I have a 3 axis machine, with a bipolar Y axis. When I home all the axes, the X and Z will do the little back and forth dance. I can monitor the pins (thanks to PCW_Mesa) and see them go high and low.

The problem comes in when I try to home the Y axis. Both steppers run the guides down to 0, hit the hall effect sensors, and stop. I can see the pin (12) for Y Home go high, but EMC doesn't seem to detect it. Instead, it just keeps "moving" the virtual cutting head and showing the position in the window as -6, -8, -12, etc.

Does anyone have any ideas on how I can interrogate EMC at a lower level to see why it's not paying attention to this signal?