The complete USB 2.0 and 3.0 specs are available on
http://www.usb.org/developers/docs/
I think it contains all electrical and protocol specifications.
Thanks... I've skimmed the USB 2.0 spec, and to be honest it does appear
to be ridiculously over-complicated for anything I need to do. I suspect
this comes from making a 'universal' interface that could handle
everything from keyboards to mass storage devices to printers to ...
(which IMHO was a mistake...)
But anyway, I'll remember where the docs are in case I have ever to work
with it..
-tony