Read values from concrete BLE characteristic Kotlin

Question

I'm trying to read values from a concrete BLE characteristic in my app but at the moment I try to read values from the desired characteristic the onCharacteristicRead function seems like not being triggered.

In very first place i use onServicesDiscovered in order to get every service from the device:

       override fun onServicesDiscovered(gatt: BluetoothGatt, status: Int) {

        Log.e("BluetoothLeService", "onServiceDiscovered()")
        if(status == BluetoothGatt.GATT_SUCCESS){
            Log.i(TAG, "**ACTION_SERVICE_DISCOVERED** $status")
            var gattServices: List<BluetoothGattService> = mBluetoothGatt!!.services
            Log.e("onServiceDiscovered", "Services count: ${gattServices.size}")
            for(gattService in gattServices){
                var serviceUUID = gattService.uuid.toString()
                Log.e("OnServicesDiscovered", "Service uuid: $serviceUUID" )
                readCharacteristic(gattService)

            }
            Log.e("OnServicesDiscovered", "---------------------------" )

            broadcastUpdate( "com.np.lekotlin.ACTION_GATT_SERVICES_DISCOVERED")

        } else {
            //Service discovery failed so log a warning
            Log.i(TAG, "onServicesDiscovered received: $status")
        }
    }

As you can see I use a for loop in order to achieve every service name and characteristic associated with every service with the readCharacteristic function

   fun readCharacteristic(service: BluetoothGattService) {
    if (mBluetoothAdapter == null || mBluetoothGatt == null) {
        Log.w(TAG, "BluetoothAdapter not initialized")
        return
    }
    var gattCharacteristic: List<BluetoothGattCharacteristic> = service.characteristics
    Log.i(TAG, "**LEO LAS ${gattCharacteristic.count()} CARACTERISTICAS DE $service**")


    for(characteristic in gattCharacteristic){
        Log.e("OnServicesDiscovered", "Service characteristic: ${characteristic.uuid}" )
        if(characteristic.uuid == characteristicRS){
            mBluetoothGatt!!.setCharacteristicNotification(characteristic, true)
            mBluetoothGatt!!.readCharacteristic(characteristic)
        }
    }
    Log.e("OnServicesDiscovered", "-----------------------------" )
}

All this process finally returns me the next result

E/BluetoothLeService: onServiceDiscovered()
I/PSoCCapSenseLedService: **ACTION_SERVICE_DISCOVERED** 0
E/onServiceDiscovered: Services count: 4
E/OnServicesDiscovered: Service uuid: 00001800-0000-1000-8000-00805f9b34fb
I/PSoCCapSenseLedService: **LEO LAS 3 CARACTERISTICAS DE android.bluetooth.BluetoothGattService@1b31ffb*
E/OnServicesDiscovered: Service characteristic: 00002a00-0000-1000-8000-00805f9b34fb
E/OnServicesDiscovered: Service characteristic: 00002a01-0000-1000-8000-00805f9b34fb
E/OnServicesDiscovered: Service characteristic: 00002a04-0000-1000-8000-00805f9b34fb
E/OnServicesDiscovered: -----------------------------
E/OnServicesDiscovered: Service uuid: 00001801-0000-1000-8000-00805f9b34fb
I/PSoCCapSenseLedService: **LEO LAS 1 CARACTERISTICAS DE android.bluetooth.BluetoothGattService@4254818**
E/OnServicesDiscovered: Service characteristic: 00002a05-0000-1000-8000-00805f9b34fb
-----------------------------
E/OnServicesDiscovered: Service uuid: 00001814-0000-1000-8000-00805f9b34fb
I/PSoCCapSenseLedService: **LEO LAS 4 CARACTERISTICAS DE android.bluetooth.BluetoothGattService@a673271**
E/OnServicesDiscovered: Service characteristic: 00002a53-0000-1000-8000-00805f9b34fb
Service characteristic: 00002a54-0000-1000-8000-00805f9b34fb
E/OnServicesDiscovered: Service characteristic: 00002a5d-0000-1000-8000-00805f9b34fb
Service characteristic: 00002a55-0000-1000-8000-00805f9b34fb
-----------------------------
E/OnServicesDiscovered: Service uuid: 0000180a-0000-1000-8000-00805f9b34fb
I/PSoCCapSenseLedService: **LEO LAS 3 CARACTERISTICAS DE android.bluetooth.BluetoothGattService@3b51856**
E/OnServicesDiscovered: Service characteristic: 00002a29-0000-1000-8000-00805f9b34fb
E/OnServicesDiscovered: Service characteristic: 00002a24-0000-1000-8000-00805f9b34fb
Service characteristic: 00002a27-0000-1000-8000-00805f9b34fb
E/OnServicesDiscovered: -----------------------------
---------------------------
D/BluetoothGatt: onConnectionUpdated() - Device=00:A0:50:00:00:0F interval=36 latency=0 timeout=500 status=0

Which is completely correct (it displays me every service on the device and every characteristic inside this service), but my problem comes when I try to read values from characteristicRS which is 00002a53-0000-1000-8000-00805f9b34fb, which is correctly reported in the return terminal, but the point is (according to my knowledge) than, in the moment I call

mBluetoothGatt!!.readCharacteristic(characteristic)

The function

override fun onCharacteristicRead(
        gatt: BluetoothGatt,
        characteristic: BluetoothGattCharacteristic,
        status: Int
    ) {
        Log.i(TAG, "HAGO COSAS")
        if (status == BluetoothGatt.GATT_SUCCESS) {
            //See if the read was successful
            Log.i(TAG, "**ACTION_DATA_READ** ${characteristic.uuid}")
            broadcastUpdate("com.np.lekotlin.ACTION_DATA_AVAILABLE"/*, characteristic*/)                 //Go broadcast an intent with the characteristic data
            data = characteristic.value
            Log.e("onCharacteristicRead", "Datos:")
            Log.e("onCharacteristicRead", "$data")

        } else {
            Log.i(TAG, "ACTION_DATA_READ: Error$status")
        }
    }

Should be triggered and returning me the values from the characteristic, but is not even entering after all. What am I forgetting?

PD: data is declared as a ByetArray

Hardik Chauhan · Accepted Answer · 2019-08-05T11:11:53.003

1

After getting all the characteristics, you will need to enable the read, write or notify permission.

Once you enable that, you will need to write the descriptor value if required so.

Or you can directly pass the command which is useful for getting the data from your ble device and you will be able to receive the data after than.

These permissions are necessary.

**EDITED

@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status){
   BluetoothGattCharacteristic characteristic = gatt.getService(SERVICE_UUID)
getCharacteristic(CHAR_UUID);
gatt.setCharacteristicNotification(characteristic, enabled);
BluetoothGattDescriptor descriptor = 
characteristic.getDescriptor(CHARACTERISTIC_CONFIG_UUID);

descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
gatt.writeDescriptor(descriptor);
}

edited Aug 05 '19 at 11:11

answered Aug 05 '19 at 10:57

Hardik Chauhan

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Could u gimme some info about this more exactly please? How can i enable the read permission? – Sosa Aug 05 '19 at 11:02
okay i am posting you a code template for reference you can google for more information – Hardik Chauhan Aug 05 '19 at 11:05
It suddendly started to notify data, lots of thanks!! – Sosa Aug 05 '19 at 11:31

Read values from concrete BLE characteristic Kotlin

1 Answers1