload(payload)) {
-      if (fastGpsPacket != null) {
-        final sender = _resolveContactByPrefixHex(fastGpsPacket.senderKey6);
-        if (sender != null) {
-          contactsProvider.updateFastGps(
-            sender.publicKey.sublist(0, 6),
-            fastGpsPacket,
-          );
-        }
         return;
       }
 
@@ -1614,64 +1611,42 @@ class AppProvider with ChangeNotifier {
         return;
       }
 
-      if (ImagePacket.isImageBinary(payload)) {
+      if (_handleIncomingImageBinaryPayload(payload)) {
-        final frag = ImagePacket.tryParseBinary(payload);
-        if (frag == null) return;
-        debugPrint('📷 [AppProvider] Binary image fragment received: $frag');
-        final session = imageProvider.session(frag.sessionId);
-        if (session == null && frag.total < 1) {
-          debugPrint(
-            '⚠️ [AppProvider] Dropping compact image fragment without envelope '
-            'for session ${frag.sessionId}',
-          );
         return;
       }
-        imageProvider.addFragment(
+      _handleIncomingVoiceBinaryPayload(payload);
-          session == null
+    };
-              ? frag
+
-              : ImagePacket(
+    connectionProvider.onChannelDataReceived =
-                  sessionId: frag.sessionId,
+        (channelIdx, pathLen, dataType, payload, snrRaw, rssiDbm) {
-                  format: session.format,
+          if (dataType != MeshCoreConstants.dataTypeDev) {
-                  index: frag.index,
+            debugPrint(
-                  total: session.total,
+              '📦 [AppProvider] Ignoring channel datagram type '
-                  data: frag.data,
+              '0x${dataType.toRadixString(16).padLeft(4, '0')} on channel $channelIdx',
-                ),
-          width: session?.width ?? 0,
-          height: session?.height ?? 0,
-        );
-        _scheduleImageMissingRetry(
-          frag.sessionId,
-          justComplete: imageProvider.isComplete(frag.sessionId),
             );
             return;
           }
 
-      if (!VoicePacket.isVoiceBinary(payload)) return;
+          if (_handleFastGpsPayload(payload)) {
-      final pkt = VoicePacket.tryParseBinary(payload);
-      if (pkt == null) return;
-      debugPrint('🎙️ [AppProvider] Binary voice packet received: $pkt');
-      final session = voiceProvider.session(pkt.sessionId);
-      if (session == null && pkt.total < 1) {
-        debugPrint(
-          '⚠️ [AppProvider] Dropping compact voice packet without envelope '
-          'for session ${pkt.sessionId}',
-        );
             return;
           }
-      final justComplete = voiceProvider.addPacket(
+          if (_handleIncomingImageBinaryPayload(
-        session == null
+            payload,
-            ? pkt
+            allowPreEnvelopeBuffer: true,
-            : VoicePacket(
+          )) {
-                sessionId: pkt.sessionId,
+            return;
-                mode: session.mode,
+          }
-                index: pkt.index,
+          if (_handleIncomingVoiceBinaryPayload(
-                total: session.total,
+            payload,
-                codec2Data: pkt.codec2Data,
+            allowPreEnvelopeBuffer: true,
-              ),
+          )) {
+            return;
+          }
+
+          debugPrint(
+            '📦 [AppProvider] Unknown developer channel payload on channel '
+            '$channelIdx: ${payload.isNotEmpty ? payload.first : -1}',
           );
-      _scheduleVoiceMissingRetry(pkt.sessionId, justComplete: justComplete);
-      // Insert or update the placeholder message in the chat list
-      _handleIncomingVoicePacket(pkt, justComplete: justComplete);
         };
 
     connectionProvider.onControlDataReceived =
@@ -2805,6 +2780,23 @@ class AppProvider with ChangeNotifier {
       return;
     }
 
+    final channelIdx = locationTrackingService.fastLocationChannelIdx;
+    if (channelIdx == null) {
+      return;
+    }
+
+    final hasTargetChannel = contactsProvider.channels.any(
+      (channel) =>
+          (channel.publicKey.length > 1 ? channel.publicKey[1] : 0) ==
+          channelIdx,
+    );
+    if (!hasTargetChannel) {
+      debugPrint(
+        '⚠️ [AppProvider] Fast GPS target channel $channelIdx is unavailable',
+      );
+      return;
+    }
+
     final publicKey = connectionProvider.deviceInfo.publicKey;
     if (publicKey == null || publicKey.length < 6) {
       return;
@@ -2822,10 +2814,14 @@ class AppProvider with ChangeNotifier {
     );
     debugPrint(
       '📍 [AppProvider] Sending fast GPS update ($reason): '
-      '${position.latitude}, ${position.longitude}',
+      '${position.latitude}, ${position.longitude} via channel $channelIdx',
     );
     try {
-      await connectionProvider.sendRawPrivateMulticast(packet.encodeBinary());
+      await connectionProvider.sendChannelData(
+        channelIdx: channelIdx,
+        dataType: MeshCoreConstants.dataTypeDev,
+        payload: packet.encodeBinary(),
+      );
     } catch (e) {
       debugPrint('⚠️ [AppProvider] Fast GPS send failed: $e');
     }
@@ -3363,6 +3359,173 @@ class AppProvider with ChangeNotifier {
     });
   }
 
+  bool _handleFastGpsPayload(Uint8List payload) {
+    final fastGpsPacket = FastGpsPacket.tryParseBinary(payload);
+    if (fastGpsPacket == null) {
+      return false;
+    }
+
+    final sender = _resolveContactByPrefixHex(fastGpsPacket.senderKey6);
+    if (sender != null) {
+      contactsProvider.updateFastGps(
+        sender.publicKey.sublist(0, 6),
+        fastGpsPacket,
+      );
+    }
+    return true;
+  }
+
+  bool _handleIncomingImageBinaryPayload(
+    Uint8List payload, {
+    bool allowPreEnvelopeBuffer = false,
+  }) {
+    if (!ImagePacket.isImageBinary(payload)) {
+      return false;
+    }
+    final frag = ImagePacket.tryParseBinary(payload);
+    if (frag == null) {
+      return true;
+    }
+    debugPrint('📷 [AppProvider] Binary image fragment received: $frag');
+    final session = imageProvider.session(frag.sessionId);
+    if (session == null && frag.total < 1) {
+      if (allowPreEnvelopeBuffer) {
+        _pendingChannelImageFragments.putIfAbsent(
+          frag.sessionId,
+          () => <int, ImagePacket>{},
+        )[frag.index] = frag;
+        debugPrint(
+          '📷 [AppProvider] Buffered compact image fragment before envelope '
+          'for session ${frag.sessionId} index=${frag.index}',
+        );
+      } else {
+        debugPrint(
+          '⚠️ [AppProvider] Dropping compact image fragment without envelope '
+          'for session ${frag.sessionId}',
+        );
+      }
+      return true;
+    }
+
+    imageProvider.addFragment(
+      session == null
+          ? frag
+          : ImagePacket(
+              sessionId: frag.sessionId,
+              format: session.format,
+              index: frag.index,
+              total: session.total,
+              data: frag.data,
+            ),
+      width: session?.width ?? 0,
+      height: session?.height ?? 0,
+    );
+    _scheduleImageMissingRetry(
+      frag.sessionId,
+      justComplete: imageProvider.isComplete(frag.sessionId),
+    );
+    return true;
+  }
+
+  bool _handleIncomingVoiceBinaryPayload(
+    Uint8List payload, {
+    bool allowPreEnvelopeBuffer = false,
+  }) {
+    if (!VoicePacket.isVoiceBinary(payload)) {
+      return false;
+    }
+    final pkt = VoicePacket.tryParseBinary(payload);
+    if (pkt == null) {
+      return true;
+    }
+    debugPrint('🎙️ [AppProvider] Binary voice packet received: $pkt');
+    final session = voiceProvider.session(pkt.sessionId);
+    if (session == null && pkt.total < 1) {
+      if (allowPreEnvelopeBuffer) {
+        _pendingChannelVoicePackets.putIfAbsent(
+          pkt.sessionId,
+          () => <int, VoicePacket>{},
+        )[pkt.index] = pkt;
+        debugPrint(
+          '🎙️ [AppProvider] Buffered compact voice packet before envelope '
+          'for session ${pkt.sessionId} index=${pkt.index}',
+        );
+      } else {
+        debugPrint(
+          '⚠️ [AppProvider] Dropping compact voice packet without envelope '
+          'for session ${pkt.sessionId}',
+        );
+      }
+      return true;
+    }
+
+    final normalizedPacket = session == null
+        ? pkt
+        : VoicePacket(
+            sessionId: pkt.sessionId,
+            mode: session.mode,
+            index: pkt.index,
+            total: session.total,
+            codec2Data: pkt.codec2Data,
+          );
+    final justComplete = voiceProvider.addPacket(normalizedPacket);
+    _scheduleVoiceMissingRetry(pkt.sessionId, justComplete: justComplete);
+    _handleIncomingVoicePacket(normalizedPacket, justComplete: justComplete);
+    return true;
+  }
+
+  void _replayPendingChannelVoicePackets(String sessionId) {
+    final pending = _pendingChannelVoicePackets.remove(sessionId);
+    final session = voiceProvider.session(sessionId);
+    if (pending == null || pending.isEmpty || session == null) {
+      return;
+    }
+
+    final indices = pending.keys.toList()..sort();
+    for (final index in indices) {
+      final packet = pending[index]!;
+      final normalizedPacket = VoicePacket(
+        sessionId: packet.sessionId,
+        mode: session.mode,
+        index: packet.index,
+        total: session.total,
+        codec2Data: packet.codec2Data,
+      );
+      final justComplete = voiceProvider.addPacket(normalizedPacket);
+      _scheduleVoiceMissingRetry(sessionId, justComplete: justComplete);
+      _handleIncomingVoicePacket(normalizedPacket, justComplete: justComplete);
+    }
+  }
+
+  void _replayPendingChannelImageFragments(String sessionId) {
+    final pending = _pendingChannelImageFragments.remove(sessionId);
+    final session = imageProvider.session(sessionId);
+    if (pending == null || pending.isEmpty || session == null) {
+      return;
+    }
+
+    final indices = pending.keys.toList()..sort();
+    for (final index in indices) {
+      final fragment = pending[index]!;
+      final normalizedFragment = ImagePacket(
+        sessionId: fragment.sessionId,
+        format: session.format,
+        index: fragment.index,
+        total: session.total,
+        data: fragment.data,
+      );
+      imageProvider.addFragment(
+        normalizedFragment,
+        width: session.width,
+        height: session.height,
+      );
+      _scheduleImageMissingRetry(
+        sessionId,
+        justComplete: imageProvider.isComplete(sessionId),
+      );
+    }
+  }
+
   /// Insert or update a voice placeholder message for binary raw-data packets.
   ///
   /// Binary voice packets arrive without a chat message, so we synthesise one
@@ -3767,6 +3930,8 @@ class AppProvider with ChangeNotifier {
     _imageMissingRetryAttempts.clear();
     _voiceSessionSenderKey6.clear();
     _imageSessionSenderKey6.clear();
+    _pendingChannelVoicePackets.clear();
+    _pendingChannelImageFragments.clear();
     _lowBatteryNotifiedNodeIds.clear();
     notifyListeners();
   }
@@ -3876,6 +4041,8 @@ class AppProvider with ChangeNotifier {
     for (final timer in _imageMissingRetryTimers.values) {
       timer.cancel();
     }
+    _pendingChannelVoicePackets.clear();
+    _pendingChannelImageFragments.clear();
     super.dispose();
   }
 }

