Originally Posted by
tnimble
I second that. I've seen USB devices sending data, that is never recevied at all as soon as a realtime procees/thread is present. IMHO USB is only suited in CNC as a medium to sent (preprocessed) gcode to a trajectory controller.
Probably the most troubleless, inexpensive and simple to setup way would be to get one of the Mesa FPGA cards, a breakoutboard or optiisolator card for it. Install EMC2 start pncconf, select your FPGA card, select the SV12 or SVST8_4 firware configure 6 PWM generators, 0 STEP generators. Hook up the VSD-E's to the PWM+DIR and encoder inputs. Tune the torque loop in the VSD-E, put it in torque mode. Start EMC and tune the position loop. Hookup error outputs from the drives, e-stops etc to the GP IO pins and configure them, write some hal components, pyvcp, etc.