Subject: Re: Idiots guide to serial ports.
To: Herb Peyerl <email@example.com>
From: David Maxwell <firstname.lastname@example.org>
Date: 12/19/2002 11:57:20
On Wed, Dec 18, 2002 at 05:48:34AM -0700, Herb Peyerl wrote:
> "Dr R.S. Brooks" <R.S.Brooks@liverpool.ac.uk> wrote:
> > Perhaps (as I did some time ago) you bought a so-called null-modem cable
> > from your local Maplin shop? AFAIR, the one I got had *most* of the
> > connections you'd expect, but with one rather important omission:
> > nothing whatsoever connected to DCD at either end! I returned it as
> > misrepresented goods.
> When we were doing documentation for the PC Weasel, we figured we'd
> document the cabling. So we buzzed out the null modem cable we had
> closest to us and found it didn't match our impression of 'null modem
> cable'. So we rounded up all the ones we had at the office. We also
> drove around town and bought one of each 'brand' of null modem cable
> and adapter we could find. Only one place had what we considered to
> be a true null modem cable. But we did manage to find 6 different
> renditions of 'null modem', only one of which had DCD connected.
It is a shame serial cables and port requirements differ so greatly.
I've spent too many hours of my life trying to figure out what signals a
device wanted to see before it would communicate.
I've found this device to be quite handy for debugging:
Part 8202 is a cheap in-line switch that lets you try 18 types of cable
David Maxwell, email@example.comfirstname.lastname@example.org -->
An organization gets what it rewards.
- Perry Metzger