//sensors on device
    private SensorManager mSensorManager;
    private Sensor mSensorAccelerometer;
    private Sensor mSensorGyroscope;
    private Sensor mSensorMagnetometer;
    private Sensor mSensorOrientation;

    //values in app
    private TextView mTextSensorAccelerometer;
    private TextView mTextSensorGyroscope;
    private TextView mTextSensorOrientation;

    //graph
    private LineChart mChartGyro, mChartAccel, mChartMagneto;

    private float xValue, yValue, zValue; // Variables to store data retrieved form sensor

    private Thread thread;
    private boolean plotData = true;

    //writing data to file
    private File fileDir, file;
    private TextView tv;
    private Context context;

    //button to start and stop
    private Button startButton;
    private Button stopButton;
    private boolean record = false;

    // Server related
    private FirebaseDatabase mFirebaseDatabase;
    private DatabaseReference mDatabase;