[ILUG] Reverse engineering serial protocol

[Kieran.Tully AT acm.org]

On Fri, 1 Oct 2004 10:47:26 +0100, Dale Dunlea <daledunlea at commergy.com> wrote:
> > Without a scope, there's not much you can do to detect baud
> > rate other than "suck it and see". However, if your rx baud
> > rate is too low, you'll just see gibberish; if it's too high,
> > you'll see bits repeated in what you receive (for example,
> > you'll never get a byte that reads 01010101 in binary, but
> > you could well get one that reads 0011001 or 00001111).
> 
> Well, that means I definitely don't have it set too high as I always get
> a single-bit transition on the last byte of a transaction. That's good
> to know.

See http://www.iol.ie/~ecarroll/autobaud.html
Expands on the heuristic Christian mentioned.
I remember writing something similar in assembler in college - fun!

> I tried placing a software spy on the windows machine but none of them
> seem to get in at boot time before the driver device locks the port.

Once you know the serial settings, maybe put a Linux machine with twin
serial ports between Windows and the touchscreen and write or find
something on Linux to log and forward the data (avoids need to makeup
a cable.).

Good luck!
-- 
Kieran Tully, Software Developer and Tenor
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