This Game Boy Flash Cart Features an RP2040 Microcontroller

Update 2-1-2024:

Zeraphim made improvements that let this flash cart work with Game Boy Color games. Information is available on the GitHub page and the Tindie store page.

In the world of retro gaming, a flash cart is a device that mimics a native game cartridge. The console thinks it is a standard cartridge with a static ROM chip, but the flash cart can actually store the ROM data from multiple games and serve it as necessary to the console. This not only lets players run downloaded ROMs, but also lets them carry multiple games in a single cartridge. If you're a Game Boy fan, Zeraphim designed an interesting flash cart built around a Raspberry Pi RP2040 microcontroller.

Most cartridges for older consoles stored the game files on ROM chips that couldn't be modified after the original data was written. That was because reliable rewriteable data storage that didn't require power for persistence wasn't available in the early days. Then later because it was more expensive and developers had no reason to give users the ability to rewrite data. But modern flash storage is cheap and plentiful, so flash carts are very practical — though the legality of sourcing ROM data is quite controversial.

This particular flash cart uses a Raspberry Pi RP2040 microcontroller as a bridge between the ROM data and the Game Boy. It has 16MB of QSPI flash storage, which is enough for two 8MB game ROMs. You can fit more if the games are smaller. However, the QSPI flash storage is relatively slow and so this flash cart isn't suitable for games that utilize the Game Boy Color's double speed mode.

You may also have issues with power if your Game Boy has an IPS screen mod, backlight, or other mod that increases the power draw. This flash cart requires more power than a real game cartridge, so it pushes the limit of what a Game Boy can supply and those mods could nudge it past the limit.

To use this flash cart, just connect it to your PC via a USB cable and use the WebUSB tool to copy the ROMs into the flash storage. Then insert the cartridge into your Game Boy. When you boot it up, you'll see a simple interface that lets you select any ROM in flash storage.

Zeraphim's RP2040 flash cart is available on Tindie for $30. It is also open source, so you can build your own using the files on GitHub.