laser diode is slighly on during axis moves

yes it sounds vague, but that's what's happening, the laser is connected to hm2_5i25.0.pwmgen.01...... and outputs appear on hm2_5i25.0.gpio.018.....
I am getting very light burning between movements of the head when the laser is commanded to be off (M68 E0 Q0)
it appears that there is small voltage fluctuations coming from the 5i25 P2 output whenever other pins are active, ie moving a joint.
I tried inverting the gpio but that put the laser on at max power, I tried a 470R resistor as a pull down on the pin (14 on P2) and that had no effect
other than this annoyance, everything is working fine.
so can anyone suggest why I get small voltage fluctuations on this output and can anything be done about it?
I can post my configs if that would help.
Eric

have you run the wiring next to the stepper. wiring?

it may be inductance

no I don't think so as I checked the output from P2 at the DB25 breakout board at the end of the DB25 cable from the 5i25 and it was jumping around even when the cable to the laser was disconnected. It seems to be steady at 0.5v when no joints are moving and the laser is off at that voltage and jumping up to 0.85v approx when I move a joint. giving a weak laser beam and that is causing the light burning when focused on the material.
I will however double check the layout, thanks for the thought

given you are using PWMGEN, what have you set the other pins at for the pwmgen?

linuxcnc.org/docs/devel/html/man/man9/hostmot2.9.html#pwmgen

Pwm cable from Mesa to laser module must be shielded if it is longer than say a meter. I would use shielded for any length, shield wired to ground on the box only on the controller side, leave shield on the laser side unconnected.
Power supplies will cause that, try to find an old laptop/ptinter/access poit/monitor power brick, those are properly shielded.
A friend had the same issue, just changing power supply fixed it.

My guess is that there is significant high frequency current flowing
in the 5I25 ground return. This may be from the step drives or a
switching power supply. This may be caused by not having a
single point ground.