Develop Reference

Android app, receiving data over BLE Module sent by Microcontroller via UART

I want to create android app, which can connect with bluetooth low energy module and can receive data. In my system microcontroller stm32f1 send data of measurements over UART to the BT LE module.
My question is how to start? I read a lot about GATT and UART Service, but still don't know how to start. Give me some information please.

You need:
UUIDs of your Service, Characteristic and Descriptor;
Permissions' Bluetooth Low Energy
The program must:
Scan BLE devices
Connect a device
Set callbacks' BLE
AndroidManifest.xml
<uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
Activity.java
// Bluetooth's variables
BluetoothAdapter bluetoothAdapter;
BluetoothLeScanner bluetoothLeScanner;
BluetoothManager bluetoothManager;
BluetoothScanCallback bluetoothScanCallback;
BluetoothGatt gattClient;
BluetoothGattCharacteristic characteristicID; // To get Value
// UUID's (set yours)
final UUID SERVICE_UUID = UUID.fromString("ab0828b1-198e-4351-b779-901fa0e0371e");
final UUID CHARACTERISTIC_UUID_ID = UUID.fromString("1a220d0a-6b06-4767-8692-243153d94d85");
final UUID DESCRIPTOR_UUID_ID = UUID.fromString("ec6e1003-884b-4a1c-850f-1cfce9cf6567");
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Bluetooth
bluetoothManager = (BluetoothManager) getSystemService(BLUETOOTH_SERVICE);
bluetoothAdapter = bluetoothManager.getAdapter();
startScan();
}
// BLUETOOTH SCAN
private void startScan(){
Log.i(TAG,"startScan()");
bluetoothScanCallback = new BluetoothScanCallback();
bluetoothLeScanner = bluetoothAdapter.getBluetoothLeScanner();
bluetoothLeScanner.startScan(bluetoothScanCallback);
}
// BLUETOOTH CONNECTION
private void connectDevice(BluetoothDevice device) {
if (device == null) Log.i(TAG,"Device is null");
GattClientCallback gattClientCallback = new GattClientCallback();
gattClient = device.connectGatt(this,false,gattClientCallback);
}
// BLE Scan Callbacks
private class BluetoothScanCallback extends ScanCallback {
#Override
public void onScanResult(int callbackType, ScanResult result) {
Log.i(TAG, "onScanResult");
if (result.getDevice().getName() != null){
if (result.getDevice().getName().equals(YOUR_DEVICE_NAME)) {
// When find your device, connect.
connectDevice(result.getDevice());
bluetoothLeScanner.stopScan(bluetoothScanCallback); // stop scan
}
}
}
#Override
public void onBatchScanResults(List<ScanResult> results) {
Log.i(TAG, "onBathScanResults");
}
#Override
public void onScanFailed(int errorCode) {
Log.i(TAG, "ErrorCode: " + errorCode);
}
}
// Bluetooth GATT Client Callback
private class GattClientCallback extends BluetoothGattCallback {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
super.onConnectionStateChange(gatt, status, newState);
Log.i(TAG,"onConnectionStateChange");
if (status == BluetoothGatt.GATT_FAILURE) {
Log.i(TAG, "onConnectionStateChange GATT FAILURE");
return;
} else if (status != BluetoothGatt.GATT_SUCCESS) {
Log.i(TAG, "onConnectionStateChange != GATT_SUCCESS");
return;
}
if (newState == BluetoothProfile.STATE_CONNECTED) {
Log.i(TAG, "onConnectionStateChange CONNECTED");
gatt.discoverServices();
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
Log.i(TAG, "onConnectionStateChange DISCONNECTED");
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
super.onServicesDiscovered(gatt, status);
Log.i(TAG,"onServicesDiscovered");
if (status != BluetoothGatt.GATT_SUCCESS) return;
// Reference your UUIDs
characteristicID = gatt.getService(SERVICE_UUID).getCharacteristic(CHARACTERISTIC_UUID_ID);
gatt.setCharacteristicNotification(characteristicID,true);
BluetoothGattDescriptor descriptor = characteristicID.getDescriptor(DESCRIPTOR_UUID_ID);
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
gatt.writeDescriptor(descriptor);
}
#Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicRead(gatt, characteristic, status);
Log.i(TAG,"onCharacteristicRead");
}
#Override
public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicWrite(gatt, characteristic, status);
Log.i(TAG,"onCharacteristicWrite");
}
#Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
super.onCharacteristicChanged(gatt, characteristic);
Log.i(TAG,"onCharacteristicChanged");
// Here you can read the characteristc's value
// new String(characteristic.getValue();
}
#Override
public void onDescriptorRead(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status) {
super.onDescriptorRead(gatt, descriptor, status);
Log.i(TAG,"onDescriptorRead");
}
#Override
public void onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status) {
super.onDescriptorWrite(gatt, descriptor, status);
Log.i(TAG,"onDescriptorWrite");
}
}
Libs:
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattDescriptor;
import android.bluetooth.BluetoothManager;
import android.bluetooth.BluetoothProfile;
import android.bluetooth.le.BluetoothLeScanner;
import android.bluetooth.le.ScanCallback;
import android.bluetooth.le.ScanResult;
Notes:
The UUIDs must be same seted on the module.
In your program you must have two callbacks: ScanCallback and GattCallback. Scan callback is to manage the scan results and the GattCallback you can manage the data input/output.
This code the basic to show how use BLE on Android, works fine for me.
You can generate UUID here: https://www.uuidgenerator.net/

Get batterylevel of more than one bluetoothdevices (beacons)

