feat(display): Sprint 7 — USB serial link to AR-Concentrador via NMEA $PARP

- Add flutter_libserialport dependency (pubspec.yaml)
- New ParpCodec: XOR-checksum NMEA parser + command builders for all PARP sentences
- New ConcentradorService: manages two independent COM ports (RX-OUT broadcast,
  TX-IN commands) at 115200/8N1; auto-fires onConnectionChanged on link drop
- AutopilotState: dual-mode operation (demo timer OR live serial); connectToSerial /
  disconnectSerial; command methods (engage/disengage/adjustSetpoint) forward to
  ConcentradorService when connected; falls back to demo on disconnect
- New PortSettingsScreen (/settings/ports): RX+TX dropdowns populated from
  SerialPort.availablePorts, persisted in SharedPreferences; Connect/Disconnect
  buttons with error display and snackbar feedback
- main.dart: auto-connect to saved ports on startup (silent fail → demo mode);
  registers /settings/ports route
- CockpitScreen: gear icon replaced with PopupMenuButton (Puertos COM / Apariencia)

AR_electronics — AR-Autopilot Project

display/lib/data/autopilot_state.dart

@@ -2,9 +2,15 @@
 //  data/autopilot_state.dart — Live autopilot data model
 // =============================================================================
 //
-//  Sprint 4: simulated demo data (vessel drifting / heading-hold correction).
+//  Dual-mode: demo simulation (Sprint 4) or live USB serial (Sprint 7).
-//  Sprint 7: internals replaced by Modbus RTU over USB serial.
+//
-//  The public API (fields + methods) must not change between sprints.
+//  Default constructor starts in demo mode (animated vessel simulation).
+//  Call [connectToSerial] to switch to live data from the AR-Concentrador.
+//  If the serial link drops, the state automatically falls back to demo.
+//
+//  The public API (fields + methods) is identical in both modes — the UI
+//  never needs to know which mode is active; it reads [isConnected] for
+//  the status indicator only.
 // =============================================================================
 
 import 'dart:async';
@@ -12,48 +18,30 @@ import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';
 
+import '../services/concentrador_service.dart';
+import '../services/parp_codec.dart';
 import '../widgets/themed/mode_selector.dart';
 
-/// Live state of the autopilot and navigation instruments.
-///
-/// Consumed by [CockpitScreen] via `context.watch<AutopilotState>()`.
-///
-/// ## Data sources (Sprint 4 → Sprint 7)
-/// Sprint 4: internal [Timer]-driven demo that simulates a vessel at sea.
-/// Sprint 7: [AutopilotStateModbus] subclass (or internal swap) feeds real
-///   Modbus RTU data received over USB serial from the AR-Concentrador.
 class AutopilotState extends ChangeNotifier {
   // ── Navigation data ──────────────────────────────────────────────────────────
-  /// Current vessel heading from NMEA 2000 backbone (degrees, magnetic, 0–359.9).
+  double headingDeg  = 125.0;
-  double headingDeg = 125.0;
-
-  /// Operator-commanded heading setpoint sent to autopilot (degrees, magnetic).
   double setpointDeg = 125.0;
-
+  double rudderDeg   = 0.0;
-  /// Rudder angle in degrees. Negative = port, positive = starboard.
+  double sogKn       = 6.2;
-  double rudderDeg = 0.0;
+  double cogDeg      = 127.0;
-
+  double rotDpm      = 0.0;
-  /// Speed over ground (knots).
+  double depthM      = 42.5;
-  double sogKn = 6.2;
-
-  /// Course over ground (degrees, true).
-  double cogDeg = 127.0;
-
-  /// Rate of turn (degrees per minute). Positive = turning starboard.
-  double rotDpm = 0.0;
-
-  /// Water depth below keel (metres).
-  double depthM = 42.5;
 
   // ── Autopilot state ──────────────────────────────────────────────────────────
-  /// Current autopilot mode as reported by the concentrador $PARP,STATUS.
   AutopilotMode mode = AutopilotMode.standby;
 
-  /// True when the Modbus RTU link to the concentrador is active.
+  /// True when the USB serial link to the concentrador is active.
-  /// Sprint 4: always false (demo mode label shown in UI).
   bool isConnected = false;
 
-  // ── Internal ─────────────────────────────────────────────────────────────────
+  // ── Serial service ───────────────────────────────────────────────────────────
+  ConcentradorService? _service;
+
+  // ── Demo simulation ──────────────────────────────────────────────────────────
   Timer? _demoTimer;
   final _rng = math.Random();
 
