This is a PS/2 to Mac Plus keyboard adapter. It uses an ATtiny806 to convert the scan codes between the two. The code to support this adapter can be found on my github repository.

• The microcontroller is an ATtiny806 in a VQFN package.
• The 10u and .1u capacitors are in a 0603 package.
• The PS/2 adapter is a Kycon KMDGX-6S-BS
• The RJ10 jack is a Wurth Elektronik 615004143821
• The code for this project is based on trekawek’s mac-plus-ps2 project.

The RJ10 cable that connects the adapter and keyboard must be a pass-through cable like what was used with the original keyboard. RJ10 telephone handset cables, while they fit the RJ10 jack, are crossover cables. You would need to cut and re-crimp one end of such a cable in order to make it work with this adapter. Otherwise you risk damaging your Mac and this adapter.

You may find some sellers on eBay who produce such cables specifically for the Mac Plus. Alternatively you could make one yourself (as I did) with these items:

• Telephone Handset Cord 2-Pack
• Transparent RJ9 Telephone Cable Plug
• Multifunction Ratcheting Crimper for Web and Phone

NOTE: RJ9, RJ10, and RJ22 are all basically the same thing. They are all 4P4C (4 Position 4 Conductor) connectors and will fit the Mac Plus and this adapter.