I want to get the battery level of more than one bluetooth device in android using the gatt service.
My current code is this (I am sorry that it looks a bit chaotic):
public void readCustomCharacteristic() {
// Initializes Bluetooth adapter.
final BluetoothManager bluetoothManager =
(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
mBluetoothAdapter.getBluetoothLeScanner().startScan(new ScanCallback() {
#Override
public void onScanResult(int callbackType, ScanResult result) {
super.onScanResult(callbackType, result);
//Log.i("Beacons", "callbacktype: " + String.valueOf(callbackType));
Log.i("Beacons", "result: " + result.toString());
BluetoothDevice btDevice = result.getDevice();
Log.i("Beacons", "Devicescan: " + (btDevice != null));
BluetoothGatt bluetoothGatt = btDevice.connectGatt(
getApplicationContext(), false, new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
//super.onConnectionStateChange(gatt, status, newState);
Log.i("Beacons", "areServicesDiscovered: " + gatt.discoverServices());
if(gatt.discoverServices()) {
onServicesDiscovered(gatt, status);
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (gatt.discoverServices()) {
//if (status == BluetoothGatt.GATT_SUCCESS) {
Log.d("Beacons", "Number of Services: " + gatt.getServices().size());
runOnUiThread(new Runnable() {
#Override
public void run() {
BluetoothGattCharacteristic chars = gatt.getServices().get(0).getCharacteristic(Battery_Level_UUID);
Log.i("Beacons", "charsstringval: " + chars.getValue().length);
}
});
}
}
});
}
});
}
I have to scan more than one beacon, and when it is scanning a device and it only getssometimes a service.
The problem is when the code wants to read the characteristic the service handle is again null. I'm desperate and I hope you can help me.

In short, because your runnable runs on a different thread, the value of gatt.getServices() may have changed.
I would simply retrieve the updated services list, check the size, and then only make the call if there is at least one service.
if (gatt.getServices().size() > 0) {
BluetoothGattCharacteristic chars = gatt.getServices().get(0).getCharacteristic(Battery_Level_UUID);
Log.i("Beacons", "charsstringval: " + chars.getValue().length);
}

Using BLE - Read GATT characteristics

I'm trying to read GATT characteristic values from a Bluetooth LE device (a Heart Rate bracelet). Its specs are:
Services
Characteristics
I have not yet figured out how to "read" the specifications and "translate" them into code.
I need to show on my app the heartbeats detected by the device. What is the way to read the GATT values? A code example would be much appreciated :)
Follow my actual source code.
SETUP THE BLUETOOT CONNECTION
private BluetoothAdapter mBluetoothAdapter;
private BluetoothGatt mBluetoothGatt;
private Handler mHandler;
private static final int REQUEST_ENABLE_BT = 1;
private static final long SCAN_PERIOD = 10000;
// ...
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bluetooth);
mHandler = new Handler();
// BLE is supported?
if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
Toast.makeText(this, "Bluetooth Low Energy non supportato", Toast.LENGTH_SHORT).show();
finish();
}
final BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
// Bluetooth is supported?
if (mBluetoothAdapter == null) {
Toast.makeText(this, "Bluetooth non supportato", Toast.LENGTH_SHORT).show();
finish();
}
}
#Override
protected void onResume() {
super.onResume();
// Bluetooth is enabled?
if (!mBluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}
scanLeDevice(true);
}
#Override
protected void onPause() {
super.onPause();
if (mBluetoothAdapter != null && mBluetoothAdapter.isEnabled()) {
scanLeDevice(false);
}
}
DISCOVER BLE DEVICES AND CONNECT WITH HEART RATE MONITOR
// Device scan callback.
private BluetoothAdapter.LeScanCallback mLeScanCallback =
new BluetoothAdapter.LeScanCallback() {
#Override
public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
runOnUiThread(new Runnable() {
#Override
public void run() {
Log.i(TAG, "Name: " + device.getName() + " (" + device.getAddress() + ")");
String deviceAddress = device.getAddress();
if (deviceAddress.equals("C0:19:37:54:9F:30")) {
connectToDevice(device);
}
}
});
}
};
public void connectToDevice(BluetoothDevice device) {
if (mBluetoothGatt == null) {
Log.i(TAG, "Attempting to connect to device " + device.getName() + " (" + device.getAddress() + ")");
mBluetoothGatt = device.connectGatt(this, true, gattCallback);
scanLeDevice(false);// will stop after first device detection
}
}
private final BluetoothGattCallback gattCallback = new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
Log.i(TAG, "Status: " + status);
switch (newState) {
case BluetoothProfile.STATE_CONNECTED:
Log.i(TAG, "STATE_CONNECTED");
//BluetoothDevice device = gatt.getDevice(); // Get device
gatt.discoverServices();
break;
case BluetoothProfile.STATE_DISCONNECTED:
Log.e(TAG, "STATE_DISCONNECTED");
break;
default:
Log.e(TAG, "STATE_OTHER");
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
List<BluetoothGattService> services = gatt.getServices();
Log.i(TAG, "Services: " + services.toString());
BluetoothGattCharacteristic bpm = services.get(2).getCharacteristics().get(0);
gatt.readCharacteristic(services.get(0).getCharacteristics().get(0));
}
#Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
// my attempt to read and print characteristics
byte[] charValue = characteristic.getValue();
byte flag = charValue[0];
Log.i(TAG, "Characteristic: " + flag);
//gatt.disconnect();
}
};

try with this inside gattCallback:
#Override
public synchronized void onCharacteristicChanged(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic) {
final byte[] dataInput = characteristic.getValue();
}
EDIT
And I think you are going to receive a byte with the hear rate data, use this function to get the int value:
public int unsignedByteToInt(byte b) {
return b & 0xFF;
}
And call it inside onCharacteristicChanged():
final byte[] dataInput = characteristic.getValue();
int hearRate = unsignedByteToInt(dataInput);
EDIT 2
Create a notification listener for the heart rate:
public void setHeartRateNotification(boolean enable){
String uuidHRCharacteristic = "YOUR CHARACTERISTIC";
BluetoothGattService mBluetoothLeService = null;
BluetoothGattCharacteristic mBluetoothGattCharacteristic = null;
for (BluetoothGattService service : mBluetoothGatt.getServices()) {
if ((service == null) || (service.getUuid() == null)) {
continue;
}
if (uuidAccelService.equalsIgnoreCase(service.getUuid().toString())) {
mBluetoothLeService = service;
}
}
if(mBluetoothLeService!=null) {
mBluetoothGattCharacteristic =
mBluetoothLeService.getCharacteristic(UUID.fromString(uuidHRCharacteristic));
}
else{
Log.i("Test","mBluetoothLeService is null");
}
if(mBluetoothGattCharacteristic!=null) {
setCharacteristicNotification(mBluetoothGattCharacteristic, enable);
Log.i("Test","setCharacteristicNotification:"+true);
}
else{
Log.i("Test","mBluetoothGattCharacteristic is null");
}
}
And set it onServiceDiscover inside gattCallback:
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
Log.i("Test", "onServicesDiscovered received: " + status);
setHeartRateNotification(true);
}

How to Scan the BLE device in background service without library?

