gps related minor fixes

pi/backend/README.md

@@ -178,6 +178,19 @@ The Pi's internal pull-down (~50kΩ) will overpower high-value external resistor
 
 Physical switches/connectors need debouncing. Current implementation requires 15 consecutive identical readings (~750ms at 20Hz) before accepting a state change. Tune `required_consecutive` in `gpio_service.py` as needed.
 
+## Utilities
+
+Standalone tools live in `pi/utils/` (not part of the backend service):
+
+| Tool | Description |
+|------|-------------|
+| `at_terminal.py` | Interactive AT command terminal for SIM7600 (pyserial). Default port: `/dev/ttyUSB2` |
+
+```bash
+python pi/utils/at_terminal.py              # default /dev/ttyUSB2
+python pi/utils/at_terminal.py /dev/ttyUSB3 # specify port
+```
+
 ## Deploy
 
 TODO: Add to `scripts/deploy.py` as second target + systemd service.

pi/backend/gps_service.py

@@ -11,7 +11,7 @@ from typing import Any
 # When True: skips gpsd entirely, generates realistic mock data
 # When False: connects to real gpsd (requires GPS device)
 # ============================================================================
-_GPS_DEBUG = True
+_GPS_DEBUG = False
 
 # gpsdclient is a modern, simple gpsd client
 # Install gpsd on Pi: sudo apt install gpsd gpsd-clients
@@ -40,8 +40,12 @@ class GPSService:
         # Callback for push-based updates
         self._on_data_callback = None
 
+        # GPS state tracking (NMEA can't distinguish "acquiring" from "lost")
+        self._has_ever_fixed = False  # True after first valid fix this session
+
         # Periodic status logging
         self._last_status_log = 0.0
+        self._last_state_emit = 0.0
         self._fix_count = 0
 
     def set_on_data(self, callback):
@@ -57,6 +61,17 @@ class GPSService:
         with self._lock:
             return self._latest.copy() if self._latest else {"error": "no data"}
 
+    def _gps_state(self, fix: dict) -> str:
+        """Determine GPS state: acquiring, fix, or lost.
+
+        NMEA doesn't distinguish 'never had fix' from 'lost signal' — both
+        report mode 1 with no position. We track it ourselves.
+        """
+        has_fix = fix.get("mode") in (2, 3) and fix.get("lat") is not None
+        if has_fix:
+            return "fix"
+        return "lost" if self._has_ever_fixed else "acquiring"
+
     def get_buffer(self) -> list[dict[str, Any]]:
         """Get buffered GPS history."""
         with self._lock:
@@ -122,7 +137,8 @@ class GPSService:
 
             self._last_status_log = time.time()
             self._fix_count = 0
-            first_fix_timeout = time.time() + 5.0  # 5s to get first fix
+            # 120s for initial cold fix, 10s for signal loss after first fix
+            fix_timeout = time.time() + 120.0
 
             for result in client.dict_stream(filter=["TPV"]):
                 if not self._running:
@@ -140,16 +156,32 @@ class GPSService:
                     "satellites": result.get("satellites"),  # from SKY messages
                 }
 
+                # Compute state and attach to fix
+                fix["gps_state"] = self._gps_state(fix)
+
                 # Check if this is a real fix (has position) or just empty TPV
                 if fix.get("lat") is None and fix.get("mode") in (None, 0, 1):
                     # No real data yet, check timeout
-                    if time.time() > first_fix_timeout:
-                        print("[GPS] No GPS fix after 5s, will retry connection")
+                    if time.time() > fix_timeout:
+                        timeout_s = "120s" if not self._has_ever_fixed else "10s"
+                        print(f"[GPS] No GPS fix after {timeout_s}, will retry connection")
                         raise ConnectionError("No GPS fix within timeout")
+                    # Emit state periodically so UI knows we're alive
+                    now = time.time()
+                    if now - self._last_state_emit >= 5.0:
+                        self._last_state_emit = now
+                        with self._lock:
+                            self._latest = fix
+                        if self._on_data_callback:
+                            self._on_data_callback(fix)
                     continue  # Skip empty fixes
 
-                # Got real data, disable timeout
-                first_fix_timeout = float('inf')
+                # Got real data — mark first fix, reset timeout to shorter window
+                if not self._has_ever_fixed:
+                    self._has_ever_fixed = True
+                    self._last_state_emit = 0.0  # Force immediate emit on transition
+                    print("[GPS] First fix acquired")
+                fix_timeout = time.time() + 10.0  # 10s timeout for signal loss
 
                 with self._lock:
                     self._latest = fix
@@ -178,8 +210,9 @@ class GPSService:
         """Generate realistic mock GPS data for development/testing.
 
