uORB: Added a new uorb_shutdown function that is called during normal shutdown procedures. It will only

call into a new UORB COMMUNICATOR ICHANNEL shutdown interface if it has been configured, otherwise it
does nothing. This allows ICHANNEL implementations to pass on a shutdown indication to a remote processor.
Implemented the shutdown interface in the muorb module for VOXL flight controllers.

src/modules/muorb/apps/muorb_main.cpp

@@ -58,7 +58,9 @@ muorb_init()
 	if (channel && channel->Initialize(enable_debug)) {
 		uORB::Manager::get_instance()->set_uorb_communicator(channel);
 
-		if (channel->Test()) { return OK; }
+		if (channel->Test()) {
+			return OK;
+		}
 	}
 
 	return -EINVAL;

src/modules/muorb/apps/uORBAppsProtobufChannel.cpp

@@ -291,6 +291,20 @@ int16_t uORB::AppsProtobufChannel::register_handler(uORBCommunicator::IChannelRx
 	return 0;
 }
 
+int16_t uORB::AppsProtobufChannel::shutdown()
+{
+	if (_ShutdownRequested) {
+		return 0;
+	}
+
+	_ShutdownRequested = true;
+
+	PX4_ERR("Sending kill command to SLPI!!!");
+	fc_sensor_kill_slpi();
+	sleep(1);
+	return 0;
+}
+
 int16_t uORB::AppsProtobufChannel::send_message(const char *messageName, int length, uint8_t *data)
 {
 	// This is done to slow down high rate debug messages.

src/modules/muorb/apps/uORBAppsProtobufChannel.hpp

@@ -147,6 +147,16 @@ public:
 	 */
 	int16_t send_message(const char *messageName, int length, uint8_t *data);
 
+	/**
+	 * @brief Interface to notify the remote entity of a shutdown.
+	 *
+	 * @return
+	 * 	0 = success; This means the shutdown is successfully sent to the receiver
+	 * 		Note: This does not mean that the receiver has received it.
+	 *  otherwise = failure.
+	 */
+	int16_t shutdown();
+
 	/**
 	 * @brief Interface to test the functions of the protobuf channel.
 	 *
@@ -169,6 +179,7 @@ private:
 	static bool                                 _Debug;
 
 	bool                                        _Initialized;
+	bool                                        _ShutdownRequested{false};
 	uint32_t                                    _MessageCounter;
 
 private: