MrFrenchLame built a Game Boy development cartridge that cuts the wait out of writing code. The cart holds a boot ROM, RAM, a reset button and a switch that swaps the ROM out for the RAM. A program on a PC talks to the bootloader over a parallel port and sends a new build into the cart’s RAM in a few seconds.

The transferred program uses the same bootloader at its start, a reset drops it back into transfer mode without reusing the switch. If a hello doesn’t arrive before a timeout, the bootloader hands control to the program already in RAM. The whole cycle is a PC, a Game Boy and a cable: compile with F7, send with F5, press reset.

It’s limited to 32K for now, though MrFrenchLame has MBC5 mappers in reserve. The parallel port is the other catch, and the post points at the GBlink WebUSB interface and an RP2040 cartridge project as workarounds. Hardware details are promised in part 2 and the software in part 3.

See more at mrfrenchlame.fr. Via Hackaday.