WIP LED HAT firmware and driver
sudo apt-get install gcc-avr avr-libc avrdude
make
Ensure SPI is enabled.
make flash
Enable I2C in raspi-config
Boards with a programmed EEPROM will have nodes populated in the device tree automatically.
Add the following module to /etc/modules:
i2c-dev
https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-bus-iio
https://archive.fosdem.org/2012/schedule/event/693/127_iio-a-new-subsystem.pdf
http://wiki.analog.com/software/linux/docs/iio/iio-trig-sysfs