Paul -- I'm very interested in this. I'd love a USB keyboard adapter that acts like an LK201.
If anyone wants a PS/2 keyboard adapter that emulates an LK201, there's Peter Bosch's Arduino Nano based lk201emu: https://github.com/peterbjornx/lk201emu His writeup on this is still in the Wayback Machine: https://web.archive.org/web/20180703165508/https://peterbjornx.nl/vtkbd/ I can no longer find a copy of Peter's schematic for this online, but at some point I grabbed a copy of it, which I'm attaching here as schem.pdf . -- Ron