I have had a turtlebot 3 for over a year. It was running ok. I decided to upgrade from ROS to ROS2. I followed instructions on the website for installing eloquent on my pc (already running ubuntu 18.4) and ubtunu server 18.04 on raspberry pi. Then I installed eloquent on the pi. I followed the setup and bring up instructions from the website. the opencr runs fine and I can teleop fine. But the LDS is not working. When I turn on the power of the turtlebot3 on the LDS turns maybe 1/8 turn. When I shutdown the pi sometimes it also turns a bit. I confirmed the serial converter board is on ttyUSB0 . I confirmed its using the same speed and port as before when it was working. I set the permisions +ag=rw and ll shows the group dialout has rw on /dev/ttyUSB0 the ubuntu user is a member of dialout. I have tried to check the connect using minicom and I get no response to the b or e command.

Any suggestions.

The fact that the motor turn a little tells me the power is ok and that some pin temporarily turns the motor on before it is turned off. I initially though it was a comms permission issue due to the new raspberry pi os. But I do not think that is the issue.