@@ -62,55 +50,92 @@ class AutopilotState extends ChangeNotifier {
   }
 
   // ---------------------------------------------------------------------------
-  //  Demo simulation (Sprint 4 only)
+  //  Serial connection
+  // ---------------------------------------------------------------------------
+
+  /// Connect to the AR-Concentrador via USB serial.
+  ///
+  /// Stops the demo timer and switches to live data.
+  /// Falls back to demo automatically if the link drops.
+  ///
+  /// Throws if the ports cannot be opened (caller should catch and show error).
+  Future<void> connectToSerial({
+    required String rxPort,
+    required String txPort,
+    int stationId = 2,
+  }) async {
+    _demoTimer?.cancel();
+    _demoTimer = null;
+
+    _service?.disconnect();
+    _service = ConcentradorService(
+      rxPort: rxPort,
+      txPort: txPort,
+      stationId: stationId,
+    );
+    _service!.onStatus = _onSerialStatus;
+    _service!.onConnectionChanged = _onConnectionChanged;
+
+    await _service!.connect(); // may throw — caller handles
+  }
+
+  /// Disconnect the serial link and return to demo mode.
+  Future<void> disconnectSerial() async {
+    await _service?.disconnect();
+    _service = null;
+    _startDemo();
+  }
+
+  void _onConnectionChanged(bool connected) {
+    isConnected = connected;
+    if (!connected) {
+      // Link dropped — fall back to animated demo so the UI stays alive.
+      _startDemo();
+    }
+    notifyListeners();
+  }
+
+  void _onSerialStatus(ParpStatus status) {
+    isConnected = true;
+    headingDeg  = status.headingDeg;
+    setpointDeg = status.setpointDeg;
+    rudderDeg   = status.rudderDeg;
+    mode        = status.mode;
+    notifyListeners();
+  }
+
+  // ---------------------------------------------------------------------------
+  //  Demo simulation
   // ---------------------------------------------------------------------------
 
   void _startDemo() {
-    _demoTimer = Timer.periodic(const Duration(milliseconds: 500), (_) {
+    _demoTimer?.cancel();
-      _tick();
+    _demoTimer = Timer.periodic(const Duration(milliseconds: 500), (_) => _tick());
-    });
   }
 
   void _tick() {
     switch (mode) {
       case AutopilotMode.standby:
-        // Vessel drifts slightly — small random walk on heading and rudder.
         headingDeg = (headingDeg + (_rng.nextDouble() - 0.5) * 0.5) % 360;
         if (headingDeg < 0) headingDeg += 360;
-        rudderDeg = (rudderDeg + (_rng.nextDouble() - 0.5) * 0.8)
+        rudderDeg  = (rudderDeg + (_rng.nextDouble() - 0.5) * 0.8).clamp(-5.0, 5.0);
-            .clamp(-5.0, 5.0);
+        rotDpm     = rudderDeg * 0.3 + (_rng.nextDouble() - 0.5) * 0.2;
-        rotDpm = rudderDeg * 0.3 + (_rng.nextDouble() - 0.5) * 0.2;
 
       case AutopilotMode.headingHold:
-        // Simulated P-controller: autopilot drives rudder toward setpoint.
-        final error = _angleDiff(setpointDeg, headingDeg);
-        rudderDeg = (error * 1.2 + (_rng.nextDouble() - 0.5) * 0.5)
-            .clamp(-35.0, 35.0);
-        headingDeg =
-            (headingDeg + error * 0.025 + (_rng.nextDouble() - 0.5) * 0.08)
-                % 360;
-        if (headingDeg < 0) headingDeg += 360;
-        rotDpm = error * 0.4;
-
       case AutopilotMode.trackKeep:
-        // Sprint 6: identical to headingHold for demo purposes.
         final error = _angleDiff(setpointDeg, headingDeg);
-        rudderDeg =
+        rudderDeg  = (error * 1.2 + (_rng.nextDouble() - 0.5) * 0.5).clamp(-35.0, 35.0);
-            (error * 1.2).clamp(-35.0, 35.0);
+        headingDeg = (headingDeg + error * 0.025 + (_rng.nextDouble() - 0.5) * 0.08) % 360;
-        headingDeg = (headingDeg + error * 0.025) % 360;
         if (headingDeg < 0) headingDeg += 360;
         rotDpm = error * 0.4;
     }
 
-    // COG tracks heading with a small lag.
+    cogDeg = (headingDeg + rudderDeg * 0.15 + (_rng.nextDouble() - 0.5) * 0.3) % 360;
-    cogDeg = (headingDeg + rudderDeg * 0.15 + (_rng.nextDouble() - 0.5) * 0.3)
-        % 360;
     if (cogDeg < 0) cogDeg += 360;
 
     notifyListeners();
   }
 
-  /// Signed difference in [−180, +180]: target − current.
   double _angleDiff(double target, double current) {
     double d = (target - current) % 360;
     if (d > 180) d -= 360;
@@ -119,32 +144,39 @@ class AutopilotState extends ChangeNotifier {
   }
 
   // ---------------------------------------------------------------------------
-  //  Commands — called by UI; Sprint 7 will also send Modbus frames here.
+  //  Commands — work in both demo and serial modes
   // ---------------------------------------------------------------------------
 
-  /// Engage heading hold on the current heading.
   void engage() {
     setpointDeg = headingDeg;
-    mode = AutopilotMode.headingHold;
+    mode        = AutopilotMode.headingHold;
+    _service?.sendEngage(headingDeg);
     notifyListeners();
   }
 
