Write data to BLE device and read its response flutter?

Question

I am facing issues with writing the commands to BLE device and receiving the data. I am writing ASCII encoded string to the Characteristic. The problem arises when its time to decode the data back. Exact data is received as it's received in iOS but when I try to decode it just gets blank. I tried decoding via UTF8 decoder and ASCII decoder but no result was obtained.

This is how I discover the devices.

@override
  void initState() {
    // TODO: implement initState
    widget.flutterBlue.scanResults.listen((List<ScanResult> results) {
      for (ScanResult result in results) {
        _addDeviceTolist(result.device);
      }
    });
    widget.flutterBlue.startScan();
  }

Connect Device:-

void _connectDevice() async {
    widget.flutterBlue.stopScan();
    print(_deviceToConnect);
    try {
      await _deviceToConnect.connect();
    } catch (e) {
      if (e.code != 'already_connected') {
        throw e;
      }
    } finally {
      _services = await _deviceToConnect.discoverServices();
    }
    _discoverDeviceServices();
    setState(() {
      _connectedDevice = _deviceToConnect;
    });
  }

Discovering the services:-

When commenting TAG-1 & TAG-2 lines the values get printed. I tried both ASCII and UTF8 decoding.

While scrolling through various issues I found out to read values from all the characteristics.

void _discoverDeviceServices() async {
    for (BluetoothService service in _services){
      for (BluetoothCharacteristic characteristic in service.characteristics){
        var value = await characteristic.read();
        print(value);
        // print(AsciiDecoder().convert(value)); /*** TAG-1***/
        // print(utf8.decode(value)); /*** TAG-2***/
        if (characteristic.properties.write){
          if (characteristic.properties.notify){
            _rx_Write_Characteristic = characteristic;
            _sendCommandToDevice();
          }
        }
      }
    }
  }

Writing commands to device:-

void _sendCommandToDevice() async {
    final command = "AT Z\r";
    final convertedCommand = AsciiEncoder().convert(command);
    await _rx_Write_Characteristic.write(convertedCommand);
    _connectedDevice.disconnect();
  }

Please help me out pointing where I got wrong in reading the response of the data written to BLE device and how exactly writing and reading of values is to be done?

Thanks!

Answer 1

It is probably String.fromCharCode you are looking for.

It seemed to give the right answer when I tested it with your values on https://dartpad.dev/

The 13 s are \r escape characters that represent carriage return