Hi.
I just measured it, with and without the limits connected, and I get 0v between GND and all pins except P13, at this one I get 26v. P13 happens to be the probe, but I disconected the cable, and same reading.
I don.t know how I could have burned anything, as I just run the usb cable from the pc, and the 12v supply.

Yet the limits, estop and probe work fine. No more false signals. :)