Trying to add a custom made topic to px4_msgs

[guillermoherreraf]

Hello @TSC21. I hope you are doing fine.

I'm trying to add a custom topic to px4_msgs based on a uORB topic that I created in the PX4 firmware. However, I have not yet managed to make it work. I know the uORB topic on the PX4 firmware works fine because I manage to use it with MAVLink. However, I would like to add some autonomous control capability with ROS2 running on a companion computer. The client is running on physical hardware (CUAV V5 nano) and I'm running the agent on a Linux machine (Ubuntu 20 and ROS Foxy). I'm running the bridge in serial configuration (UART).

First of all I generated the CustomCmd.msg with the uorb_to_ros_msgs.py script located in px4-ws/msg/tools. I copied the generated file into the px4_ros_com_ros2/src/px4_msgs/msg folder.

I also went to the generated agent folder in the PX4 firmware workspace, px4-ws/build/<target-platform>/src/modules/micrortps_bridge/micrortps_agent and copied the 6 generated files into the px4_ros_com_ros2/src/px4_ros_com/src/micrortps_agent folder

• custom_cmd.cpp
• custom_cmd.h
• custom_cmdPubSubTypes.cpp
• custom_cmdPubSubTypes.h
• custom_cmd_Subscriber.cpp
• custom_cmd_Subscriber.h

I copied the generated custom_cmd.idl and CustomCmd.msg files into the px4_ros_com_ros2/install/px4_msgs/share/px4_msgs/msg folder.

I copied the generated custom_cmd.idl into the px4_ros_com_ros2/buildl/px4_msgs/rosidl_adapter/px4_msgs/msg folder and added the following line of code, /home/user/px4_ros_com_ros2/build/px4_msgs/rosidl_adapter/px4_msgs:msg/crane_cmd.idl, into the px4_ros_com_ros2/buildl/px4_msgs/rosidl_adapter/px4_msgs.idls file.

On the PX4 firmware side, I added the following lines into the uorb_rtps_message_ids.yaml

  - msg: custom_cmd
    id: 141
    receive: true

And on the agent side I added

  - id: 141
    msg: CustomCmd
    receive: true

I recompiled the px4_ros_com_ros2 workspace after all these changes but I still do not manage to see my custom topic on the list which is displayed when running the agent.

I would appreciate any help as I've been stuck with this issue for a few days now. Thank you in advance!

[TSC21]

First of all I generated the CustomCmd.msg with the uorb_to_ros_msgs.py script located in px4-ws/msg/tools. I copied the generated file into the px4_ros_com_ros2/src/px4_msgs/msg folder.

So far so good.

I also went to the generated agent folder in the PX4 firmware workspace, px4-ws/build/<target-platform>/src/modules/micrortps_bridge/micrortps_agent and copied the 6 generated files into the px4_ros_com_ros2/src/px4_ros_com/src/micrortps_agent folder

• custom_cmd.cpp
• custom_cmd.h
• custom_cmdPubSubTypes.cpp
• custom_cmdPubSubTypes.h
• custom_cmd_Subscriber.cpp
• custom_cmd_Subscriber.h

I copied the generated custom_cmd.idl and CustomCmd.msg files into the px4_ros_com_ros2/install/px4_msgs/share/px4_msgs/msg folder.

I copied the generated custom_cmd.idl into the px4_ros_com_ros2/buildl/px4_msgs/rosidl_adapter/px4_msgs/msg folder and added the following line of code, /home/user/px4_ros_com_ros2/build/px4_msgs/rosidl_adapter/px4_msgs:msg/crane_cmd.idl, into the px4_ros_com_ros2/buildl/px4_msgs/rosidl_adapter/px4_msgs.idls file.

This is not how this is done. After you copied .msg to px4_msgs, you have to rebuild px4_msgs, and it will automatically generate the idl files and typesupport used by px4_ros_com to generate the micrortps_agent code.

On the PX4 firmware side, I added the following lines into the uorb_rtps_message_ids.yaml

  - msg: custom_cmd
    id: 141
    receive: true

And on the agent side I added

  - id: 141
    msg: CustomCmd
    receive: true

This step is also correct. So all together:

1. Create the uORB .msg file under PX4-Autopilot/msg/
2. Generate the ROS .msg using the uorb_to_ros_msgs.py script and copy it to px4_msgs under you colcon/ament workspace
3. Do the changes on both yaml files in PX4-Autopilot/msg/tools and px4_ros_com/templates as you did above
4. Build your colcon/ament workspace with both updated px4_ros_com and px4_msgs

[guillermoherreraf]

Thanks a lot for your help @TSC21 and your fast response. I managed to add the topic to the list when I run the agent. I will verify now that my messages actually arrive to the board.

[TSC21]

Thanks a lot for your help @TSC21 and your fast response. I managed to add the topic to the list when I run the agent. I will verify now that my messages actually arrive to the board.

Ok. If all is good, please feel free to close this issue.

[karishmapatnaik]

Thank you for the response! I could get it working too by following the above steps.

[karishmapatnaik]

Hi, Continuing on this issue, I tried the above and I can see the topics in the Rqt window under topics of the agent. However, as soon as I start the client node from px4 console, the following appears on the agent terminal and there is no data inflow when subscribed to this new topic: Unexpected topic ID 'xxx' to publish Please make sure the agent is capable of parsing the message associated to the topic ID 'xxx'. Is this a warning of some sort or is it directly related to the issue I am facing? I built the colcon workspace multiple times and the yaml files have been changed to include the msg IDs on both px4/msg/tools and px4_ros_com/templates . Also, I could verify from an external module that the new uORB topic is successfully publishing data, but I have issue sending it over to ROS2. Any help is appreciated, thanks a lot. The msg IDs are, on client side:

• msg: custom_msg id: 165 send: true On agent side
• id: 165 msg: CustomMsg send: true

[karishmapatnaik]

Update: I had to clean and build the colcon ws and it works!

[guillermoherreraf]

Hello again @TSC21 Hope you are doing well. I'm trying to publish (directly from the terminal) to the custom cmd topic I created a few weeks ago. When I start publishing, in the terminal running the agent it indicates "subscriber matched", but I'm not receiving the commands on the PX4 firmware side. [micrortps_agent] CustomCmd subscriber matched Any clue what may be happening here?

[TSC21]

Hello again @TSC21 Hope you are doing well. I'm trying to publish (directly from the terminal) to the custom cmd topic I created a few weeks ago. When I start publishing, in the terminal running the agent it indicates "subscriber matched", but I'm not receiving the commands on the PX4 firmware side. [micrortps_agent] CustomCmd subscriber matched Any clue what may be happening here?

Hard to tell without more context. Do you have the micrortps_client running and setup properly? Do you have that same topic being published on the micrortps_client? You need to make sure that your client is able to receive the message ID 141.

Also this is not related to this repo in specific so I ask you to move this to px4_ros_com issues.