USB charging, part 2: implementation

Heh. I tried that once. It doesn't work because nobody else can be bothered to figure out how something works, and nobody else knows the *rationale* for the development choices either, which are often crucial to document (indeed, Neil has a few questions in this very article which are more or less rationale questions and which even perfect knowledge of how it works now could not answer).

Of course everything I write nowadays is perfectly documented ahead of time and why has my nose grown so long that it's getting in the way of my typing?