Flutter_blue: Issue with writeCharacteristic()

Created on 21 Mar 2019 · 19Comments · Source: pauldemarco/flutter_blue

I am trying to connect to an Adafruit nrf8001 hooked up to an Arduino. It uses the UART service with the UUID 6E400001-B5A3-F393-E0A9-E50E24DCCA9E as defined here. I communicates with the TX and RX characteristics. I can connect to the device perfectly fine, but when I try to write to the TX characteristic, I get the error:

D/FlutterBluePlugin(20492): [onCharacteristicWrite] uuid: 6e400002-b5a3-f393-e0a9-e50e24dcca9e status: 128
E/flutter (20492): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: Exception: Failed to write the characteristic
E/flutter (20492): #0      BluetoothDevice.writeCharacteristic.<anonymous closure> 
    ../…/src/bluetooth_device.dart:132
... full output below

I set up my scanning for devices with:

setState(() {
  _scanning = true;
});
_scanSubscription =
  flutterBlue.scan(timeout: Duration(minutes: 1)).listen((scanResult) {
    if (scanResult.advertisementData.connectable) {
      setState(() {
        scanResults[scanResult.device.id] = scanResult;
      });
    }
  }, onDone: _cancelScanning);

and then I connect with:

setState(() {
  _deviceConnection = flutterBlue.connect(device).listen((s) {
    if (s == BluetoothDeviceState.connected) {
      print('Connected');
      setState(() {
        _device = device;
        _connected = true;
        _statusMessage = 'Connected to Cycler';
      });
      _cancelScanning();
      _discoverServices();
    } else {
      print('Not Connected');
      print(s.toString());
    }
  });
});

I then find the UART service and related characteristics as follows:

_discoverServices() {
  setState(() {
    _statusMessage = 'Discovering device services';
  });
  _device.discoverServices().then((s) {
    setState(() {
      _statusMessage = 'Services discovered';
      _deviceServices = s;
    });
    _findUART();
  });
}

_findUART() {
  if (_deviceServices != null && _deviceServices.isNotEmpty) {
    _deviceServices.forEach((service) {
      //servicesList.add(Text(service.uuid.toString()));
      if (service.uuid.toString().toLowerCase() ==
          '6E400001-B5A3-F393-E0A9-E50E24DCCA9E'.toLowerCase()) {
        print('UART found');
        _uartService = service;
        service.characteristics.forEach((c) {
          if (c.uuid.toString().toLowerCase() ==
              '6E400002-B5A3-F393-E0A9-E50E24DCCA9E'.toLowerCase()) {
            _tx = c;
            print('TX found');
          } else if (c.uuid.toString().toLowerCase() ==
              '6E400003-B5A3-F393-E0A9-E50E24DCCA9E'.toLowerCase()) {
            _rx = c;
            print('RX found');
          }
        });
      }
    });
  }
}

Then I have a button onPressed: linked to the method _sendTest

_sendTest() async {
  final value = await _device.writeCharacteristic(_tx, [0x12, 0x34],
      type: CharacteristicWriteType.withResponse);
  print(value);
}

Using Flutter 1.2.1. Running on Samsung Galaxy S8. Please let me know if you need any more relevant information.