I am trying to connect BLE device with android application. I am getting the device name,Mac Address and rssi value in foreground. I dont know how to scan the device in background and get the details of that particular device like MAC address,rssi value.

You have to do all in the background for that start sticky service and in onStartCommand of that services start scanning.
package com.myapp.services;
import java.util.List;
import android.annotation.TargetApi;
import android.app.Service;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattService;
import android.bluetooth.BluetoothManager;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Handler;
import android.os.IBinder;
import android.os.Looper;
import android.preference.PreferenceManager;
import android.support.v4.content.LocalBroadcastManager;
import android.text.TextUtils;
import android.widget.Toast;
import com.myapp.R;
/**Both RX and RSSI (Received Signal Strength Indication) are indications of the power level being received
* by an antenna
* The difference between RX and RSSI is that RX is measured in milliWatts (mW) or decibel-milliwatts (dBm)
* whereas RSSI is a signal strength percentage—the higher the RSSI number, the stronger the signal
*
*/
#TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
public class BeaconService extends Service implements BluetoothAdapter.LeScanCallback{
private static final String TAG = BeaconService.class.getSimpleName();
private BluetoothGatt btGatt;
private BluetoothAdapter mBluetoothAdapter;
#Override
public void onCreate() {
super.onCreate();
writeLine("Automate service created...");
getBTService();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
writeLine("Automate service start...");
if (!isBluetoothSupported()) {
Toast.makeText(this, R.string.ble_not_supported, Toast.LENGTH_SHORT).show();
stopSelf();
}else{
if(mBluetoothAdapter!=null && mBluetoothAdapter.isEnabled()){
startBLEscan();
}else{
stopSelf();
}
}
return START_STICKY;
}
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onDestroy() {
writeLine("Automate service destroyed...");
stopBLEscan();
super.onDestroy();
if(btGatt!=null){
btGatt.disconnect();
btGatt.close();
btGatt = null;
}
}
#Override
public boolean stopService(Intent name) {
writeLine("Automate service stop...");
stopSelf();
return super.stopService(name);
}
// Initializes a Bluetooth adapter. For API level 18 and above, get a reference to
// BluetoothAdapter through BluetoothManager.
public BluetoothAdapter getBTService(){
BluetoothManager btManager = (BluetoothManager) getApplicationContext().getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = (BluetoothAdapter) btManager.getAdapter();
return mBluetoothAdapter;
}
public boolean isBluetoothSupported() {
return this.getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE);
}
public void startBLEscan(){
mBluetoothAdapter.startLeScan(this);
}
public void stopBLEscan(){
mBluetoothAdapter.stopLeScan(this);
}
/**
*
* #param enable
*/
public void scanLeDevice(final boolean enable) {
if (enable) {
startBLEscan();
} else {
stopBLEscan();
}
}
public static void enableDisableBluetooth(boolean enable){
BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (bluetoothAdapter != null) {
if(enable) {
bluetoothAdapter.enable();
}else{
bluetoothAdapter.disable();
}
}
}
#Override
public void onLeScan(final BluetoothDevice device, final int rssi, byte[] scanRecord) {
if(device!=null && device.getName()!=null){
//Log.d(TAG + " onLeScan: ", "Name: "+device.getName() + "Address: "+device.getAddress()+ "RSSI: "+rssi);
if(rssi > -90 && rssi <-1){
writeLine("Automate service BLE device in range: "+ device.getName()+ " "+rssi);
if (device.getName().equalsIgnoreCase("NCS_Beacon") || device.getName().equalsIgnoreCase("estimote")) {
//This Main looper thread is main for connect gatt, don't remove it
// Although you need to pass an appropriate context getApplicationContext(),
//Here if you use Looper.getMainLooper() it will stop getting callback and give internal exception fail to register //callback
new Handler(getApplicationContext().getMainLooper()).post(new Runnable() {
#Override
public void run() {
btGatt = device.connectGatt(getApplicationContext(), false, bleGattCallback);
Log.e(TAG, "onLeScan btGatt value returning from connectGatt "+btGatt);
}
});
}
stopBLEscan();
}else{
//Log.v("Device Scan Activity", device.getAddress()+" "+"BT device is still too far - not connecting");
}
}
}
BluetoothGattCallback bleGattCallback = new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(final BluetoothGatt gatt, int status, int newState) {
super.onConnectionStateChange(gatt, status, newState);
writeLine("Automate service connection state: "+ newState);
if (newState == android.bluetooth.BluetoothProfile.STATE_CONNECTED){
writeLine("Automate service connection state: STATE_CONNECTED");
Log.v("BLEService", "BLE Connected now discover services");
Log.v("BLEService", "BLE Connected");
new Thread(new Runnable() {
#Override
public void run() {
writeLine("Automate service go for discover services");
gatt.discoverServices();
}
}).start();
}else if (newState == android.bluetooth.BluetoothProfile.STATE_DISCONNECTED){
writeLine("Automate service connection state: STATE_DISCONNECTED");
Log.v("BLEService", "BLE Disconnected");
}
}
#Override
public void onServicesDiscovered(final BluetoothGatt gatt, int status) {
super.onServicesDiscovered(gatt, status);
if (status == BluetoothGatt.GATT_SUCCESS) {
writeLine("Automate service discover service: GATT_SUCCESS");
Log.v("BLEService", "BLE Services onServicesDiscovered");
//Get service
List<BluetoothGattService> services = gatt.getServices();
writeLine("Automate service discover service imei: " +imei);
}
}
#Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicRead(gatt, characteristic, status);
}
#Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
super.onCharacteristicChanged(gatt, characteristic);
}
};
private void writeLine(final String message) {
Handler h = new Handler(getApplicationContext().getMainLooper());
// Although you need to pass an appropriate context
h.post(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),message,Toast.LENGTH_SHORT).show();
}
});
}
}
In manifest.xml
<uses-feature
android:name="android.hardware.bluetooth_le"
android:required="true" />
<!-- Permission for bluetooth -->
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<service
android:name="com.myapp.services.BeaconService"
android:enabled="true"
android:exported="false" />

