gps manipulations tailored to sim7600h hat

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

@@ -40,6 +40,9 @@ 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._fix_count = 0
@@ -57,6 +60,17 @@ 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 +136,8 @@ 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 +155,23 @@ 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:
+                    if time.time() > fix_timeout:
-                        print("[GPS] No GPS fix after 5s, will retry connection")
+                        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")
                     continue  # Skip empty fixes
 
-                # Got real data, disable timeout
+                # Got real data — mark first fix, reset timeout to shorter window
-                first_fix_timeout = float('inf')
+                if not self._has_ever_fixed:
+                    self._has_ever_fixed = True
+                    print("[GPS] First fix acquired")
+                fix_timeout = time.time() + 10.0  # 10s timeout for signal loss
 
                 with self._lock:
                     self._latest = fix
@@ -178,8 +200,9 @@ 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 +212,9 @@ class GPSService:
         signal_lost = False
         signal_lost_until = 0.0
 
+        # Simulate cold start acquisition (~3s)
+        acquiring_until = time.time() + 3.0
+
         # Base position (Tokyo area)
         base_lat = 35.6762
         base_lon = 139.6503
@@ -202,16 +228,20 @@ class GPSService:
             self._connected = True
             now = time.time()
 
-            # Check for signal loss simulation
+            # Simulate initial acquisition period
-            if signal_lost:
+            if now < acquiring_until:
-                if now >= signal_lost_until:
+                signal_lost = True  # No fix yet
-                    signal_lost = False
+            elif signal_lost and now >= signal_lost_until:
+                signal_lost = False
+                if self._has_ever_fixed:
                     print("[GPS] Signal recovered (stub)")
-            else:
+                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
-                    signal_lost_until = now + 2 # fixed 2s loss
+                    signal_lost_until = now + 2  # fixed 2s loss
                     print("[GPS] Signal loss simulation (stub)")
 
             if signal_lost:
@@ -232,6 +262,9 @@ 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 +276,9 @@ 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/main.py

@@ -180,9 +180,11 @@ def throttle_flusher():
 @app.route("/health")
 def health():
     """Health check endpoint."""
+    gps_latest = gps.get_latest()
     return jsonify({
         "status": "ok",
         "gps_connected": gps.connected,
+        "gps_state": gps_latest.get("gps_state", "acquiring"),
         "arduino_connected": arduino.connected,
         "ws_clients": len(connected_clients),
     })

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

@@ -60,6 +60,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
 
   // Placeholder values for system bar
   int? _gpsSatellites;
+  String? _gpsState;
   int? _lteSignal;
 
   // WebSocket connection state
@@ -109,6 +110,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
         _gpsSpeed = data.speed;
         _gpsTrack = data.track;
         _gpsSatellites = data.satellites;
+        _gpsState = data.gpsState;
       });
     });
 
@@ -144,6 +146,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
       _gpsSpeed = cachedGps.speed;
       _gpsTrack = cachedGps.track;
       _gpsSatellites = cachedGps.satellites;
+      _gpsState = cachedGps.gpsState;
     }
 
     _wsState = WebSocketService.instance.connectionState;
@@ -200,6 +203,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
                   // System status bar
                   SystemBar(
                     gpsSatellites: _gpsSatellites,
+                    gpsState: _gpsState,
                     lteSignal: _lteSignal,
                     piTemp: _piTemp,
                     voltage: _voltage,
@@ -237,7 +241,7 @@ 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 +53,7 @@ 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?,
     );
   }
 }

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
+    if (!_hasSignal) return 'N/A';
-    return '${(heading! % 360).round()}'; // No need for the degree symbol
+    return '${(heading! % 360).round()}';
   }
 
   String get _compassDirection {
@@ -56,7 +58,7 @@ 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,

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',
+                  value: gpsState == 'acquiring' ? 'ACQ'
-                  isAbnormal: gpsSatellites == null || gpsSatellites == 0,
+                       : gpsState == 'fix' ? (gpsSatellites?.toString() ?? 'N/A')
+                       : '0',  // lost or unknown
+                  isAbnormal: gpsState != 'fix',
                   alignment: Alignment.centerLeft,
                   labelSize: labelSize,
                   valueSize: valueSize,