F8 channel reading was using wrong ADC. Thanks afaghm!
To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://circuitpython.org/libraries).
To use in CPython, `pip3 install adafruit-circuitpython-as7341`.
Read the [docs](http://circuitpython.readthedocs.io/projects/as7341/en/latest/) for info on how to use it.