-  /// Return to STANDBY (manual helm).
   void disengage() {
     mode = AutopilotMode.standby;
+    _service?.sendDisengage();
     notifyListeners();
   }
 
-  /// Adjust the heading setpoint while in heading-hold mode.
-  /// No-op in STANDBY or TRACK.
   void adjustSetpoint(double deltaDeg) {
     if (mode != AutopilotMode.headingHold) return;
     setpointDeg = (setpointDeg + deltaDeg) % 360;
     if (setpointDeg < 0) setpointDeg += 360;
+
+    // Route to the appropriate serial command
+    if (_service != null && isConnected) {
+      if (deltaDeg == -10) _service!.sendPortTen(setpointDeg);
+      else if (deltaDeg == -1) _service!.sendPortOne(setpointDeg);
+      else if (deltaDeg == 1) _service!.sendStbdOne(setpointDeg);
+      else if (deltaDeg == 10) _service!.sendStbdTen(setpointDeg);
+      else _service!.sendSetHeading(setpointDeg);
+    }
+
     notifyListeners();
   }
 
-  /// Handle ModeSelector taps.
   void selectMode(AutopilotMode newMode) {
     switch (newMode) {
       case AutopilotMode.standby:
@@ -152,16 +184,22 @@ class AutopilotState extends ChangeNotifier {
       case AutopilotMode.headingHold:
         engage();
       case AutopilotMode.trackKeep:
-        // Sprint 6: engage track-keep mode (requires GPS cross-track error).
+        mode        = AutopilotMode.trackKeep;
-        mode = AutopilotMode.trackKeep;
         setpointDeg = headingDeg;
         notifyListeners();
     }
   }
 
+  // ---------------------------------------------------------------------------
+  //  Port discovery (delegate to service layer)
+  // ---------------------------------------------------------------------------
+
+  static List<String> availablePorts() => ConcentradorService.availablePorts();
+
   @override
   void dispose() {
     _demoTimer?.cancel();
+    _service?.disconnect();
     super.dispose();
   }
 }

display/lib/main.dart

@@ -1,25 +1,48 @@
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 
 import 'data/autopilot_state.dart';
 import 'theme/theme_provider.dart';
 import 'screens/cockpit/cockpit_screen.dart';
 import 'screens/settings/appearance_settings.dart';
+import 'screens/settings/port_settings_screen.dart';
+
+// SharedPreferences keys — must match port_settings_screen.dart
+const _kRxKey = 'port.rx';
+const _kTxKey = 'port.tx';
 
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
+
+  // Load persisted theme before first frame.
   final themeProvider = await AutopilotThemeProvider.load();
+
+  // Create state object early so we can attempt auto-connect.
+  final autopilotState = AutopilotState();
+
+  // Attempt to reconnect to the last-used COM ports silently.
+  // If the ports are not available (hardware unplugged, different PC, etc.)
+  // the exception is swallowed and the UI stays in demo mode.
+  try {
+    final prefs = await SharedPreferences.getInstance();
+    final rxPort = prefs.getString(_kRxKey);
+    final txPort = prefs.getString(_kTxKey);
+    if (rxPort != null && txPort != null) {
+      await autopilotState.connectToSerial(rxPort: rxPort, txPort: txPort);
+    }
+  } catch (_) {
+    // Hardware not available — stay in demo mode.
+  }
+
   runApp(
     MultiProvider(
       providers: [
         ChangeNotifierProvider<AutopilotThemeProvider>.value(
           value: themeProvider,
         ),
-        // AutopilotState drives the cockpit UI.
+        ChangeNotifierProvider<AutopilotState>.value(
-        // Sprint 4: internal demo timer (vessel simulation).
+          value: autopilotState,
-        // Sprint 7: replace with AutopilotStateModbus or wire Modbus RTU here.
-        ChangeNotifierProvider<AutopilotState>(
-          create: (_) => AutopilotState(),
         ),
       ],
       child: const ArAutopilotApp(),
@@ -38,9 +61,9 @@ class ArAutopilotApp extends StatelessWidget {
       theme: ThemeData(useMaterial3: true),
       initialRoute: CockpitScreen.routeName,
       routes: {
-        CockpitScreen.routeName: (_) => const CockpitScreen(),
+        CockpitScreen.routeName:         (_) => const CockpitScreen(),
-        AppearanceSettingsScreen.routeName: (_) =>
+        AppearanceSettingsScreen.routeName: (_) => const AppearanceSettingsScreen(),
-            const AppearanceSettingsScreen(),
+        PortSettingsScreen.routeName:    (_) => const PortSettingsScreen(),
       },
     );
   }

display/lib/screens/cockpit/cockpit_screen.dart

@@ -31,6 +31,7 @@ import '../../widgets/themed/mode_selector.dart';
 import '../../widgets/themed/rudder_indicator.dart';
 import '../../widgets/themed/status_chip.dart';
 import '../settings/appearance_settings.dart';
+import '../settings/port_settings_screen.dart';
 
