I2C_4 seemingly broken

[jgoney]

I posted on the forum about this here, but tl;dr is that I can't get I2C_4 to work at all. I have no problems getting I2C_1 to work (on either set of supported pins), but I2C_4 does not work for me on either pin set.

I made a Gist for it here. If anyone could try it out just to sanity check it for me, that would already be a huge help.

Please let me know if you need any additional info or context.