What is SpaceFN and why you should give it a try
The SpaceFN concept - setting up your space key as a layer switch when held - is probably one of the most useful tweaks in the keyboard hobby. Let me explain how it works. My SpaceFN article on kbd.news made some rounds recently - quite surprisingly given the age of this concept. This piece you're reading is a condensed version of the full post. If you're left with unanswered questions, you'll most likely find the info you're looking for in the original write-up. On my imaginary top list of the most useful keyboard features, tweaks and hacks, SpaceFN would deserve a podium finish for sure. But what makes it so special? In short: SpaceFN is easy to implement, easy to learn, costs nothing, can be used with any keyboard, and can improve your productivity instantly. I will list its benefits below, but can state right at this point that the SpaceFN concept, setting up your space key as a layer switch when held, is clearly one of the most useful tweaks in the keyboard hobby....
Apr 30, 2024
edit: I missunderstood your 'macos' for 'macros' instead of "MacOS". I have no idea if it works in the boot options of MacOS. However, it works like a normal keyboard, so I don't expect anything special. For the USB MIDI, I don't know if you want this device to play midi sounds or if you want it to act like a piano to your computer. In both cases you will probably have to write software yourself.
QMK supports USB-Midi :) you can assign keys to CC and other midi actions! I don't think it's heavily documented right now.