 class CockpitScreen extends StatelessWidget {
   const CockpitScreen({super.key});
@@ -138,14 +139,47 @@ class _TopBar extends StatelessWidget {
             status: ap.isConnected ? StatusLevel.ok : StatusLevel.warn,
           ),
           const SizedBox(width: 16),
-          GestureDetector(
+          PopupMenuButton<String>(
-            onTap: () => Navigator.pushNamed(
+            icon: Icon(
-                context, AppearanceSettingsScreen.routeName),
-            child: Icon(
               Icons.settings_outlined,
               color: theme.textMuted,
               size: 22,
             ),
+            color: theme.backgroundMid,
+            shape: RoundedRectangleBorder(
+              borderRadius: BorderRadius.circular(8),
+              side: BorderSide(color: theme.panelBorder),
+            ),
+            onSelected: (route) => Navigator.pushNamed(context, route),
+            itemBuilder: (_) => [
+              PopupMenuItem(
+                value: PortSettingsScreen.routeName,
+                child: Row(
+                  children: [
+                    Icon(Icons.usb, color: theme.accentMid, size: 18),
+                    const SizedBox(width: 10),
+                    Text(
+                      'Puertos COM',
+                      style: TextStyle(color: theme.textMain, fontSize: 13),
+                    ),
+                  ],
+                ),
+              ),
+              PopupMenuItem(
+                value: AppearanceSettingsScreen.routeName,
+                child: Row(
+                  children: [
+                    Icon(Icons.palette_outlined,
+                        color: theme.accentMid, size: 18),
+                    const SizedBox(width: 10),
+                    Text(
+                      'Apariencia',
+                      style: TextStyle(color: theme.textMain, fontSize: 13),
+                    ),
+                  ],
+                ),
+              ),
+            ],
           ),
         ],
       ),

