OpenStickFirmware is open source software designed to handle any and all tasks required in a custom Fight Stick. It can handle being the brains of your entire stick, or just handling the bells and whistles while your Brook board talks to your console.
About The Project
OSF is built with CircuitPython and intended to run on any board it supports. Not only does this make the customization process friendlier for non-developers, but it also means a significant amount of power can be had for a mere four dollars.
Once you're installed CircuitPython on your device of choice, setting up OSF is as simple as downloading the files from this repository and placing them on the drive that appears on your computer.
There's no need to compile anything or download additional software.
Basic configuration is handled in config.py. In here, you can configure whether or not your board has WS2812b (or similar) LEDs, which pins each button is connected to and so on.
Currently, the only required buttons are left, down, right and up. Anything you don't need can just be commented out.
See the open issues for a list of proposed features (and known issues).