Well, hello again,

    'Sniffing a bus' has had more responses than I could never imaging,
i has come interesting, and it has give me some ideas, well, i would
like to summarize all posts in this one.

    As Robert Rolf told me, my Subject : wasn't correct, so I verify.

    Also, he said:

/*
  ' Use a comparator to measure the direction of the voltage drop of a
low value resistor placed in series between the master and slave. The
I*R drop will be of different polarity depending on who is driving the
line. Record the comparator output during bit low times (or stuff it
into a D flip flop (with R/C delay) and latch it with the rising edge of
the bus). Alternatively, add the series resistance, but use the
comparator to sense whether the pulldown was right to ground (near side
of R) or nearly ground (far side). You have to pick an R value that
won't adversely affect your bus, but gives you enough difference that
you can easily sense who pulled the bus low. Since both devices are
CMOS, I'd suggest back to back schottky diodes for a 0.3V drop and still
have good current drive.

Robert ' */

   Some comments about this:

     To measure I*R i need some comparators, then i have two choices A/D
(internals) and use external comparators.
David VanHorn says that if i use externals then i could have problems
with noise and sample timing, because i want to do it very fast...
/*
 ' You'd have to be able to sample pretty fast, and doing it with
external comparators would be problematic as well, due to
over/undershoot, ringing, and other forms of noise on the line.'
  David VanHorn'
*/
... so in the case I would like to sample pretty fast, would internal
A/D work fine with that ? what do you think ? But that is not the case,
my line works with a baud rate, that is fixed starting the communication
(at start it works at 9600 baud), so i like the idea of comparators...
but i don't get that think of using schottky diodes that Robert says,
would the diodes resistance represent R in the measure of R*I ?

  I am imaging two diodes in parallel, and one of them inverted, like a
transmision gate, and where is signal, then that way is the one
transmitting...ummm...i don't know if someone understand what i am
triying to say, but i am getting things clear...

Anyways,

   Thanks everybody !!
   Keep it c00l !!

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