display/lib/screens/settings/port_settings_screen.dart

@@ -0,0 +1,367 @@
+// =============================================================================
+//  screens/settings/port_settings_screen.dart — COM port configuration
+// =============================================================================
+//
+//  Lets the operator choose which COM port is the concentrador RX-OUT
+//  (the one the display reads from) and which is the TX-IN
+//  (the one the display writes commands to).
+//
+//  Ports are persisted in SharedPreferences and auto-applied at startup.
+//
+//  Layout:
+//    • Two dropdowns — RX port, TX port — populated from available COM ports
+//    • [Conectar] button — tries to open both ports; shows error if it fails
+//    • [Desconectar] button — drops to demo mode
+//    • Status row — green ● CONECTADO / grey ● DEMO
+// =============================================================================
+
+import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import '../../data/autopilot_state.dart';
+import '../../theme/autopilot_theme.dart';
+import '../../theme/theme_provider.dart';
+
+class PortSettingsScreen extends StatefulWidget {
+  const PortSettingsScreen({super.key});
+
+  static const String routeName = '/settings/ports';
+
+  @override
+  State<PortSettingsScreen> createState() => _PortSettingsScreenState();
+}
+
+class _PortSettingsScreenState extends State<PortSettingsScreen> {
+  static const _kRxKey = 'port.rx';
+  static const _kTxKey = 'port.tx';
+
+  List<String> _ports = [];
+  String? _rxPort;
+  String? _txPort;
+  bool _connecting = false;
+  String? _errorMsg;
+
+  @override
+  void initState() {
+    super.initState();
+    _loadPorts();
+  }
+
+  Future<void> _loadPorts() async {
+    final available = AutopilotState.availablePorts();
+    final prefs = await SharedPreferences.getInstance();
+    setState(() {
+      _ports = available;
+      _rxPort = prefs.getString(_kRxKey);
+      _txPort = prefs.getString(_kTxKey);
+      // If saved port no longer exists, clear it.
+      if (_rxPort != null && !_ports.contains(_rxPort)) _rxPort = null;
+      if (_txPort != null && !_ports.contains(_txPort)) _txPort = null;
+    });
+  }
+
+  Future<void> _connect() async {
+    if (_rxPort == null || _txPort == null) return;
+    setState(() {
+      _connecting = true;
+      _errorMsg = null;
+    });
+
+    try {
+      final ap = context.read<AutopilotState>();
+      await ap.connectToSerial(rxPort: _rxPort!, txPort: _txPort!);
+
+      // Persist the working configuration
+      final prefs = await SharedPreferences.getInstance();
+      await prefs.setString(_kRxKey, _rxPort!);
+      await prefs.setString(_kTxKey, _txPort!);
+
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(
+            content: Text('Conectado — RX: $_rxPort  TX: $_txPort'),
+            backgroundColor: Colors.green.shade700,
+            duration: const Duration(seconds: 3),
+          ),
+        );
+        Navigator.pop(context);
+      }
+    } catch (e) {
+      setState(() => _errorMsg = 'Error al abrir puertos: $e');
+    } finally {
+      if (mounted) setState(() => _connecting = false);
+    }
+  }
+
+  Future<void> _disconnect() async {
+    final ap = context.read<AutopilotState>();
+    await ap.disconnectSerial();
+    if (mounted) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(
+          content: Text('Desconectado — modo demo activo'),
+          duration: Duration(seconds: 2),
+        ),
+      );
+      Navigator.pop(context);
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = context.watch<AutopilotThemeProvider>().current;
+    final ap    = context.watch<AutopilotState>();
+
+    return Scaffold(
+      backgroundColor: theme.background,
+      appBar: AppBar(
+        backgroundColor: theme.backgroundMid,
+        foregroundColor: theme.textMain,
+        elevation: 0,
+        title: Text(
+          'Conexión al Concentrador',
+          style: TextStyle(color: theme.textMain, fontWeight: FontWeight.w600),
+        ),
+      ),
+      body: AnimatedContainer(
+        duration: const Duration(milliseconds: 400),
+        decoration: theme.backgroundDecoration,
+        child: ListView(
+          padding: const EdgeInsets.all(20),
+          children: [
+            // ── Status ────────────────────────────────────────────────────────
+            _StatusRow(theme: theme, connected: ap.isConnected),
+            const SizedBox(height: 24),
+
+            // ── Port selection ────────────────────────────────────────────────
+            _SectionLabel(label: 'Puerto RX (leer datos del concentrador)', theme: theme),
+            const SizedBox(height: 8),
+            _PortDropdown(
+              theme: theme,
+              value: _rxPort,
+              ports: _ports,
+              onChanged: (v) => setState(() => _rxPort = v),
+            ),
+            const SizedBox(height: 16),
+
+            _SectionLabel(label: 'Puerto TX (enviar comandos al concentrador)', theme: theme),
+            const SizedBox(height: 8),
+            _PortDropdown(
+              theme: theme,
+              value: _txPort,
+              ports: _ports,
+              onChanged: (v) => setState(() => _txPort = v),
+            ),
+            const SizedBox(height: 8),
+
+            // Note
+            Text(
+              'Conectar el cable USB-OUT del concentrador al puerto RX,\n'
+              'y el USB-IN al puerto TX. Ambos a 115 200 baud, 8N1.',
+              style: TextStyle(color: theme.textMuted, fontSize: 11),
+            ),
+            const SizedBox(height: 24),
+
+            // ── Error message ─────────────────────────────────────────────────
+            if (_errorMsg != null) ...[
+              Container(
+                padding: const EdgeInsets.all(12),
+                decoration: BoxDecoration(
+                  color: theme.disengageBackground.colors.first.withValues(alpha: 0.15),