Use service to scan and connect ble devices when application is in background in android.
package com.example.tracker.service;
import android.app.Service;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattService;
import android.bluetooth.BluetoothManager;
import android.bluetooth.le.BluetoothLeScanner;
import android.bluetooth.le.ScanFilter;
import android.bluetooth.le.ScanSettings;
import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.ServiceConnection;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Handler;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.support.v4.widget.SwipeRefreshLayout;
import android.util.Log;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.SeekBar;
import android.widget.Toast;
import com.google.firebase.auth.FirebaseAuth;
import com.example.tracker.R;
import com.example.tracker.utils.SampleGattAttributes;
import com.example.tracker.utils.SharedPreferencesUtils;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.UUID;
import static com.example.tracker.constant.SharedFreferencesConstant.KEY_SP_MOBILE_NUMBER;
/**
* Created by Jprashant on 12/9/17.
*/
public class BackgroundService extends Service{
private int scanPeriod;
Context context;
String TAG="BackgroundService";
private BluetoothAdapter mBluetoothAdapter;
private boolean mScanning;
private Handler mHandler;
public String[] advDataTypes = new String[256];
ArrayList<BluetoothDevice> bluetoothDeviceArrayList=new ArrayList<>();
ArrayList<BluetoothDevice> bluetoothDeviceArrayListTwo=new ArrayList<>();
private static final int REQUEST_ENABLE_BT = 1;
// Stops scanning after 10 seconds.
private static final long SCAN_PERIOD = 10000;
/*Connect Ble Device*/
String deviceId;
public static String arrayDidOpnSec2;
BluetoothGattService gattService4;
public static ArrayList<BluetoothGattCharacteristic> lastCharacteristic;
// AlertDialog.Builder alertDialog;
private float avgRssi = 0.0f;
// private Dialog dialog;
private BluetoothLeService mBluetoothLeService;
private boolean mConnected = false;
private ArrayList<ArrayList<BluetoothGattCharacteristic>> mGattCharacteristics = new ArrayList();
//service and char uuid
private static final int TRACKER_ON_OFF = 2;
private static final UUID TRACER_TRIPPLE_PRESS_SERVICE=UUID.fromString("edfec62e-9910-0bac-5241-d8bda6932a2f");
private static final UUID TRACKER_TRIPPLE_PRESS_CHAR=UUID.fromString("772ae377-b3d2-4f8e-4042-5481d1e0098c");
private static final UUID IMMEDIATE_ALERT_UUID = UUID.fromString("00001802-0000-1000-8000-00805f9b34fb");
private static final UUID ALERT_LEVEL_UUID = UUID.fromString("00002a06-0000-1000-8000-00805f9b34fb");
private Button btnSMS;
public static String mDeviceName,mDeviceAddress,connectionStatus;
/*-------------------------------------------------------------------------------*/
public static final String PREFS_NAME = "PreferencesFile";
public int deviceCount = 0;
public String[] mData = new String[400];
private Handler mHandler1;
private ListView listItems;
/*--------for > 21--------------*/
private BluetoothLeScanner mLEScanner;
private ScanSettings settings;
private List<ScanFilter> filters;
private BluetoothGatt mGatt;
public BackgroundService() {
}
public BackgroundService(Context context) {
this.context = context;
}
#Nullable
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
// getting systems default ringtone
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),"CALL YOUR METHOD",Toast.LENGTH_LONG).show();
mHandler = new Handler();
// Use this check to determine whether BLE is supported on the device. Then you can
// selectively disable BLE-related features.
if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
Toast.makeText(context, R.string.ble_not_supported, Toast.LENGTH_SHORT).show();
}
// Initializes a Bluetooth adapter. For API level 18 and above, get a reference to
// BluetoothAdapter through BluetoothManager.
final BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
// Checks if Bluetooth is supported on the device.
if (mBluetoothAdapter == null) {
Toast.makeText(context, R.string.error_bluetooth_not_supported, Toast.LENGTH_SHORT).show();
return;
}
for (int i = 0; i < 256; i += REQUEST_ENABLE_BT) {
advDataTypes[i] = "Unknown Data Type";
}
advDataTypes[REQUEST_ENABLE_BT] = "Flags";
advDataTypes[2] = "Incomplete List of 16-bit Service Class UUIDs";
advDataTypes[3] = "Complete List of 16-bit Service Class UUIDs";
advDataTypes[4] = "Incomplete List of 32-bit Service Class UUIDs";
advDataTypes[5] = "Complete List of 32-bit Service Class UUIDs";
advDataTypes[6] = "Incomplete List of 128-bit Service Class UUIDs";
advDataTypes[7] = "Complete List of 128-bit Service Class UUIDs";
advDataTypes[8] = "Shortened Local Name";
advDataTypes[9] = "Complete Local Name";
advDataTypes[10] = "Tx Power Level";
advDataTypes[13] = "Class of LocalDevice";
