I've been refreshing the range of USB keyboards I sell in my Etsy store. Every time I get a new batch of boards, I always tweak the design a bit. I'm refining the design, and adding new features each time. This time, I updated all of them to bring them all up to a similar level. I had added mode switches to the Commodore 64 and ZX Spectrum, but in various different ways. I have now settled on one standard set of options and rolled that out across all the designs.
first USB keyboard I built was the ZX81, about 4 or 5 years ago. I wrote it up a year or so later on the blog. Things have changed quite a bit since then.
Tynemouth Software Etsy store, or get one with an integrated Raspberry Pi. Or you can order a ZX81 USB keyboard controller below: