I’m picky about my keyboards. I like them wireless, I like a full layout, and I like good mechanical switches. This is a hard combination to find for sale, as most mechanical keyboards nowadays are marketed towards gamers, and they don’t like the potential latency of wireless keyboards. Even the hobbyist DIY keyboard resources typically revolve around minimalist layouts.
So fine, I’ll make something. This is probably for the best anyway, since my favorite keyswitches are no longer being made. My favorites were the original Apple Extended Keyboard (using undamped ALPS switches), and the lesser-known line of keyboards using the NMB “space invaders” switches. My college roommate had one of those NMB keyboards with his 80286 PC, and I kept that keyboard to this day; a few years ago I hardwired a PS2-to-USB adapter inside it.
I wanted wireless, though, and there were a few different ways of achieving this. The first pass was very hacky. I picked up a cheap $20 logitech wireless keyboard that had a full layout, and mapped out the matrix that its keys used. (Keyboards work by having a grid of rows and columns, and every time you press a key it connects that row and that column. A microcontroller scans across them, looking for connections. The layout of rows/columns to keys varies widely across models, based on PCB layout and other factors.) At this point I could have designed a new PCB for a keyboard that used the same matrix, and attached it to the controller board from the logitech keyboard, but PCB manufacturers charge by the square inch, and these keyboards are large.
Instead, I took my test Apple keyboard, and removed its PCB entirely, and hand-wired connections between keys to match the Logitech matrix. Lest things get too crowded between keys, I used thin magnet wire to connect them. It was not pretty on the back. At this point the only thing holding the keys in was the fact that some (especially early) mechanical keyboards have the keys mounted through a metal plate before being connected to the PCB.
Well, it worked, but the metal plate didn’t provide enough stability; I had to pop a keycap off to fix a flaky keyswitch, and it ended up pulling the whole keyswitch out of the plate, ripping the thin magnet wires out of the back in the process.
If I were to try this approach again, I’d grab a bunch of the enabler boards and connect them with hookup wire or something. But I wasn’t going to try this approach again; for subsequent versions, I wanted to replace the original keyboard’s microcontroller with something that would interface with a modern bluetooth-enabled microcontroller. I had all the information I needed about the Apple keyboard from this site, but those are more expensive for tinkering, so I focused on the NMB models. (Quick note, though: if you like the “clacky” feel of the first Apple Extended Keyboard as opposed to the softened sound and feel of the AEK2, you can take the AEK2, open up each keyswitch, and remove a couple of rubber dampers from each one, and reassemble.)