Poet, programmer, and game designer Allison Parrish has built a music instrument with a difference — by turning a Nintendo Game Boy Color into an optical theremin, as part of a project building and using a custom Raspberry Pi RP2040-equipped cartridge.
“Now that I can send values back and forth between [Nintendo] Game Boy software and the microcontroller on my custom Game Boy cart,” Parrish explains of the project, “I did what anyone in my situation would do: I made a Game Boy photoresistor theremin.”
The instrument is simple enough, and the heart of it is the Nintendo Game Boy Color itself — a handheld games console released in 1998, entirely unmodified and still fully compatible with the games for which it was designed. Rather than a game, though, its cartridge slot holds Parrish’s custom cart powered by a Raspberry Pi RP2040, trailing wires out to a solderless breadboard with a photoresistor. Wave your hand over the board to dim the light reaching the photoresistor, and listen to the Game Boy’s speaker respond.
Parrish’s custom cartridge goes beyond most so-called “flash carts” thanks to one very clever feature: “The [Raspberry Pi] RP2040 [microcontroller] is connected to SRAM CS2 (so software on the RP2040 can read AND write to the data bus),” she explains. There’s also an on-board tactile switch, accessible while the cartridge is inserted in the Game Boy, which can be used as a general-purpose input or to trigger multi-cart switching, and a USB Type-C connector for easy data transfer.
The theremin is powered by a custom cartridge hosting a Raspberry Pi RP2040 microcontroller. (📷: Allison Parrish)
This is far from the first time Parrish has experimented with Nintendo’s classic handheld hardware, either. Back in 2022 she showed off a device that never was: a Nintendo Game Boy Pocket SP, created by sawing a Game Boy Pocket motherboard in half and placing it in a clamshell case inspired by the later Game Boy Advance SP — using custom-designed flexible PCBs to route between the two halves of the original board.
More information on the project is available from Parrish’s Mastodon account, including a recent update showing the cartridge running a program created in her custom-written stack-based programming language.
