Laser Not Working with MPCNC/Marlin

I am able to control my MPCNC and laser in Repetier without issues. However, I can’t get Lightburn to activate the laser. I can move the MPCNC X and Y coordinates, but when I hit button to test fire, nothing happens. When I play a file, the machine moves around but does not fire laser. I remapped pins in Marlin using the fan. Selected M106/107 for controlling laser in Lightburn. Still nothing.

Any ideas?

Do you know what GCode instructions it requires to turn on / off the laser? What does Repetier emit for that?

M107 and M106
M106 P0 S255
M107 P0

What is the ‘P0’ part for? I’ve never seen that before.

I believe that is just telling the laser to go to 0 power.

No, that line is M106 (laser on) S255 (power value). P0 appears to be “tool index zero”, but that’s the default, so it shouldn’t be required. (And, I have seen it before - we even support different tool indices, I just very rarely use Marlin)

Draw a box in LightBurn, and click the ‘Save GCode’ button, then look at the resulting file in a text editor and compare that to what Repetier generates. There’s nothing magic here - if you compare the GCode from the two programs it should be easy to see what’s different between them.

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