Robin,
Very nice work.
I've been playing with a similar idea, but took the approach of grabbing the position after it has been processed by the DRO. Your way is MUCH better. Also, buffering the signal back at the source is brilliant. It solves one of the biggest problems people have with their DROs, noise.
For faster positioning (I'm sure you've already considered this), you could do a hybrid control operation, where you use the stepper w/o feedback to get close, pause while the scale catches up, then finish with the scale providing the feedback.
May I be your US distributor?
- Don