I think I’ve got the same problem with my lowrider 3 running on an SKR Pro, although I checked all settings mentioned above I don’t get it to setup a serial communication with the board.
I used the Marlin setup as pointed out but no comms.
With the GRBL setup there’s communication but laser isn’t working of course.
Could anyone upload there working machine settings so I can use those?
Please open a new topic, even for the same problem.
By riding on an existing topic it is less visible and not everyone that would want to help reads old threads marked as solved.
Can you provide the specifics of your machine?
Which machine type, which SKR board and Marlin firmware?
What communication is working (motion? Homing?) and what isn’t (Just the laser? No output or just low output?)