Here's the full error:

```
E/flutter (20492): #0 ../…/src/bluetooth_d E/flutter (20492): #1 E/flutter (20492): #2 E/flutter (20492): #3 E/flutter (20492): #4 E/flutter (20492): #5 E/flutter (20492): #6 E/flutter (20492): #7 E/flutter (20492): #8 E/flutter (20492): #9 E/flutter (20492): #10 E/flutter (20492): #11 E/flutter (20492): #12 E/flutter (20492): #13 E/flutter (20492): #14 E/flutter (20492): #15 E/flutter (20492): #16 E/flutter (20492): #17 E/flutter (20492): #18 E/flutter (20492): #19 E/flutter (20492): #20 E/flutter (20492): #21 E/flutter (20492): #22 E/flutter (20492): #23 E/flutter (20492): #24 E/flutter (20492): #25 E/flutter (20492): #26 E/flutter (20492): #27 E/flutter (20492): #28 E/flutter (20492): #29 E/flutter (20492): #30 E/flutter (20492): #31 E/flutter (20492): #32 E/flutter (20492): #33 E/flutter (20492): #34 E/flutter (20492): #35 E/flutter (20492): #36 E/flutter (20492): #37 E/flutter (20492): #38 E/flutter (20492): #39 E/flutter (20492): #40 E/flutter (20492): #41 E/flutter (20492): #42 E/flutter (20492): #43 E/flutter (20492): #44 E/flutter (20492): #45 E/flutter (20492): #46 E/flutter (20492): #47 E/flutter (20492): #48 E/flutter (20492): #49 E/flutter (20492): #50 E/flutter (20492): #51 E/flutter (20492): #52 E/flutter (20492): #53 E/flutter (20492): #54 BluetoothDevice.writeCharacteristic.
evice.dart:132
_rootRunUnary (dart:async/zone.dart:1132:38)
_CustomZone.runUnary (dart:async/zone.dart:1029:19)
_FutureListener.handleValue (dart:async/future_impl.dart:126:18)
Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:639:45)
Future._propagateToListeners (dart:async/future_impl.dart:668:32)
Future._complete (dart:async/future_impl.dart:473:7)
_cancelAndValue (dart:async/stream_pipe.dart:63:12)
Stream.first. (dart:async/stream.dart:1170:11)
_rootRunUnary (dart:async/zone.dart:1132:38)
_CustomZone.runUnary (dart:async/zone.dart:1029:19)
_CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
_BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
_BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
_ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:132:11)
_WhereStream._handleData (dart:async/stream_pipe.dart:207:12)
_ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:164:13)
_rootRunUnary (dart:async/zone.dart:1132:38)
_CustomZone.runUnary (dart:async/zone.dart:1029:19)
_CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
_BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
_BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
_ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:132:11)
_MapStream._handleData (dart:async/stream_pipe.dart:232:10)
_ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:164:13)
_rootRunUnary (dart:async/zone.dart:1132:38)
_CustomZone.runUnary (dart:async/zone.dart:1029:19)
_CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
_BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
_BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
_ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:132:11)
_MapStream._handleData (dart:async/stream_pipe.dart:232:10)
_ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:164:13)
_rootRunUnary (dart:async/zone.dart:1132:38)
_CustomZone.runUnary (dart:async/zone.dart:1029:19)
_CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
_BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
_BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
_ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:132:11)
_WhereStream._handleData (dart:async/stream_pipe.dart:207:12)
_ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:164:13)
_rootRunUnary (dart:async/zone.dart:1132:38)
_CustomZone.runUnary (dart:async/zone.dart:1029:19)
_CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
_BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
_DelayedData.perform (dart:async/stream_impl.dart:591:14)
_StreamImplEvents.handleNext (dart:async/stream_impl.dart:707:11)
_PendingEvents.schedule. (dart:async/stream_impl.dart:667:7)
_rootRun (dart:async/zone.dart:1120:38)
_CustomZone.run (dart:async/zone.dart:1021:19)
_CustomZone.runGuarded (dart:async/zone.dart:923:7)
_CustomZone.bindCallbackGuarded. (dart:async/zone.dart:963:23)
_rootRun (dart:async/zone.dart:1124:13)
_CustomZone.run (dart:async/zone.dart:1021:19)
_CustomZone.runGuarded (dart:async/zone.dar

Source

BradHacker

👍2

Most helpful comment

Just guessing- but have you tried without CharacteristicWriteType.withResponse ? I found that to be a problem before on iOS.

okachobi on 21 Mar 2019

👍2 🚀1 ❤1 🎉1 😄1

All 19 comments

Just guessing- but have you tried without CharacteristicWriteType.withResponse ? I found that to be a problem before on iOS.

okachobi on 21 Mar 2019

👍2 🚀1 ❤1 🎉1 😄1

I have tried that before.

BradHacker on 21 Mar 2019

Hey,

I'm also having a similar problem with writing a characteristic, but only on Android devices.

