Hello, I also wish to know this. I tried connecting a switch to one of the axis(LX-, LX+, LY-,LY+,etc) to GND and actuating the switch does nothing on USB CNC. I also tried to jumper one of the axis to GND in an attempt to completely bypass the switch and this also didn't produce any visible change. I've searched the internet and found nothing about wiring limit switches to this particular board.