[aprssig] RS232 sniffer

Steve Noskowicz noskosteve at yahoo.com
Sat Feb 16 10:47:48 CST 2008


  With the Kiss paradigm... For simple "activity monitors" I have a couple of
commercial DB-25 units  and they are nothing more than bi-color (Red-Green)
LEDs and resistors to the signal common line - no level comparators or other
electronics.  I've never measured them to see the resistor values, but they are
bright enough to see indoors in the day-time or normal room light.  I'd use
high intensity LEDs, and large resistors, if I was making one.

  I also built my own three DB-9 connector hardware RS-232 _data_ sniffer ro be
used witn an additional computer to monitor either direction, with the flip of
a switch.  The design should be obvious.  Connect Tx and Rx lines normally
between the two communicating devices.  Then, as desired or required, either
loop back the control lines or route them through normally between the two
communicating devices.   Only connect the Snooper's Rx port line to the desires
data line (Rx or Tx - Pin 2 or 3). The Snooper's control lines can be connected
to the required other device (I gorget which would be best) OR make the Snooper
computer blind to control and just use the Rx line.
   The other post has another hardware one and I've got two others around here
somewhere, but couldn't find the links.  Using just one or two diodes and
resistors you can monitor BOTH directions of a half-duplex RS-232 connection
with NO switch.  I didn't read the other post to see it it did this.

 I was told  this Free software works very well and downloaded it, but haven't
used the folowing software data monitor:

Take your pick, 73, Steve, K9DCI

--- Andrew Rich <vk4tec at people.net.au> wrote:

> Hi,
> I am thinking of putting together an RS232 sniffer for the shack.
> Pretty simple, just some LED's for activity.
> What would be the best way ?
> Can compartors be used to show activity ? I am looking for lots of them ,
> hence lots of pins to watch.
> We have break out boxes, but they never really seem to have all the
> connections we want, for a CRO etc
> Ideas ?
> A circuit to switch on with a +1.2 or greater volts
> Not sure what to do about the -ve swing. or even bother - activity is the
> aim.
> MAX232 only has 1/2 in it what I want to do
> ----------------------------------------------------------------------------
> Andrew Rich VK4TEC

73, Steve, K9DCI

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