Spurious values in joystick reads

[caternuson]

NOTE This issue by @ATMakersBill transferred from original repo.

Every once in a while joystick x and y readings jump to 255. It seems like it's every 5-10 seconds.

I added a check to simply ignore any reading where either is exactly 255. We should either find a way to detect these (perhaps there's a pattern) or just filter them at the library level. That would require caching the values and keeping old ones if the read was invalid (or just re-reading).

[caternuson]

@ATMakersBill I could not recreate this using an Itsy M4 and running the nunchuk_simpletest.py example. I let it run for several minutes and never saw spurious joystick read values.

If this is still happening and you can recreate it, please provide details on hardware setup and test code.

[caternuson]

Closing for now. Can re-open if this happens again and can be re-created.