This Game Boy Cartridge Has Its Own OLED Screen

The original Nintendo Game Boy is now more than 30 years old, but it still has an active community of enthusiasts who make new hardware or modify existing hardware. That includes people who make new game cartridges. To make those, they use "repro" (short for "reproduction") PCBs that contain re-flashable chips and Game Boy-compatible edge connectors. FacelessTech noticed that those PCBs are quite compact and built a shortened Ghost Cart that is about half the height of a standard cartridge. For his newest project, he used that extra space to add an OLED screen to a Game Boy cartridge.

This build requires a repro flash cart board, but those are affordable commodity items. There are different designs on the market, but most take up less than half of a normal cartridge shell and those are the kind you want. The only other requirement is that the board needs to have accessible power pads. When the Game Boy turns on, it passes power to the cartridge. FacelessTech used that power to run the OLED screen and the Arduino that controls it. However, those pull too much power and interfere with flashing. That's why there is a hardware switch that disconnects the power wires when you want to flash a new game onto the cartridge.

The display is a small 128x32 OLED screen with a common SSD1306 driver. An Arduino Pro Micro controls that screen and can display whatever text you like. But it doesn't communicate with the flash cart at all, so you have to update the text if you flash a new game. A custom PCB connects the OLED to the Arduino, which avoids messy wiring. FacelessTech designed a 3D-printable cartridge shell to house those components. When inserted into an original Game Boy, the screen is visible on the back side. The cartridge does work with other Game Boy versions thanks to the standard backwards compatibility, but keep in mind that it will stick out on some models.

If you want to build your own cartridge like this one, FacelessTech uploaded the files to GitHub.