lib/providers/connection_provider.dart

@@ -105,8 +105,6 @@ class ConnectionProvider with ChangeNotifier {
 
   bool _isScanning = false;
   bool get isScanning => _isScanning;
-  bool _isSpectrumScanActive = false;
-  bool get isSpectrumScanActive => _isSpectrumScanActive;
   final Set<int> _pendingDeletedChannelIndices = <int>{};
 
   String? _error;
@@ -212,6 +210,15 @@ class ConnectionProvider with ChangeNotifier {
   onMessageEchoDetected;
   Function(Uint8List publicKeyPrefix, Uint8List statusData)? onStatusResponse;
   Function(Uint8List payload, int snrRaw, int rssiDbm)? onRawDataReceived;
+  Function(
+    int channelIdx,
+    int pathLen,
+    int dataType,
+    Uint8List payload,
+    int snrRaw,
+    int? rssiDbm,
+  )?
+  onChannelDataReceived;
   Function(Uint8List payload, int snrRaw, int rssiDbm, int pathLen)?
   onControlDataReceived;
   Contact? Function(Uint8List contactPublicKey)? resolveContactForDmCallback;
@@ -463,10 +470,6 @@ class ConnectionProvider with ChangeNotifier {
     };
 
     service.onMessageWaiting = () {
-      if (_isSpectrumScanActive) {
-        debugPrint('📥 [Provider] MSG_WAITING ignored during spectrum scan');
-        return;
-      }
       if (!(canStartAutomaticMessageSyncCallback?.call() ?? true)) {
         _pendingAutomaticMessageSync = true;
         debugPrint(
@@ -533,6 +536,16 @@ class ConnectionProvider with ChangeNotifier {
 
     service.onRawDataReceived = (payload, snrRaw, rssiDbm) =>
         onRawDataReceived?.call(payload, snrRaw, rssiDbm);
+    service.onChannelDataReceived =
+        (channelIdx, pathLen, dataType, payload, snrRaw, rssiDbm) =>
+            onChannelDataReceived?.call(
+              channelIdx,
+              pathLen,
+              dataType,
+              payload,
+              snrRaw,
+              rssiDbm,
+            );
     service.onControlDataReceived = (payload, snrRaw, rssiDbm, pathLen) =>
         onControlDataReceived?.call(payload, snrRaw, rssiDbm, pathLen);
 
@@ -548,9 +561,6 @@ class ConnectionProvider with ChangeNotifier {
         semanticVersion: deviceInfo['semanticVersion'] as String?,
         clientRepeat: deviceInfo['clientRepeat'] as bool?,
         pathHashMode: deviceInfo['pathHashMode'] as int?,
-        supportsSpectrumScan: deviceInfo['supportsSpectrumScan'] as bool?,
-        spectrumScanMinKhz: deviceInfo['spectrumScanMinKhz'] as int?,
-        spectrumScanMaxKhz: deviceInfo['spectrumScanMaxKhz'] as int?,
       );
       notifyListeners();
     };
@@ -1804,6 +1814,30 @@ class ConnectionProvider with ChangeNotifier {
     );
   }
 
+  Future<void> sendChannelData({
+    required int channelIdx,
+    required int dataType,
+    required Uint8List payload,
+  }) async {
+    if (!_activeService.isConnected) {
+      _error = 'Not connected to device';
+      notifyListeners();
+      return;
+    }
+
+    try {
+      await _activeService.sendChannelData(
+        channelIdx: channelIdx,
+        dataType: dataType,
+        payload: payload,
+      );
+    } catch (e) {
+      _error = 'Failed to send channel data: $e';
+      notifyListeners();
+      rethrow;
+    }
+  }
+
   /// Request telemetry from contact
   ///
   /// COMPATIBILITY NOTE: This method sends CMD_SEND_TELEMETRY_REQ (39).
@@ -2238,43 +2272,6 @@ class ConnectionProvider with ChangeNotifier {
     }
   }
 
-  Future<SpectrumScanResult?> scanSpectrum({
-    required int startFrequencyKhz,
-    required int stopFrequencyKhz,
-    required int bandwidthKhz,
-    required int stepKhz,
-    required int dwellMs,
-    required int thresholdDb,
-  }) async {
-    if (!_activeService.isConnected) {
-      _error = 'Not connected to device';
-      notifyListeners();
-      return null;
-    }
-
-    try {
-      _isSpectrumScanActive = true;
-      _activeService.setSpectrumScanActive(true);
-      notifyListeners();
-      return await _activeService.scanSpectrum(
-        startFrequencyKhz: startFrequencyKhz,
-        stopFrequencyKhz: stopFrequencyKhz,
-        bandwidthKhz: bandwidthKhz,
-        stepKhz: stepKhz,
-        dwellMs: dwellMs,
-        thresholdDb: thresholdDb,
-      );
-    } catch (e) {
-      _error = 'Failed to scan spectrum: $e';
-      notifyListeners();
-      return null;
-    } finally {
-      _isSpectrumScanActive = false;
-      _activeService.setSpectrumScanActive(false);
-      notifyListeners();
-    }
-  }
-
   /// Set transmit power
   Future<void> setTxPower(int powerDbm) async {
     if (!_activeService.isConnected) {
@@ -2464,7 +2461,6 @@ class ConnectionProvider with ChangeNotifier {
   }
 
   Future<void> refreshDeviceInfo() async {
-    if (_isSpectrumScanActive) return;
     if (!_activeService.isConnected) {
       _error = 'Not connected to device';
       notifyListeners();
@@ -2537,7 +2533,6 @@ class ConnectionProvider with ChangeNotifier {
   /// Sync messages from device queue
   /// Call this repeatedly until no more messages are available
   Future<bool> syncNextMessage() async {
-    if (_isSpectrumScanActive) return false;
     // Prevent re-entrancy and too-fast triggers
     if (_isSyncingMessages) {
       // Another sync (single or loop) is in progress
@@ -2576,10 +2571,6 @@ class ConnectionProvider with ChangeNotifier {
 
