So, I am new to Android development and I am trying to connect my device to multiple BLE devices (T-Wristband) to receive frequent notifications (IMU sensor data less than 20 bytes at 50Hz).
When connecting to multiple devices, I miss data from one or more devices. I suspect the reason is that my BluetoothGattCallback method, onCharacteristicChanged, is working on the same thread for all devices (Note: I have checked that by logging Thread.currentThread.getName()).
What I have tried:
1. Android 4.3: How to connect to multiple Bluetooth Low Energy devices
I suspect everyone adding delays is just allowing the BLE system to complete the action you have asked before you submit another one.
Problem: I cannot add delays when receiving notifications since it would interfere with my sampling rate, and I am not sure when I might receive new notifications from another device, or even the same device.
2. Android BLE multiple connections
To achieve multiple BLE connections you have to store multiple
BluetoothGattobjects and use those objects for a differentdevice.
In this regard: I have tried writing a custom class for my device, TTGODevice, which saves an instance of the corresponding BluetoothGatt upon connection:
public class TTGODevice {
/* Bunch of psf constants */
private BluetoothDevice device;
private Context context;
private Accelerometer acc;
private BluetoothGatt server;
private int deviceStatus;
private final BluetoothGattCallback bluetoothGattCallback = new BluetoothGattCallback() { ...
};
public TTGODevice(Context context, BluetoothDevice device) {
this.device = device;
this.context = context;
this.acc = new Accelerometer(); // My custom class for accelerometer on the T-Wristband device(s)
}
public void connect(boolean autoConnect) {
server = device.connectGatt(context, false, bluetoothGattCallback);
}
/*Getters for device, server, and deviceStatus*/
}
In the BluetoothGattCallback, I override my onCharacteristicChanged as below:
@Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
byte[] bytes = characteristic.getValue();
// updating the Accelerometer
acc.update(bytes);
Log.d(TAG, "onCharacteristicChanged: " + Thread.currentThread().getName());
}
I have also tried using the exact instance of my server in the callback above, but I am out of luck.
byte[] bytes = server.getService(SERVICE_UUID).getCharacteristic(CHARACTERISTIC_UUID).getValue();
Long story short, I have been unsuccessful. I would appreciate any other relevant threads.
[Note: I have been suggested to use Fragments and/or ViewModels. I am not sure how they are relevant.]
