This is a super interesting document. Contains lots of not so obvious solutions to I/O problems / tasks.
Thanks for posting that link.
The lesson learnt is that the different micro processors are not that different, analog I/O, digital I/O, PWM is the same for all. Maybe voltage levels and programming languages / environments are different but most principals are the same. So we can learn a lot from reading documents for other brands than Arduino / Atmega.
MikMo