   /// Sync all waiting messages from device
   Future<int> syncAllMessages({bool force = false}) async {
-    if (_isSpectrumScanActive) {
-      debugPrint('⏸️ [Provider] Message sync skipped during spectrum scan');
-      return 0;
-    }
     if (!force && !(canStartAutomaticMessageSyncCallback?.call() ?? true)) {
       _pendingAutomaticMessageSync = true;
       debugPrint(

lib/screens/home_screen.dart

@@ -23,13 +23,11 @@ import 'device_config_screen.dart';
 import 'packet_log_screen.dart';
 import 'live_traffic_screen.dart';
 import 'profiles_screen.dart';
-import 'spectrum_scan_screen.dart';
 import '../utils/toast_logger.dart';
 import '../l10n/app_localizations.dart';
 import '../widgets/permission_request_dialog.dart';
 import '../widgets/connection_dialog.dart';
 import '../utils/battery_display_helper.dart';
-import '../services/developer_mode_service.dart';
 import '../services/mesh_map_nodes_service.dart';
 import '../services/profile_device_key_resolver.dart';
 import '../services/profile_manager.dart';
@@ -68,7 +66,6 @@ class _HomeScreenState extends State<HomeScreen>
   int _currentIndex = 0;
   bool _isMapFullscreen = false;
   bool _showRxTxIndicators = true;
-  bool _isDeveloperModeEnabled = false;
   bool _isMapEnabled = true;
   bool _isContactsEnabled = true;
   bool _isSensorsEnabled = false;
@@ -107,7 +104,6 @@ class _HomeScreenState extends State<HomeScreen>
     // Initialize synchronously so first build always has a valid controller.
     _initTabController();
     _loadRxTxPreference();
-    _loadDeveloperModePreference();
     MeshMapNodesService.syncInBackgroundIfStale();
 
     // Show permission dialog after the first frame if needed
@@ -291,14 +287,6 @@ class _HomeScreenState extends State<HomeScreen>
     }
   }
 
-  Future<void> _loadDeveloperModePreference() async {
-    final isEnabled = await DeveloperModeService.isEnabled();
-    if (!mounted) return;
-    setState(() {
-      _isDeveloperModeEnabled = isEnabled;
-    });
-  }
-
   void _showPermissionDialog() {
     if (!mounted) return;
 
@@ -811,32 +799,6 @@ class _HomeScreenState extends State<HomeScreen>
                         .read<ProfileManager>()
                         .profilesEnabled;
 
-                    if (_isDeveloperModeEnabled) {
-                      items.add(
-                        PopupMenuItem(
-                          child: Row(
-                            children: [
-                              const Icon(Icons.radar),
-                              SizedBox(width: 8),
-                              Text(AppLocalizations.of(context)!.spectrumScan),
-                            ],
-                          ),
-                          onTap: () {
-                            final navigator = Navigator.of(context);
-                            Future.delayed(Duration.zero, () {
-                              if (!mounted) return;
-                              navigator.push(
-                                MaterialPageRoute(
-                                  builder: (context) =>
-                                      const SpectrumScanScreen(),
-                                ),
-                              );
-                            });
-                          },
-                        ),
-                      );
-                    }
-
                     items.add(
                       PopupMenuItem(
                         child: Row(
@@ -954,7 +916,6 @@ class _HomeScreenState extends State<HomeScreen>
                               ),
                             );
                             _loadRxTxPreference();
-                            _loadDeveloperModePreference();
                           });
                         },
                       ),

lib/screens/messages_tab.dart

@@ -6,6 +6,7 @@ import 'dart:math' as math;
 import 'dart:typed_data';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:meshcore_client/meshcore_client.dart' show MeshCoreConstants;
 import 'package:provider/provider.dart';
 import 'package:geolocator/geolocator.dart';
 import '../providers/messages_provider.dart';
@@ -114,7 +115,9 @@ class _ComposerActionTile extends StatelessWidget {
                   width: 38,
                   height: 38,
                   decoration: BoxDecoration(
-                    color: effectiveColor.withValues(alpha: enabled ? 0.14 : 0.10),
+                    color: effectiveColor.withValues(
+                      alpha: enabled ? 0.14 : 0.10,
+                    ),
                     borderRadius: BorderRadius.circular(14),
                   ),
                   alignment: Alignment.center,
@@ -964,6 +967,7 @@ class _MessagesTabState extends State<MessagesTab> {
     if (!shouldContinue) return;
     if (!mounted) return;
     final connectionProvider = context.read<ConnectionProvider>();
+    final messagesProvider = context.read<MessagesProvider>();
     if (!connectionProvider.deviceInfo.isConnected) {
       ToastLogger.error(context, 'Not connected to device');
       return;
@@ -975,6 +979,7 @@ class _MessagesTabState extends State<MessagesTab> {
     final rawBytes = await picked.readAsBytes();
 
     setState(() => _isSendingImage = true);
+    String? failedMessageId;
     try {
       // Compress AVIF using user-selected size, compression and color mode.
       final maxSize = await ImagePreferences.getMaxSize();
@@ -1052,8 +1057,8 @@ class _MessagesTabState extends State<MessagesTab> {
       imageProvider.cacheOutgoingSession(sessionId, fragments, envelope);
 
       // Add local placeholder message.
-      final messagesProvider = context.read<MessagesProvider>();
       final msgId = 'img_${sessionId}_sent';
+      failedMessageId = msgId;
       final isChannel =
           _destinationType ==
           MessageDestinationPreferences.destinationTypeChannel;
@@ -1111,10 +1116,23 @@ class _MessagesTabState extends State<MessagesTab> {
         'chunk=${imageDataBytesPerFragment}B',
       );
 
+      if (isChannel) {
+        for (final fragment in fragments) {
+          await connectionProvider.sendChannelData(
+            channelIdx: channelIdx ?? 0,
+            dataType: MeshCoreConstants.dataTypeDev,
+            payload: fragment.encodeBinary(),
+          );
+        }
+      }
+
       // Image fragments are always served on demand after an explicit IR2
       // fetch request, including direct contacts.
     } catch (e, st) {
       debugPrint('❌ [Image] _pickAndSendImage: $e\n$st');
+      if (failedMessageId != null) {
+        messagesProvider.markMessageFailed(failedMessageId);
+      }
       if (!mounted) return;
       ToastLogger.error(context, 'Image send failed');
     } finally {
@@ -1423,6 +1441,15 @@ class _MessagesTabState extends State<MessagesTab> {
     }
 
     debugPrint('🎙️ [Voice] envelope sent for session $sessionId');
+    if (isChannel) {
+      for (final packet in encodedPackets) {
+        await connectionProvider.sendChannelData(
+          channelIdx: channelIdx ?? 0,
+          dataType: MeshCoreConstants.dataTypeDev,
+          payload: packet.encodeBinary(),
+        );
+      }
+    }
     // Mark the placeholder message as "sent" (ackTag=0, timeout=0 = no ACK tracking).
     // addSentMessage() forces deliveryStatus.sending; we upgrade it here so the
     // bubble shows "Sent" instead of "Sending" once all packets are on the wire.
@@ -1759,7 +1786,8 @@ class _MessagesTabState extends State<MessagesTab> {
                           shrinkWrap: true,
                           physics: const NeverScrollableScrollPhysics(),
                           itemCount: actions.length,
-                          gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
+                          gridDelegate:
+                              const SliverGridDelegateWithFixedCrossAxisCount(
                                 crossAxisCount: 2,
                                 mainAxisSpacing: 12,
                                 crossAxisSpacing: 12,

lib/screens/settings_screen.dart

@@ -16,6 +16,7 @@ import '../providers/app_provider.dart';
 import '../providers/connection_provider.dart';
 import '../providers/drawing_provider.dart';
 import '../providers/map_provider.dart';
+import '../models/contact.dart';
 import '../models/config_profile.dart';
 import '../services/location_tracking_service.dart';
 import '../services/locale_preferences.dart';
@@ -79,6 +80,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
   bool _fastLocationUpdatesEnabled = false;
   double _fastLocationMovementThresholdMeters = 10.0;
   int _fastLocationActiveCadenceSeconds = 10;
+  int? _fastLocationChannelIdx;
   bool _rotateMapWithHeading = false;
   bool _showMapDebugInfo = false;
   bool _openMapInFullscreen = false;
@@ -314,6 +316,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
           _locationService.fastLocationMovementThresholdMeters;
       _fastLocationActiveCadenceSeconds =
           _locationService.fastLocationActiveCadenceSeconds;
+      _fastLocationChannelIdx = _locationService.fastLocationChannelIdx;
     });
   }
 
@@ -407,6 +410,79 @@ class _SettingsScreenState extends State<SettingsScreen> {
     });
   }
 
