So I still have the old cable for the IR probe laying around. I plugged it in and the IR probe works as intended now. So there has got to be something wrong in the cable I made.
I measure the resistance on all the wires for the IR probe, and they are 0.3 ohms or less. I plugged the new cable into the duet and measured a voltage of ~3.16V between the data pin and ground, it showed a reading on the panel due of around P960. I plugged the old cable into the duet and measured a voltage of ~0.660V between the data pin and ground, it showed a reading on the panel due of around P170.
I'm not sure what could be causing this. I pinned the connectors correctly. The older cable is longer and has portions of cat5 on it. Any idea? I'd really like to use the new cable.
What's really confusing is that with the old wire, the IR probe works exactly as intended, showing 0, then only showing 535/536, then showing 1000. With the new wire the value bounces all over the place.