如何从 BLE 设备接收数据？

Question

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?

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.

Answer 1

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);
}

Answer 2

First of all, read the bluetooth overview . Check if bluetooth permissions have been added to the project.

One thing that is wrong here is that isConnected=true is set too early, because you can consider that you are connected after ble services has been discovered and (status == BluetoothGatt.GATT_SUCCESS) . Otherwise, you can't read and write characteristics.

A good starting point can be this repo from google. It is old project and I'm not sure if you have to update some dependency to make it compile, but nothing important.

Establish a connection and start reading bytes is easy, but if you want establish a reliable connection with ble device, due to android fragmentation and manufacturerers that don't follow the bluetooth specs, it can be super difficult, almost imposible to make a bluetooth low energy that works perfect for all devices.

Once you have started to read some bytes, I suggest this video to learn some important tricks about. If you want go deeper, read carefully this fantastic resource about ble .

Once you start to get desperate with ble, probably it will be a good moment to read this list of known issues

Finally, you will discover that the best thing that you can do with ble low energy in android is use open source libraries like the Nordic semiconductor ble library or RxAndroid Ble .

But before use a ble library, it is a good practice understand what is doing the library and understand why you need it.

EDIT: I have never used appcelerator, but here you have a bluetooth module for appcelerator titanium.

Answer 3

You have the wrong uuid for the Client Characteristic Configuration Descriptor. It should be 00002902-0000-1000-8000-00805f9b34fb but you have written 6E400002-B5A3-F393-E0A9-E50E24DCCA9E.