+  String _describeFastLocationChannel(List<Contact> channels) {
+    final channelIdx = _fastLocationChannelIdx;
+    if (channelIdx == null) {
+      return 'Not set';
+    }
+
+    for (final channel in channels) {
+      final idx = channel.publicKey.length > 1 ? channel.publicKey[1] : 0;
+      if (idx == channelIdx) {
+        return '${channel.getLocalizedDisplayName(context)} (slot $channelIdx)';
+      }
+    }
+
+    return 'Channel $channelIdx unavailable';
+  }
+
+  Future<void> _editFastLocationChannel() async {
+    final channels =
+        List<Contact>.from(context.read<ContactsProvider>().channels)
+          ..sort((a, b) {
+            final aIdx = a.publicKey.length > 1 ? a.publicKey[1] : 0;
+            final bIdx = b.publicKey.length > 1 ? b.publicKey[1] : 0;
+            return aIdx.compareTo(bIdx);
+          });
+
+    final selected = await showModalBottomSheet<int?>(
+      context: context,
+      builder: (sheetContext) => SafeArea(
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            ListTile(
+              leading: const Icon(Icons.block),
+              title: const Text('Disable fast GPS publishing'),
+              trailing: _fastLocationChannelIdx == null
+                  ? const Icon(Icons.check)
+                  : null,
+              onTap: () => Navigator.pop(sheetContext, -1),
+            ),
+            for (final channel in channels)
+              ListTile(
+                leading: const Icon(Icons.tag),
+                title: Text(channel.getLocalizedDisplayName(sheetContext)),
+                subtitle: Text(
+                  'Channel ${channel.publicKey.length > 1 ? channel.publicKey[1] : 0}',
+                ),
+                trailing:
+                    _fastLocationChannelIdx ==
+                        (channel.publicKey.length > 1
+                            ? channel.publicKey[1]
+                            : 0)
+                    ? const Icon(Icons.check)
+                    : null,
+                onTap: () => Navigator.pop(
+                  sheetContext,
+                  channel.publicKey.length > 1 ? channel.publicKey[1] : 0,
+                ),
+              ),
+          ],
+        ),
+      ),
+    );
+
+    if (selected == null) return;
+    await _locationService.updateFastLocationChannelIdx(
+      selected < 0 ? null : selected,
+    );
+    if (!mounted) return;
+    setState(() {
+      _fastLocationChannelIdx = _locationService.fastLocationChannelIdx;
+    });
+  }
+
   Future<void> _saveImageMaxSize(int size) async {
     await ImagePreferences.setMaxSize(size);
     if (!mounted) return;
@@ -1766,6 +1842,17 @@ class _SettingsScreenState extends State<SettingsScreen> {
               trailing: const Icon(Icons.chevron_right),
               onTap: _editFastLocationActiveCadence,
             ),
+            ListTile(
+              leading: const Icon(Icons.forum),
+              title: const Text('Fast GPS target channel'),
+              subtitle: Text(
+                _describeFastLocationChannel(
+                  context.watch<ContactsProvider>().channels,
+                ),
+              ),
+              trailing: const Icon(Icons.chevron_right),
+              onTap: _editFastLocationChannel,
+            ),
             ListTile(
               leading: Icon(Icons.location_on),
               title: Text(AppLocalizations.of(context)!.locationPermission),

