This code can be used to run TMK keyboard logic on top of [ChibiOS], meaning that you can run TMK on whatever [ChibiOS] supports. The notable examples are ARM-based Teensies (3.x and LC) and on the boards with STM32 MCUs.
- To use, [get a zip of chibios](https://github.com/ChibiOS/ChibiOS/archive/a7df9a891067621e8e1a5c2a2c0ceada82403afe.zip) and unpack/rename it to `tmk_core/tool/chibios/chibios`; or you can just clone [the repo](https://github.com/ChibiOS/ChibiOS) there. For Freescale/NXP Kinetis support (meaning ARM Teensies and the Infinity keyboard), you'll also need [a zip of chibios-contrib](https://github.com/ChibiOS/ChibiOS-Contrib/archive/e1311c4db6cd366cf760673f769e925741ac0ad3.zip), unpacked/renamed to `tmk_core/tool/chibios/chibios-contrib`. Likewise, for git-savvy people, just clone [the repo](https://github.com/ChibiOS/ChibiOS-Contrib) there.
- Note: the abovementioned directories are the defaults. You can have the two chibios repositories wherever you want, just define their location in `CHIBIOS` and `CHIBIOS_CONTRIB` variables in your `Makefile`.
- You will also need to install an ARM toolchain, for instance from [here](https://launchpad.net/gcc-arm-embedded). On linux, this is usually also present as a package for your distribution (as `gcc-arm` or something similar). On OS X, you can use [homebrew](http://brew.sh/) with an appropriate tap.
- Some comments about ChibiOS syntax and the most commonly used GPIO functions are, as well as an example for ARM Teensies, is [here](https://github.com/tmk/tmk_keyboard/blob/master/keyboard/teensy_lc_onekey/instructions.md).
- For gcc options, inspect `tmk_core/tool/chibios/chibios.mk`. For instance, I enabled `-Wno-missing-field-initializers`, because TMK common bits generated a lot of warnings on that.
- USB string descriptors are messy. I did not find a way to cleanly generate the right structures from actual strings, so the definitions in individual keyboards' `config.h` are ugly as heck.
- It is easy to add some code for testing (e.g. blink LED, do stuff on button press, etc...) - just create another thread in `main.c`, it will run independently of the keyboard business.
- Jumping to (the built-in) bootloaders on STM32 works, but it is not entirely pleasant, since it is very much MCU dependent. So, one needs to dig out the right address to jump to, and either pass it to the compiler in the `Makefile`, or better, define it in `<your_kb>/bootloader_defs.h`. An additional startup code is also needed; the best way to deal with this is to define custom board files. (Example forthcoming.) In any case, there are no problems for Teensies.
- eeprom / bootmagic for STM32 (will be chip dependent; eeprom needs to be emulated in flash, which means less writes; wear-levelling?) There is a semi-official ST "driver" for eeprom, with wear-levelling, but I think it consumes a lot of RAM (like 2 pages, i.e. 1kB or so).
- K20x and KL2x Freescale/NXP chips (i.e. Teensy 3.x/LC, mchck, FRDM-KL2{5,6}Z, FRDM-K20D50M), via the [ChibiOS-Contrib](https://github.com/ChibiOS/ChibiOS-Contrib) repository.
- There is also support for AVR8, but the USB stack is not implemented for them yet (some news on that front recently though), and also the kernel itself takes about 1k of RAM. I think people managed to get ChibiOS running on atmega32[8p/u4] though.
- There is also support for Nordic NRF51822 (the chip in Adafruit's Bluefruit bluetooth-low-energy boards), but be aware that that chip does *not* have USB, and the BLE softdevice (i.e. Bluetooth) is not supported directly at the moment.
- There is a working example of a STM32F042-based keyboard: [firmware here](https://github.com/flabbergast/flabber_kbs/tree/master/kb45p) and [hardware (kicad) here](https://github.com/flabbergast/kicad/tree/master/kb45p). You can check this example firmware for custom board files, and a more complicated matrix than just one key.
