Posting my Pico controller code (see the bottom of this post for text file attachments) for SNES-to-2600 controller if anyone wants to look at it. When I have time, I'll add comments to it... sorry, I know how much everyone loves code with no comments.

I should really make a GitHub project for this. This was previously written for a single controller version (pic below), which I tested with multiple games an my local Retro game café - Replay Games.

The latest 4-controller monstrosity version of this can be seen in a photo below. I'm only using SNES controllers for testing because I haven't figured out yet how to do USB gamepad support. I'd really like to support SN30 Pro USB controllers by 8BitDo. But RAW USB controller communication is not my strong suit.

main.c i2c_helper.h

Non Technical Drawings of the Pico-based Monstrosity Schematic