         Simulates:
+        - Initial acquisition delay (~3s before first fix)
         - Normal 3D fix with satellites
-        - Occasional signal loss (~3% chance per second, lasts ~5s)
+        - Occasional signal loss (~30% chance per second, lasts ~2s)
         - Wandering position near Tokyo
         """
         self._last_status_log = time.time()
@@ -189,6 +222,9 @@ class GPSService:
         signal_lost = False
         signal_lost_until = 0.0
 
+        # Simulate cold start acquisition (~30s)
+        acquiring_until = time.time() + 30.0
+
         # Base position (Tokyo area)
         base_lat = 35.6762
         base_lon = 139.6503
@@ -202,12 +238,16 @@ class GPSService:
             self._connected = True
             now = time.time()
 
-            # Check for signal loss simulation
-            if signal_lost:
-                if now >= signal_lost_until:
+            # Simulate initial acquisition period
+            if now < acquiring_until:
+                signal_lost = True  # No fix yet
+            elif signal_lost and now >= signal_lost_until:
                 signal_lost = False
+                if self._has_ever_fixed:
                     print("[GPS] Signal recovered (stub)")
                 else:
+                    print("[GPS] First fix acquired (stub)")
+            elif not signal_lost:
                 # ~30% chance per second to lose signal
                 if random.random() < 0.3:
                     signal_lost = True
@@ -232,6 +272,9 @@ class GPSService:
                 heading = (heading + random.uniform(1, 3)) % 360
                 speed = max(0, min(30, speed + random.uniform(-2, 2)))
 
+                if not self._has_ever_fixed:
+                    self._has_ever_fixed = True
+
                 fix = {
                     "time": time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime()),
                     "lat": base_lat + random.uniform(-0.001, 0.001),
@@ -243,6 +286,9 @@ class GPSService:
                     "satellites": random.randint(6, 12),
                 }
 
+            # Attach state — same logic as real GPS path
+            fix["gps_state"] = self._gps_state(fix)
+
             with self._lock:
                 self._latest = fix
                 if fix.get("lat") is not None:

