Re: Splitting serial cables ?

In article <dro0rq$6qp$1@xxxxxxxxxxxxx>,
moroney@xxxxxxxxxxxxxxxxxxxxxxx (Michael Moroney) writes:
> bill@xxxxxxxxxxx (Bill Gunshannon) writes:
>
>> I would expect devices today to be much more likely to
>>stick to standards as it avoids a whole bunch of finger pointing when
>>things don't work. Be aware!!
>
> Not necessarily. Consumer UPS's from a few years ago used serial ports
> speaking RS232 to control them, but they used a DB-9 using a pinout
> entirely different from the standard (if it is a standard) pinout
> widely used today.

So does the PC. As near as I can figure this was just another gimmic
to sell you a "special" cable". Beyond that everything was RS232C
signal lev els with some of them merely using things like DSR, DTR, CTS
and DCD which are merely off/on type signals. But which pins you use has
nothing to do with wether or not the two devices will recognize the signal
levels. If your space signal never traverses 0v the receiving device is
free to ignore it completely and still be considered within spec.

> In fact, if you used a standard cable to a PC and
> tried to transmit, many would power off, taking the PC with it.

See my comment above. And then visit APC's site. Lo and behold, they
sell that "special" cable so your PC and their UPS can talk. Of course,
you can also find numerous Linux FAQs that tell you how to make your own.
Even more important when you figure that each company had their own scheme
for wiring up that DB9. Hmmmm...... I wonder if that could have been
because the standard never specified DB9 pinouts? :-)

>
> Today they use USB, who knows if that's standard.

Which has nothing to do with the original discusion.

Personally, I don't care. I just thought it was worth warning the
person planning on hooking up multiple RS232 devices together that
regardless of past sucesses there really is no guarantee this will
work, As I said, I had to trouble shoot such a case and then I had
to try and convince an EE Professor that there really was nothing
wrong with the device in question, it just wasn't using RS232.

bill

--
Bill Gunshannon | de-moc-ra-cy (di mok' ra see) n. Three wolves
bill@xxxxxxxxxxxxxxx | and a sheep voting on what's for dinner.
University of Scranton |
Scranton, Pennsylvania | #include <std.disclaimer.h>
.

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