advDataTypes[14] = "Simple Pairing Hash";
advDataTypes[15] = "Simple Pairing Randomizer R";
advDataTypes[16] = "LocalDevice ID";
advDataTypes[17] = "Security Manager Out of Band Flags";
advDataTypes[18] = "Slave Connection Interval Range";
advDataTypes[20] = "List of 16-bit Solicitaion UUIDs";
advDataTypes[21] = "List of 128-bit Solicitaion UUIDs";
advDataTypes[22] = "Service Data";
advDataTypes[23] = "Public Target Address";
advDataTypes[24] = "Random Target Address";
advDataTypes[25] = "Appearance";
advDataTypes[26] = "Advertising Interval";
advDataTypes[61] = "3D Information Data";
advDataTypes[255] = "Manufacturer Specific Data";
scanPeriod = getApplicationContext().getSharedPreferences(PREFS_NAME, 0).getInt("scan_interval", 6000);
scanTrackerDevices();
}
}, 10000);
return START_STICKY;
}
#Override
public void onDestroy() {
super.onDestroy();
}
public void scanTrackerDevices(){
Log.e(TAG,"scanTrackerDevices");
if (!mBluetoothAdapter.isEnabled()) {
if (!mBluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
}
}
scanLeDevice(true);
}
private void scanLeDevice(final boolean enable) {
bluetoothDeviceArrayList.clear();
if (enable) {
// Stops scanning after a pre-defined scan period.
mHandler.postDelayed(new Runnable() {
#Override
public void run() {
mScanning = false;
mBluetoothAdapter.stopLeScan(mLeScanCallback);
int arraySize=bluetoothDeviceArrayListTwo.size();
Log.e(TAG,"bluetoothDeviceArrayListTwo Size in scan :"+arraySize);
for (int i=0;i<bluetoothDeviceArrayListTwo.size();i++){
BluetoothDevice bluetoothDevice=bluetoothDeviceArrayListTwo.get(i);
Log.e(TAG,"Device Name in scan :"+bluetoothDevice.getName());
Log.e(TAG,"Device Address in scan :"+bluetoothDevice.getAddress());
if (i==0){
mBluetoothLeService.connect(bluetoothDevice.getAddress());
}
}
}
}, scanPeriod);
mScanning = true;
mBluetoothAdapter.startLeScan(mLeScanCallback);
} else {
mScanning = false;
mBluetoothAdapter.stopLeScan(mLeScanCallback);
}
}
private BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() {
public void onLeScan(final BluetoothDevice device, final int rssi, final byte[] scanRecord) {
String d = "";
String rd = "";
String h = "0123456789ABCDEF";
int ln = 0;
int i = 0;
while (i < scanRecord.length) {
int x = scanRecord[i] & 255;
rd = new StringBuilder(String.valueOf(rd)).append(h.substring(x / 16, (x / 16) + REQUEST_ENABLE_BT)).append(h.substring(x % 16, (x % 16) +REQUEST_ENABLE_BT)).toString();
if (i == ln) {
ln = (i + x) + REQUEST_ENABLE_BT;
if (x == 0) {
break;
}
d = new StringBuilder(String.valueOf(d)).append("\r\n Length: ").append(h.substring(x / 16, (x / 16) + REQUEST_ENABLE_BT)).append(h.substring(x % 16, (x % 16) +REQUEST_ENABLE_BT)).toString();
i += REQUEST_ENABLE_BT;
x = scanRecord[i] & 255;
d = new StringBuilder(String.valueOf(d)).append(", Type :").append(h.substring(x / 16, (x / 16) + REQUEST_ENABLE_BT)).append(h.substring(x % 16, (x % 16) + REQUEST_ENABLE_BT)).append(" = ").append(advDataTypes[x]).append(", Value: ").toString();
rd = new StringBuilder(String.valueOf(rd)).append(h.substring(x / 16, (x / 16) + REQUEST_ENABLE_BT)).append(h.substring(x % 16, (x % 16) + REQUEST_ENABLE_BT)).toString();
} else {
d = new StringBuilder(String.valueOf(d)).append(" ").append(h.substring(x / 16, (x / 16) + REQUEST_ENABLE_BT)).append(h.substring(x % 16, (x % 16) +REQUEST_ENABLE_BT)).toString();
}
i += REQUEST_ENABLE_BT;
}
Log.e(TAG,"UUID : "+device.getUuids());
String[] arrayDeviceName=String.valueOf(device.getName()).split(" ");
String deviceName0=arrayDeviceName[0];
bluetoothDeviceArrayListTwo.add(device);
}
};
/*-------------------Connect BLE---------------------------------------------*/
private Handler mHandler2;
public final BroadcastReceiver mGattUpdateReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent)
{
String action = intent.getAction();
if (BluetoothLeService.ACTION_GATT_CONNECTED.equals(action))
{
numberOfRssi = 0;
avgRssi = 0.0f;
mConnected = true;
updateConnectionState(R.string.connected);
mHandler2.postDelayed(startRssi, 300);
Log.e(TAG,"ACTION_GATT_CONNECTED");
}
else if (BluetoothLeService.ACTION_GATT_DISCONNECTED.equals(action)) {
mConnected = false;
updateConnectionState(R.string.disconnected);
Log.e(TAG,"ACTION_GATT_DISCONNECTED");
} else if (BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED.equals(action)) {
displayGattServicesForDimmer(mBluetoothLeService.getSupportedGattServices());// For dimmer
Log.e(TAG,"ACTION_GATT_SERVICES_DISCOVERED");
} else if (BluetoothLeService.ACTION_DATA_AVAILABLE.equals(action)) {
Log.e(TAG,"ACTION_DATA_AVAILABLE");
String unknownServiceString = context.getResources().getString(R.string.unknown_service);
displayDimmerData("<<" + SampleGattAttributes.lookup(intent.getStringExtra(BluetoothLeService.CHARACTERISTIC_UUID), unknownServiceString) + ">> Value: " + intent.getStringExtra(BluetoothLeService.EXTRA_DATA) + "]");