pi/backend/lte_service.py

@@ -0,0 +1,178 @@
+"""LTE service - polls ModemManager for signal quality and connection state."""
+
+import random
+import subprocess
+import re
+import threading
+import time
+from typing import Any
+
+# ============================================================================
+# DEBUG MODE - Set True for development without modem hardware
+# When True: skips mmcli entirely, generates mock LTE data
+# When False: polls real ModemManager via mmcli
+# ============================================================================
+_LTE_DEBUG = True
+
+
+class LteService:
+    """Threaded LTE modem status poller.
+
+    Polls `mmcli -m 0` every 5 seconds, parses signal quality, connection
+    state, operator, and access technology. Emits dict via callback.
+
+    No history buffer — historical signal strength isn't useful.
+    """
+
+    def __init__(self, poll_interval: float = 5.0):
+        self.poll_interval = poll_interval
+
+        self._latest: dict[str, Any] = {}
+        self._connected = False  # True when mmcli responds (modem alive)
+        self._running = False
+        self._thread: threading.Thread | None = None
+        self._lock = threading.Lock()
+
+        # Callback for push-based updates
+        self._on_data_callback = None
+
+    def set_on_data(self, callback):
+        """Set callback for new LTE data. Called with data dict."""
+        self._on_data_callback = callback
+
+    @property
+    def connected(self) -> bool:
+        """Whether the modem is reachable via mmcli."""
+        return self._connected
+
+    def get_latest(self) -> dict[str, Any]:
+        """Get most recent LTE status."""
+        with self._lock:
+            return self._latest.copy() if self._latest else {"error": "no data"}
+
+    def start(self):
+        """Start background LTE poller thread."""
+        if self._running:
+            return
+        self._running = True
+        self._thread = threading.Thread(target=self._poll_loop, daemon=True)
+        self._thread.start()
+        print("[LTE] Service started")
+
+    def stop(self):
+        """Stop background poller."""
+        self._running = False
+        if self._thread:
+            self._thread.join(timeout=2.0)
+
+    def _poll_loop(self):
+        """Main poll loop."""
+        print("[LTE] Poller thread running")
+        while self._running:
+            try:
+                if _LTE_DEBUG:
+                    data = self._stub_poll()
+                else:
+                    data = self._real_poll()
+
+                with self._lock:
+                    self._latest = data
+
+                if self._on_data_callback:
+                    self._on_data_callback(data)
+
+            except Exception as e:
+                print(f"[LTE] Poll error: {e}")
+                self._connected = False
+
+            time.sleep(self.poll_interval)
+
+    def _real_poll(self) -> dict[str, Any]:
+        """Poll mmcli -m 0 and parse output."""
+        try:
+            result = subprocess.run(
+                ["mmcli", "-m", "0"],
+                capture_output=True,
+                text=True,
+                timeout=5.0,
+            )
+
+            if result.returncode != 0:
+                self._connected = False
+                return {
+                    "connected": False,
+                    "signal": 0,
+                    "operator": None,
+                    "access_tech": None,
+                }
+
+            output = result.stdout
+            self._connected = True
+
+            # Parse signal quality: "signal quality: 68 (recent)"
+            signal = 0
+            m = re.search(r"signal quality:\s*(\d+)", output)
+            if m:
+                signal = int(m.group(1))
+
+            # Parse state: "state: connected" / "registered" / "searching" etc.
+            state = None
+            m = re.search(r"^\s*state:\s*(\S+)", output, re.MULTILINE)
+            if m:
+                state = m.group(1).strip("'\"")
+
+            # Parse operator: "operator name: KDDI KDDI"
+            operator = None
+            m = re.search(r"operator name:\s*(.+)", output)
+            if m:
+                operator = m.group(1).strip()
+
+            # Parse access tech: "access tech: lte"
+            access_tech = None
+            m = re.search(r"access tech:\s*(\S+)", output)
+            if m:
+                access_tech = m.group(1).strip("'\"")
+
+            network_connected = state in ("connected", "registered")
+
+            return {
+                "connected": network_connected,
+                "signal": signal,
+                "operator": operator,
+                "access_tech": access_tech,
+            }
+
+        except subprocess.TimeoutExpired:
+            print("[LTE] mmcli timed out")
+            self._connected = False
+            return {
+                "connected": False,
+                "signal": 0,
+                "operator": None,
+                "access_tech": None,
+            }
+        except FileNotFoundError:
+            print("[LTE] mmcli not found, falling back to stub mode")
+            self._connected = False
+            return self._stub_poll()
+
+    # Stub state lives across polls
+    _stub_signal: float = 70.0
+
+    def _stub_poll(self) -> dict[str, Any]:
+        """Generate mock LTE data for development.
+
+        Simulates connected state with signal wandering 60-80.
+        """
+        self._connected = True
+
+        # Random walk signal, clamped to 60-80
+        self._stub_signal += random.uniform(-3, 3)
+        self._stub_signal = max(60, min(80, self._stub_signal))
+
+        return {
+            "connected": True,
+            "signal": int(self._stub_signal),
+            "operator": "STUB",
+            "access_tech": "lte",
+        }

pi/backend/main.py

@@ -9,6 +9,7 @@ from flask_socketio import SocketIO, emit
 from gps_service import GPSService
 from arduino_service import ArduinoService
 from gpio_service import GPIOService
+from lte_service import LteService
 from throttle import Throttle
 
 app = Flask(__name__)
@@ -21,10 +22,12 @@ socketio = SocketIO(app, async_mode="gevent", cors_allowed_origins="*")
 gps = GPSService()
 arduino = ArduinoService()
 gpio = GPIOService()
+lte = LteService()
 
-# Throttles for emission rate limiting (20Hz for arduino, 1Hz for GPS)
+# Throttles for emission rate limiting (20Hz for arduino, 1Hz for GPS, 5s for LTE)
 arduino_throttle = Throttle(min_interval=0.05)  # 20Hz max
 gps_throttle = Throttle(min_interval=1.0)      # 1Hz max
+lte_throttle = Throttle(min_interval=5.0)      # Every 5s — signal doesn't need real-time
 
