This idea showed up on r/mk something like 8 months ago but didn't really get much response. The main issue with getting a split keyboard to work, especially a hand wired one, is getting two pieces of hardware to act as one. Ergodox and Lets Split both use a pair of controllers plus some io expander shenanigans (I think). So my newbie mind thought "why not just 'wire' two two boards together?" A single piece keyboard would have the 4 to 6 rows of wire running across and 6 to 8 columns that need to reach over to the controller. That means 10 to 14 wires. Network cable has 8 wires so that isn't enough. I've seen mention of a ribbon cable which presumably come in whatever wire count you need. But what about an hdmi cable? They have 19 wires which would be enough for almost anything.
Use a
breakout board on either half to make soldering easier and for easier transport. Just don't misplace your cable.
On a related note is there any reason 5 of the wires in the hdmi couldn't be used to act as a usb cable to add one to the slave side of the board which would allow the addition of a separate numberpad if desired? I'm not even sure if the USB header pins on the Teensy 3.5 or 3.6 would support that but it's an idea.
