ROS2 QoS settings are dynamic?

asked 2022-04-08 15:46:40 -0500

299 ●14 ●28 ●28 http://www.perfectsecurity.us/

Having trouble getting nodes on two computers communicating. One is Raspberry Pi and other is HP laptop. Wireless router is in another level and one room away. Machines can secure shell and ping, but ROS2 nodes don't show topics between the two machines. Both have Ubuntu 20.04 and Galactic. Could the problem be the QoS settings don't allow communication because of quality issues? If I move them both to same level (basement) as router, will settings update automatically? Can I change settings manually to allow communication?

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Short answer is "no", the QoS settings are not generally dynamic. Some tools find and report QoS problems, e.g., the "node graph" in rqt will show problems. Also try ros2 topic info -v /mytopic to see what's going on. I don't know how well these tools report on problems across machines.

clyde ( 2022-04-10 13:37:48 -0500 )edit

Also, if you haven't, be sure to try a simple talker / listener across machines, e.g., https://roboticsbackend.com/ros2-mult...

clyde ( 2022-04-10 13:38:12 -0500 )edit

Thank you for the comments!

Rodolfo8 ( 2022-04-12 15:20:43 -0500 )edit

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answered 2022-04-12 15:19:56 -0500

Rodolfo8

299 ●14 ●28 ●28 http://www.perfectsecurity.us/

I moved both computers to be nearer the access point and the problem was solved. It seems that clearly the wireless strength was not sufficient before. The Raspberry Pi antenna isn't strong, it's just a squiggle of copper in the corner of the tiny circuit board. When one mounts the board on the robot, if USB connections are "up", then often the antenna will be "down."

It would be nice if there were more feedback from the ROS2 DDS system about the connection strength, more than just "works" or "doesn't work." How hard would this feedback be to include? As I read about settings for QoS it sounds very complicated. I hardly know how to start to improve settings!

I could write a page or two, working with an expert, so that non-expert users may understand how to approach this matter.

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