iOS is working fine.

E/flutter ( 7662): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: PlatformException(write_characteristic_error, writeCharacteristic failed, null)
E/flutter ( 7662): #0 StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:564:7)
E/flutter ( 7662): #1 MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:302:33)
E/flutter ( 7662):
E/flutter ( 7662): #2 BluetoothDevice.writeCharacteristic (file:///Users/earyzhe/dev/SDKs/flutter/.pub-cache/hosted/pub.dartlang.org/flutter_blue-0.5.0/lib/src/bluetooth_device.dart:114:10)
E/flutter ( 7662):
E/flutter ( 7662): #3 BluetoothInstance._turnSwitchOff (package:battery_saver/bluetooth_functions.dart:131:13)
E/flutter ( 7662):
E/flutter ( 7662): #4 BluetoothInstance.stopCharging (package:battery_saver/bluetooth_functions.dart:40:5)
E/flutter ( 7662): #5 MainBloc.batteryChargeChanged (package:battery_saver/bloc.dart:87:18)
E/flutter ( 7662): #6 _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter ( 7662): #7 _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter ( 7662): #8 _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
E/flutter ( 7662): #9 _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
E/flutter ( 7662): #10 _DelayedData.perform (dart:async/stream_impl.dart:591:14)
E/flutter ( 7662): #11 _StreamImplEvents.handleNext (dart:async/stream_impl.dart:707:11)
E/flutter ( 7662): #12 _PendingEvents.schedule. (dart:async/stream_impl.dart:667:7)
E/flutter ( 7662): #13 _rootRun (dart:async/zone.dart:1120:38)
E/flutter ( 7662): #14 _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter ( 7662): #15 _CustomZone.runGuarded (dart:async/zone.dart:923:7)
E/flutter ( 7662): #16 _CustomZone.bindCallbackGuarded. (dart:async/zone.dart:963:23)
E/flutter ( 7662): #17 _rootRun (dart:async/zone.dart:1124:13)
E/flutter ( 7662): #18 _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter ( 7662): #19 _CustomZone.runGuarded (dart:async/zone.dart:923:7)
E/flutter ( 7662): #20 _CustomZone.bindCallbackGuarded. (dart:async/zone.dart:963:23)
E/flutter ( 7662): #21 _microtaskLoop (dart:async/schedule_microtask.dart:41:21)
E/flutter ( 7662): #22 _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5)
`

earyzhe on 24 Mar 2019

👍1

Hmm.... I can't find any documentation on the error code 128 I was getting. I've been looking for a few days. Anyone? Using Samsung Galaxy S8, haven't tested with iOS as of now.

BradHacker on 26 Mar 2019

On iOS with iPhone 7 i still get an error

[VERBOSE-2:ui_dart_state.cc(148)] Unhandled Exception: Exception: Failed to write the characteristic
#0      BluetoothDevice.writeCharacteristic.<anonymous closure> 
../…/src/bluetooth_device.dart:132
#1      _rootRunUnary (dart:async/zone.dart:1132:38)
#2      _CustomZone.runUnary (dart:async/zone.dart:1029:19)
#3      _FutureListener.handleValue (dart:async/future_impl.dart:126:18)
#4      Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:639:45)
#5      Future._propagateToListeners (dart:async/future_impl.dart:668:32)
#6      Future._complete (dart:async/future_impl.dart:473:7)
#7      _cancelAndValue (dart:async/stream_pipe.dart:63:12)
#8      Stream.first.<anonymous closure> (dart:async/stream.dart:1170:11)
#9      _rootRunUnary (dart:async/zone.dart:1132:38)
#10     _CustomZone.runUnary (dart:async/zone.dart:1029:19)
#11     _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
#12     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#13     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
#14     _ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:132:11)
#15     _WhereStream._handleData (dart:async/stream_pipe.dart:207:12)
#16     _ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:164:13)
#17     _rootRunUnary (dart:async/zone.dart:1132:38)
#18     _CustomZone.runUnary (dart:async/zone.dart:1029:19)
#19     _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
#20     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#21     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
#22     _ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:132:11)
#23     _MapStream._handleData (dart:async/stream_pipe.dart:232:10)
#24     _ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:164:13)
#25     _rootRunUnary (dart:async/zone.dart:1132:38)
#26     _CustomZone.runUnary (dart:async/zone.dart:1029:19)
#27     _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
#28     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#29     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
#30     _ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:132:11)
#31     _MapStream._handleData (dart:async/stream_pipe.dart:232:10)
#32     _ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:164:13)
#33     _rootRunUnary (dart:async/zone.dart:1132:38)
#34     _CustomZone.runUnary (dart:async/zone.dart:1029:19)