 # Track connected clients
 connected_clients = set()
@@ -57,6 +60,10 @@ def handle_connect():
     if "error" not in gps_data:
         emit("gps", gps_data)
 
+    lte_data = lte.get_latest()
+    if "error" not in lte_data:
+        emit("lte", lte_data)
+
 
 @socketio.on("disconnect")
 def handle_disconnect():
@@ -133,6 +140,10 @@ def on_arduino_data(data):
     data = dict(data)  # Don't mutate original
     data["theme_switch"] = gpio.theme_switch
     
+    # backend voltage offset correction
+    if "voltage" in data:
+        data["voltage"] += 0.2  # Calibration offset
+
     def emit_fn(d):
         socketio.emit("arduino", d)
 
@@ -147,6 +158,14 @@ def on_gps_data(data):
     gps_throttle.maybe_emit(data, emit_fn)
 
 
+def on_lte_data(data):
+    """Called by LteService when new status polled."""
+    def emit_fn(d):
+        socketio.emit("lte", d)
+
+    lte_throttle.maybe_emit(data, emit_fn)
+
+
 def on_arduino_ack(cmd, status, extra):
     """Called by ArduinoService when ACK received from Arduino."""
     socketio.emit("ack", {
@@ -172,6 +191,9 @@ def throttle_flusher():
         if gps_throttle.has_pending:
             gps_throttle.flush(lambda d: socketio.emit("gps", d))
 
+        if lte_throttle.has_pending:
+            lte_throttle.flush(lambda d: socketio.emit("lte", d))
+
 
 # -----------------------------------------------------------------------------
 # REST API (backward compatibility)
@@ -180,10 +202,15 @@ def throttle_flusher():
 @app.route("/health")
 def health():
     """Health check endpoint."""
+    gps_latest = gps.get_latest()
+    lte_latest = lte.get_latest()
     return jsonify({
         "status": "ok",
         "gps_connected": gps.connected,
+        "gps_state": gps_latest.get("gps_state", "acquiring"),
         "arduino_connected": arduino.connected,
+        "lte_connected": lte.connected,
+        "lte_signal": lte_latest.get("signal"),
         "ws_clients": len(connected_clients),
     })
 
@@ -200,6 +227,12 @@ def gps_history():
     return jsonify(gps.get_buffer())
 
 
+@app.route("/lte")
+def lte_data():
+    """Current LTE modem status."""
+    return jsonify(lte.get_latest())
+
+
 @app.route("/arduino")
 def arduino_data():
     """Current Arduino telemetry (voltage, rpm, etc)."""
@@ -222,11 +255,13 @@ def main():
     arduino.set_on_data(on_arduino_data)
     arduino.set_on_ack(on_arduino_ack)
     gps.set_on_data(on_gps_data)
+    lte.set_on_data(on_lte_data)
 
     # Start services
     gps.start()
     arduino.start()
     gpio.start()
+    lte.start()
 
     # Start throttle flusher in background
     socketio.start_background_task(throttle_flusher)
@@ -239,6 +274,7 @@ def main():
         arduino.stop()
         gps.stop()
         gpio.stop()
+        lte.stop()
 
 
 if __name__ == "__main__":

pi/backend/utils/at_terminal.py

@@ -0,0 +1,49 @@
+"""Quick AT command terminal - minicom but less hostile.
+
+Usage:
+    python at_terminal.py [port]
+
+Default port: /dev/ttyUSB2 (SIM7600 AT command interface)
+"""
+
+import sys
+import serial
+import threading
+
+PORT = sys.argv[1] if len(sys.argv) > 1 else "/dev/ttyUSB2"
+BAUD = 115200
+
+
+def reader(ser):
+    """Background thread: print everything the modem sends."""
+    while True:
+        try:
+            data = ser.read(ser.in_waiting or 1)
+            if data:
+                sys.stdout.write(data.decode("utf-8", errors="replace"))
+                sys.stdout.flush()
+        except Exception:
+            break
+
+
+def main():
+    print(f"Opening {PORT} @ {BAUD} baud")
+    print("Type AT commands. Ctrl+C to quit.\n")
+
+    ser = serial.Serial(PORT, BAUD, timeout=0.1)
+
+    t = threading.Thread(target=reader, args=(ser,), daemon=True)
+    t.start()
+
+    try:
+        while True:
+            line = input()
+            ser.write((line + "\r\n").encode())
+    except (KeyboardInterrupt, EOFError):
+        print("\nBye.")
+    finally:
+        ser.close()
+
+
+if __name__ == "__main__":
+    main()

