Data Skipping when the transfer rate is high

I am working on health-related device which relies on getting the data from a piezoelectric sensor and transmitting the data through Arduino using the hc 05 module. The data transfer rate is exceptionally high (about 20 ms intervals) and I am getting values that have some skipped digits. I have made a wrapper class for sending and receiving data and also using special delimiters as data already to eliminate data arriving randomly.

Here is the methods of Bluetooth Class, I have used Provider for state management

class BluetoothProvider extends ChangeNotifier {

  BluetoothState bluetoothState = BluetoothState.UNKNOWN;
  FlutterBluetoothSerial bluetooth = FlutterBluetoothSerial.instance;
  BluetoothConnection? connection;
  bool isDisconnecting = false;
  StreamSubscription<Uint8List>? dataStreamSubscription;
  StreamController<DataPoint?> dataPointStream = StreamController.broadcast();
  //other vars

  BluetoothProvider() {
    init();
  }

  Future<void> init() async {
    bluetooth = FlutterBluetoothSerial.instance;
    bool isEnabled = await bluetooth.isEnabled ?? false;
    bool isBluetoothAvailable = await Permission.bluetoothConnect.isGranted;
    if (isBluetoothAvailable) {
      if (!isEnabled) {
        await enableBluetooth();
      } else {
        await Future.wait([getPairedDevices(), getName()]);
      }

      bluetooth.state.then((state) {
        bluetoothState = state;
        notifyListeners();
      });
      deviceState = 0;
      streamSubscription =
          bluetooth.onStateChanged().distinct().listen((event) {
        bluetoothState = event;
        notifyListeners();
      });
      bluetooth.onStateChanged().asBroadcastStream().listen((event) {
        bluetoothState = event;
        notifyListeners();
      });
      streamSubscription?.onData((data) {
        bluetoothState = data;
      });
      streamSubscription?.onError((error) {
        // printlog('Error: $error');
      });
      bluetooth.onStateChanged().handleError((error) {
        // printlog('Error: $error');
      });
    }
  }

  //other methods

  List<String>? computeData(Uint8List data) {
    List<String>? smallFunction() {
      String text = utf8.decode(data);
      String startingSymbol = '\$';
      for (int i = 0; i < text.length; i++) {
        buffer.add(text[i]);
        if (text[i] == startingSymbol && findElement(startingSymbol) != -1) {
          List<String> tempBuffer = buffer.sublist(0, buffer.length - 1);
          buffer.clear();
          return tempBuffer;
        }
      }
      return null;
    }

    List<String>? dataString = smallFunction();
    if (dataString != null && dataString.length > 2) {
      return dataString;
    } else {
      return null;
    }
  }

  void clearBuffer(String startingSymbol) {
    buffer.clear();
  }

  Future<bool> send(String text) async {
    text = text.trim();
    connection!.output.add(Uint8List.fromList(utf8.encode("$text\r\n")));
    try {
      await connection!.output.allSent;
      deviceState = text == "1" ? 1 : -1;
      notifyListeners();
      return true;
    } catch (e) {
      // printlog(e.toString());
      return false;
    }
  }
}

This class only handles the sending the data and computeData(Uint8List data) method only sends the incoming data into buffer such that proper data manipulation can be done afterwards.

I am using a DataPoint class to store the points receiving from the sensor. The x value is the time in millisecond and y is the sensor value.

    class DataPoint {
      // x and y values
      double x;
      double y;
      double? ynew;

      DataPoint({required this.x, required this.y, this.ynew});

      @override
      String toString() {
        return 'DataPoint{x: $x, y: $y, ynew: $ynew}';    
      }
    }

Below is the code when I convert the data coming from the Bluetooth into List and then convert it to a Datapoint Object

_dataStreamSubscription?.onData((data) {
      if (!mounted) {
        return;
      }
      /*
        getting that data and putting it in buffer to avoid random order of incoming data
        It temporarily stores data if is incomplete and gives List<String> if the all values are recieved in correct order
       */
      List<String>? tempData =
          Provider.of<BluetoothProvider>(context, listen: false)
              .computeData(data);
      if (tempData?.isNotEmpty ?? false) {
        DataPoint? tempPoint = BluetoothDataProvider.bluetoothDataProvider
            .addParsedData(tempData!, '&', '#');
        //adding to dataStream 
        Provider.of<BluetoothProvider>(context, listen:false).dataPointStream.add(tempPoint);
      }
    });
    Provider.of<BluetoothProvider>(context,listen: false).dataPointStream.stream.listen((tempPoint) {
      print(tempPoint.toString());
      if (tempPoint?.x != null && tempPoint?.y != null && tempPoint!=null) {
        if (tempPoint.y != 0 && tempPoint.x!=0) {
          tempPoint.x = (tempPoint.x) / 1000;
          updateChartData(tempPoint);
        }
      }
    });

Ignore the values as floating point How Data should come	How data is coming in flutter

Data is in format : $(Value1)&(Value2) when sending from arduino

I have experimented with native android apps that have Bluetooth serial functionality, it works perfectly fine. Some values are getting skipped and some digits are missing from a certain value. Any help would be appreciated.

edufolly / flutter_bluetooth_serial

Data Skipping when the transfer rate is high #194