This should cover every Nintendo game cartridge, but it was made specifically for the Game Boy (DMG/Color/Advance). It currently just counts up the address pins and reads the data, with no defined range to read from.
Next hardware step is designing an adapter to map the pins for each console, and then making a PCB for both.
Next software step is writing cases for each of the memory mappers used in the cartridges... For each console... so only ~50 cases...
I wanted to make this because these universal readers cost ~$150-200 including adapters. Instead, I decided to spend $30 + $1000+ of my time
I don't have either for the actual cartridge reading, only specs for memory mappers. I found a pinout of the cartridge and I'm just toggling the 6 control pins until things work to find out how to read data. I'm still not 100% sure how they work or their timings.
I'll make a writeup and YT video when I'm done documenting it. I couldn't find any good information about it online besides some writeups that seemed to leave out information on the control pins, or old sites on archive.org, so hopefully it'll help someone else.