pi/ui/lib/app_root.dart

@@ -41,6 +41,7 @@ class _AppRootState extends State<AppRoot> {
     // Show all items from the start so the row doesn't jump around
     _updateStatus('Config', '...');
     _updateStatus('UART', '...');
+    _updateStatus('GPS', '...');
     _updateStatus('Navigator', '...');
 
     // Config must load first (everything else depends on it)
@@ -48,11 +49,13 @@ class _AppRootState extends State<AppRoot> {
     await ConfigService.instance.load();
     _updateStatus('Config', 'Ready');
 
-    // UART health check and navigator image preload run truly in parallel
+    // UART, GPS, and navigator image preload run truly in parallel
     _updateStatus('UART', 'Connecting');
+    _updateStatus('GPS', 'Waiting');
     _updateStatus('Navigator', 'Loading');
     await Future.wait([
       _waitForUart(),
+      _waitForGps(),
       _preloadNavigatorImages(),
     ]);
 
@@ -100,6 +103,39 @@ class _AppRootState extends State<AppRoot> {
     _updateStatus('UART', 'Timeout');
   }
 
+  /// Poll backend health endpoint until GPS has a fix, or bail after 7.5s
+  Future<void> _waitForGps() async {
+    final backendUrl = ConfigService.instance.backendUrl;
+    const bailOut = Duration(milliseconds: 7500);
+    const retryDelay = Duration(seconds: 1);
+    final deadline = DateTime.now().add(bailOut);
+
+    _updateStatus('GPS', 'Acquiring');
+
+    while (DateTime.now().isBefore(deadline)) {
+      try {
+        final response = await http
+            .get(Uri.parse('$backendUrl/health'))
+            .timeout(const Duration(seconds: 2));
+
+        if (response.statusCode == 200) {
+          final data = jsonDecode(response.body) as Map<String, dynamic>;
+          if (data['gps_state'] == 'fix') {
+            _updateStatus('GPS', 'Ready');
+            return;
+          }
+        }
+      } catch (e) {
+        // Backend not reachable yet - keep trying
+      }
+
+      await Future.delayed(retryDelay);
+    }
+
+    // Bail out - dashboard will show live GPS state when it arrives
+    _updateStatus('GPS', 'Timeout');
+  }
+
   /// Preload navigator images into Flutter's image cache
   ///
   /// Scans for all PNGs in the navigator folder and precaches them.

pi/ui/lib/screens/dashboard_screen.dart

@@ -37,6 +37,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
   // WebSocket stream subscriptions
   StreamSubscription<ArduinoData>? _arduinoSub;
   StreamSubscription<GpsData>? _gpsSub;
+  StreamSubscription<LteData>? _lteSub;
   StreamSubscription<WsConnectionState>? _connectionSub;
 
   // Pi temperature - direct file read (safety critical)
@@ -60,6 +61,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
 
   // Placeholder values for system bar
   int? _gpsSatellites;
+  String? _gpsState;
   int? _lteSignal;
 
   // WebSocket connection state
@@ -109,6 +111,14 @@ class _DashboardScreenState extends State<DashboardScreen> {
         _gpsSpeed = data.speed;
         _gpsTrack = data.track;
         _gpsSatellites = data.satellites;
+        _gpsState = data.gpsState;
+      });
+    });
+
+    // Subscribe to LTE data stream
+    _lteSub = WebSocketService.instance.lteStream.listen((data) {
+      setState(() {
+        _lteSignal = data.signal;
       });
     });
 
@@ -144,12 +154,16 @@ class _DashboardScreenState extends State<DashboardScreen> {
       _gpsSpeed = cachedGps.speed;
       _gpsTrack = cachedGps.track;
       _gpsSatellites = cachedGps.satellites;
+      _gpsState = cachedGps.gpsState;
     }
 
     _wsState = WebSocketService.instance.connectionState;
 