lib/screens/spectrum_scan_screen.dart

@@ -1,602 +0,0 @@
-import 'package:flutter/material.dart';
-import 'package:meshcore_client/meshcore_client.dart';
-import 'package:provider/provider.dart';
-import '../models/device_info.dart';
-import '../providers/connection_provider.dart';
-import '../widgets/device/spectrum_scan_panel.dart';
-import '../l10n/app_localizations.dart';
-
-class SpectrumScanScreen extends StatefulWidget {
-  const SpectrumScanScreen({super.key});
-
-  @override
-  State<SpectrumScanScreen> createState() => _SpectrumScanScreenState();
-}
-
-class _SpectrumScanScreenState extends State<SpectrumScanScreen> {
-  static const List<String> _bandwidthOptions = [
-    '7.8 kHz',
-    '10.4 kHz',
-    '15.6 kHz',
-    '20.8 kHz',
-    '31.25 kHz',
-    '41.7 kHz',
-    '62.5 kHz',
-    '125 kHz',
-    '250 kHz',
-    '500 kHz',
-  ];
-
-  String _selectedBandwidth = '62.5 kHz';
-  bool _isSpectrumScanRunning = false;
-  bool _rangeInitialized = false;
-  String? _lastRangeSourceKey;
-  late double _scanRangeMinMhz;
-  late double _scanRangeMaxMhz;
-  late RangeValues _scanRangeValues;
-  List<SpectrumScanCandidate> _scanCandidates = const [];
-  int? _selectedScanFrequencyKhz;
-  int _completedScanSectors = 0;
-  int _totalScanSectors = 0;
-
-  List<SpectrumScanCandidate> get _recommendedScanCandidates =>
-      _scanCandidates.take(8).toList();
-
-  @override
-  void initState() {
-    super.initState();
-    final deviceInfo = _deviceInfo;
-    if (deviceInfo.radioBw != null &&
-        deviceInfo.radioBw! >= 0 &&
-        deviceInfo.radioBw! < _bandwidthOptions.length) {
-      _selectedBandwidth = _bandwidthOptions[deviceInfo.radioBw!];
-    }
-    _syncRangeFromDevice(deviceInfo);
-    _selectedScanFrequencyKhz = deviceInfo.radioFreq;
-  }
-
-  DeviceInfo get _deviceInfo => context.read<ConnectionProvider>().deviceInfo;
-
-  @override
-  void didChangeDependencies() {
-    super.didChangeDependencies();
-    _syncRangeFromDevice(context.watch<ConnectionProvider>().deviceInfo);
-  }
-
-  void _syncRangeFromDevice(DeviceInfo deviceInfo) {
-    final minKhz = deviceInfo.spectrumScanMinKhz;
-    final maxKhz = deviceInfo.spectrumScanMaxKhz;
-    late double normalizedMinMhz;
-    late double normalizedMaxMhz;
-    late String sourceKey;
-
-    if (minKhz != null && maxKhz != null && maxKhz > minKhz) {
-      final normalized = _normalizeScanRange(
-        minKhz / 1000.0,
-        maxKhz / 1000.0,
-        deviceInfo.radioFreq != null ? deviceInfo.radioFreq! / 1000.0 : null,
-      );
-      normalizedMinMhz = normalized.$1;
-      normalizedMaxMhz = normalized.$2;
-      sourceKey = 'fw:$minKhz:$maxKhz';
-    } else {
-      final normalized = _normalizeScanRange(
-        null,
-        null,
-        deviceInfo.radioFreq != null ? deviceInfo.radioFreq! / 1000.0 : null,
-      );
-      normalizedMinMhz = normalized.$1;
-      normalizedMaxMhz = normalized.$2;
-      sourceKey =
-          'fallback:${deviceInfo.radioFreq != null ? deviceInfo.radioFreq! ~/ 1000 : 869525}';
-    }
-
-    if (_rangeInitialized && _lastRangeSourceKey == sourceKey) {
-      return;
-    }
-
-    _scanRangeMinMhz = normalizedMinMhz;
-    _scanRangeMaxMhz = normalizedMaxMhz;
-
-    if (_scanRangeMaxMhz <= _scanRangeMinMhz) {
-      _scanRangeMaxMhz = _scanRangeMinMhz + 0.5;
-    }
-
-    _scanRangeValues = RangeValues(_scanRangeMinMhz, _scanRangeMaxMhz);
-    _rangeInitialized = true;
-    _lastRangeSourceKey = sourceKey;
-  }
-
-  (double, double) _normalizeScanRange(
-    double? minMhz,
-    double? maxMhz,
-    double? centerMhz,
-  ) {
-    const hardMinMhz = 800.0;
-    const hardMaxMhz = 950.0;
-    final center = centerMhz ?? 869.525;
-
-    if (minMhz != null && maxMhz != null) {
-      final clampedMin = minMhz.clamp(hardMinMhz, hardMaxMhz);
-      final clampedMax = maxMhz.clamp(hardMinMhz, hardMaxMhz);
-      if (clampedMax > clampedMin) {
-        return (clampedMin, clampedMax);
-      }
-    }
-
-    if (center >= 900.0 && center <= 930.0) {
-      return (902.0, 928.0);
-    }
-
-    return (863.0, 870.0);
-  }
-
-  double _bandwidthToKhz(String bw) {
-    switch (bw) {
-      case '7.8 kHz':
-        return 7.8;
-      case '10.4 kHz':
-        return 10.4;
-      case '15.6 kHz':
-        return 15.6;
-      case '20.8 kHz':
-        return 20.8;
-      case '31.25 kHz':
-        return 31.25;
-      case '41.7 kHz':
-        return 41.7;
-      case '62.5 kHz':
-        return 62.5;
-      case '125 kHz':
-        return 125.0;
-      case '250 kHz':
-        return 250.0;
-      case '500 kHz':
-        return 500.0;
-      default:
-        return 62.5;
-    }
-  }
-
-  String _currentParamProfile(DeviceInfo deviceInfo) {
-    final sf = deviceInfo.radioSf ?? 8;
-    final cr = deviceInfo.radioCr ?? 8;
-    return 'BW $_selectedBandwidth  |  SF$sf  |  CR 4/$cr';
-  }
-
-  String _recommendationTitle(int index) {
-    switch (index) {
-      case 0:
-        return 'Best candidate';
-      case 1:
-        return 'Alternate';
-      case 2:
-        return 'Fallback';
-      default:
-        return 'Candidate ${index + 1}';
-    }
-  }
-
-  List<int> _possibleBracketFrequenciesKhz() {
-    final bandwidthKhz = _bandwidthToKhz(_selectedBandwidth);
-    final halfBandwidthKhz = bandwidthKhz / 2.0;
-    final startKhz = (_scanRangeValues.start * 1000).round();
-    final stopKhz = (_scanRangeValues.end * 1000).round();
-    final firstCenterKhz = (startKhz + halfBandwidthKhz).round();
-    final lastCenterKhz = (stopKhz - halfBandwidthKhz).round();
-
-    if (lastCenterKhz < firstCenterKhz) {
-      return const [];
-    }
-
-    final stepKhz = bandwidthKhz >= 125.0 ? bandwidthKhz.round() : 25;
-    final centers = <int>[];
-    for (
-      var centerKhz = firstCenterKhz;
-      centerKhz <= lastCenterKhz && centers.length < 8;
-      centerKhz += stepKhz
-    ) {
-      centers.add(centerKhz);
-    }
-
-    if (centers.isEmpty || centers.last != lastCenterKhz) {
-      centers.add(lastCenterKhz);
-    }
-
-    return centers.toSet().toList()..sort();
-  }
-
-  void _resetDerivedScanResults() {
-    _scanCandidates = const [];
-    _selectedScanFrequencyKhz = null;
-  }
-
-  List<(int startKhz, int stopKhz)> _buildScanSectors(double bandwidthKhz) {
-    final startKhz = (_scanRangeValues.start * 1000).round();
-    final stopKhz = (_scanRangeValues.end * 1000).round();
-    final sectorWidthKhz = (bandwidthKhz * 24).round().clamp(250, 1200);
-    final overlapKhz = bandwidthKhz.round().clamp(8, 500);
-    final sectors = <(int startKhz, int stopKhz)>[];
-
-    var sectorStartKhz = startKhz;
-    while (sectorStartKhz < stopKhz) {
-      final sectorStopKhz = (sectorStartKhz + sectorWidthKhz).clamp(
-        sectorStartKhz + overlapKhz,
-        stopKhz,
-      );
-      sectors.add((sectorStartKhz, sectorStopKhz));
-      if (sectorStopKhz >= stopKhz) {
-        break;
-      }
-      sectorStartKhz = sectorStopKhz - overlapKhz;
-    }
-
-    return sectors;
-  }
-
-  List<SpectrumScanCandidate> _mergeSectorCandidates(
-    Iterable<SpectrumScanCandidate> candidates,
-  ) {
-    final byFrequency = <int, SpectrumScanCandidate>{};
-    for (final candidate in candidates) {
-      final existing = byFrequency[candidate.centerFrequencyKhz];
-      if (existing == null ||
-          candidate.occupancyPercent < existing.occupancyPercent ||
-          (candidate.occupancyPercent == existing.occupancyPercent &&
-              candidate.peakRssiDbm < existing.peakRssiDbm) ||
-          (candidate.occupancyPercent == existing.occupancyPercent &&
-              candidate.peakRssiDbm == existing.peakRssiDbm &&
-              candidate.avgRssiDbm < existing.avgRssiDbm)) {
-        byFrequency[candidate.centerFrequencyKhz] = candidate;
-      }
-    }
-
-    final merged = byFrequency.values.toList()
-      ..sort((a, b) {
-        final occupancyCompare = a.occupancyPercent.compareTo(
-          b.occupancyPercent,
-        );
-        if (occupancyCompare != 0) return occupancyCompare;
-        final peakCompare = a.peakRssiDbm.compareTo(b.peakRssiDbm);
-        if (peakCompare != 0) return peakCompare;
-        return a.avgRssiDbm.compareTo(b.avgRssiDbm);
-      });
-    return merged;
-  }
-
-  Future<void> _runSpectrumScan() async {
-    final connectionProvider = context.read<ConnectionProvider>();
-    final bandwidthKhz = _bandwidthToKhz(_selectedBandwidth);
-    final sectors = _buildScanSectors(bandwidthKhz);
-    final sectorCandidates = <SpectrumScanCandidate>[];
-
-    setState(() {
-      _isSpectrumScanRunning = true;
-      _resetDerivedScanResults();
-      _completedScanSectors = 0;
-      _totalScanSectors = sectors.length;
-    });
-
-    try {
-      for (var i = 0; i < sectors.length; i++) {
-        final sector = sectors[i];
-        final result = await connectionProvider.scanSpectrum(
-          startFrequencyKhz: sector.$1,
-          stopFrequencyKhz: sector.$2,
-          bandwidthKhz: bandwidthKhz.round(),
-          stepKhz: (bandwidthKhz / 2).round().clamp(1, 1000),
-          dwellMs: 160,
-          thresholdDb: 8,
-        );
-        if (result != null) {
-          sectorCandidates.addAll(result.candidates);
-          final mergedCandidates = _mergeSectorCandidates(sectorCandidates);
-          if (mounted) {
-            setState(() {
-              _scanCandidates = mergedCandidates;
-              if (_selectedScanFrequencyKhz == null &&
-                  mergedCandidates.isNotEmpty) {
-                _selectedScanFrequencyKhz =
-                    mergedCandidates.first.centerFrequencyKhz;
-              }
-              _completedScanSectors = i + 1;
-            });
-          }
-        } else if (mounted) {
-          setState(() {
-            _completedScanSectors = i + 1;
-          });
-        }
-      }
-    } finally {
-      if (mounted) {
-        setState(() {
-          _isSpectrumScanRunning = false;
-          if (_completedScanSectors == 0) {
-            _totalScanSectors = sectors.length;
-          }
-        });
-      }
-    }
-
-    if (!mounted) return;
-
-    final mergedCandidates = _mergeSectorCandidates(sectorCandidates);
-    if (mergedCandidates.isEmpty) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(
-          content: Text(AppLocalizations.of(context)!.spectrumScanReturnedNoCandidateFrequencies),
-          backgroundColor: Colors.red,
-        ),
-      );
-      return;
-    }
-
-    setState(() {
-      _scanCandidates = mergedCandidates;
-      _selectedScanFrequencyKhz = mergedCandidates.first.centerFrequencyKhz;
-    });
-  }
-
