ArduinoCore-EFM32 -- Arduino core for Tomu and EFM32HG boards

WORK IN PROGRESS

This repo will eventually house a working Arduino core for Tomu and similar EFM32HG boards.

The EFM32HG is a pretty great chip:

• ARM Cortex-M+ @ 25 MHz
• Crystalless USB w/ built-in 3.3V regulator for minimal part count
• 64 kB flash / 8 kB RAM
• Capacitive touch sensors
• Super low-power

And thanks to the Tomu project:

• USB DFU bootloader - "toboot"

This README will serve as a notepad as I work through the process.

Cribbing a lot from:

• https://github.com/adafruit/ArduinoCore-samd
• https://github.com/arduino-org/arduino-core-stm32f4

Also see:

• https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5-3rd-party-Hardware-specification
• https://github.com/arduino/Arduino/wiki/Build-Process
• https://github.com/arduino/Arduino/wiki/Unofficial-list-of-3rd-party-boards-support-urls

Plan:

• Start by cribbing basic boards.txt & platform.txt from other ARM Cortex-M0+ projects
• To start, use Gecko SDK instead of libopencm3 (which supports EFM32HG now) because libopencm3 doesn't have all the peripheral libraries built out yet (particularly interesting to me are LEUART, USART (for SPI & UART), MSC (for self-programming of flash to emulate EEPROM).
• Embed Gecko SDK for now, in pre-release I believe the license can allow for this. Eventually make it a separate package that's downloaded?
• Rely on Tomu's toboot for DFU upload. It seems a good DFU implementation.
• Rely on Arduino's dfu-util package. Be sure to check out dfu-prefix and dfu-suffix commands to use before dfu-util.

Progress:

• Create directory structure skeleton
• Copied bits of SAMD and STFM32 cores to platform.txt and boards.txt
• Enabled it with:

  cd ~/Documents/Arduino/hardware
  mkdir todbot && cd todbot
  ln -s ~/projects/ArduinoCore-EFM32 .

  And then getting it to be seen by opening Boards Manager window then closing it (protip: Use System keyboard shortcuts to assign Cmd-Shift-B to "Board Manager...")