I am just working on this same thing, I used a PDMX spindle sensor and wired the signal up to the A axis home limit switch input on a Bob Cambell breakout board. The spindle sensor requires 5 volts but the breakout board had a 12 volt power supply for this sensor so I used a couple of resistors soldered in the wire to reduce this down to 5 volts. Set up the input signal for index to pin 15 in the ports and pins, at least that's what the cambell board uses for this input.