displayDimmer2(intent.getStringExtra(BluetoothLeService.EXTRA_DATA));
} else if (BluetoothLeService.ACTION_GATT_RSSI_UPDATE.equals(action)) {
updateRssi(intent.getIntExtra(BluetoothLeService.EXTRA_DATA, -400));
} else if (BluetoothLeService.ACTION_GATT_WRITE_FAILED.equals(action)) {
Log.e(TAG,"ACTION_GATT_WRITE_FAILED");
}
}
};
/*------------------------------------------------------------------------*/
#Override
public void onCreate() {
super.onCreate();
// -------------------Connect Ble--------------------------------------
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(BluetoothLeService.ACTION_GATT_CONNECTED);
intentFilter.addAction(BluetoothLeService.ACTION_GATT_DISCONNECTED);
intentFilter.addAction(BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED);
intentFilter.addAction(BluetoothLeService.ACTION_DATA_AVAILABLE);
intentFilter.addAction(BluetoothLeService.ACTION_GATT_RSSI_UPDATE);
intentFilter.addAction(BluetoothLeService.ACTION_GATT_WRITE_FAILED);
Log.e(TAG,"OnResume()");
getApplicationContext().registerReceiver(mGattUpdateReceiver, intentFilter);
getApplicationContext().bindService(new Intent(getApplicationContext(), BluetoothLeService.class), mServiceConnection, 1);
mHandler2=new Handler();
}
private BluetoothGattCharacteristic mNotifyCharacteristic;
private final ServiceConnection mServiceConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName componentName, IBinder service) {
mBluetoothLeService = ((BluetoothLeService.LocalBinder) service).getService();
if (!mBluetoothLeService.initialize()) {
Log.e(TAG, "Unable to initialize Bluetooth");
}
}
public void onServiceDisconnected(ComponentName componentName) {
mBluetoothLeService = null;
}
};
private boolean notificationActive = true;
private int numberOfRssi = 0;
private Runnable startRssi = new Runnable() {
public void run() {
if (mConnected) {
mBluetoothLeService.readRemoteRssi();
mHandler2.postDelayed(startRssi, 200);
}
}
};
public BluetoothGatt getmGatt() {
return mGatt;
}
//code from DeviceControlActivity
private void updateConnectionState(final int resourceId) {
connectionStatus= String.valueOf(resourceId);
Log.e(TAG,"Resource ID"+resourceId);
}
private void displayDimmerData(String data){
Log.e(TAG,"Display Data :"+data);
}
private void displayDimmer2(String data){
Log.e(TAG,"display Dimmer2"+data);
String sosString = data.substring(0, Math.min(data.length(), 3));
Log.e(TAG,"SOS String :"+sosString);
if (sosString.equals("SOS")){
Intent callIntent = new Intent(Intent.ACTION_CALL);
callIntent.setData(Uri.parse("tel:"+ SharedPreferencesUtils.getStringFromSharedPreferences(KEY_SP_MOBILE_NUMBER,getApplicationContext())));
callIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
getApplicationContext().startActivity(callIntent);
}
}
private void updateRssi(int data) {
if (data > -400) {
if (this.numberOfRssi > 10) {
this.avgRssi = ((9.0f * this.avgRssi) + ((float) data)) / 10.0f;
} else {
this.avgRssi = (this.avgRssi + ((float) data)) / 2.0f;
this.numberOfRssi++;
}
connectionStatus="Connected, RSSI:" + data + ", Avg:" + Math.round(this.avgRssi);
}
}
/*-------------------------disaplay gatt service for dimmer----------------------*/
private void displayGattServicesForDimmer(List<BluetoothGattService> gattServices) {
if (gattServices != null) {
String unknownServiceString = getResources().getString(R.string.unknown_service);
String unknownCharaString = getResources().getString(R.string.unknown_characteristic);
ArrayList<HashMap<String, String>> gattServiceData = new ArrayList();
ArrayList<ArrayList<HashMap<String, String>>> gattCharacteristicData = new ArrayList();
this.mGattCharacteristics = new ArrayList();
for (BluetoothGattService gattService : gattServices) {
HashMap<String, String> currentServiceData = new HashMap();
String uuid = gattService.getUuid().toString();
currentServiceData.put("NAME", SampleGattAttributes.lookup(uuid, unknownServiceString));
currentServiceData.put("UUID", uuid);
gattServiceData.add(currentServiceData);
ArrayList<HashMap<String, String>> gattCharacteristicGroupData = new ArrayList();
List<BluetoothGattCharacteristic> gattCharacteristics = gattService.getCharacteristics();
ArrayList<BluetoothGattCharacteristic> charas = new ArrayList();
for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) {
charas.add(gattCharacteristic);
HashMap<String, String> currentCharaData = new HashMap();
uuid = gattCharacteristic.getUuid().toString();
currentCharaData.put("NAME", "\t\t\t<<" + SampleGattAttributes.lookup(uuid, unknownCharaString) + ">>");
currentCharaData.put("UUID", "\t\t\tUUID: 0x" + uuid.substring(4, 8) + ", Properties: " + translateProperties(gattCharacteristic.getProperties()));
gattCharacteristicGroupData.add(currentCharaData);
