wpf - c# Bluetooth LE - ValueChanged never called - additional configuration necessary? -


this question exact duplicate of:

my question kinda update last question: c# bluetooth le - write configuration error - valuechanged never called

the problem is, connect wpf c#-application ble device, characteristic.valuechanged never called. maybe miss configuration or need send additionall configuration device, idk.

here method connecting application device:

private async task connecttowatcher(deviceinformation deviceinfo) {     try {         // device         bluetoothledevice device = await bluetoothledevice.fromidasync(deviceinfo.id);          // gatt service         thread.sleep(150);         var gattservicesresult = await device.getgattservicesforuuidasync(new guid(rx_service_uuid));         service = gattservicesresult.services[0];          // gatt characteristic         thread.sleep(150);         var gattcharacteristicsresult = await service.getcharacteristicsforuuidasync(new guid(rx_char_uuid));         characteristic = gattcharacteristicsresult.characteristics[0];          // register notifications         thread.sleep(150);          characteristic.valuechanged += (sender, args) => {             debug.writeline($"[{device.name}] received notification containing {args.characteristicvalue.length} bytes");         };          enabletxnotification();      } catch (exception ex) when ((uint)ex.hresult == 0x800710df) {         debug.writeline("bluetooth error 1");         // error_device_not_available because bluetooth radio not on.     } }

and here's method sending configuration:

public async void enabletxnotification()     {         debug.writeline("enabletxnotification");          var gattcharacteristicsresult = await service.getcharacteristicsforuuidasync(new guid(tx_char_uuid));         if (gattcharacteristicsresult == null                 || gattcharacteristicsresult.status != gattcommunicationstatus.success                 || gattcharacteristicsresult.characteristics == null                 || gattcharacteristicsresult.characteristics?.count < 1)         {             debug.writeline(" failed find gatt characteristic.");             return;         }         txcharacteristic = gattcharacteristicsresult.characteristics[0];          txcharacteristic.valuechanged += (sender, args) => {             debug.writeline("[{device.name}] received notification containing {args.characteristicvalue.length} bytes");         };          debug.writeline(" writing cccd...");         gattwriteresult result =             await txcharacteristic.writeclientcharacteristicconfigurationdescriptorwithresultasync(gattclientcharacteristicconfigurationdescriptorvalue.notify);         debug.writeline($" characteristics write result: status={result.status}, protocolerror={result.protocolerror}"); }

the last line creates output status=success. still no valuechanged method (i suspect second 1 unnecassary) being called when use device. i'm running out of ideas. can help?

you should first verify characteristicconfigurationdescriptor "notify", if not should set notify , define valuechanged listener. try change "connecttowatcher" following code:

private async task connecttowatcher(deviceinformation deviceinfo) { try {     // device     bluetoothledevice device = await bluetoothledevice.fromidasync(deviceinfo.id);      // gatt service     thread.sleep(150);     var gattservicesresult = await device.getgattservicesforuuidasync(new guid(rx_service_uuid));     service = gattservicesresult.services[0];      // gatt characteristic     thread.sleep(150);     var gattcharacteristicsresult = await service.getcharacteristicsforuuidasync(new guid(rx_char_uuid));     characteristic = gattcharacteristicsresult.characteristics[0];      // check characteristic configuration descriptor     var currentdescriptorvalue = await characteristic.readclientcharacteristicconfigurationdescriptorasync();      if (currentdescriptorvalue.clientcharacteristicconfigurationdescriptor != gattclientcharacteristicconfigurationdescriptorvalue.notify)     {          var status = await characteristic.writeclientcharacteristicconfigurationdescriptorasync(gattclientcharacteristicconfigurationdescriptorvalue.notify);     }      // register notifications     thread.sleep(150);      characteristic.valuechanged += (sender, args) => {         debug.writeline($"[{device.name}] received notification containing {args.characteristicvalue.length} bytes");     };      enabletxnotification();  } catch (exception ex) when ((uint)ex.hresult == 0x800710df) {     debug.writeline("bluetooth error 1");     // error_device_not_available because bluetooth radio not on. }

}

hope helped


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