Is the schematics for the electronics available somewhere? I like to add auto-levelling to my Vertex, but I need to know which inputs I can use…
Looking into the firmware, it seems that the firmware supports a 3drag controller. But as far as I can see, the 3drag controller only support 4 steppers, and with 2 nozzles I guess 5 steppers are needed?
Ahh!!! Thank you raby! 
The Vertex board have a connector with free pins (it seems its C2 on board),the row of pins under zStop in the schematic. Please keep us updated on progress and share your implementation. I guess many of us would like to “steel with pride”.
I think I will simply add the z-probe it in serial to the current z stop switch… I will of course share anything I come up with…