-  Future<void> _applySelectedScanFrequency() async {
-    if (_selectedScanFrequencyKhz == null) return;
-
-    final connectionProvider = context.read<ConnectionProvider>();
-    final deviceInfo = connectionProvider.deviceInfo;
-
-    await connectionProvider.setRadioParams(
-      frequency: _selectedScanFrequencyKhz!,
-      bandwidth: _bandwidthOptions.indexOf(_selectedBandwidth),
-      spreadingFactor: deviceInfo.radioSf ?? 8,
-      codingRate: deviceInfo.radioCr ?? 8,
-      repeat: deviceInfo.clientRepeat,
-    );
-    await connectionProvider.refreshDeviceInfo();
-
-    if (!mounted) return;
-    ScaffoldMessenger.of(context).showSnackBar(
-      SnackBar(
-        content: Text(
-          'Applied ${(_selectedScanFrequencyKhz! / 1000.0).toStringAsFixed(3)} MHz',
-        ),
-        backgroundColor: Colors.green,
-      ),
-    );
-  }
-
-  int? _currentPreviewFrequencyKhz(DeviceInfo deviceInfo) {
-    if (_selectedScanFrequencyKhz != null) {
-      return _selectedScanFrequencyKhz;
-    }
-    return deviceInfo.radioFreq;
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    final deviceInfo = context.watch<ConnectionProvider>().deviceInfo;
-    final theme = Theme.of(context);
-    final possibleBracketFrequencies = _possibleBracketFrequenciesKhz();
-    final recommendedScanCandidates = _recommendedScanCandidates;
-    final recommendationFrequencies = recommendedScanCandidates.isNotEmpty
-        ? recommendedScanCandidates
-              .map((candidate) => candidate.centerFrequencyKhz)
-              .toList()
-        : possibleBracketFrequencies;
-
-    return Scaffold(
-      appBar: AppBar(title: Text(AppLocalizations.of(context)!.spectrumScan)),
-      body: ListView(
-        padding: const EdgeInsets.all(16),
-        children: [
-          Card(
-            child: Padding(
-              padding: const EdgeInsets.all(16),
-              child: Column(
-                crossAxisAlignment: CrossAxisAlignment.start,
-                children: [
-                  DropdownButtonFormField<String>(
-                    initialValue: _selectedBandwidth,
-                    decoration: const InputDecoration(
-                      labelText: 'Bandwidth',
-                      border: OutlineInputBorder(),
-                      helperText:
-                          'Scan and apply frequencies for this bandwidth',
-                    ),
-                    items: _bandwidthOptions.map((value) {
-                      return DropdownMenuItem<String>(
-                        value: value,
-                        child: Text(value),
-                      );
-                    }).toList(),
-                    onChanged: (value) {
-                      if (value == null) return;
-                      setState(() {
-                        _selectedBandwidth = value;
-                        _resetDerivedScanResults();
-                      });
-                    },
-                  ),
-                  const SizedBox(height: 16),
-                  Text(
-                    deviceInfo.spectrumScanMinKhz != null &&
-                            deviceInfo.spectrumScanMaxKhz != null
-                        ? 'Firmware scan range: ${_scanRangeMinMhz.toStringAsFixed(3)}-${_scanRangeMaxMhz.toStringAsFixed(3)} MHz'
-                        : 'Fallback scan range selected from current band. MeshCore commonly uses EU868 or US915.',
-                    style: theme.textTheme.bodySmall?.copyWith(
-                      color: theme.colorScheme.onSurfaceVariant,
-                    ),
-                  ),
-                  if (_isSpectrumScanRunning) ...[
-                    const SizedBox(height: 8),
-                    Text(
-                      'Scanning sector ${_completedScanSectors + 1} of $_totalScanSectors. Results update as each sector completes.',
-                      style: theme.textTheme.bodySmall?.copyWith(
-                        color: theme.colorScheme.primary,
-                        fontWeight: FontWeight.w600,
-                      ),
-                    ),
-                  ],
-                  const SizedBox(height: 12),
-                  SpectrumScanPanel(
-                    theme: theme,
-                    scanSupported: deviceInfo.supportsSpectrumScan == true,
-                    isRunning: _isSpectrumScanRunning,
-                    rangeMinMhz: _scanRangeMinMhz,
-                    rangeMaxMhz: _scanRangeMaxMhz,
-                    rangeValues: _scanRangeValues,
-                    bandwidthKhz: _bandwidthToKhz(_selectedBandwidth),
-                    selectedFrequencyKhz: _currentPreviewFrequencyKhz(
-                      deviceInfo,
-                    ),
-                    graphCandidates: _scanCandidates,
-                    selectableCandidates: recommendedScanCandidates,
-                    onRangeChanged: (values) {
-                      setState(() {
-                        _scanRangeValues = values;
-                        _resetDerivedScanResults();
-                      });
-                    },
-                    onCandidateChanged: (value) {
-                      setState(() {
-                        _selectedScanFrequencyKhz = value;
-                      });
-                    },
-                    onRunScan: _runSpectrumScan,
-                    onApplySelected: _applySelectedScanFrequency,
-                  ),
-                  if (recommendationFrequencies.isNotEmpty) ...[
-                    const SizedBox(height: 18),
-                    Text(
-                      _scanCandidates.isNotEmpty
-                          ? 'Recommended profiles'
-                          : 'Possible brackets',
-                      style: theme.textTheme.titleMedium?.copyWith(
-                        fontWeight: FontWeight.w700,
-                      ),
-                    ),
-                    const SizedBox(height: 8),
-                    Text(
-                      _scanCandidates.isNotEmpty
-                          ? 'Suggested frequencies from the latest scan with the radio parameters to keep alongside them.'
-                          : 'Usable frequency brackets derived from the selected span and bandwidth, even without live scan data.',
-                      style: theme.textTheme.bodySmall?.copyWith(
-                        color: theme.colorScheme.onSurfaceVariant,
-                      ),
-                    ),
-                    const SizedBox(height: 12),
-                    for (
-                      var i = 0;
-                      i < recommendationFrequencies.length;
-                      i++
-                    ) ...[
-                      _RecommendationTile(
-                        title: _recommendationTitle(i),
-                        frequencyKhz: recommendationFrequencies[i],
-                        candidate: recommendedScanCandidates.isNotEmpty
-                            ? recommendedScanCandidates[i]
-                            : null,
-                        bandwidthKhz: _bandwidthToKhz(_selectedBandwidth),
-                        paramsLabel: _currentParamProfile(deviceInfo),
-                        isSelected:
-                            _selectedScanFrequencyKhz ==
-                            recommendationFrequencies[i],
-                        onSelect: () {
-                          setState(() {
-                            _selectedScanFrequencyKhz =
-                                recommendationFrequencies[i];
-                          });
-                        },
-                      ),
-                      if (i != recommendationFrequencies.length - 1)
-                        const SizedBox(height: 10),
-                    ],
-                  ],
-                ],
-              ),
-            ),
-          ),
-        ],
-      ),
-    );
-  }
-}
-
-class _RecommendationTile extends StatelessWidget {
-  final String title;
-  final int frequencyKhz;
-  final SpectrumScanCandidate? candidate;
-  final double bandwidthKhz;
-  final String paramsLabel;
-  final bool isSelected;
-  final VoidCallback onSelect;
-
-  const _RecommendationTile({
-    required this.title,
-    required this.frequencyKhz,
-    required this.candidate,
-    required this.bandwidthKhz,
-    required this.paramsLabel,
-    required this.isSelected,
-    required this.onSelect,
-  });
-
-  @override
-  Widget build(BuildContext context) {
-    final theme = Theme.of(context);
-    final scheme = theme.colorScheme;
-
-    return InkWell(
-      onTap: onSelect,
-      borderRadius: BorderRadius.circular(14),
-      child: Container(
-        padding: const EdgeInsets.all(14),
-        decoration: BoxDecoration(
-          color: isSelected
-              ? scheme.primaryContainer.withValues(alpha: 0.55)
-              : scheme.surfaceContainerHighest.withValues(alpha: 0.35),
-          borderRadius: BorderRadius.circular(14),
-          border: Border.all(
-            color: isSelected ? scheme.primary : scheme.outlineVariant,
-          ),
-        ),
-        child: Column(
-          crossAxisAlignment: CrossAxisAlignment.start,
-          children: [
-            Row(
-              children: [
-                Expanded(
-                  child: Text(
-                    title,
-                    style: theme.textTheme.titleSmall?.copyWith(
-                      fontWeight: FontWeight.w700,
-                    ),
-                  ),
-                ),
-                if (isSelected)
-                  Icon(Icons.check_circle, color: scheme.primary, size: 18),
-              ],
-            ),
-            const SizedBox(height: 8),
-            Text(
-              '${(frequencyKhz / 1000.0).toStringAsFixed(3)} MHz',
-              style: theme.textTheme.headlineSmall?.copyWith(
-                fontWeight: FontWeight.w800,
-              ),
-            ),
-            const SizedBox(height: 6),
-            Text(paramsLabel, style: theme.textTheme.bodyMedium),
-            const SizedBox(height: 6),
-            Text(
-              candidate != null
-                  ? 'Occupancy ${candidate!.occupancyPercent}%  |  Avg ${candidate!.avgRssiDbm} dBm  |  Peak ${candidate!.peakRssiDbm} dBm'
-                  : 'Bracket ${(frequencyKhz / 1000.0 - bandwidthKhz / 2000.0).toStringAsFixed(3)}-${(frequencyKhz / 1000.0 + bandwidthKhz / 2000.0).toStringAsFixed(3)} MHz',
-              style: theme.textTheme.bodySmall?.copyWith(
-                color: scheme.onSurfaceVariant,
-              ),
-            ),
-          ],
-        ),
-      ),
-    );
-  }
-}