Log.i(TAG,"CUrrent CHARACTERISTIC DATA"+currentCharaData);
Log.i(TAG,"UUID : "+uuid.substring(4, 8));
Log.i(TAG,"Proprties : "+gattCharacteristic.getProperties());
Log.i(TAG,"Translate Proprties : "+translateProperties(gattCharacteristic.getProperties()));
Log.i(TAG,"char list"+gattCharacteristicData.toString());
}
gattService4=gattService;
this.mGattCharacteristics.add(charas);
}
if (mGattCharacteristics.get(3)!=null) {
lastCharacteristic = new ArrayList<>(mGattCharacteristics.get(3));
enableNotifyOfCharcteristicForDimmer(lastCharacteristic);
}
}
}
private String translateProperties(int properties) {
String s = "";
if ((properties & 1) > 0) {
s = new StringBuilder(String.valueOf(s)).append("/Broadcast").toString();
}
if ((properties & 2) > 0) {
s = new StringBuilder(String.valueOf(s)).append("/Read").toString();
}
if ((properties & 4) > 0) {
s = new StringBuilder(String.valueOf(s)).append("/WriteWithoutResponse").toString();
}
if ((properties & 8) > 0) {
s = new StringBuilder(String.valueOf(s)).append("/Write").toString();
}
if ((properties & 16) > 0) {
s = new StringBuilder(String.valueOf(s)).append("/Notify").toString();
}
if ((properties & 32) > 0) {
s = new StringBuilder(String.valueOf(s)).append("/Indicate").toString();
}
if ((properties & 64) > 0) {
s = new StringBuilder(String.valueOf(s)).append("/SignedWrite").toString();
}
if ((properties & 128) > 0) {
s = new StringBuilder(String.valueOf(s)).append("/ExtendedProperties").toString();
}
if (s.length() > 1) {
return s.substring(1);
}
return s;
}
// Enable Characteristic for dimmer
public void enableNotifyOfCharcteristicForDimmer(ArrayList<BluetoothGattCharacteristic> lastCharacteristic){
if(mGattCharacteristics!=null) {
checkCharacteristicPresent(lastCharacteristic.get(0));
mBluetoothLeService.setCharacteristicNotification(lastCharacteristic.get(0), true);
notificationActive = true;
Log.e(TAG,"Characteristic index : "+0+":\nM GATT CHARACTERISTIC AT "+"Service 4 : CHAR"+ 0 +" :" +lastCharacteristic.get(0).toString());
checkCharacteristicPresent(lastCharacteristic.get(1));
mBluetoothLeService.setCharacteristicNotification(lastCharacteristic.get(1), true);
notificationActive = true;
Log.e(TAG,"Characteristic index : "+1+":\nM GATT CHARACTERISTIC AT "+"Service 4 : CHAR"+ 1 +" :" +lastCharacteristic.get(1).toString());
checkCharacteristicPresent(lastCharacteristic.get(2));
mBluetoothLeService.setCharacteristicNotification(lastCharacteristic.get(2), true);
notificationActive = true;
Log.e(TAG,"Characteristic index : "+2+":\nM GATT CHARACTERISTIC AT "+"Service 4 : CHAR"+ 2 +" :" +lastCharacteristic.get(2).toString());
checkCharacteristicPresent(lastCharacteristic.get(3));
mBluetoothLeService.setCharacteristicNotification(lastCharacteristic.get(3), true);
notificationActive = true;
Log.e(TAG,"Characteristic index : "+3+":\nM GATT CHARACTERISTIC AT "+"Service 4 : CHAR"+ 3 +" :" +lastCharacteristic.get(3).toString());
checkCharacteristicPresent(lastCharacteristic.get(4));
mBluetoothLeService.setCharacteristicNotification(lastCharacteristic.get(4), true);
notificationActive = true;
Log.e(TAG,"Characteristic index : "+4+":\nM GATT CHARACTERISTIC AT "+"Service 4 : CHAR"+ 4 +" :" +lastCharacteristic.get(4).toString());
checkCharacteristicPresent(lastCharacteristic.get(5));
mBluetoothLeService.setCharacteristicNotification(lastCharacteristic.get(5), true);
notificationActive = true;
Log.e(TAG,"Characteristic index : "+5+":\nM GATT CHARACTERISTIC AT "+"Service 4 : CHAR"+ 5 +" :" +lastCharacteristic.get(5).toString());
checkCharacteristicPresent(lastCharacteristic.get(2));
mBluetoothLeService.setCharacteristicNotification(lastCharacteristic.get(2), true);
notificationActive = true;
Log.e(TAG,"Characteristic index : "+2+":\nM GATT CHARACTERISTIC AT "+"Service 4 : CHAR"+ 2 +" :" +lastCharacteristic.get(2).toString());
}
}
// Check the type of characteristic i.e READ/WRITE/NOTIFY
public void checkCharacteristicPresent(BluetoothGattCharacteristic characteristic) {
int charaProp = characteristic.getProperties();
Log.e(TAG, "checkCharacteristicPresent Prop : " + charaProp);
mBluetoothLeService.setCurrentCharacteristic(characteristic);
if ((charaProp & 2) > 0) {
Log.e(TAG, "CharProp & 2 : " + charaProp);
mBluetoothLeService.readCharacteristic(characteristic);
}
if ((charaProp & 16) > 0) {
Log.e(TAG, "CharProp & 16 : " + charaProp);
mNotifyCharacteristic = characteristic;
} else {
if (mNotifyCharacteristic != null) {
mBluetoothLeService.setCharacteristicNotification(mNotifyCharacteristic, false);
mNotifyCharacteristic = null;
}
}
if ((charaProp & 8) > 0 || (charaProp & 4) > 0) {
Log.e(TAG, "CharProp & 4 : " + charaProp);
} else {
Log.e(TAG, "Else : " + charaProp);
}
}
}
Write this code in manifest.xml
<service android:name=".service.BackgroundService" />

