Everything is hackable nowadays, and keyboards are no exception. Some time ago when I was searching for a replacement for my good ol' HHKB, I got fascinated by the concept of programmable keyboards. I worked with my keyboards all the time, and kept changing the key bindings in all kinds of software to suit my weird taste. With a programmable keyboard, I can take those weird bindings of mine anywhere with me. How awesome is that?
More searches. One of the results led me to the HHKB Alternative Controller page. To sum it up, some brilliant people designed a controller board precisely for the HHKB, and it's powered by the same chip (ATmega32U4) on Arduino boards. In other words, that thing is programmable from inside out. It's even open-sourced! But I'm not an iron-and-soldering guy, instead, I bought one from the designer, and all I had to do were loosening some screws and connecting the controller board to my old keyboard. Now I have a programmable HHKB!
To Actually Program the Keyboard
You need the TMK keyboard firmware. The QMK firmware is more like the de facto standard for programming keyboards nowadays, because it supports more keyboards and have more fancy features, but I simply followed the instructions given by the designer of the HHKB alt. controller, and used TMK instead [1]. This is really a random choice, but TMK is powerful enough that I lack the motivation to actully switch to QMK.
| [1] | To make it clear, the designer of the HHKB alt. controller and the current maintainer of the TMK firmware is exactly the same person. |
That said, it's easy enough to follow the documentation scattered across the tmk_core/doc directory, and soon discover your own way of customizing your firmware. If you're looking for more advanced/more interesting stuff, there are designated hook APIs (tmk_core/doc/hook.txt). Moreover, you can override core functions annotated with __attribute__((weak)) for extra fun, but this is by no means documented so be careful.
An Opinionated Config
My customization was based on the stock config came with the alt. controller board, which was identical with stock HHKBs. I basically just added new layers to suit my needs, and here's a brief list of the extra features:
- A dedicated layer for mouse keys and cursor movement keys (arrow keys, Pg Up/Dn, Home/End etc.) in Vim style (i.e. H/J/K/L for going left/down/up/right). I used this layer a lot, for browsing through web pages and navigating inside some dumb command lines.
- Dynamic macros. This is the same feature found in the QMK firmware. I almost regretted implementing this myself, since it required too much effort, and I ended up rarely using it. I'd say my implementation is quite hacky too, but I don't feel like investing more time to improve it.
- A layer filled with KC_NO, to emulate a locked keyboard. My toddler would sometimes reach for the keyboard while I was away from the desk, and locking the screen seems not enough.
- A layer for Penti Chorded Keyboard mode. This mode enables one-handed typing, while my typing fingers can always stay in their home positions. This is quite useful when I need to do some quick-and-dirty editing but don't want to move my other hand away from the mouse. The Topre switches are a bit too stiff for chords requiring three or more keys though.
- Space Cadet Shift keys. The left/right Shift keys are configured to act like this: when tapped, emit a left/right parenthesis; when held down with other keys, act as normal Shift keys. This behavior may interfere with some IMEs [2], where they use the shift keys to switch input modes. I solved this by simply have vanilla Shift keys mapped in another layer.
- Automatically insert right parentheses. There's an Auto Paren mode that I made. When activated, tapping the left Shift key would insert a pair of parentheses, and then put the cursor in between; tapping the right Shift key would just push the cursor one character away to the right. This makes all those dumb text editors look a bit smarter.
- The Enter key also acts as right Control when held down. Symmetry achieved!
| [2] | Input Method Engines |
With all these features and some excessive debug messages, I used up all the ROM space available on that tiny controller chip. At least I can keep my hands off the firmware for now, until I feel like hacking again. And after being taught these new tricks, maybe my good ol' HHKB can hold up to some more thocking years.