screening / glitchy operation - sanity check

[dsc]

I've done some further testing on this, here's my findings:

1) as soon as I plug the DC supply in, there's noise on the PIC lines. It doesn't matter if the PIC lines connected to the driver or not, the noise is still there:



It's periodical, with a period of 11.5us, which gives a frequency of around 87kHz.

2) plugging the PIC control lines to the driver, causes the low levels to jump up by around 100mV, I wasn't expecting that to be honest:



3) there's loads of spikes on top of the PWM signal, see here:



Not sure this makes a lot of difference, the high level trigger for the HBS86 is > 3.5VDC and low is < 0.5VDC, so it should behave itself.

Any ideas on how to tame this? screening to earth doesn't seem to affect the noise at all. I've also tried ferrites, with not a lot of luck.

Regards,
dsc.