lib/services/location_tracking_service.dart

@@ -49,6 +49,7 @@ class LocationTrackingService {
       'fast_location_movement_threshold_meters';
   static const String _prefKeyFastActiveCadence =
       'fast_location_active_cadence_seconds';
+  static const String _prefKeyFastChannelIdx = 'fast_location_channel_idx';
 
   String _scopedKey(String baseKey) {
     return ProfileStorageScope.scopedKey(baseKey);
@@ -79,6 +80,9 @@ class LocationTrackingService {
   /// Cadence for active-use fast GPS updates
   int fastLocationActiveCadenceSeconds = 10;
 
+  /// Target channel index for fast GPS updates; null means disabled/unset.
+  int? fastLocationChannelIdx;
+
   // ============================================================================
   // State Properties
   // ============================================================================
@@ -528,8 +532,14 @@ class LocationTrackingService {
     _refreshFastLocationTimer();
   }
 
+  Future<void> updateFastLocationChannelIdx(int? channelIdx) async {
+    fastLocationChannelIdx = channelIdx;
+    await saveSettings();
+    _refreshFastLocationTimer();
+  }
+
   void _evaluateFastLocationMovement(Position position) {
-    if (!fastLocationUpdatesEnabled) return;
+    if (!fastLocationUpdatesEnabled || fastLocationChannelIdx == null) return;
     final previous = _lastFastLocationSentPosition;
     if (previous == null) {
       _emitFastLocationUpdate(position, reason: 'initial');
@@ -552,6 +562,7 @@ class LocationTrackingService {
     _fastLocationTimer = null;
     if (!isTracking ||
         !fastLocationUpdatesEnabled ||
+        fastLocationChannelIdx == null ||
         !_isFastLocationActiveUse) {
       return;
     }
@@ -567,7 +578,7 @@ class LocationTrackingService {
   }
 
   void _emitFastLocationUpdate(Position position, {required String reason}) {
-    if (!fastLocationUpdatesEnabled) return;
+    if (!fastLocationUpdatesEnabled || fastLocationChannelIdx == null) return;
 
     final now = DateTime.now();
     final previous = _lastFastLocationSentPosition;
@@ -669,6 +680,7 @@ class LocationTrackingService {
           5,
           60,
         );
+    fastLocationChannelIdx = prefs.getInt(_scopedKey(_prefKeyFastChannelIdx));
 
     debugPrint('✅ [LocationTracking] Settings loaded');
     debugPrint('    Min distance: ${minDistanceMeters}m');
@@ -680,6 +692,7 @@ class LocationTrackingService {
       '    Fast movement threshold: ${fastLocationMovementThresholdMeters}m',
     );
     debugPrint('    Fast active cadence: ${fastLocationActiveCadenceSeconds}s');
+    debugPrint('    Fast channel idx: ${fastLocationChannelIdx ?? "unset"}');
   }
 
   /// Save settings to SharedPreferences
@@ -709,6 +722,12 @@ class LocationTrackingService {
       _scopedKey(_prefKeyFastActiveCadence),
       fastLocationActiveCadenceSeconds,
     );
+    final channelKey = _scopedKey(_prefKeyFastChannelIdx);
+    if (fastLocationChannelIdx == null) {
+      await prefs.remove(channelKey);
+    } else {
+      await prefs.setInt(channelKey, fastLocationChannelIdx!);
+    }
 
