MAVLink: Queue transponder reports and send them at full data rate

This will ensure that no transponder reports are dropped and that all received reports are passed on to the GCS and other devices.

src/modules/mavlink/mavlink_messages.cpp

@@ -1178,6 +1178,11 @@ public:
 		return new MavlinkStreamADSBVehicle(mavlink);
 	}
 
+	virtual bool const_rate()
+	{
+		return true;
+	}
+
 	unsigned get_size()
 	{
 		return (_pos_time > 0) ? MAVLINK_MSG_ID_ADSB_VEHICLE_LEN + MAVLINK_NUM_NON_PAYLOAD_BYTES : 0;
@@ -1201,7 +1206,7 @@ protected:
 	{
 		struct transponder_report_s pos;
 
-		if (_pos_sub->update(&_pos_time, &pos)) {
+		while (_pos_sub->update(&_pos_time, &pos)) {
 			mavlink_adsb_vehicle_t msg = {};
 
 			msg.ICAO_address = pos.ICAO_address;

src/modules/mavlink/mavlink_receiver.cpp

@@ -2087,7 +2087,7 @@ void MavlinkReceiver::handle_message_adsb_vehicle(mavlink_message_t *msg)
 	//warnx("code: %d callsign: %s, vel: %8.4f", (int)t.ICAO_address, t.callsign, (double)t.hor_velocity);
 
 	if (_transponder_report_pub == nullptr) {
-		_transponder_report_pub = orb_advertise(ORB_ID(transponder_report), &t);
+		_transponder_report_pub = orb_advertise_queue(ORB_ID(transponder_report), &t, transponder_report_s::ORB_QUEUE_LENGTH);
 
 	} else {
 		orb_publish(ORB_ID(transponder_report), _transponder_report_pub, &t);