Android BLE notifications for Glucose

Question

I tired to use Android BLE SDK to communication with my Glucose device. I need setCharacteristicNotification for UUID 2a18 and 2a34. I refer to the Android official SDK as follows:

http://developer.android.com/guide/topics/connectivity/bluetooth-le.html#notification

BluetoothGattCharacteristic charGM = 
mConnGatt.getService(UUID.fromString(BleUuid.SERVICE_GLUCOSE))
    .getCharacteristic(UUID.fromString(BleUuid.CHAR_GLUCOSE_MEASUREMENT_STRING));
mConnGatt.setCharacteristicNotification(charGM, enabled);
BluetoothGattDescriptor descGM = charGM.getDescriptor(UUID.fromString(BleUuid.CHAR_CLIENT_CHARACTERISTIC_CONFIG_STRING));
descGM.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mConnGatt.writeDescriptor(descGM);

BUT it can not even enter the onCharacteristicChanged callback.

my onCharacteristicChanged as follows:

        public void onCharacteristicChanged(BluetoothGatt gatt,
                                        BluetoothGattCharacteristic characteristic) {
        broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        runOnUiThread(new Runnable() {
            public void run() {
                Toast.makeText(getApplicationContext(),"onCharacteristicChanged",Toast.LENGTH_LONG).show();
                setProgressBarIndeterminateVisibility(false);
            };
        });
    }

if I set Battery Level notification as follows, it works.

BluetoothGattCharacteristic charBarrery = 
    mConnGatt.getService(UUID.fromString(BleUuid.SERVICE_BATTERY))
        .getCharacteristic(UUID.fromString(BleUuid.CHAR_BATTERY_LEVEL_STRING));
mConnGatt.setCharacteristicNotification(charBarrery, enabled);
BluetoothGattDescriptor descBarrery = charBarrery.getDescriptor(UUID.fromString(BleUuid.CHAR_CLIENT_CHARACTERISTIC_CONFIG_STRING));
descBarrery.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mConnGatt.writeDescriptor(descBarrery);

I dont know what is different with Battery and Glucose notifications.

If anyone knew what should I do, so please help me.

additional:

when I used battery service, my logcat as follows:

07-29 10:28:17.924: D/BluetoothGatt(947): setCharacteristicNotification() - uuid: 00002a19-0000-1000-8000-00805f9b34fb enable: true
07-29 10:28:17.924: D/BluetoothGatt(947): writeDescriptor() - uuid: 00002902-0000-1000-8000-00805f9b34fb
07-29 10:28:18.484: D/BluetoothGatt(947): onDescriptorWrite() - Device=B4:AB:2C:06:9E:F4 UUID=00002a19-0000-1000-8000-00805f9b34fb
07-29 10:28:18.604: D/BluetoothGatt(947): onNotify() - Device=B4:AB:2C:06:9E:F4 UUID=00002a19-0000-1000-8000-00805f9b34fb

but when I use Glucose, my logcat lose onNotify(), like this:

07-29 10:31:23.729: D/BluetoothGatt(1763): setCharacteristicNotification() - uuid: 00002a18-0000-1000-8000-00805f9b34fb enable: true
07-29 10:31:23.729: D/BluetoothGatt(1763): writeDescriptor() - uuid: 00002902-0000-1000-8000-00805f9b34fb
07-29 10:31:24.324: D/BluetoothGatt(1763): onDescriptorWrite() - Device=B4:AB:2C:06:9E:F4 UUID=00002a18-0000-1000-8000-00805f9b34fb

I dont know why logcat lose the onNotify()...

additional(8/4):

Thanks for your reply ! I tried to enable indications on Record Access Control Point characteristic but failed.. My Process as follows:

