I really wanted a PS/2 to Amiga adapter, so I ended up making this PCB in Eagle CAD based on information freely available on the Internet. I ended up making one that can use both USB and PS/2 connector, and the option to change between Amiga and Atari ST mode with jumpers. It also works on Commodore 64 in certain applications.
This thing work on a lot of USB mouses, but not all. It requires the mouse have the PS/2 protocol to work. A lot of mouses with PS/2 plug also included a PS/2 to USB adapter. Thats a good indicator to see if it works.
This is plug and play. No need to install drivers.
It does fit the Atari too. I had to make it super slim, because of the way they designed the case.
This is how I assemble these.
From the left, you can see I start with the Microchip. Then I move on to solder the DB-9 connector. Third, I do the capacitor, then the jumper pins. Lastly, I decide wether to install a USB or PS/2 socket. I do it like this because it is easier to install the smallest components first, moving over to the bigger last.
This image shows the two different modes. To the Left its set to Amiga mode, and to the right its set to Atari mode.
This project with PCB and parts can be purchased on ebay: https://www.ebay.com/usr/kirsti_73
or from Sellmyretro.com