Create a new function to send command to devices (BLE)

Questions/Help
#1

I wanna create a bluetooth app that can control my devices.
I use flutter_blue and modify its example.
(https://pub.dev/packages/flutter_blue)

I have successfully a litle by adding the following lines (from line 178)

             (c) => CharacteristicTile(
                characteristic: c,
                onReadPressed: () => c.read(),
                onWritePressed: () async {                      
                  List<int> value = await c.read();
                  if (value.toString() == "[1]"){
                    await c.write([0]);
                  }
                  else{
                    await c.write([1]);
                  }
                  await c.read();
                },

`And I can toggle the light in my device by pressing in this button

97458203_702354000565894_6272616662827008000_n
97458203_702354000565894_6272616662827008000_n360×800 28.8 KB

But, I wanna create a specific button to toggle the light. As you can see I created a RaisedButton.
Although I have created a button, I do not know how to create a _toggle function for it? Probably pass some parameters to that function. I have tried many ways but it seems that I have not gone in the right direction

_turnOn(List<BluetoothService> services) async { 
//List<BluetoothService> services = await device.discoverServices();
services.forEach((service) async {
// do something with service
  var characteristics = service.characteristics;
  for(BluetoothCharacteristic c in characteristics) {
      List<int> value = await c.read();
      print(value);
      await c.write([1]);
  }      
});

}

#2

Hello, and welcome!
This part of the code for the onWritePressed callback looks exactly like a toggle to me: it reads the value, if it is ‘on’ then write it ‘off’, else (is ‘off’) then write it ‘on’.

onWritePressed: () async {                      
   List<int> value = await c.read();
    if (value.toString() == "[1]"){
        await c.write([0]);
    }
    else {
        await c.write([1]);
    }
    await c.read();
 }

I don’t fully understand the last c.read(), but there will be a reason for it.

Hth

#3

The c.read() is to update the data on the screen, and the onWritePressed callback is work well !
But as you can see, I want to toogle the light by pressing the ON_OFF button

         RaisedButton(
          child: Text("ON_OFF"),
          onPressed: null,
        ),

But I can’t create a new function to do it.

#4

I see, it seems you should pass the specific service you want to toggle on/off to the onPressed callback function of this RaisedButton, but at the moment I cannot tell you how to do (I don’t have enough experience with streams i suppose), sorry.

#5

Thank you about idea,
I have succeeded when do that

  for(BluetoothCharacteristic c in characteristics) {
  if (service.uuid.toString() == "bae55b96-7d19-458d-970c-50613d801bc9"){
    if (c.uuid.toString() == "76e137ac-b15f-49d7-9c4c-e278e6492ad9") {
      List<int> value = await c.read();
      if (value.toString() == "[1]"){
        await c.write([0]);
      }
      else if (value.toString() == "[0]"){
        await c.write([1]);
      }          
    }
  }

But as I see it, there are many services and characteristics in the device.
I wondered if there was any way to tell which service and characteristic I needed to send commands to ?

#6

I’ve been reading more about the flutter_blue API, and about bluetooth in general here: https://www.oreilly.com/library/view/getting-started-with/9781491900550/ch04.html. It’s just a guess, but maybe descriptors can be usefull to identify the right service?

Characteristic User Description Descriptor

As the name implies, this descriptor contains a user-readable description for the characteristic within which it is placed. This is a UTF-8 string that could read, for example, “Temperature in the living room.”

From the package’s API doc:

var descriptors = characteristic.descriptors;
for(BluetoothDescriptor d in descriptors) {
    List<int> value = await d.read();
    print(value);
}

hth.

#7

Thank you, I will try it

#8

I followed your idea. And this is the result:

D/FlutterBluePlugin(13804): [onDescriptorRead] uuid: 00002902-0000-1000-8000-00805f9b34fb status: 0
I/flutter (13804): [0, 0]
D/FlutterBluePlugin(13804): [onDescriptorRead] uuid: 00002901-0000-1000-800 0-0805f9b34fb status: 0
I/flutter (13804): [110, 117, 108, 108]
#9

:confused: well, not too helpful indeed. I was hoping you could get the Characteristic User Description Descriptor out of the descriptors. It seems that’s not the case, sorry.

#10

This may not be relevant to you anymore but maybe this can help someone in the future. I have spent that last day figuring this out.

Like you, I am using that same example, I’ve added a raised button and this is what I had to put in the onPressed function.

              var SERVICE = '0000aaaa-ead2-11e7-80c1-9a214cf093ae';
              var CHARACTERISTIC = '00005555-ead2-11e7-80c1-9a214cf093ae';

              List<BluetoothService> services = await device.discoverServices();
              services.forEach((service) {

                if (service.uuid.toString() == SERVICE) {
                  service.characteristics.forEach((characteristic) {
                    if (characteristic.uuid.toString() == CHARACTERISTIC) {
                      characteristic.write(utf8.encode(jsonEncode(_Credentials.toJson())));
                      print(service.deviceId);
#11

can you please send me your project file