attach method

Stream<IMUData> attach(Stream<List<int>> dataResponse)

Attach this RxIMU to the Frame's dataResponse characteristic stream.

Implementation

Stream<IMUData> attach(Stream<List<int>> dataResponse) {
  // TODO check for illegal state - attach() already called on this RxIMU etc?
  // might be possible though after a clean close(), do I want to prevent it?

  // the subscription to the underlying data stream
  StreamSubscription<List<int>>? dataResponseSubs;

  // Our stream controller that transforms the dataResponse elements into IMUData events
  _controller = StreamController();

  _controller!.onListen = () {
    dataResponseSubs = dataResponse
      .where((data) => data[0] == imuFlag)
      .listen((data) {
        Uint8List bytes = Uint8List.fromList(data);
        // reinterpret the bytes after offset 2 as signed 16-bit integers
        Int16List s16 = bytes.buffer.asInt16List(2);

        // Get raw values
        var rawCompass = (s16[0], s16[1], s16[2]);
        var rawAccel = (s16[3], s16[4], s16[5]);

        // Add to buffers
        _compassBuffer.add(rawCompass);
        _accelBuffer.add(rawAccel);

        _controller!.add(IMUData(
          compass: _compassBuffer.average,
          accel: _accelBuffer.average,
          raw: IMURawData(
            compass: rawCompass,
            accel: rawAccel,
          ),
        ));

    }, onDone: _controller!.close, onError: _controller!.addError);
    _log.fine('ImuDataResponse stream subscribed');
  };

  _controller!.onCancel = () {
    _log.fine('ImuDataResponse stream unsubscribed');
    dataResponseSubs?.cancel();
    _controller!.close();
  };

  return _controller!.stream;
}