In the early days of GUI interfaces, one common type of mouse was known as a “bus mouse”. This kind of mouse placed all the intelligence inside the computer or a decoder board, with little more than microswitches and rotary encoders inside the mouse itself.
Later, more and more smarts were moved into the mouse, with the transition to protocols like PS/2 on PCs, ADB on Macs, and finally USB as the standard since the late ‘90s.
In this guide, I’ll show how to use a CircuitPython board to convert the classic NeXT Computers bus mouse to work on a modern computer with USB HID.
The techniques in this guide may also be helpful in converting other classic bus mice to USB HID.
Since there are just a few pins used, the Adafruit QT Py form factor is perfect for this project. You should be able to use almost any device that supports CircuitPython and USB HID, but I chose the QT Py RP2040.
Note that if you have a NeXT Computers keyboard too, you can do a project that works with both keyboard and mouse in a daisy chain. Check out that guide here!