I once acquired a Macintosh Plus in a pretty good condition locally, but neither with a mouse nor keyboard. A keyboard show up some weeks later, but I struggled to find a compatible mouse locally in Switzerland.
From my undergrad student time, I somehow recalled that early optical mouse sensors actually had quadrature outputs, simulating the behavior of mechnical mice with a shutter wheel. That should fit!
The project was triggered after digging out the mouse, a DB-9 connector and an old Ethernet cable from an E-Waste container at work. (here already assembled together)
![notion image](https://www.notion.so/image/https%3A%2F%2Fs3-us-west-2.amazonaws.com%2Fsecure.notion-static.com%2F5999ad3c-0a79-46be-b98c-2eb94dfe4d04%2FUntitled.png?table=block&id=d9308714-bf69-4056-ae0f-637b1b287aaa&cache=v2)
Inside, the ADNS-2051 optical mouse chip directly outputs quadrature signals as required by a Macintosh. No conversion using a microcontroller or any other circuitry is needed.
![notion image](https://www.notion.so/image/https%3A%2F%2Fs3-us-west-2.amazonaws.com%2Fsecure.notion-static.com%2Fe4390986-57a9-40c4-ba06-909ea146e523%2FUntitled.png?table=block&id=345e82da-18b9-4f61-940d-870af58dfdd2&cache=v2)
Beautiful, ADNS-2051 actually directly outputs quadrature signals:
![notion image](https://www.notion.so/image/https%3A%2F%2Fs3-us-west-2.amazonaws.com%2Fsecure.notion-static.com%2Fe65224f4-5b18-429c-9630-839bc71605d1%2FUntitled.png?table=block&id=4c54c560-3ede-443b-a843-8d29d8e53d04&cache=v2)
So it's enough to solder X1/X2/Y1/Y2 lines to the chip itself (XA/XB/YA/YB). Two blue wires tapped into ground, Orange one to +5V and Orange-White to the button tactile switch.
Ready to use it with my faithful Plus :)
![notion image](https://www.notion.so/image/https%3A%2F%2Fs3-us-west-2.amazonaws.com%2Fsecure.notion-static.com%2Fabd06328-e2cd-4890-8c99-41671a77fc3e%2FUntitled.png?table=block&id=1352d613-9b75-4bc7-85f5-cab0c93e2b5c&cache=v2)
Aaaand it works!
![notion image](https://www.notion.so/image/https%3A%2F%2Fs3-us-west-2.amazonaws.com%2Fsecure.notion-static.com%2Fe5c7bd59-a740-4e68-a632-64e95132ef34%2Fu3pkhcsuehw61.gif?table=block&id=c2ed8255-e510-495b-8e04-36e8119171c2&cache=v2)