Pi vitals module

pi/ui/lib/screens/dashboard_screen.dart

@@ -2,9 +2,10 @@ import 'dart:async';
 import 'dart:math';
 import 'package:flutter/material.dart';
 
+import '../services/pi_io.dart';
 import '../widgets/stat_box.dart';
 
-/// Main dashboard - placeholder with random updating values
+/// Main dashboard - displays Pi vitals and placeholder stats
 class DashboardScreen extends StatefulWidget {
   const DashboardScreen({super.key});
 
@@ -16,7 +17,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
   final _random = Random();
   Timer? _timer;
 
-  int _speed = 0;
+  double? _piTemp;
   int _rpm = 0;
   double _voltage = 12.6;
   int _temp = 25;
@@ -24,10 +25,14 @@ class _DashboardScreenState extends State<DashboardScreen> {
   @override
   void initState() {
     super.initState();
-    // Update random values every 500ms - simulates live data
+
+    // Update values periodically
     _timer = Timer.periodic(const Duration(milliseconds: 500), (_) {
       setState(() {
-        _speed = _random.nextInt(120);
+        // Pi temp - sync read from cache, async refresh happens in background
+        _piTemp = PiIO.instance.getTemperature();
+
+        // Placeholder random data - will be replaced with real sensors
         _rpm = 1000 + _random.nextInt(8000);
         _voltage = 11.5 + _random.nextDouble() * 2;
         _temp = 20 + _random.nextInt(60);
@@ -72,14 +77,14 @@ class _DashboardScreenState extends State<DashboardScreen> {
 
             const SizedBox(height: 48),
 
-            // Main speed display
+            // Main Pi temperature display
             Expanded(
               child: Center(
                 child: Column(
                   mainAxisAlignment: MainAxisAlignment.center,
                   children: [
                     Text(
-                      '$_speed',
+                      _piTemp != null ? _piTemp!.toStringAsFixed(1) : '—',
                       style: const TextStyle(
                         fontSize: 180,
                         fontWeight: FontWeight.w200,
@@ -88,7 +93,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
                       ),
                     ),
                     Text(
-                      'km/h',
+                      'Pi Temp',
                       style: Theme.of(context).textTheme.headlineSmall?.copyWith(
                         color: Colors.grey,
                       ),
@@ -103,7 +108,7 @@ class _DashboardScreenState extends State<DashboardScreen> {
               mainAxisAlignment: MainAxisAlignment.spaceAround,
               children: [
                 StatBox(label: 'RPM', value: _rpm.toString()),
-                StatBox(label: 'TEMP', value: '$_temp°C'),
+                StatBox(label: 'ENG', value: '$_temp°C'),
                 StatBox(label: 'GEAR', value: '—'),
               ],
             ),

pi/ui/lib/services/pi_io.dart

@@ -0,0 +1,55 @@
+import 'dart:io';
+
+/// Abstraction for Raspberry Pi hardware I/O
+///
+/// Uses fire-and-forget async reads with synchronous cache returns.
+/// UI always gets immediate response, cache updates in background.
+class PiIO {
+  PiIO._() {
+    // Kick off initial read
+    _refreshTemperature();
+  }
+  static final instance = PiIO._();
+
+  // Thermal zone file path (returns millidegrees)
+  static const _thermalPath = '/sys/class/thermal/thermal_zone0/temp';
+
+  // Cache
+  double? _tempCache;
+  bool _tempReadInProgress = false;
+
+  /// Get CPU temperature in Celsius (synchronous, returns cached value)
+  ///
+  /// Returns immediately with cached value (or null if no read has completed).
+  /// Triggers background refresh if not already in progress.
+  double? getTemperature() {
+    // Fire off background read if not already running
+    if (!_tempReadInProgress) {
+      _refreshTemperature();
+    }
+    return _tempCache;
+  }
+
+  /// Background read - updates cache when complete
+  Future<void> _refreshTemperature() async {
+    if (_tempReadInProgress) return;
+    _tempReadInProgress = true;
+
+    try {
+      final file = File(_thermalPath);
+      if (await file.exists()) {
+        final content = await file.readAsString();
+        _tempCache = int.parse(content.trim()) / 1000.0;
+      }
+    } catch (e) {
+      // Not on Pi, or permission issue - cache stays as-is
+    } finally {
+      _tempReadInProgress = false;
+    }
+  }
+
+  /// Force clear cache (next getTemperature will return null until read completes)
+  void clearCache() {
+    _tempCache = null;
+  }
+}