1. Enable notifications on Glucose Measurement characteristic and Glucose Measurement Context characteristic & Enable indications on Record Access Control Point characteristic

     public void onServicesDiscovered(BluetoothGatt gatt, int status) { for (BluetoothGattService service : gatt.getServices()) { if ((service == null) || (service.getUuid() == null)) { continue; } if (BleUuid.SERVICE_GLUCOSE.equalsIgnoreCase(service .getUuid().toString())) { BluetoothGattCharacteristic charGM = mConnGatt.getService(UUID.fromString(BleUuid.SERVICE_GLUCOSE)) .getCharacteristic(UUID.fromString(BleUuid.CHAR_GLUCOSE_MEASUREMENT_STRING)); mConnGatt.setCharacteristicNotification(charGM, enabled); BluetoothGattDescriptor descGM = charGM.getDescriptor(UUID.fromString(BleUuid.CHAR_CLIENT_CHARACTERISTIC_CONFIG_STRING)); descGM.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE); mConnGatt.writeDescriptor(descGM); BluetoothGattCharacteristic charGMC = mConnGatt.getService(UUID.fromString(BleUuid.SERVICE_GLUCOSE)) .getCharacteristic(UUID.fromString(BleUuid.CHAR_GLUCOSE_MEASUREMENT_CONTEXT_STRING)); mConnGatt.setCharacteristicNotification(charGMC, enabled); BluetoothGattDescriptor descGMC = charGMC.getDescriptor(UUID.fromString(BleUuid.CHAR_CLIENT_CHARACTERISTIC_CONFIG_STRING)); descGMC.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE); mConnGatt.writeDescriptor(descGMC); BluetoothGattCharacteristic charRACP = mConnGatt.getService(UUID.fromString(BleUuid.SERVICE_GLUCOSE)) .getCharacteristic(UUID.fromString(BleUuid.CHAR_RECORD_ACCESS_CONTROL_POINT_STRING)); mConnGatt.setCharacteristicNotification(charRACP, enabled); BluetoothGattDescriptor descRACP = charRACP.getDescriptor(UUID.fromString(BleUuid.CHAR_CLIENT_CHARACTERISTIC_CONFIG_STRING)); descRACP.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE); mConnGatt.writeDescriptor(descRACP); BluetoothGattCharacteristic charBarrery = mConnGatt.getService(UUID.fromString(BleUuid.SERVICE_BATTERY)) .getCharacteristic(UUID.fromString(BleUuid.CHAR_BATTERY_LEVEL_STRING)); mConnGatt.setCharacteristicNotification(charBarrery, enabled); BluetoothGattDescriptor descBarrery = charBarrery.getDescriptor(UUID.fromString(BleUuid.CHAR_CLIENT_CHARACTERISTIC_CONFIG_STRING)); descBarrery.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE); mConnGatt.writeDescriptor(descBarrery); runOnUiThread(new Runnable() { public void run() { btnUpdateData.setEnabled(true); }; }); } } }; 

2. Send 0x0101 to record access control point

     case R.id.btnUpdateData: try{ //***SEND 0x0101 TO RECORD ACCESS CONTROL POINT BluetoothGattCharacteristic writeRACPchar = mConnGatt.getService(UUID.fromString(BleUuid.SERVICE_GLUCOSE)) .getCharacteristic(UUID.fromString(BleUuid.CHAR_RECORD_ACCESS_CONTROL_POINT_STRING)); byte[] data = new byte[1]; data[0] = (byte)0x0101; writeRACPchar.setValue(data); mConnGatt.writeCharacteristic(writeRACPchar); }catch(Exception e){ e.printStackTrace(); } break; 

3. my callback function

    @Override public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) { broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic); } @Override public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) { }; @Override public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) { broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic); } 

