To build the adapter, the following components are necessary:
The cable has colored wires, but color coding is not guaranteed and has to be checked with a multimeter in continuity mode. Unused wires have to be isolated. A good way to do this is putting a thin heat shrink tube over a folded wire with isolation intact.
The components are to be wired as follows:
Make sure the two PCBs are well isolated from each other.
Uploading the firmware is done in the usual manner, i.e. the Pi is connected to a PC via a micro USB cable while BOOTSEL button is pressed. The Pi appears as USB flash drive and usb_to_ps1_mouse.uf2 is copied to it (https://github.com/Franticware/usb-to-playstation-mouse/releases/latest). USB mouse must not be connected to the adapter while programming (obviously).
https://hackaday.com/2022/07/12/pi-pico-provides-practical-playstation-pointing/
https://www.high-voltage.cz/sortky/potrebujete-playstation-mouse-zbastlete-si-ji/
To express your support of this project, you can use your favorite service to listen to a music track I produced. It is not much, but it is the only digital product I am offering commercially as of writing this. Thank you!
Share your build here: https://github.com/Franticware/usb-to-playstation-mouse/discussions/1
@deefha for lending me his original SCPH-1090 PlayStation Mouse