Touch probe woe's

[Neale]

It is a little-known and barely documented fact that there is one version of Mach3 that is able to support two probe inputs with independently-set parameters (active low, etc). It might well be easier to combine the two inputs electronically as already described here, but I bought a second-hand CNC mill whose control box had separate inputs for touch probe and height setter, so I needed to explore how it was done - particularly as I wanted to modify the probing routines to suit. I did consider the electronic signal combiner, but on my machine the input sockets were directly connected to a custom motherboard that would have been difficult to modify, and an outboard box would just have been a bit of a fiddle. And the existing machine ran with the "two input" configuration, so it needed exploration! By going through the provided probing routines, I found that they used an undocumented Mach3 feature that allowed a macro to switch between inputs to select an appropriate probe and I was able to adopt this to use in my own probing code. I wrote it up here.

If you feel happier with electronics than code, then the external signal combiner is probably the way to go, but I like fiddling with both and was happy to find a software solution!

Then I scrapped the ESS and replaced it with a UC300ETH and UCCNC software, which support two probe inputs out of the box, so the problem just went away!