-    // Placeholder: LTE signal (TODO: wire up when LTE service exists)
-    _lteSignal = null;
+    // Init from cached LTE data
+    final cachedLte = WebSocketService.instance.latestLte;
+    if (cachedLte != null) {
+      _lteSignal = cachedLte.signal;
+    }
 
     // DEBUG: flip-flop theme + navigator every 2s
     TestFlipFlopService.instance.start(navigatorKey: _navigatorKey);
@@ -160,6 +174,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
     _piTempTimer?.cancel();
     _arduinoSub?.cancel();
     _gpsSub?.cancel();
+    _lteSub?.cancel();
     _connectionSub?.cancel();
     TestFlipFlopService.instance.stop();
     super.dispose();
@@ -200,6 +215,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
                   // System status bar
                   SystemBar(
                     gpsSatellites: _gpsSatellites,
+                    gpsState: _gpsState,
                     lteSignal: _lteSignal,
                     piTemp: _piTemp,
                     voltage: _voltage,
@@ -237,7 +253,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
                       mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                       children: [
                         StatBox(value: _formatInt(_rpm), label: 'RPM', isWarning: () => (_rpm ?? 0) > 4000),
-                        GpsCompass(heading: _gpsTrack),
+                        GpsCompass(heading: _gpsTrack, gpsState: _gpsState),
                         StatBox(value: _formatGear(_gear), label: 'GEAR'),
                       ],
                     ),

pi/ui/lib/services/backend_service.dart

@@ -40,8 +40,9 @@ class GpsData {
   final double? track;
   final int? mode; // 0=no fix, 2=2D, 3=3D
   final int? satellites;
+  final String? gpsState; // "acquiring", "fix", or "lost"
 
-  GpsData({this.lat, this.lon, this.speed, this.alt, this.track, this.mode, this.satellites});
+  GpsData({this.lat, this.lon, this.speed, this.alt, this.track, this.mode, this.satellites, this.gpsState});
 
   factory GpsData.fromJson(Map<String, dynamic> json) {
     return GpsData(
@@ -52,6 +53,26 @@ class GpsData {
       track: (json['track'] as num?)?.toDouble(),
       mode: (json['mode'] as num?)?.toInt(),
       satellites: (json['satellites'] as num?)?.toInt(),
+      gpsState: json['gps_state'] as String?,
+    );
+  }
+}
+
+/// Data from LTE modem (signal quality, connection state)
+class LteData {
+  final bool? connected;
+  final int? signal; // 0-100 percent
+  final String? operator_;
+  final String? accessTech;
+
+  LteData({this.connected, this.signal, this.operator_, this.accessTech});
+
+  factory LteData.fromJson(Map<String, dynamic> json) {
+    return LteData(
+      connected: json['connected'] as bool?,
+      signal: (json['signal'] as num?)?.toInt(),
+      operator_: json['operator'] as String?,
+      accessTech: json['access_tech'] as String?,
     );
   }
 }

pi/ui/lib/services/websocket_service.dart

@@ -65,11 +65,13 @@ class WebSocketService {
   // Latest values for sync access (backward compat)
   ArduinoData? _latestArduino;
   GpsData? _latestGps;
+  LteData? _latestLte;
   BackendStatus? _latestStatus;
 
   // Stream controllers
   late StreamController<ArduinoData> _arduinoController;
   late StreamController<GpsData> _gpsController;
+  late StreamController<LteData> _lteController;
   late StreamController<BackendStatus> _statusController;
   late StreamController<CommandAck> _ackController;
   late StreamController<BackendAlert> _alertController;
@@ -83,6 +85,7 @@ class WebSocketService {
   void _setupStreams() {
     _arduinoController = StreamController<ArduinoData>.broadcast();
     _gpsController = StreamController<GpsData>.broadcast();
+    _lteController = StreamController<LteData>.broadcast();
     _statusController = StreamController<BackendStatus>.broadcast();
     _ackController = StreamController<CommandAck>.broadcast();
     _alertController = StreamController<BackendAlert>.broadcast();
@@ -107,6 +110,9 @@ class WebSocketService {
   /// Stream of GPS updates
   Stream<GpsData> get gpsStream => _gpsController.stream;
 
