mavlink: store last heartbeat time in telemetry_status topic

src/modules/mavlink/mavlink_receiver.cpp

@@ -106,6 +106,7 @@ MavlinkReceiver::MavlinkReceiver(Mavlink *parent) :
 	_telemetry_status_pub(-1),
 	_rc_pub(-1),
 	_manual_pub(-1),
+	_telemetry_heartbeat_time(0),
 	_hil_frames(0),
 	_old_timestamp(0),
 	_hil_local_proj_inited(0),
@@ -150,6 +151,10 @@ MavlinkReceiver::handle_message(mavlink_message_t *msg)
 		handle_message_manual_control(msg);
 		break;
 
+	case MAVLINK_MSG_ID_HEARTBEAT:
+		handle_message_heartbeat(msg);
+		break;
+
 	default:
 		break;
 	}
@@ -411,6 +416,7 @@ MavlinkReceiver::handle_message_radio_status(mavlink_message_t *msg)
 	memset(&tstatus, 0, sizeof(tstatus));
 
 	tstatus.timestamp = hrt_absolute_time();
+	tstatus.heartbeat_time = _telemetry_heartbeat_time;
 	tstatus.type = TELEMETRY_STATUS_RADIO_TYPE_3DR_RADIO;
 	tstatus.rssi = rstatus.rssi;
 	tstatus.remote_rssi = rstatus.remrssi;
@@ -451,6 +457,18 @@ MavlinkReceiver::handle_message_manual_control(mavlink_message_t *msg)
 	}
 }
 
+void
+MavlinkReceiver::handle_message_heartbeat(mavlink_message_t *msg)
+{
+	mavlink_heartbeat_t hb;
+	mavlink_msg_heartbeat_decode(msg, &hb);
+
+	/* ignore own heartbeats, accept only heartbeats from GCS */
+	if (msg->sysid != mavlink_system.sysid && hb.type == MAV_TYPE_GCS) {
+		_telemetry_heartbeat_time = hrt_absolute_time();
+	}
+}
+
 void
 MavlinkReceiver::handle_message_hil_sensor(mavlink_message_t *msg)
 {

src/modules/uORB/topics/telemetry_status.h

@@ -57,6 +57,7 @@ enum TELEMETRY_STATUS_RADIO_TYPE {
 
 struct telemetry_status_s {
 	uint64_t timestamp;
+	uint64_t heartbeat_time;	/**< Time of last received heartbeat from remote system */
 	enum TELEMETRY_STATUS_RADIO_TYPE type;	/**< type of the radio hardware     */
 	uint8_t rssi;				/**< local signal strength                      */
 	uint8_t remote_rssi;			/**< remote signal strength                     */