PS/2 to MSX mouse with an Arduino Nano

I was able to put together a cheap PS/2-to-MSX mouse interface using an Arduino Nano. The project works by using the Arduino Nano as the bridge between a standard PS/2 mouse and the MSX mouse port.

The design is based on denjhang’s MSX Nano Mouse 2025 repository, which provides both the Gerber files for the PCB and the firmware source code. Having those files available made the build straightforward and inexpensive: I could order the board, assemble the small set of components, flash the Nano, and connect a PS/2 mouse.

I used a cheap Arduino Nano clone, so getting the firmware uploaded required a little experimentation in the Arduino IDE. The important part was selecting ATmega328P (Old Bootloader) as the processor option and using the 2014 .ino file from the repository.

I tested the adapter successfully in both SymbOS and GeoBench. In each case, the mouse was recognized and usable, making it a practical low-cost option for adding mouse support to an MSX setup.

If you want to build one yourself, the Gerber files, code, and project documentation are available in the MSX-nano-mouse-2025 repository.