+                  borderRadius: BorderRadius.circular(6),
+                  border: Border.all(color: theme.disengageBorder.withValues(alpha: 0.4)),
+                ),
+                child: Text(
+                  _errorMsg!,
+                  style: TextStyle(color: theme.disengageText, fontSize: 12),
+                ),
+              ),
+              const SizedBox(height: 16),
+            ],
+
+            // ── Buttons ───────────────────────────────────────────────────────
+            Row(
+              children: [
+                Expanded(
+                  child: _ActionButton(
+                    theme: theme,
+                    label: _connecting ? 'Conectando…' : 'Conectar',
+                    enabled: !_connecting && _rxPort != null && _txPort != null,
+                    primary: true,
+                    onPressed: _connect,
+                  ),
+                ),
+                const SizedBox(width: 12),
+                Expanded(
+                  child: _ActionButton(
+                    theme: theme,
+                    label: 'Desconectar',
+                    enabled: ap.isConnected && !_connecting,
+                    primary: false,
+                    onPressed: _disconnect,
+                  ),
+                ),
+              ],
+            ),
+            const SizedBox(height: 16),
+
+            // ── Refresh ports ─────────────────────────────────────────────────
+            TextButton(
+              onPressed: _loadPorts,
+              child: Text(
+                'Actualizar lista de puertos',
+                style: TextStyle(color: theme.textMuted, fontSize: 12),
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+// ── Private widgets ───────────────────────────────────────────────────────────
+
+class _StatusRow extends StatelessWidget {
+  const _StatusRow({required this.theme, required this.connected});
+  final AutopilotTheme theme;
+  final bool connected;
+
+  @override
+  Widget build(BuildContext context) {
+    final color = connected ? theme.okColor : theme.textMuted;
+    final label = connected ? 'CONECTADO AL CONCENTRADOR' : 'MODO DEMO (sin conexión)';
+    return Row(
+      children: [
+        Container(
+          width: 10,
+          height: 10,
+          decoration: BoxDecoration(
+            shape: BoxShape.circle,
+            color: color,
+            boxShadow: connected
+                ? [BoxShadow(color: color.withValues(alpha: 0.5), blurRadius: 8)]
+                : null,
+          ),
+        ),
+        const SizedBox(width: 10),
+        Text(
+          label,
+          style: TextStyle(
+            color: color,
+            fontSize: 12,
+            fontWeight: FontWeight.w600,
+            letterSpacing: 0.8,
+          ),
+        ),
+      ],
+    );
+  }
+}
+
+class _SectionLabel extends StatelessWidget {
+  const _SectionLabel({required this.label, required this.theme});
+  final String label;
+  final AutopilotTheme theme;
+
+  @override
+  Widget build(BuildContext context) => Text(
+        label.toUpperCase(),
+        style: TextStyle(
+          color: theme.textMuted,
+          fontSize: 10,
+          letterSpacing: 1.2,
+          fontWeight: FontWeight.w600,
+        ),
+      );
+}
+
+class _PortDropdown extends StatelessWidget {
+  const _PortDropdown({
+    required this.theme,
+    required this.value,
+    required this.ports,
+    required this.onChanged,
+  });
+  final AutopilotTheme theme;
+  final String? value;
+  final List<String> ports;
+  final ValueChanged<String?> onChanged;
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      padding: const EdgeInsets.symmetric(horizontal: 14),
+      decoration: BoxDecoration(
+        gradient: theme.panelBackground,
+        borderRadius: BorderRadius.circular(6),
+        border: Border.all(color: theme.panelBorder),
+      ),
+      child: DropdownButtonHideUnderline(
+        child: DropdownButton<String>(
+          value: ports.contains(value) ? value : null,
+          hint: Text(
+            ports.isEmpty ? 'Sin puertos disponibles' : 'Seleccionar puerto…',
+            style: TextStyle(color: theme.textMuted, fontSize: 13),
+          ),
+          dropdownColor: theme.backgroundMid,
+          style: TextStyle(color: theme.textMain, fontSize: 13),
+          icon: Icon(Icons.expand_more, color: theme.textMuted),
+          isExpanded: true,
+          items: ports
+              .map((p) => DropdownMenuItem(value: p, child: Text(p)))
+              .toList(),
+          onChanged: onChanged,
+        ),
+      ),
+    );
+  }
+}
+
+class _ActionButton extends StatelessWidget {
+  const _ActionButton({
+    required this.theme,
+    required this.label,
+    required this.enabled,
+    required this.primary,
+    required this.onPressed,
+  });
+  final AutopilotTheme theme;
+  final String label;
+  final bool enabled;
+  final bool primary;
+  final VoidCallback onPressed;
+
+  @override
+  Widget build(BuildContext context) {
+    final color = primary ? theme.okColor : theme.accentMid;
+    return GestureDetector(
+      onTap: enabled ? onPressed : null,
+      child: AnimatedContainer(
+        duration: const Duration(milliseconds: 150),
+        padding: const EdgeInsets.symmetric(vertical: 14),
+        alignment: Alignment.center,
+        decoration: BoxDecoration(
+          color: enabled
+              ? color.withValues(alpha: 0.15)
+              : theme.backgroundDeep,
+          borderRadius: BorderRadius.circular(7),
+          border: Border.all(
+            color: enabled ? color : theme.panelBorder,
+            width: 1.5,
+          ),
+        ),
+        child: Text(
+          label,
+          style: TextStyle(
+            color: enabled ? color : theme.textDisabled,
+            fontSize: 13,
+            fontWeight: FontWeight.w700,
+            letterSpacing: 1,
+          ),
+        ),
+      ),
+    );
+  }
+}

