Filter S300 placeholder frames

lib/core/bluetooth/bt_poller.dart

@@ -87,6 +87,12 @@ class BtPoller {
       final Uint8List frame =
           Uint8List.fromList(_rxBuf.sublist(startIdx, startIdx + 128));
 
+      if (ecuType == EcuType.s300 && _isS300PlaceholderFrame(frame)) {
+        droppedFrames++;
+        _rxBuf.removeRange(0, startIdx + 128);
+        continue;
+      }
+
       final checksumOk = validateFrame(frame);
       final canUseFrame = checksumOk || ecuType == EcuType.s300;
 
@@ -119,4 +125,31 @@ class BtPoller {
     stop();
     _frameController.close();
   }
+
+  bool _isS300PlaceholderFrame(Uint8List frame) {
+    if (frame.length != 128) return false;
+
+    // The S300 Bluetooth stream can interleave a valid-checksum placeholder
+    // frame that is not the SManager live sensor frame. It has a fixed header
+    // and zero/overflow values for speed, TPS, injection and ignition, then it
+    // overwrites the dashboard with stale/empty values. Filter only this exact
+    // signature so true idle/stopped live frames can still pass.
+    return frame[0] == 0x1B &&
+        frame[1] == 0x00 &&
+        frame[2] == 0x14 &&
+        frame[3] == 0x00 &&
+        frame[4] == 0x00 &&
+        frame[5] == 0xFF &&
+        frame[6] == 0xFF &&
+        frame[7] == 0xF2 &&
+        frame[8] == 0x03 &&
+        frame[9] == 0x18 &&
+        frame[10] == 0x00 &&
+        frame[11] == 0x00 &&
+        frame[12] == 0x10 &&
+        frame[13] == 0x00 &&
+        frame[14] == 0x00 &&
+        frame[15] == 0x00 &&
+        frame[16] == 0xC4;
+  }
 }