Spindle PWM / PDM glitch

Hi all,

I am at the beginning of a LinuxCNC setup phase. I am using a parallel port to control the motors.

I am having an issue with the Spindle speed - every few seconds (randomly) it momentarily increases speed, then comes back down. It's only very brief.

I have placed an oscilloscope onto the PWM signal, I can that the PC is generating a single extra wide pulse, which is making this happen.

It does the same if I use PDM, or vary the frequency for PWM (100, 500, 1000Hz).

Can anyone help with this issue?

Kind regards
Pedro

 

Thank you for your reply @tommylight.

My bad - for some unknown reason, the BIOS had the PCI bus frequency at 333MHz. I've put it back to the standard 100MHz - all good now.

Where do I find the latency warnings?

Kind regards
Pedro