README.md

mavlinklog_publisher

A ROS2 node intended for the publishing of human readable messages from a companion computer to QGroundControl via a flight controller running PX4. The node subscribes to the LogMsg defined in this package and published a MavlinkLog message to the flight controller via the XRCE-DDS bridge. This functionality enables ROS2 nodes on the companion computer to display messages in QGroundControl, which is especially useful when operating in offboard mode.

Build/Run

The mavlinklog_publisher package is built and run like any other ROS2 package.

source /opt/ros/humble/setup.bash 
cd ~/ros2_ws/
colcon build --packages-select mavlinklog_publisher
source install/local_setup.bash
ros2 run mavlinklog_publisher mavlinklog_publisher_node

Command-Line Arguments

Argument	Description	Default Value	Required?
uav_name	Prepends uav_name to ROS topics. Useful if using a topic namespace.	None	No
message_on_start	Prints message to QGC when node is started	True	No

NOTE See more in depth instructions on how to build and run below.

Testing in SITL

Pre-requisites

These instructions assume you have already installed and tested the following:

• PX4 toolchain
• PX4 Gazebo simulation
• uxrce_dds bridge
• ROS2 humble
• QGroundControl

NOTE Exact commands may vary depending on the PX4 and gazebo versions you are using.

1. If you have not done so already, clone and build the px4_msgs and Micro-XRCE-DDS-Agent packages.

   cd ~/ros2_ws/src/
   git clone https://github.com/PX4/px4_msgs.git
   git clone -b ros2 https://github.com/eProsima/Micro-XRCE-DDS-Agent.git
   cd ~/ros2_ws/
   colcon build --packages-select px4_msgs microxrcedds_agent
   

   NOTE Ensure you have checked out the branch corresponding to the version of PX4 you are using. You must already have ROS2 Humble installed.

2. Clone and build mavlink_log_publisher repo

   git clone https://github.com/TedObrien/mavlinklog_publisher.git
   cd ~/ros2_ws/
   source install/local_setup.bash 
   colcon build --packages-select mavlinklog_publisher
   

3. Update PX4 dds_topics.yaml file to add the mavlink_log uorb message to the list of subscriptions

   nano ~/PX4-Autopilot/src/modules/uxrce_dds_client/dds_topics.yaml
   

   Add the following 2 lines under subscriptions:

   subscriptions:
   
     - topic: /fmu/in/mavlink_log
       type: px4_msgs::msg::MavlinkLog
   
   

   NOTE More detailed instruction on updating this yaml file can be found here

4. Launch px4 sitl gazebo simulation. In this example a topic namespace is being used.

   cd ~/PX4-Autopilot/
   PX4_UXRCE_DDS_NS=uav1 make px4_sitl gz_x500 
   

   NOTE you will need to make clean first if you previously built the target.

5. Start uXRCE-DDS bridge

   source ~/ros2_ws/install/local_setup.bash
   MicroXRCEAgent udp4 -p 8888
   

   Confirm mavlink_log ROS2 has been created with ros2 topic list. Look for the output.

   /uav1/fmu/in/mavlink_log
   

6. Open QgroundControl

7. Start mavlinklog_publisher

   uav_id parameter needs to be specified as as a topic namespace was used when launching px4_sitl

   ros2 run mavlinklog_publisher mavlinklog_publisher_node --ros-args -p uav_name:=uav1
   

   Confirm the log_msg topic has been created with ros2 topic list

   /uav1/log_msg
   

   Publish a message from the command line to QGroundControl:

   ros2 topic pub --once /uav1/log_msg mavlinklog_publisher/msg/LogMsg '{level: 1, message: "Hello World!"}'
   

   Confirm the message has been displayed by QGroundControl

Integrating into other ROS nodes

The script /src/logmsg_publisher.cpp is an example of how to publish to the mavlinklog_publisher_node from other nodes.

To run:

ros2 run mavlinklog_publisher talker

The severity of the message sent to QGC can can be modified. See the LogMsg definition