For instance, a decent PS/2 to USB adapter will cost you as much as the Zero did, if not more. But if you just need to drive your Pi Zero from your old Model M (we hear you!) you’ve got to do it ...

The guys at Nerdkits have put together this tutorial on connecting a PS/2 keyboard to a microcontroller. Though this tutorial is written for one of the kits they sell, you should be able to apply ...