Limit Switch Issues

I wonder if anyone here can help me figure out what's going on with my machine inputs?

I've been trying to get limit switches working with my machine and running in to some issues. I have proximity limit switches and a Leadshine MX4660 driver. I have the switches hooked up to the inputs on the driver. I'm able to see that the switches are tripping correctly (they have indicator LEDs) and I can see that the voltage drops from near 12v to 0.2v or so to ground (using a multimeter on the input).

However, some strange things are happening on the software side. I configured linuxcnc to map the inputs to homing/limit. And indeed if I jog to trigger the limit, perhaps 1 in 3 times I will see the emergency shutoff trigger as expected. But obviously if I try to autohome, the system runs itself into the bumper. Furthermore, trying to use the HAL meter, I always see the pin state as true (expected when the sensor isn't triggering since it's +12v), and I always see the homing/limit state as false.

The fact that it sometimes triggers the limit condition (and pops up the correct error with either the X or Y axis) is super weird. The voltages I measure with my multimeter (at least at the input to the driver - I don't know how to measure the parallel port voltages) are extremely consistent, so I don't think there's a short or something.

Does anybody have a clue what's going wrong here? Any better place to ask?

Thanks in advance

Some things to check...

Are the proximity switches getting the proper supply voltage per their datasheet?

Look at the hal file for your configuration and make sure that the correct function names are assigned to the correct parallel port pins....
I have seen in my own experience recently with wheezy 2.7 pncconf doesn't configure things correctly sometimes so it's always good to check your hal and ini files to be sure there are no obvious errors.

Bogie