I wanted to add some features like vi cursor and mouse keys to my [HHKB][HHKB] but its controller is not programmable and firmware source code is not open, of course. This means customizing this keyboard needs to replace original controller with programmable one.
If your target is **HHKB JP** you need to set `HHKB_JP` build option in `Makefile` or use `Makefile.jp` instead of `Makefile`.
If you use other than **TMK Alt Controller Board** set proper `MCU`, `BOOTLOADER_SIZE` and other build options in `Makefile` and `config.h`. At least PJRC Teensy requires changing `BOOTLOADER_SIZE` to 512.
Several version of keymap are available in advance but you are recommended to define your favorite layout yourself. Just `make` with `KEYMAP` option like:
You have some options for hardware. Development boards with USB AVR family(ATMega32U4, AT90USB1286) like Teensy will work while MegaAVR with [V-USB] library is also cheaper option for DIY.
Design files are available at [Keyboard Controller Board for HHKB(KiCad project)](https://github.com/tmk/HHKB_controller) and see [Controller Distribution thread](http://geekhack.org/index.php?topic=56494.0) if you get an assembled one.
###2. PJRC Teensy
See [this thread](http://geekhack.org/index.php?topic=57008.0).