+  /// Stream of LTE status updates
+  Stream<LteData> get lteStream => _lteController.stream;
+
   /// Stream of backend status updates
   Stream<BackendStatus> get statusStream => _statusController.stream;
 
@@ -139,6 +145,9 @@ class WebSocketService {
   /// Latest GPS data (may be null if not yet received)
   GpsData? get latestGps => _latestGps;
 
+  /// Latest LTE data (may be null if not yet received)
+  LteData? get latestLte => _latestLte;
+
   /// Latest backend status
   BackendStatus? get latestStatus => _latestStatus;
 
@@ -208,6 +217,15 @@ class WebSocketService {
       }
     });
 
+    _socket!.on('lte', (data) {
+      if (data is Map<String, dynamic>) {
+        final lte = LteData.fromJson(data);
+        _latestLte = lte;
+        _lteController.add(lte);
+        _log('lte: ${lte.signal ?? "-"}% ${lte.operator_ ?? "-"} ${lte.accessTech ?? "-"}');
+      }
+    });
+
     _socket!.on('status', (data) {
       if (data is Map<String, dynamic>) {
         final status = BackendStatus(
@@ -323,6 +341,7 @@ class WebSocketService {
     disconnect();
     _arduinoController.close();
     _gpsController.close();
+    _lteController.close();
     _statusController.close();
     _ackController.close();
     _alertController.close();

pi/ui/lib/widgets/gps_compass.dart

@@ -4,14 +4,16 @@ import '../theme/app_theme.dart';
 
 class GpsCompass extends StatelessWidget {
   final double? heading;
+  final String? gpsState; // "acquiring", "fix", "lost"
 
-  const GpsCompass({super.key, this.heading});
+  const GpsCompass({super.key, this.heading, this.gpsState});
 
   bool get _hasSignal => heading != null;
+  bool get _isAcquiring => gpsState == 'acquiring';
 
   String get _displayHeading {
-    if (!_hasSignal) return 'N/A'; // Just make it clear; redundant anyways, this only gets called when _hasSignal
-    return '${(heading! % 360).round()}'; // No need for the degree symbol
+    if (!_hasSignal) return 'N/A';
+    return '${(heading! % 360).round()}';
   }
 
   String get _compassDirection {
@@ -56,10 +58,10 @@ class GpsCompass extends StatelessWidget {
           child: FittedBox(
             fit: BoxFit.contain,
             child: Text(
-              _hasSignal ? "${_displayHeading} ${_compassDirection}" : "N/A",
+              _hasSignal ? "${_displayHeading} ${_compassDirection}" : (_isAcquiring ? "ACQ" : "N/A"),
               style: TextStyle(
                 fontSize: 80,
-                color: theme.subdued,
+                color: theme.subdued, // less emphasis on text, let the icon have semantic colour
                 fontFamily: 'DIN1451',
               ),
             ),

pi/ui/lib/widgets/system_bar.dart

@@ -7,6 +7,7 @@ import '../theme/app_theme.dart';
 /// Shows GPS satellites, LTE signal, Pi temp, voltage, WS status at a glance.
 class SystemBar extends StatelessWidget {
   final int? gpsSatellites; // null = disconnected
+  final String? gpsState; // "acquiring", "fix", "lost"
   final int? lteSignal; // null = disconnected, 0-4 bars
   final double? piTemp; // null = unavailable
   final double? voltage; // null = Arduino disconnected
@@ -15,6 +16,7 @@ class SystemBar extends StatelessWidget {
   const SystemBar({
     super.key,
     this.gpsSatellites,
+    this.gpsState,
     this.lteSignal,
     this.piTemp,
     this.voltage,
@@ -65,8 +67,10 @@ class SystemBar extends StatelessWidget {
                 ),
                 _Indicator(
                   label: 'GPS',
-                  value: gpsSatellites?.toString() ?? 'N/A',
-                  isAbnormal: gpsSatellites == null || gpsSatellites == 0,
+                  value: gpsState == 'acquiring' ? 'ACQ'
+                       : gpsState == 'fix' ? (gpsSatellites?.toString() ?? 'N/A')
+                       : '0',  // lost or unknown
+                  isAbnormal: gpsState != 'fix' || gpsSatellites == null,
                   alignment: Alignment.centerLeft,
                   labelSize: labelSize,
                   valueSize: valueSize,