def _get_acceleration(self, data):
        '''Return acceleration mG'''
        if (data[7:8] == 0x7FFF or
                data[9:10] == 0x7FFF or
                data[11:12] == 0x7FFF):
            return (None, None, None)

        acc_x = twos_complement((data[7] << 8) + data[8], 16)
        acc_y = twos_complement((data[9] << 8) + data[10], 16)
        acc_z = twos_complement((data[11] << 8) + data[12], 16)
        return (acc_x, acc_y, acc_z)
Return acceleration mG