PCB milling machine

pgf wrote:

does EMC2 have a driver for direct phase control of unipolar motors? last i looked (many years ago) it did not. (i have some old code that worked with the old HAL interace that does this -- i haven't looked at getting it to work with "modern" HAL.)

Yes, there are a number of modes of the stepgen component that output direct phase drive info for unipolar motors (and bipolar, I think, with suitable interface circuits).
basic info here:
www.linuxcnc.org/docview/html/man/man9/stepgen.9.html
And a rather over-complicated version here:
www.linuxcnc.org/docview/html/hal_rtcomps.html#sec:Stepgen