display/lib/services/concentrador_service.dart

@@ -0,0 +1,197 @@
+// =============================================================================
+//  services/concentrador_service.dart — USB serial link to AR-Concentrador
+// =============================================================================
+//
+//  The AR-Concentrador exposes two separate CH340N virtual COM ports:
+//    rxPort  — USB-OUT: concentrador broadcasts $PARP,STATUS + NMEA at 2 Hz
+//    txPort  — USB-IN : display sends $PARP commands to the concentrador
+//
+//  Both ports run at 115 200 baud, 8N1, no flow control.
+//
+//  Usage:
+//    final svc = ConcentradorService(rxPort: 'COM3', txPort: 'COM4', stationId: 2);
+//    svc.onStatus = (status) { ... };
+//    svc.onConnectionChanged = (connected) { ... };
+//    await svc.connect();
+//    svc.sendEngage(headingDeg: 125.0);
+//    svc.disconnect();
+// =============================================================================
+
+import 'dart:async';
+import 'dart:typed_data';
+
+import 'package:flutter_libserialport/flutter_libserialport.dart';
+
+import 'parp_codec.dart';
+
+/// Callback type for status updates from the concentrador.
+typedef StatusCallback = void Function(ParpStatus status);
+
+/// Callback type for connection state changes.
+typedef ConnectionCallback = void Function(bool connected);
+
+class ConcentradorService {
+  ConcentradorService({
+    required this.rxPort,
+    required this.txPort,
+    this.stationId = 2,
+    this.baudRate = 115200,
+  });
+
+  final String rxPort;
+  final String txPort;
+  final int stationId;
+  final int baudRate;
+
+  /// Called whenever a valid $PARP,STATUS sentence is received.
+  StatusCallback? onStatus;
+
+  /// Called when the connection state changes.
+  ConnectionCallback? onConnectionChanged;
+
+  SerialPort? _rx;
+  SerialPort? _tx;
+  SerialPortReader? _reader;
+  StreamSubscription<Uint8List>? _rxSub;
+
+  bool _connected = false;
+  bool get isConnected => _connected;
+
+  // Accumulation buffer for partial sentences
+  final StringBuffer _buf = StringBuffer();
+
+  // ---------------------------------------------------------------------------
+  //  Connection lifecycle
+  // ---------------------------------------------------------------------------
+
+  /// Open both serial ports and start listening for STATUS sentences.
+  ///
+  /// Throws [SerialPortError] if either port cannot be opened.
+  Future<void> connect() async {
+    await disconnect(); // clean slate
+
+    _rx = SerialPort(rxPort);
+    _tx = SerialPort(txPort);
+
+    _configPort(_rx!);
+    _configPort(_tx!);
+
+    if (!_rx!.openRead()) {
+      throw SerialPortError('Cannot open RX port $rxPort');
+    }
+    if (!_tx!.openWrite()) {
+      throw SerialPortError('Cannot open TX port $txPort');
+    }
+
+    _reader = SerialPortReader(_rx!);
+    _rxSub = _reader!.stream.listen(
+      _onData,
+      onError: (_) => _handleDisconnect(),
+      onDone: _handleDisconnect,
+    );
+
+    _connected = true;
+    onConnectionChanged?.call(true);
+  }
+
+  /// Close both ports gracefully.
+  Future<void> disconnect() async {
+    _rxSub?.cancel();
+    _rxSub = null;
+    _reader = null;
+
+    _rx?.close();
+    _tx?.close();
+    _rx = null;
+    _tx = null;
+
+    if (_connected) {
+      _connected = false;
+      onConnectionChanged?.call(false);
+    }
+  }
+
+  // ---------------------------------------------------------------------------
+  //  Command senders
+  // ---------------------------------------------------------------------------
+
+  void sendEngage(double headingDeg) =>
+      _send(ParpCodec.engage(stationId, headingDeg));
+
+  void sendDisengage() =>
+      _send(ParpCodec.disengage(stationId));
+
+  void sendSetHeading(double headingDeg) =>
+      _send(ParpCodec.setHeading(stationId, headingDeg));
+
+  void sendPortOne(double setpointDeg) =>
+      _send(ParpCodec.portOne(stationId, setpointDeg));
+
+  void sendStbdOne(double setpointDeg) =>
+      _send(ParpCodec.stbdOne(stationId, setpointDeg));
+
+  void sendPortTen(double setpointDeg) =>
+      _send(ParpCodec.portTen(stationId, setpointDeg));
+
+  void sendStbdTen(double setpointDeg) =>
+      _send(ParpCodec.stbdTen(stationId, setpointDeg));
+
+  void sendReqCmd() =>
+      _send(ParpCodec.reqCmd(stationId));
+
+  void sendRelCmd() =>
+      _send(ParpCodec.relCmd(stationId));
+
+  // ---------------------------------------------------------------------------
+  //  Port listing (for settings screen)
+  // ---------------------------------------------------------------------------
+
+  /// All serial ports currently visible to the OS.
+  static List<String> availablePorts() => SerialPort.availablePorts;
+
+  // ---------------------------------------------------------------------------
+  //  Private
+  // ---------------------------------------------------------------------------
+
+  void _configPort(SerialPort port) {
+    final cfg = SerialPortConfig()
+      ..baudRate = baudRate
+      ..bits = 8
+      ..stopBits = 1
+      ..parity = SerialPortParity.none
+      ..setFlowControl(SerialPortFlowControl.none);
+    port.config = cfg;
+  }
+
+  void _onData(Uint8List data) {
+    _buf.write(String.fromCharCodes(data));
+    final raw = _buf.toString();
+    final lines = raw.split('\n');
+
+    // Keep the last (possibly incomplete) chunk in the buffer.
+    _buf.clear();
+    _buf.write(lines.last);
+
+    for (int i = 0; i < lines.length - 1; i++) {
+      final line = lines[i].trim();
+      if (line.isEmpty) continue;
+      final status = ParpCodec.parseStatus(line);
+      if (status != null) {
+        onStatus?.call(status);
+      }
+    }
+  }
+
+  void _send(String sentence) {
+    if (_tx == null || !_connected) return;
+    try {
+      _tx!.write(Uint8List.fromList(sentence.codeUnits));
+    } catch (_) {
+      _handleDisconnect();
+    }
+  }
+
+  void _handleDisconnect() {
+    disconnect();
+  }
+}

