[ale] eavesdropping on serial port

[John Mills]

Hi -

Yes, this isn't too difficult. Basically, one RS-232C line can usually 
drive two RS-232C receivers. I took four mini-D9 connectors and:

1) Wired a Male (#1) 1:1 to a Female (#2) as a pass-through,
2) Wired a Male (#3) so its RxData line tapped off the RxData line of #1, 
and
3) Wired the remaining Female (#4) so its RxData line tapped off the 
RxData line of #2 (which is the TxData line of #1)

I chose the gender and pinouts of #3 and #4 to conveniently match the two 
serial ports on the back of my PC Linux. In Linux I started a pair of 
Minicoms, one receiving from #3 and the other from #4, and compared the 
serial data each of them captured.

There are dedicated capture programs to merge such streams - I had one in 
Windows, but not in Linux. "Eyeball" filtering worked for my problem, but 
you may want to cobble some software to keep the two streams separate but 
correlated.

I posted the break-out schematic as 'ASCII art' on ALE back in 2000 or 
2001, but I'll have to dig a bit to find it. You might do better hitting 
the ALE archive against this e-mail address.

Meanwhile, HTH.

Let us know what you learn.

  - Mills

On Sun, 8 Feb 2009, Atlanta Geek wrote:

> gents,
> I'm playing with a 2.4 GHz spectrum analyzer that I got from
> dunehaven.com. It plugs into an Arduino board. Together they are still
> < 1/2 the price of a wi-spy.
>
> Unfortunately the software is windows only. Which would have been fine
> by me since I just needed the hardware for a coding project.
> Unfortunately little details have been found about the protocol.
>
>  Does anyone know how I can eavesdrop on the serial port of a windows
> app so I can reverse engineer the protocol.
> I've asked the designer for info.  Either the protocol or the source
> for the Arduino board but he hasnt responded much yet.
> Any suggestions.
>
> -- 
> http://www.atlantageek.com
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