Prusa: specific requirements on M106/M107 and incorrect M114 reading

[xmirakulix (X)]

Hi, I am a new user and tinkered around for a few days with different SW-packages, I must say I love Lightburn as of now. Unfortunately I have problems getting it to fully work with my retrofitted Prusa MK3S+

The Problem: the Prusa firmware spins the fan (and thus the laser) on M106 to 100% for a fraction of a second before going to the intended Sxx value, if the fan was off before. So I must avoid turning the laser off with M107, instead I need to send M106 S1.
It would really be great if I could set this in the machine settings when using a “Marlin” based device.

Workaround: Create a “Custom GCode” device, there I can set the required settings which brings me further, but then I run into another problem:

LB doesn’t evaluate the answer to an M114 correctly, thus the shown coordinates in the move tab always stay 0. I can consequently jog XYZ in one direction, but not backwards.
Console shows “X:60.00 Y:70.00 Z:0.15 E:0.00 Count X: 60.00 Y:70.00 Z:0.15 E:0.00” when I click the button to get the current position, but the position shown stays X 0 Y 0 Z 0 U 0

Can somebody help me getting my laser to work?

Details about my setup, tell me if any additional info required:

• Neje E40 on Prusa MK3S+ with FW 3.14.1
• Laser connected to part-fan of the printer (thus M106 to steer the PWM)
• LB 2.0.02 on MacOS, Connected via USB

[NicholasL (Nicholas Leqeta)]

@xmirakulix

LB doesn’t evaluate the answer to an M114 correctly, thus the shown coordinates in the move tab always stay 0. I can consequently jog XYZ in one direction, but not backwards.
Console shows “X:60.00 Y:70.00 Z:0.1

If you use the previous LightBurn version: 1.7.08, do the M114 coordinates come through into the Move Window properly? (I’ve had a couple of reports now that 2.0 has broken something with the M114 ‘Get Position’ values not being read into LightBurn Move Window as they previously did).

[xmirakulix (X)]

@NicholasL

If you use the previous LightBurn version: 1.7.08, do the M114 coordinates come through into the Move Window properly?

Yes, that part worked in 1.7

[RonO (Ron Ostafichuk)]

Can you check the device setting in LB 2.0.02 ? From the main menu, choose Laser Tools→Device Settings, then turn on the Machine coordinates option and exit. I reproduced the problem with my Marlin device, and this fixed it.