How can I receive data from a BLE Device?

user11798208 :

Cool? So, I am developing a Java BLE Android Module using Eclipse (to code the module and Appcelerator (to make the Android App). I am trying to receive data from a BLE Device and show it on an Android Phone. I can scan the device and connect to it.

But I really, really can't receive any data from it. I have tried at least 10 different stuff but... The main problem is that I don't know the BLE API very well, and I am a little noobie in Java. Can anyone please help a poor soul to actually read the data from the device? Thanks in advance!

The main problem is setting the Bluetooth Characteristic UUID (which I have). I just don't know how to do it... Bellow are the codes for the Module...

public class AndroidbleModule extends KrollModule {

  public static final String LCAT = "BLE";
  private BluetoothManager btManager;
  private BluetoothAdapter btAdapter;
  private BluetoothDevice btDevice;
  private TiApplication appContext;
  private Activity activity;
  private KrollFunction onFound;
  private KrollFunction onConnections;
  private BluetoothLeScanner btScanner;
  private UUID uuid;

  BluetoothGatt bluetoothGatt;
  BluetoothGattCharacteristic btChar;
  BluetoothGattCallbackHandler btData;
  KrollDict kd;
  Boolean isConnected = false;
  BluetoothGatt connectedGatt;

  private ScanCallback scanCallback = new ScanCallback() {
  @Override
  public void onScanResult(int callbackType, ScanResult result) {

  BluetoothDevice device = result.getDevice();
    if (device != null) {
    BluetoothDeviceProxy btDeviceProxy = new 
  BluetoothDeviceProxy(device);
    if (device.getName() != null) {
      Log.d(LCAT, "Found: " + device.getName() + " " + 
  device.getAddress());  
    ArrayList<String> ids = new ArrayList<String>();    
    if (device.getUuids() != null) {
             for (ParcelUuid id1 : device.getUuids()) {
    ids.add(id1.toString());
    }
    }
    btDevice = device;
    kd = new KrollDict();
    kd.put("name", btDevice.getName());
    kd.put("macaddress", btDevice.getAddress());
    fireEvent("nb_DevicesFound", kd); 

    btScanner.stopScan(scanCallback);
      }
     }
    }
  };

  @Kroll.method
  public boolean connect()
  {
   try {
    bluetoothGatt = btDevice.connectGatt(appContext, true,
    new BluetoothGattCallbackHandler(AndroidbleModule.this));
    if (bluetoothGatt != null) {
    System.out.println("*****     *****     Connected to: =====>>>>>    " + btDevice.getAddress() + " " + btDevice.getName());
    this.fireEvent("nb_onConnect",null);
    isConnected = true;
    bluetoothGatt = connectedGatt;
        }
  } catch (Exception e) {
    isConnected = false;
    this.fireEvent("nb_NoConnection", null);
    }
   return true;
  };

  @Kroll.method
  public void readData() 
  {
  System.out.println("WHAT THE HELL DO I DO????");
  }

}

public final class BluetoothGattCallbackHandler extends 
  BluetoothGattCallback {

private static final String LCAT = AndroidbleModule.LCAT;
private KrollProxy proxy;
private static final String UUID_SERVICE_TS002004 = "6E400001-B5A3-F393-E0A9-E50E24DCCA9E";
private static final String UUID_CHARACTERISTIC_WRITE_TS002004 = "6E400002-B5A3-F393-E0A9-E50E24DCCA9E";
private static final String UUID_CHARACTERISTIC_NOTIFY_TS002004 = "6E400003-B5A3-F393-E0A9-E50E24DCCA9E";
BluetoothGattCharacteristic btCharacteristic;

public BluetoothGattCallbackHandler(KrollProxy proxy) {
    super();
    this.proxy = proxy;
  }

  @Override
  public void onConnectionStateChange(final BluetoothGatt gatt,
    final int status, final int newState) {
    KrollDict kd = new KrollDict();
    kd.put("newState", newState);
    kd.put("status", status);
    if (proxy.hasListeners("didConnectionStateChange")) {
        proxy.fireEvent("didConnectionStateChange", kd);
    }
    gatt.discoverServices();
    }

  @Override
  public void onServicesDiscovered(BluetoothGatt gatt, int status) {
       super.onServicesDiscovered(gatt, status);
       Log.i(LCAT,"onServicesDiscovered");
       if (status != BluetoothGatt.GATT_SUCCESS) return;
       btCharacteristic = 
gatt.getService(UUID.fromString(UUID_SERVICE_TS002004)).getCharacteristic(UUID.fromString(UUID_CHARACTERISTIC_NOTIFY_TS002004));
       gatt.setCharacteristicNotification(btCharacteristic,true);

       BluetoothGattDescriptor descriptor = btCharacteristic.getDescriptor(UUID.fromString(UUID_CHARACTERISTIC_WRITE_TS002004));

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

  @Override
  public void onCharacteristicChanged(BluetoothGatt gatt,
    final BluetoothGattCharacteristic characteristic) {
    byte[] data = characteristic.getValue();
    Log.i(LCAT, "Char changed " + data.toString());
    for (BluetoothGattDescriptor descriptor : 
 characteristic.getDescriptors()) {
 descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE;
    }
  }

  @Override
  public void onCharacteristicRead(BluetoothGatt gatt, 
  BluetoothGattCharacteristic characteristic, int status) {
        super.onCharacteristicRead(gatt, characteristic, status);
        Log.i(LCAT,"onCharacteristicRead");
    }

  @Override
  public void onDescriptorRead(BluetoothGatt gatt, 
  BluetoothGattDescriptor descriptor, int status) {
       super.onDescriptorRead(gatt, descriptor, status);
       Log.i(LCAT,"onDescriptorRead");
  }

}

I expect to some good soul that will go to Heaven to have mercy on me and help me get those sweet bytes of data. =)

gbossa :

One of the things that is missing in your code, is to Set Notifications, so the Central can listen to the Peripheral's response. Try something like this:

public void setNotifications() {
    BluetoothGattService service = bluetoothGatt.getService(SERVICE_UUID);
    BluetoothGattCharacteristic characteristic = service.getCharacteristic(CHARACTERISTIC_UUID);

    BluetoothGattDescriptor descriptor = characteristic.getDescriptor(DESCRIPTOR_UUID);
    descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
    characteristic.addDescriptor(descriptor);
    characteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
    bluetoothGatt.writeDescriptor(descriptor);

    bluetoothGatt.setCharacteristicNotification(characteristic, true);
}

After that, you can send commands to the device and hear it's return.

public void returnData(String data) {
    BluetoothGattService service = bluetoothGatt.getService(SERVICE_UUID);
    BluetoothGattCharacteristic characteristic = service.getCharacteristic(CHARACTERISTIC_UUID);
    String dataString = data;
    dataString.getBytes();
    writeCharacteristic.setValue(dataString);
    writeCharacteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
    bluetoothGatt.writeCharacteristic(writeCharacteristic);
}