Thanks gents. My knowledge of electronics is a bit lacking so I would be hesitant to try and split the built in encoder output to the ESS driver and use it into an arduino or something. The shaft does run through the stepper but the build in encoder is mounted on that back part. Haven't fiddled with it in a while but if I recall correctly you can plot the encoder position on those graphs in protune so I'll drop them an email and ask if they are willing to give a little insight into the serial protocol. Did not even think about the absolute/incremental thing. These are likely incremetal so I guess its not going to be very helpful for something like zeroing.

What actually triggered this search again was the laser scanning thread. I bought a laser distance sensor several years back but it was never practical to use as there's no way I could get a real-time xy in mach3 via vb script so the best I could do was to stop and read hight at each xy in the loop which defeats the purpose of using a sensor that can pump height at a reasonable rate. I just ended up with an an expensive probe and was hoping to toy with that again.