Hi Ian,
Thanks so much for your detailed response and ideas. We are hoping to build several more machines in the future, so the Arduino Mega will be on our list of potential candidates as we evaluate machine #2. Considering that for 50 outputs we need 100 different vbscripts (one to turn on, one to turn off for each output) it would be nice to use just an S word. Perhaps Mach 4 will support passing arguments to VB macros?
Am I correct in understanding that if we want to use the Arduino Mega I would need to learn a bit of C programming?
One thing that has been really nice about using the ModIO is the great customer support that Peter Homann provides.
Thanks so much,
Sam