     debugPrint('✅ [LocationTracking] Settings saved');
   }

lib/widgets/device/spectrum_scan_panel.dart

@@ -1,387 +0,0 @@
-import 'package:flutter/material.dart';
-import 'package:meshcore_client/meshcore_client.dart';
-import '../../l10n/app_localizations.dart';
-
-class SpectrumScanPanel extends StatelessWidget {
-  final ThemeData theme;
-  final bool scanSupported;
-  final bool isRunning;
-  final double rangeMinMhz;
-  final double rangeMaxMhz;
-  final RangeValues rangeValues;
-  final double bandwidthKhz;
-  final int? selectedFrequencyKhz;
-  final List<SpectrumScanCandidate> graphCandidates;
-  final List<SpectrumScanCandidate> selectableCandidates;
-  final ValueChanged<RangeValues> onRangeChanged;
-  final ValueChanged<int?> onCandidateChanged;
-  final VoidCallback onRunScan;
-  final VoidCallback onApplySelected;
-
-  const SpectrumScanPanel({
-    super.key,
-    required this.theme,
-    required this.scanSupported,
-    required this.isRunning,
-    required this.rangeMinMhz,
-    required this.rangeMaxMhz,
-    required this.rangeValues,
-    required this.bandwidthKhz,
-    required this.selectedFrequencyKhz,
-    required this.graphCandidates,
-    required this.selectableCandidates,
-    required this.onRangeChanged,
-    required this.onCandidateChanged,
-    required this.onRunScan,
-    required this.onApplySelected,
-  });
-
-  @override
-  Widget build(BuildContext context) {
-    return Container(
-      padding: const EdgeInsets.all(14),
-      decoration: BoxDecoration(
-        color: theme.colorScheme.surfaceContainerHighest.withValues(
-          alpha: 0.45,
-        ),
-        borderRadius: BorderRadius.circular(18),
-        border: Border.all(color: theme.colorScheme.outlineVariant),
-      ),
-      child: Column(
-        crossAxisAlignment: CrossAxisAlignment.start,
-        children: [
-          Row(
-            children: [
-              Icon(Icons.tune, color: theme.colorScheme.primary),
-              const SizedBox(width: 10),
-              Expanded(
-                child: Text(
-                  'Power Scan',
-                  style: theme.textTheme.titleMedium?.copyWith(
-                    fontWeight: FontWeight.w700,
-                  ),
-                ),
-              ),
-              FilledButton.icon(
-                onPressed: scanSupported && !isRunning ? onRunScan : null,
-                icon: isRunning
-                    ? const SizedBox(
-                        width: 16,
-                        height: 16,
-                        child: CircularProgressIndicator(strokeWidth: 2),
-                      )
-                    : const Icon(Icons.radar),
-                label: Text(
-                  scanSupported
-                      ? (isRunning ? 'Scanning' : 'Scan')
-                      : 'Unavailable',
-                ),
-              ),
-            ],
-          ),
-          const SizedBox(height: 8),
-          Text(
-            scanSupported
-                ? 'Full range with bandwidth footprint. Firmware enforces hardware band limits and pauses the mesh while scanning.'
-                : 'Full range with bandwidth footprint. This companion does not support spectrum scan mode, so scanning is disabled.',
-            style: theme.textTheme.bodySmall?.copyWith(
-              color: theme.colorScheme.onSurfaceVariant,
-            ),
-          ),
-          const SizedBox(height: 14),
-          _FrequencyRangePreview(
-            minMhz: rangeMinMhz,
-            maxMhz: rangeMaxMhz,
-            selectedRange: rangeValues,
-            selectedBandwidthKhz: bandwidthKhz,
-            selectedFrequencyKhz: selectedFrequencyKhz,
-            candidates: graphCandidates,
-          ),
-          const SizedBox(height: 10),
-          Wrap(
-            spacing: 14,
-            runSpacing: 6,
-            children: [
-              _LegendChip(
-                color: theme.colorScheme.primary,
-                label: AppLocalizations.of(context)!.quiet,
-              ),
-              _LegendChip(
-                color: Colors.orange,
-                label: AppLocalizations.of(context)!.moderate,
-              ),
-              _LegendChip(
-                color: theme.colorScheme.error,
-                label: AppLocalizations.of(context)!.busy,
-              ),
-            ],
-          ),
-          const SizedBox(height: 10),
-          Row(
-            mainAxisAlignment: MainAxisAlignment.spaceBetween,
-            children: [
-              Text(
-                '${rangeValues.start.toStringAsFixed(3)} MHz',
-                style: theme.textTheme.labelMedium,
-              ),
-              Text(
-                '${rangeValues.end.toStringAsFixed(3)} MHz',
-                style: theme.textTheme.labelMedium,
-              ),
-            ],
-          ),
-          RangeSlider(
-            values: rangeValues,
-            min: rangeMinMhz,
-            max: rangeMaxMhz,
-            divisions: (((rangeMaxMhz - rangeMinMhz) * 20).round()).clamp(
-              1,
-              400,
-            ),
-            labels: RangeLabels(
-              rangeValues.start.toStringAsFixed(3),
-              rangeValues.end.toStringAsFixed(3),
-            ),
-            onChanged: onRangeChanged,
-          ),
-          if (selectableCandidates.isEmpty) ...[
-            const SizedBox(height: 6),
-            Container(
-              width: double.infinity,
-              padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 12),
-              decoration: BoxDecoration(
-                color: theme.colorScheme.surfaceContainerLow,
-                borderRadius: BorderRadius.circular(12),
-                border: Border.all(color: theme.colorScheme.outlineVariant),
-              ),
-              child: Text(
-                scanSupported
-                    ? 'No scan results yet. Adjust the range and run a scan to populate candidate frequencies.'
-                    : 'Spectrum preview only. This companion can display the configured span, but cannot scan for open channels.',
-                style: theme.textTheme.bodySmall?.copyWith(
-                  color: theme.colorScheme.onSurfaceVariant,
-                ),
-              ),
-            ),
-          ] else ...[
-            const SizedBox(height: 10),
-            DropdownButtonFormField<int>(
-              initialValue: selectedFrequencyKhz,
-              isExpanded: true,
-              decoration: const InputDecoration(
-                labelText: 'Candidate frequency',
-                border: OutlineInputBorder(),
-                helperText: 'Best frequencies for the current bandwidth',
-              ),
-              items: selectableCandidates.map((candidate) {
-                return DropdownMenuItem<int>(
-                  value: candidate.centerFrequencyKhz,
-                  child: Column(
-                    crossAxisAlignment: CrossAxisAlignment.start,
-                    mainAxisSize: MainAxisSize.min,
-                    children: [
-                      Text(
-                        '${candidate.centerFrequencyMhz.toStringAsFixed(3)} MHz',
-                        overflow: TextOverflow.ellipsis,
-                      ),
-                      Text(
-                        '${candidate.occupancyPercent}% occupied  |  peak ${candidate.peakRssiDbm} dBm',
-                        style: theme.textTheme.bodySmall?.copyWith(
-                          color: theme.colorScheme.onSurfaceVariant,
-                        ),
-                        overflow: TextOverflow.ellipsis,
-                      ),
-                    ],
-                  ),
-                );
-              }).toList(),
-              selectedItemBuilder: (context) {
-                return selectableCandidates.map((candidate) {
-                  return Align(
-                    alignment: Alignment.centerLeft,
-                    child: Text(
-                      '${candidate.centerFrequencyMhz.toStringAsFixed(3)} MHz',
-                      overflow: TextOverflow.ellipsis,
-                    ),
-                  );
-                }).toList();
-              },
-              onChanged: onCandidateChanged,
-            ),
-            const SizedBox(height: 10),
-            Align(
-              alignment: Alignment.centerRight,
-              child: OutlinedButton.icon(
-                onPressed: selectedFrequencyKhz == null
-                    ? null
-                    : onApplySelected,
-                icon: Icon(Icons.north_east),
-                label: Text(AppLocalizations.of(context)!.useSelectedFrequency),
-              ),
-            ),
-          ],
-        ],
-      ),
-    );
-  }
-}
-
-class _LegendChip extends StatelessWidget {
-  final Color color;
-  final String label;
-
-  const _LegendChip({required this.color, required this.label});
-
-  @override
-  Widget build(BuildContext context) {
-    return Row(
-      mainAxisSize: MainAxisSize.min,
-      children: [
-        Container(
-          width: 10,
-          height: 10,
-          decoration: BoxDecoration(color: color, shape: BoxShape.circle),
-        ),
-        const SizedBox(width: 6),
-        Text(label, style: Theme.of(context).textTheme.labelMedium),
-      ],
-    );
-  }
-}
-
-class _FrequencyRangePreview extends StatelessWidget {
-  final double minMhz;
-  final double maxMhz;
-  final RangeValues selectedRange;
-  final double selectedBandwidthKhz;
-  final int? selectedFrequencyKhz;
-  final List<SpectrumScanCandidate> candidates;
-
-  const _FrequencyRangePreview({
-    required this.minMhz,
-    required this.maxMhz,
-    required this.selectedRange,
-    required this.selectedBandwidthKhz,
-    required this.selectedFrequencyKhz,
-    required this.candidates,
-  });
-
-  double _positionFor(double mhz) {
-    final span = maxMhz - minMhz;
-    if (span <= 0) return 0;
-    return ((mhz - minMhz) / span).clamp(0.0, 1.0);
-  }
-
-  Color _candidateColor(BuildContext context, int occupancyPercent) {
-    final scheme = Theme.of(context).colorScheme;
-    if (occupancyPercent <= 10) return scheme.primary;
-    if (occupancyPercent <= 35) return Colors.orange;
-    return scheme.error;
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    final scheme = Theme.of(context).colorScheme;
-    final spanMhz = maxMhz - minMhz;
-    final selectedFreqMhz = selectedFrequencyKhz != null
-        ? selectedFrequencyKhz! / 1000.0
-        : null;
-    final bwMhz = selectedBandwidthKhz / 1000.0;
-
-    return LayoutBuilder(
-      builder: (context, constraints) {
-        final width = constraints.maxWidth;
-        final rangeLeft = _positionFor(selectedRange.start) * width;
-        final rangeRight = _positionFor(selectedRange.end) * width;
-
-        double? bwLeft;
-        double? bwWidth;
-        if (selectedFreqMhz != null && spanMhz > 0) {
-          bwLeft = _positionFor(selectedFreqMhz - (bwMhz / 2)) * width;
-          final bwRight = _positionFor(selectedFreqMhz + (bwMhz / 2)) * width;
-          bwWidth = (bwRight - bwLeft).clamp(4.0, width);
-        }
-
-        return Container(
-          height: 108,
-          decoration: BoxDecoration(
-            borderRadius: BorderRadius.circular(16),
-            color: scheme.surfaceContainerLow,
-            border: Border.all(color: scheme.outlineVariant),
-          ),
-          child: Stack(
-            children: [
-              Positioned.fill(
-                child: Padding(
-                  padding: const EdgeInsets.symmetric(
-                    horizontal: 10,
-                    vertical: 12,
-                  ),
-                  child: DecoratedBox(
-                    decoration: BoxDecoration(
-                      borderRadius: BorderRadius.circular(12),
-                      color: scheme.surfaceContainerHigh,
-                    ),
-                  ),
-                ),
-              ),
-              Positioned(
-                left: rangeLeft,
-                top: 12,
-                width: (rangeRight - rangeLeft).clamp(8.0, width),
-                height: 56,
-                child: DecoratedBox(
-                  decoration: BoxDecoration(
-                    borderRadius: BorderRadius.circular(12),
-                    color: scheme.primaryContainer,
-                    border: Border.all(color: scheme.primary),
-                  ),
-                ),
-              ),
-              if (bwLeft != null && bwWidth != null)
-                Positioned(
-                  left: bwLeft,
-                  top: 28,
-                  width: bwWidth,
-                  height: 24,
-                  child: DecoratedBox(
-                    decoration: BoxDecoration(
-                      borderRadius: BorderRadius.circular(999),
-                      color: scheme.tertiaryContainer,
-                      border: Border.all(color: scheme.tertiary),
-                    ),
-                  ),
-                ),
-              for (final candidate in candidates)
-                Positioned(
-                  left: (_positionFor(candidate.centerFrequencyMhz) * width)
-                      .clamp(10.0, width - 18.0),
-                  top: 72,
-                  child: Column(
-                    children: [
-                      Container(
-                        width: 10,
-                        height: 10,
-                        decoration: BoxDecoration(
-                          shape: BoxShape.circle,
-                          color: _candidateColor(
-                            context,
-                            candidate.occupancyPercent,
-                          ),
-                        ),
-                      ),
-                      const SizedBox(height: 4),
-                      Text(
-                        candidate.centerFrequencyMhz.toStringAsFixed(3),
-                        style: Theme.of(context).textTheme.labelSmall,
-                      ),
-                    ],
-                  ),
-                ),
-            ],
-          ),
-        );
-      },
-    );
-  }
-}

pubspec.lock

@@ -827,8 +827,8 @@ packages:
     dependency: "direct main"
     description:
       path: "."
-      ref: main
+      ref: dfc5b82c3f8a7f160ca77e45dc65a9eb39cebc5a
-      resolved-ref: "71902401e9a6bc7d2ed1193f8961e7256646ab76"
+      resolved-ref: dfc5b82c3f8a7f160ca77e45dc65a9eb39cebc5a
       url: "https://github.com/dz0ny/meshcore_client.git"
     source: git
     version: "0.1.0"

pubspec.yaml

@@ -44,7 +44,7 @@ dependencies:
   meshcore_client:
     git:
       url: https://github.com/dz0ny/meshcore_client.git
-      ref: main
+      ref: dfc5b82c3f8a7f160ca77e45dc65a9eb39cebc5a
 
   # Codec2 ultra-low-bitrate speech codec (FFI plugin)
   codec2_flutter:

test/services/location_tracking_service_test.dart

@@ -0,0 +1,40 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import 'package:meshcore_sar_app/services/location_tracking_service.dart';
+import 'package:meshcore_sar_app/services/profiles_feature_service.dart';
+
+void main() {
+  final service = LocationTrackingService();
+
+  setUp(() {
+    SharedPreferences.setMockInitialValues({});
+    ProfileStorageScope.setScope(
+      profilesEnabled: false,
+      activeProfileId: 'default',
+    );
+    service.fastLocationUpdatesEnabled = false;
+    service.fastLocationMovementThresholdMeters = 10.0;
+    service.fastLocationActiveCadenceSeconds = 10;
+    service.fastLocationChannelIdx = null;
+  });
+
+  test('persists and restores fast location channel idx', () async {
+    await service.updateFastLocationChannelIdx(3);
+
+    service.fastLocationChannelIdx = null;
+    await service.loadSettings();
+
+    expect(service.fastLocationChannelIdx, 3);
+  });
+
+  test('clears persisted fast location channel idx when unset', () async {
+    await service.updateFastLocationChannelIdx(7);
+    await service.updateFastLocationChannelIdx(null);
+
+    service.fastLocationChannelIdx = 99;
+    await service.loadSettings();
+
+    expect(service.fastLocationChannelIdx, isNull);
+  });
+}