display/lib/services/parp_codec.dart

@@ -0,0 +1,144 @@
+// =============================================================================
+//  services/parp_codec.dart — $PARP sentence parser and builder
+// =============================================================================
+//
+//  Protocol reference: docs/concentrador_protocol.md
+//
+//  Inbound ($PARP,STATUS — broadcast by concentrador at 2 Hz):
+//    $PARP,STATUS,<mode>,<setpoint>,<heading>,<rudder>,<commander>*XX\r\n
+//    Example: $PARP,STATUS,HEADING_HOLD,125.0,125.3,2.5,01*3A
+//
+//  Outbound ($PARP commands — sent by display to concentrador):
+//    $PARP,<CMD>,<value>,<station_id>*XX\r\n
+//    Example: $PARP,ENGAGE,0.0,02*XX
+// =============================================================================
+
+import '../widgets/themed/mode_selector.dart';
+
+/// Parsed content of a $PARP,STATUS sentence.
+class ParpStatus {
+  const ParpStatus({
+    required this.mode,
+    required this.setpointDeg,
+    required this.headingDeg,
+    required this.rudderDeg,
+    required this.commander,
+  });
+
+  final AutopilotMode mode;
+  final double setpointDeg;
+  final double headingDeg;
+  final double rudderDeg;
+  final int commander; // station ID of the current commander (0 = none)
+}
+
+/// Stateless NMEA $PARP sentence codec.
+abstract final class ParpCodec {
+  // ---------------------------------------------------------------------------
+  //  Inbound parser
+  // ---------------------------------------------------------------------------
+
+  /// Parse a complete NMEA sentence string (with or without leading $).
+  ///
+  /// Returns [ParpStatus] if the sentence is a valid $PARP,STATUS with correct
+  /// checksum. Returns null for any other sentence type or if CRC fails.
+  static ParpStatus? parseStatus(String sentence) {
+    // Strip whitespace / CRLF
+    final s = sentence.trim();
+
+    // Locate checksum delimiter
+    final starIdx = s.lastIndexOf('*');
+    if (starIdx < 0) return null;
+
+    final body = s.startsWith('\$') ? s.substring(1, starIdx) : s.substring(0, starIdx);
+    final crcHex = s.substring(starIdx + 1);
+
+    // Verify checksum
+    if (!_crcOk(body, crcHex)) return null;
+
+    // Tokenise
+    final parts = body.split(',');
+    if (parts.length < 7) return null;
+    if (parts[0] != 'PARP' || parts[1] != 'STATUS') return null;
+
+    final mode = _parseMode(parts[2]);
+    final setpoint = double.tryParse(parts[3]);
+    final heading = double.tryParse(parts[4]);
+    final rudder = double.tryParse(parts[5]);
+    final commander = int.tryParse(parts[6]);
+
+    if (setpoint == null || heading == null || rudder == null || commander == null) {
+      return null;
+    }
+
+    return ParpStatus(
+      mode: mode,
+      setpointDeg: setpoint,
+      headingDeg: heading,
+      rudderDeg: rudder,
+      commander: commander,
+    );
+  }
+
+  // ---------------------------------------------------------------------------
+  //  Outbound builders
+  // ---------------------------------------------------------------------------
+
+  static String engage(int stationId, double currentHeadingDeg) =>
+      _build('ENGAGE', currentHeadingDeg, stationId);
+
+  static String disengage(int stationId) =>
+      _build('DISENGAGE', 0.0, stationId);
+
+  static String setHeading(int stationId, double headingDeg) =>
+      _build('SETHEADING', headingDeg, stationId);
+
+  static String portOne(int stationId, double currentSetpoint) =>
+      _build('PORTONE', currentSetpoint, stationId);
+
+  static String stbdOne(int stationId, double currentSetpoint) =>
+      _build('STBDONE', currentSetpoint, stationId);
+
+  static String portTen(int stationId, double currentSetpoint) =>
+      _build('PORTTEN', currentSetpoint, stationId);
+
+  static String stbdTen(int stationId, double currentSetpoint) =>
+      _build('STBDTEN', currentSetpoint, stationId);
+
+  static String reqCmd(int stationId) =>
+      _build('REQCMD', 0.0, stationId);
+
+  static String relCmd(int stationId) =>
+      _build('RELCMD', 0.0, stationId);
+
+  // ---------------------------------------------------------------------------
+  //  Private helpers
+  // ---------------------------------------------------------------------------
+
+  static String _build(String cmd, double value, int stationId) {
+    final body = 'PARP,$cmd,${value.toStringAsFixed(1)},'
+        '${stationId.toString().padLeft(2, '0')}';
+    final crc = _computeCrc(body);
+    return '\$$body*${crc.toRadixString(16).toUpperCase().padLeft(2, '0')}\r\n';
+  }
+
+  static int _computeCrc(String body) {
+    int crc = 0;
+    for (final ch in body.codeUnits) {
+      crc ^= ch;
+    }
+    return crc;
+  }
+
+  static bool _crcOk(String body, String crcHex) {
+    final expected = _computeCrc(body);
+    final received = int.tryParse(crcHex, radix: 16);
+    return received != null && received == expected;
+  }
+
+  static AutopilotMode _parseMode(String raw) => switch (raw) {
+        'HEADING_HOLD' => AutopilotMode.headingHold,
+        'TRACK' => AutopilotMode.trackKeep,
+        _ => AutopilotMode.standby,
+      };
+}

display/pubspec.yaml

@@ -13,6 +13,8 @@ dependencies:
   provider: ^6.1.2
   # Theme persistence — stores selected theme id locally on the display device
   shared_preferences: ^2.3.2
+  # USB serial communication with AR-Concentrador (CH340N virtual COM ports)
+  flutter_libserialport: ^0.2.1
 
 dev_dependencies:
   flutter_test: