RTCM: use MAVLINK_MSG_ID_GPS_RTCM_DATA mavlink message (supports fragmentation)

msg/gps_inject_data.msg

 uint8 len			# length of data
-uint8[110] data			# data to write to GPS device
+uint8 flags         		# LSB: 1=fragmented
+uint8[182] data		# data to write to GPS device (RTCM message)

src/drivers/gps/gps.cpp

@@ -441,6 +441,11 @@ void GPS::handleInjectDataTopic()
 		if (updated) {
 			struct gps_inject_data_s msg;
 			orb_copy(ORB_ID(gps_inject_data), orb_inject_data_cur_fd, &msg);
+
+			/* Write the message to the gps device. Note that the message could be fragmented.
+			 * But as we don't write anywhere else to the device during operation, we don't
+			 * need to assemble the message first.
+			 */
 			injectData(msg.data, msg.len);
 
 			_orb_inject_data_next = (_orb_inject_data_next + 1) % _orb_inject_data_fd_count;

src/modules/mavlink/mavlink_receiver.cpp

@@ -250,8 +250,8 @@ MavlinkReceiver::handle_message(mavlink_message_t *msg)
 		handle_message_adsb_vehicle(msg);
 		break;
 
-	case MAVLINK_MSG_ID_GPS_INJECT_DATA:
-		handle_message_gps_inject_data(msg);
+	case MAVLINK_MSG_ID_GPS_RTCM_DATA:
+		handle_message_gps_rtcm_data(msg);
 		break;
 
 	default:
@@ -1775,16 +1775,17 @@ void MavlinkReceiver::handle_message_adsb_vehicle(mavlink_message_t *msg)
 	}
 }
 
-void MavlinkReceiver::handle_message_gps_inject_data(mavlink_message_t *msg)
+void MavlinkReceiver::handle_message_gps_rtcm_data(mavlink_message_t *msg)
 {
-	mavlink_gps_inject_data_t gps_inject_data_msg;
+	mavlink_gps_rtcm_data_t gps_rtcm_data_msg;
 	gps_inject_data_s gps_inject_data_topic;
 
-	mavlink_msg_gps_inject_data_decode(msg, &gps_inject_data_msg);
+	mavlink_msg_gps_rtcm_data_decode(msg, &gps_rtcm_data_msg);
 
-	gps_inject_data_topic.len = gps_inject_data_msg.len;
-	memcpy(gps_inject_data_topic.data, gps_inject_data_msg.data,
-	       math::min((int)sizeof(gps_inject_data_topic.data), (int)sizeof(uint8_t) * gps_inject_data_msg.len));
+	gps_inject_data_topic.len = gps_rtcm_data_msg.len;
+	gps_inject_data_topic.flags = gps_rtcm_data_msg.flags;
+	memcpy(gps_inject_data_topic.data, gps_rtcm_data_msg.data,
+	       math::min((int)sizeof(gps_inject_data_topic.data), (int)sizeof(uint8_t) * gps_rtcm_data_msg.len));
 
 	orb_advert_t &pub = _gps_inject_data_pub[_gps_inject_data_next_idx];
 

src/modules/mavlink/mavlink_receiver.h

@@ -141,7 +141,7 @@ private:
 	void handle_message_distance_sensor(mavlink_message_t *msg);
 	void handle_message_follow_target(mavlink_message_t *msg);
 	void handle_message_adsb_vehicle(mavlink_message_t *msg);
-	void handle_message_gps_inject_data(mavlink_message_t *msg);
+	void handle_message_gps_rtcm_data(mavlink_message_t *msg);
 
 	void *receive_thread(void *arg);