#35     _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
#36     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#37     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
#38     _ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:132:11)
#39     _WhereStream._handleData (dart:async/stream_pipe.dart:207:12)
#40     _ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:164:13)
#41     _rootRunUnary (dart:async/zone.dart:1132:38)
#42     _CustomZone.runUnary (dart:async/zone.dart:1029:19)
#43     _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
#44     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#45     _DelayedData.perform (dart:async/stream_impl.dart:591:14)
#46     _StreamImplEvents.handleNext (dart:async/stream_impl.dart:707:11)
#47     _PendingEvents.schedule.<anonymous closure> (dart:async/stream_impl.dart:667:7)
#48     _rootRun (dart:async/zone.dart:1120:38)
#49     _CustomZone.run (dart:async/zone.dart:1021:19)
#50     _CustomZone.runGuarded (dart:async/zone.dart:923:7)
#51     _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:963:23)

BradHacker on 26 Mar 2019

Just guessing- but have you tried without CharacteristicWriteType.withResponse ? I found that to be a problem before on iOS.

If we don't use CharacteristicWriteType.withResponse, what alternatives do we have?

LastMonopoly on 12 Apr 2019

Just guessing- but have you tried without CharacteristicWriteType.withResponse ? I found that to be a problem before on iOS.

If we don't use CharacteristicWriteType.withResponse, what alternatives do we have?

CharacteristicWriteType.withoutResponse

ericstephen on 17 Apr 2019

Just guessing- but have you tried without CharacteristicWriteType.withResponse ? I found that to be a problem before on iOS.

If we don't use CharacteristicWriteType.withResponse, what alternatives do we have?

CharacteristicWriteType.withoutResponse

Using CharacteristicWriteType.withoutResponse, the error doesn't show, but the information is never sent.

BradHacker on 20 Apr 2019

Brad,
Just partially used your example and it's working for me. main.dart here -> http://sayaw.net/main_dart.txt

sonnny on 22 May 2019

Please note sonny's example requires version 0.5.0
Version 0.6.0 will break it

zwells0225 on 28 Jun 2019

For some reason, the code just recently began working using CharacteristicWriteType.withoutResponse. I think I updated flutter so not sure if there were any updates during that time. My code is here

BradHacker on 16 Jul 2019

I am having the same issue with the example application provided with flutter_blue. Is there a particular version of fluttter_blue(0.5.0?) and a certain version of flutter the only solution to fix this issue?

siddharthshah87 on 22 Jul 2019

👍1

hey, guys, I am having the same issue, any update?

xuzhengquan on 23 Jul 2019

👍1

Also getting the status 128 issue when my message size exceeds 244 bytes.

VaivanOmmeren on 25 Jul 2019

My code works using flutter_blue: ^0.5.0. I only send a few bytes of info to keep latency low. Again, a link to my working code: https://github.com/BradHacker/cycler-controller

There is an Arduino on the other end that reads the values sent and does some logic to control a humanoid robot. Everything seems to work bluetooth wise. Having some issues on the Arduino end that have nothing to do with bluetooth (primarily being just plain out of pins using an Uno).

I'm a student and currently on summer break so I have to wait till September to begin working again on the robot. We ordered some Teensy 3.6 boards to replace them which will only improve the processing time. I highly recommend these boards.

BradHacker on 25 Jul 2019

flutter_blue 0.6.2 PlatformException (PlatformException(write_characteristic_error, service (daebb240 - 00ffffffff ) could not be located on the device, null))method used:

await vibChar.write(startVibrating, withoutResponse: true);

how flutter_blue knows that he is talking to correct device? im writing simply to characteristic, and i have no place to specify device.

kamilk91 on 16 Oct 2019

I have this issue specifically if I connect to a bottle, write and get data successfully, disconnect, but then try to connect again. Any ideas why this might be?

jacobokoenig on 29 Dec 2019

👍1

Guys, the code and troubleshooting in this thread helped me build my product faster. Parts of the code in the question and answers should be included in the official documentation and readme. I spent almost 6 hours trying to find answers online and in code.

realrk95 on 28 Nov 2020

hi, I have been trying to connect mi band 5 to my flutter app using flutter_blue but I'm getting an empty array which means characteristics are null. I can't find the issue why specifically happening this and if I can get help to solve this issue it will be a great help.

thank you for your time and considerations!