Debuging ROS on a Jetson Xavier

Question

I have configured ROS melodic based on the RACECARJ and MIT-Racecar Github repos. Everything runs perfectly on my desktop Linux 18.04 machine.

The script should be able to install the same also on my Nvdia Jetson Xavier with Jetpack 4.2. Everything runs without and error. My nodes (basically the motor controller and the PS3 controller) get detected. However, the car is not moving at all.

I have just started to work with ROS and have no clue how I have to debug this. Should I use Wireshark to compare which packages are received on the 11311 port on my desktop machine as well as on the Xavier? I'd like to see which messages the ROS is sending. I doubt it sends any at all.

I have read about using qtr to debug some stuff graphically. Sadly this didn't work so far. Despite installing ros-melodic-desktop-full with this script. qtr is unrecognized. I was already able to verify that each devices works on its own. I can send commands to the motorcontoller with python and I am able to read the joystick with jstest /dev/input/js0. Unplugging one of them when the ros-script is running gets immediately detected.

Answer 1

First thing's first

It is not qtr, it is rqt. I think you mean rqt_graph. Basically, it shows all of the ROS nodes, topics, and publishing and subscribing going on. If you type rqt and then press TAB, you can see all the options. I suggest you google rqt more.

Command line

Well, the first step is to make sure that all the ROS nodes are running.

rosnode list

Then I would look at the topics

rostopic list

You can then listen on the ROS topics using this command

rostopic echo /the_topic

You are looking for any missing or incorrect or unconnected ROS topics that need to be connected. That should get you going to start. I would make more recommendations, but this question is a bit broad for any more specific details.

(If this answer helped you, a check mark is appreciated :)