&

    private void broadcastUpdate(final String action,
        final BluetoothGattCharacteristic characteristic) {
        final Intent intent = new Intent(action);
        if (BleUuid.CHAR_SERIAL_NUMBEAR_STRING
                .equalsIgnoreCase(characteristic.getUuid().toString())) {
            displayResult(characteristic.getStringValue(0));
        }else if(BleUuid.CHAR_MANUFACTURER_NAME_STRING
                .equalsIgnoreCase(characteristic.getUuid().toString())){
            displayResult(characteristic.getStringValue(0));
        } else if(BleUuid.CHAR_BATTERY_LEVEL_STRING
                .equalsIgnoreCase(characteristic.getUuid().toString())){
            final byte[] data = characteristic.getValue();
            String dataStr = "";
            dataStr = String.format("%02X", data[0]);
            int a = Integer.parseInt(dataStr, 16);
            String result = "battery level: " + Integer.toString(a)+ "%";
            displayResult(result);
        } else {
            // For all other profiles, writes the data formatted in HEX.
            final byte[] data = characteristic.getValue();
            if (data != null && data.length > 0) {
                final StringBuilder stringBuilder = new StringBuilder(data.length);
                for(byte byteChar : data)
                    stringBuilder.append(String.format("%02X ", byteChar));
                displayResult(stringBuilder.toString());
            }
        }
}

&

    private void displayResult(String result){
    adUpdateData.add(result);
    runOnUiThread(new Runnable() {
        public void run() {
            lvUpdateData.setAdapter(adUpdateData);
        };
    });
}

I'm trying to understand that "GLS_SPEC" pdf... I used Nordic Semiconductor's Glucose Service sample application, and it could works. I try to learn how to reach that function.

I noted some log like "unregisterIRListener() is called" shows on LogCat, but I'm not sure that whether about my question or not...

Thanks for reading.

Answer 1

there is a logical difference in Glucose and Battery service. When you enable Battery Level notifications usually (depending on the implementation) a device sends you battery level immediately. That's why you get onNotify there. Of course in some implementations it notifies you only when the value changes, or with other rule, but in you case it looks like it behaves like this.

Glucose service works different. In the Glucose Service ( https://developer.bluetooth.org/gatt/services/Pages/ServiceViewer.aspx?u=org.bluetooth.service.glucose.xml ) you have 3 mandatory characteristics. Let's skip the Glucose Feature here. One of them is Glucose Measurement where you get glucose reading notifications. Your implementation to enable these notifications is correct, it will work. But in order to get notifications you have to request for them using Record Access Control Point characteristic. It allows you to get all glucose readings, only the latest, only the first, delete saved readings from the device etc. For example, when you:

1. Enable notifications on Glucose Measurement characteristic (like you did)
2. Enable indications on Record Access Control Point characteristic
3. Send fe 0x0101 = Report stored records | All records

you should get N notifications on Glucose Measurement char. followed by an indication on RACP char. with value: 0x06000101 = Response for "Report stored records" | success. N may be 0 if no readings are saved on the glucose device. If you're using Nordic Semiconductor's Glucose Service sample application you may try pressing button 0(?) to generate a new result on the board (up to 20) and request again.

Read the GLS documentation: https://www.bluetooth.org/en-us/specification/adopted-specifications -> GLS -> PDF for more information about Glucose Service and Record Access Control Point format.

EDIT

You're writing the Record Access Control Point value wrong. Here's the working code:

case R.id.btnUpdateData:
    try{
        //***SEND 0x0101 TO RECORD ACCESS CONTROL POINT   
        BluetoothGattCharacteristic writeRACPchar = 
                mConnGatt.getService(UUID.fromString(BleUuid.SERVICE_GLUCOSE))
                    .getCharacteristic(UUID.fromString(BleUuid.CHAR_RECORD_ACCESS_CONTROL_POINT_STRING));
        byte[] data = new byte[2];
        data[0] = 0x01; // Report Stored records
        data[1] = 0x01; // All records
        writeRACPchar.setValue(data);

        // or:
        // byte[] data = new byte[2];
        // writeRACPchar.setValue(data);
        // writeRACPchar.setIntValue(BluetoothGattCharacteristic.FORMAT_UINT8, 1, 0); // Report Stored records
        // writeRACPchar.setIntValue(BluetoothGattCharacteristic.FORMAT_UINT8, 1, 1); // Read all (offset 1)
        mConnGatt.writeCharacteristic(writeRACPchar);
    }catch(Exception e){
        e.printStackTrace();
    }
    break;

You have to write 2 bytes, each byte is 8 buts which may be written as 2-digit HEX, fe 0xAB r 0x01. The value 0x0101 has 2 bytes and you may not