Add car-off shutdown detection to LIN_to_IR firmware

Arduino/LIN_to_IR/LIN_to_IR.cpp

@@ -85,6 +85,7 @@ uint32_t get_mce_code(uint8_t button) {
     case 4: return 0x800f0421; // RIGHT
     case 5: return 0x800f0422; // ENTER / OK
     case 6: return 0x800f0423; // BACK
+    case 7: return 0x800f046f; // F12 (Shutdown)
     default: return 0;
   }
 }
@@ -105,6 +106,8 @@ unsigned long last_frame_time = 0;
 uint8_t current_button = 0;
 uint8_t toggle_bit = 0;
 unsigned long last_ir_send_time = 0;
+unsigned long last_lin_activity_time = 0;
+bool is_car_on = false;
 
 void process_button_state(uint8_t active_button) {
   unsigned long now = millis();
@@ -179,10 +182,15 @@ void setup() {
   LINBusSerial.begin(9600);
   frame = LinFrame();
   last_frame_time = millis();
+  last_lin_activity_time = millis();
 }
 
 void loop() {
   if (LINBusSerial.available()) {
+    last_lin_activity_time = millis();
+    if (!is_car_on) {
+      is_car_on = true;
+    }
     b = LINBusSerial.read();
     n = frame.num_bytes();
 
@@ -201,4 +209,13 @@ void loop() {
   if (millis() - last_frame_time > 200) {
     current_button = 0;
   }
+
+  // Car off detection: if no LIN activity for 5 seconds, send F12 to trigger shutdown
+  if (is_car_on && (millis() - last_lin_activity_time > 5000)) {
+    is_car_on = false;
+    for (int i = 0; i < 3; i++) {
+      send_ir_for_button(7, i & 1);
+      delay(100);
+    }
+  }
 }