Took me a while but I now have it stepping

Not usefully stepping, just moving back and forth in 4 axes at 4 different speeds, over and over again. Looking good.

I am running everything on one timer interrupt. The interrupt collects 4 absolute co-ordinates from the buffer, along with a couple of speeds. It moves there. It comes back for more. Simples.

I was thinking to make the Z and W axes optional but there is no point it's so blooming fast. 40kHz step rates look easy, I could probably wind it up to 70kHz mid line. I usually run at 3kHz top whack.

These ARM Coretex processors may have a bit of a vertical learning curve but are well worth the effort. They have so many built in goodies I am barely scratching the surface.