The reason I want a step and dir output is that I want the contraption to be my handwheel when the PC is not there and I want to use the mill in manual mode. I just want to feed the steppers with pulses from my "handwheels" to make it a non-CNC mill in "fly-by-wire" mode. I don't have handwheels anymore. If I had, the axes would creep when milling because of the high efficiency of the ballscrews, it must be kept in place by active motors.

I also want the AVR to send continous pulses on command (button) to regain the auto-feed I had to remove because it was incompatible with the ballscrews.

Finally I would like to be able to send "cheater pulses" to reposition after toolchange. I've seen in the forums that this could be a bit inconvenient using some control programs.

Greg: If I run a resistor from the output back to the +input, that would give hysteresis, not reduced gain? I think that's what Mariss say in #16. If I run it back to the -input, it will reduce gain. Am I right?

If your code is in C, it would be very interesting. If its PIC assembly, I'm afraid it will be about as clear to me that this thread is to HuFlungDung. :-) PIC assembly is one reason I use AVR.