The Super Nintendo aka SNES was an iconic console of the 16-bit era. The Nintendo Mouse was originally developed as a bundled accessory for Mario Paint. It has two buttons and an SNES connector. Later, third party games would also use this mouse accessory.
In this guide, I'll show how to connect the SNES mouse (actually, a modern third-party version known as the the Hyper Click Retro Style Mouse) to a PC or Mac using CircuitPython to convert the original protocol into USB HID. As far as I know, this will also work with the original mouse, but as I don't own one, I haven't tested it.
Instead of using a difficult-to-source connector and custom PCB, this guide takes the approach of using a SNES controller extension cable which is soldered to the microcontroller board.
While this guide is written for the QT Py RP2040, the controller communicates using the standard SPI protocol, which means it's possible to adapt the code to just about any CircuitPython board simply by changing the pins that are used.
Once you've got the project wired up, it's also a great platform for connecting any other SNES compatible controller — just modify the source code according to the data the controller sends.