Docs are here: http://tannewt-micropython.readthedocs.io/en/microcontroller/
It differs from upstream's machine in the following ways:
* Python API is identical across ports due to code structure. (Lives in shared-bindings)
* Focuses on abstracting common functionality (AnalogIn) and not representing structure (ADC).
* Documentation lives with code making it easy to ensure they match.
* Pin is split into references (board.D13 and microcontroller.pin.PA17) and functionality (DigitalInOut).
* All nativeio classes claim underlying hardware resources when inited on construction, support Context Managers (aka with statements) and have deinit methods which release the claimed hardware.
* All constructors take pin references rather than peripheral ids. Its up to the implementation to find hardware or throw and exception.
This implementation provides the same interface and uses the same
datastructures as used by BootROM, i.e. is a drop-in replacement for it.
But it offers one advantage: it allows to run single iteration of
event-pumping loop.
Original BootROM function are renamed, prefixed with underscore. There's
a switch which allows to use forward calls to them, for compatibility
testing.
The implementation also includes workarounds for hardware timer handler,
and these workarounds may be SDK version specific.