By Allison Parrish I set out a while ago to make a Game Boy cartridge from scratch. This is not a novel goal; bootleg Game Boy cartridges have existed almost as long as the Game Boy itself has, and there are many third-party cartridges now available for purchase, or that have copyleft designs. But I wanted to know how Game Boy cartridges work. I was also excited to use the PIO functionality of the RP2040 microcontroller. Now, after a few years (!) of research and design, I have made my design fo...