Control mode where the height is send as an absolute setpoint (intended
        to be the distance to the surface under the Crazflie).

        vx and vy are in m/s
        yawrate is in degrees/s

def send_hover_setpoint(self, vx, vy, yawrate, zdistance):
        """
        Control mode where the height is send as an absolute setpoint (intended
        to be the distance to the surface under the Crazflie).

        vx and vy are in m/s
        yawrate is in degrees/s
        """
        pk = CRTPPacket()
        pk.port = CRTPPort.COMMANDER_GENERIC
        pk.data = struct.pack('<Bffff', TYPE_HOVER,
                              vx, vy, yawrate, zdistance)
        self._cf.send_packet(pk)