Custom cnc/laser machine used to connect but now dows not

Hi all, Newb here :slight_smile: I have a custom build cnc/laser machine with a Bigtreetech SKR v1.3 motherboard running Marlin 2.0.7. My laser is a Neje 30w (7.5w output?).
I had a friend give me a copy of Lightburn and i had it installed and it would connect and see my machine over USB. I found out it was a “not so legal” copy so I uninstalled in and downloaded the trial version from the Lightburn website. I installed it, and manually set up my machine since it would not recognize it during the initial “find my machine” on startup of Lightburn. I don’t understand why the previously installed version would connect but the latest version will not. I’ve swapped out usb cables to no avail as well. Any ideas? Thanks!

Depending on the type of controller you have, you might have to manually choose the port that the laser is connected to, by clicking where you see ‘(Choose)’ in the Laser Window: Connecting to the Laser - LightBurn Software Documentation


You might also need to turn on the “Enable DTR signal” switch in Edit > Device Settings. Older versions had a bug where that setting was ignored and it was always on.

Thanks for your response. I managed to find the issue. I had forgotten to change the Laser control commands setting from m106/m107 to m3/m5. I did try toggling the DTR signal but didn’t seem to make much difference in my case. All seems to be working properly now. Thanks!