Bit-banged USB?!?!

On Feb 16, 12:39=A0pm, John Devereux <j...@devereux.me.uk> wrote:
> Tim Wescott <t...@seemywebsite.com> writes:
> > On Wed, 15 Feb 2012 22:18:01 -0600, Les Cargill wrote:
>
> >> Tim Wescott wrote:
> >>> I came across this schematic (well, my son dragged it into my
> >>> attention):
> >>>http://www.otd.kr/data/file/
> > pj_LIMKB/1964092542_24157b90_Aikon28LIMKB29-
> >>> SMD_Schematic.PNG
>
> >>> This is for a universal keyboard controller. =A0The thing that is rea=
lly
> >>> catching my eye, though, is that the thing appears to be set up to bi=
t-
> >>> bang the USB.
>
> >>> Has anyone ever heard of doing this? =A0Tried it? =A0Succeeded? =A0US=
B slow
> >>> is 1.5MHz, so there's a remote possibility that one might possibly ha=
ve
> >>> enough time to do something if the processor isn't doing much else (t=
he
> >>> processor in the above schematic is clocking at 12MHz), but I'm prett=
y
> >>> astonished that they're even managing that.
>
> >> That's from PD0(RXD) and PD2(INT0)? Are those configured then as just
> >> PIO (emphasis O)?
>
> >> Pretty crazy, but keyboard events are relatively infrequent - hundreds
> >> per second at most.
>
> > I have absolutely no clue how it's configured -- the source code isn't
> > available. =A0I'm still trying to get past bit-banged USB.
>
> Not done it myself, but I know that there has been code around for ages
> for Atmel. Low speed USB is relatively.... low speed, and AIUI USB was
> designed to be relatively simple on the device side.
>

Exactly, the Atmel code is called V-USB ( http://www.obdev.at/products/vusb=
/index.html
)
and there are many projects based on it: http://www.obdev.at/products/vusb/=
projects.html
).
I have successfully used it for some MIDI-USB devices:
http://www.ise.pw.edu.pl/~wzab/MIDI/perkusja/index.html
http://www.ise.pw.edu.pl/~wzab/MIDI/pedal/index.html

The V-USB is fully open-sourced.
--
Wojtek

> --
>
> John Devereux