I'm very interested in this, but then, I am a techy...

It's not because of the start/speed control aspect, as this is pretty straightforward if you have a BOB or motion controller with adequate analogue output. OK, linearity might not be absolutely spot-on but I doubt that for most practical purposes that matters. However, the idea of being able to read back VFD parameters (spindle speed, etc) to display on the PC screen sounds attractive. Personally, I would not have considered this because I had no idea what a Mach3 brain was so would have never gone looking for this kind of information. I've probably missed something obvious, but I don't find the Mach3 documentation leaps out at me. Easy enough to do the basics but you seem to be somewhat on your own if you go just a little off-piste. For example, do a Google search for "mach3 brain" and the best result seems to be a YouTube video. Personally, I would rather have a decent manual in front of me!

But maybe I've just missed some hidden site full of Mach3 docs, so if anyone can tell me where it is... In the meantime, I shall follow this thread with interest.