Since I couldn’t find the answer with an easy search 30 minutes before doing this, figured I’d post our findings here.
We tested how many buttons (boolean inputs) and POVs a single USB input connected to the driver station could have.
To conduct this test, we simulated a controller with 50 buttons using vJoy and printed to console it’s buttons with the joy.getRawButton(int) method and changed the values with the vJoy input mocker. That was all done on a 2019 imaged roboRIO.
We found that 32 boolean inputs was the highest amount it (the driver station, HID stuff, WPI internal classes, whatever) could handle.
We tested the same with POVs, but since vJoy only supports up to 4 POVs, we don’t know if any more than that are accessible. (4 POV angles were able to be read and printed out by the DS)