[svofski] has a friend who is a pixel artist. They really wanted to try out their skills on a c64, but were missing a mouse. The original mouse for the c64 was not only serial, but used a different method of communication than more modern mice. [svofski] built this adapter to translate the ps/2 data to something the c64 can use. The writeup describes the build in detail and even has the PCB and source code available for download.