Your mouse once understood two protocols. What's your excuse? Before Bluetooth and USB, computers had PS/2 ports. Microsoft ...

[danjovic] has you covered with the open-source EXPS/2 keyboard adapter. It will allow you to connect either a PS/2 keyboard or a USB keyboard in fallback mode to the Expert using an ATMega328P ...

There was a time when if you bought a USB mouse, in the box was also an adapter to allow it to be used with the older PS/2 interface. And if you were to go back a few more years into the past ...