The system is actually pretty simple: it comes down to a stripped down cheapo USB keyboard, with custom switches and a board.
It's pretty easy, remove the tabs or the screws and take everything out of the case. At this point you should trace all the keys you need by looking at the traces top and bottom. I chose to save the keys I needed using the binary system for the two traces that are connected. assets/traces.csv stores this data for my keyboard (Trust Classicline BE.). (images for that keyboard assets/img)
At this point you can connect two wires to the traces that are the wanted keys, and in the middle a press switch that can easily be pushed, or for some things you could add a toggle switch, but you'll probably have to check your software repeat rate.
What I've bought:
- 8 three-position flip switches at €1 per
These switches are pretty expensive, you better buy them on aliexpress or some other chinese website to keep costs lower.
You can then layout the switches on some board, my design will be in design.svg [WIP] (first sketch is at sketch.jpg).
