I wanted to optimize the PCB for the usual Amiga mouse adapter. Using a SOIC-18 footprint IC I was able to make it so small that the limiting factor is the size of the USB connector.

I have ordered a set of these PCBs for myself and testet that they work before I made this project page.

Program the PIC before soldering to the PCB. I just hold the IC tightly onto an adaptor board for my TL866II Plus to program.

Bend the legs of the USB-A connector back and cut off 1 mm of the ends before installing on the board. The metal casing should have a slot to allow this without shorting. Also straighten the side lugs so that they go through the oval holes.

Requires a mouse with PS/2 protocol and USB connector. Alternatively the mouse wires can be soldered directly to the PCB and a small zip tie through the oval holes to secure the cable. Make sure you check the pinout to align with the pads first. Pin 7 of the DB9 is 5V and pin 8 is ground.

Here are 3D-printable cases for it when soldering the mouse sires directly to the PCB:

https://cults3d.com/en/3d-model/various/housing-for-micro-amiga-mouse-adapter

Credits:

Ultimate Amiga PS/2 Wheel Mouse Controller by Denis Sotchenko (https://web.archive.org/web/20191018184134/http://ps2m.sotchenko.ru/index.html)

USB schematic by Henryk Richter (http://bax.comlab.uni-rostock.de/en/hardware/ps2-amiga-maus/)

Micro circuit board design by Tor Arne Hustvedt