private void getDatastream(byte sysid, byte compid, MAVLink.MAV_DATA_STREAM id, byte hzrate)
{
mavlink_request_data_stream_t req = new mavlink_request_data_stream_t();
req.target_system = sysid;
req.target_component = compid;
req.req_message_rate = hzrate;
req.start_stop = 1; // start
req.req_stream_id = (byte) id; // id
// send each one twice.
generatePacket((byte) MAVLINK_MSG_ID.REQUEST_DATA_STREAM, req, sysid, compid);
generatePacket((byte) MAVLINK_MSG_ID.REQUEST_DATA_STREAM, req, sysid, compid);
}