Android BLE notifications packet loss

I am working on a hardware device which sends a continuous stream of data over BLE to an Android App. The android app receives this data as GATT notifications, then processes this data and saves it to a database.
The configuration details of the project are as follows:
Phone - Moto E 1st Generation
Android Version - Android 5.1 - Lollipop 
iOS - iPhone 4 & 5, tested on iOS 7 & 8
Hardware - CC2541
Connection_Interval : 40 ms (Set in the firmware of the hardware).
Packets Sent Per Connection Interval : 4 (Set in the firmware of the hardware).
THE PROBLEM
When data is transmitted from the hardware device to the BLE data capture app running on Android phone, all the data packets are not received. It receives only about 35-45 packets, whereas the expected number of packets is 50.
What is more surprising is that when we used the BLE packet sniffer, there was a perfect match between the data sniffed and displayed by the Android phone (which is incomplete / incorrect data). This leads me to believe that the hardware is behaving differently when connecting to the Android phone and not sending all of the data.
When we use the same hardware with an iOS BLE data capture app, the data is received correctly.
I am puzzled and clueless about this behaviour of BLE data capture in Android. How the app on iOS device is able to capture all the data correctly whereas app on android phone is not able to capture data properly at all? 
Has anyone experienced such a problem of packet loss / incorrect data when using BLE app on Android?  Any inputs are welcome. Thank you so much for your help in advance.
The android App is using the standard BLE code to connect to the device over BLE. The Android code that I am using is shown below:
import android.annotation.TargetApi;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattDescriptor;
import android.bluetooth.BluetoothGattService;
import android.bluetooth.BluetoothManager;
import android.bluetooth.BluetoothProfile;
import android.bluetooth.le.BluetoothLeScanner;
import android.bluetooth.le.ScanCallback;
import android.bluetooth.le.ScanFilter;
import android.bluetooth.le.ScanResult;
import android.bluetooth.le.ScanSettings;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.nfc.Tag;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
#TargetApi(21)
public class BLETestActivity extends Activity {
private BluetoothAdapter mBluetoothAdapter;
private int REQUEST_ENABLE_BT = 1;
private Handler mHandler;
private static final long SCAN_PERIOD = 10000;
private BluetoothLeScanner mLEScanner;
private ScanSettings settings;
private List<ScanFilter> filters;
private BluetoothGatt mGatt;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bletest);
mHandler = new Handler();
if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
Toast.makeText(this, "BLE Not Supported",
Toast.LENGTH_SHORT).show();
finish();
}
final BluetoothManager bluetoothManager =
(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
}
#Override
protected void onResume() {
super.onResume();
if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
} else {
if (Build.VERSION.SDK_INT >= 21) {
Log.i("innnnn","spinnnn - " + Build.VERSION.SDK_INT);
mLEScanner = mBluetoothAdapter.getBluetoothLeScanner();
settings = new ScanSettings.Builder()
.setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
.build();
filters = new ArrayList<ScanFilter>();
}
scanLeDevice(true);
}
}
#Override
protected void onPause() {
super.onPause();
if (mBluetoothAdapter != null && mBluetoothAdapter.isEnabled()) {
scanLeDevice(false);
}
}
#Override
protected void onDestroy() {
if (mGatt == null) {
return;
}
mGatt.close();
mGatt = null;
super.onDestroy();
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REQUEST_ENABLE_BT) {
if (resultCode == Activity.RESULT_CANCELED) {
//Bluetooth not enabled.
finish();
return;
}
}
super.onActivityResult(requestCode, resultCode, data);
}
private void scanLeDevice(final boolean enable) {
if (enable) {
mHandler.postDelayed(new Runnable() {
#Override
public void run() {
if (Build.VERSION.SDK_INT < 21) {
mBluetoothAdapter.stopLeScan(mLeScanCallback);
} else {
mLEScanner.stopScan(mScanCallback);
}
}
}, SCAN_PERIOD);
if (Build.VERSION.SDK_INT < 21) {
mBluetoothAdapter.startLeScan(mLeScanCallback);
} else {
mLEScanner.startScan(filters, settings, mScanCallback);
}
} else {
if (Build.VERSION.SDK_INT < 21) {
mBluetoothAdapter.stopLeScan(mLeScanCallback);
} else {
mLEScanner.stopScan(mScanCallback);
}
}
}
private ScanCallback mScanCallback = null;/* new ScanCallback() {
#Override
public void onScanResult(int callbackType, ScanResult result) {
Log.i("callbackType", String.valueOf(callbackType));
Log.i("result", result.toString());
BluetoothDevice btDevice = result.getDevice();
connectToDevice(btDevice);
}
#Override
public void onBatchScanResults(List<ScanResult> results) {
for (ScanResult sr : results) {
Log.i("ScanResult - Results", sr.toString());
}
}
#Override
public void onScanFailed(int errorCode) {
Log.e("Scan Failed", "Error Code: " + errorCode);
}
};*/
private BluetoothAdapter.LeScanCallback mLeScanCallback =
new BluetoothAdapter.LeScanCallback() {
#Override
public void onLeScan(final BluetoothDevice device, int rssi,
byte[] scanRecord) {
runOnUiThread(new Runnable() {
#Override
public void run() {
Log.i("onLeScan", device.toString());
connectToDevice(device);
}
});
}
};
public void connectToDevice(BluetoothDevice device) {
if (mGatt == null) {
mGatt = device.connectGatt(this, false, gattCallback);
scanLeDevice(false);// will stop after first device detection
}
}
private final BluetoothGattCallback gattCallback = new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
Log.i("onConnectionStateChange", "Status: " + status);
switch (newState) {
case BluetoothProfile.STATE_CONNECTED:
Log.i("gattCallback", "STATE_CONNECTED");
gatt.discoverServices();
break;
case BluetoothProfile.STATE_DISCONNECTED:
Log.e("gattCallback", "STATE_DISCONNECTED");
break;
default:
Log.e("gattCallback", "STATE_OTHER");
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
List<BluetoothGattService> services = gatt.getServices();
// Log.i("onServicesDiscovered", services.toString());
for(int i=0;i<services.size();i++) {
List<BluetoothGattCharacteristic> charList = services.get(i).getCharacteristics();
for (int j = 0; j < charList.size();j++) {
BluetoothGattCharacteristic characteristic = charList.get(j);
if (characteristic.getUuid().compareTo(Constants.HEART_DATA_UUID) == 0) {
Log.i(BLETestActivity.class.getSimpleName(), "Characteristic UUID is " + characteristic.getUuid());
mGatt.setCharacteristicNotification(characteristic, true);
BluetoothGattDescriptor descriptor = characteristic.getDescriptor(Constants.HEART_DATA_DESCRIPTOR_UUID);
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mGatt.writeDescriptor(descriptor);
}
}
}
}
public void onCharacteristicChanged(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic) {
// Retrieve the byte values
// Convert them to hex values
byte[] data = characteristic.getValue();
// The following array contains data in the follwing form:
// 0-1 - running counter counts
// 2-4, 5-7, 8-10 - Sample 1 data for channel 1, channel2 and channel 3
// 11-13, 14-16, 17-19 - Sample 2 data for channel 1, channel 2 and channel 3
// Log.i(TAG," ------ " + Thread.currentThread().getId());
String heartBeatDataInHex = bytesToHex(data);
// An error packet is received after every 17 samples.
// Checking to make sure that this is not an error packet
if (!(heartBeatDataInHex.substring(4, 10).equalsIgnoreCase("FFFFFF") && heartBeatDataInHex.substring(26, 40).equalsIgnoreCase("FFFFFFFFFFFFFF"))) {
Log.i("testdata", heartBeatDataInHex + " ---- " + Thread.currentThread().getId());
}
}
#Override
public void onCharacteristicRead(BluetoothGatt gatt,
BluetoothGattCharacteristic
characteristic, int status) {
Log.i("onCharacteristicRead", characteristic.toString());
gatt.disconnect();
}
};
private String bytesToHex(byte[] bytes) {
final char[] hexArray = "0123456789ABCDEF".toCharArray();
char[] hexChars = new char[bytes.length * 2];
for ( int j = 0; j < bytes.length; j++ ) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
}

I've had similar problem!
I have made some testing and I've determined that the minimum connection interval is 48ms with android api level 18.
(connection interval for BLE on Galaxy S3 Android 4.3).
Posible solution:
Make the connection interval slower (less than 48ms).
From api level 21 to upper, you can change CONNECTION_PRIORITY android developer to modify the interval connection but this implies more consumption of energy.