docs/85355: [patch] Error in the pin numbers of the described connector in the Handbook (serial).

Tue Aug 30 09:50:28 UTC 2005

The following reply was made to PR docs/85355; it has been noted by GNATS.

From: "Julien Gabel" <jpeg at thilelli.net>
To: "Gary W. Swearingen" <garys at opusnet.com>
Cc: "Yar Tikhiy" <yar at comp.chem.msu.su>,
 bug-followup at FreeBSD.org
Subject: Re: docs/85355: [patch] Error in the pin numbers of the described 
     connector in the Handbook (serial).
Date: Tue, 30 Aug 2005 11:48:35 +0200 (CEST)

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 >> It might be reasonable to tell that in general, a null-modem cable
 >> is for connecting a DTE directly to another DTE.  AFAIK, null-modem
 >> cables can be constructed for synchronous comms, too.  Then, the
 >> topic can be narrowed down to async comms.

 > I doubt if Julien wants to do more rewrites on the section.  But I
 > can't resist replying anyway; maybe Yar wants to rewrite it later.

 In fact i don't really want to do a rewrite of this particular section,
 especially since i don't have a _good_ knowledge on this topic.  The
 purpose of the initial PR was to correct what seems to be an error in
 the proposed table (and eventually a pointer to more information), based
 on a very recent experience to get a trace after a panic via a serial
 console... and so a null-modem cable.

 > It probably should have some of the cable stuff from the "Serial
 > Ports" section which says that a null-modem is AKA DTE-to-DTE cable
 > and what DTE is, eg, a computer.  And terminals traditionally have
 > included teletypes and printers. (Once there were no CRTs or LCDs.)

 >> To me, www.hardwarebook.net doen't seem the definite resource.
 >> IMHO, if the topic is rather wide, the reader should better be
 >> hinted to do a (re)search on the Net instead of pointed to a single
 >> resource, which is likely to become incomplete, outdated, or down.

 > I was thinking the same things.

 Ok.  Is it worth to mention a specialized book ("RS-232 Made Easy",
 for example) or not?

 >> We may show two or three different designs in the handbook if we
 >> can tell the reader about their merits.  The problem with the design
 >> currently in the handbook is that it is erroneous *and* bogus.  I'd
 >> suggest adding another row to the table so that it becomes evident
 >> that DTR on this side is connected to DSR+DCD on the other side
 >> while DTR on the other side is connected to DSR+DCD on this side.

 > The Note below the pin-out is supposed to make it evident, and with
 > the Note the design is symmetric.

 I tend to think the note is ok here, too.

 Please find a new patch attached which resumes the recent comments
 about the different null-modem designs, mainly based on the first
 reply from Gary.  I think it was the most concise and do not require
 a large rewriting or reorganization of the serial chapter (which can
 always be made later).

 Note: there are two versions of the patch.  One with a reference to
 the "RS-232 Made Easy" reference book, one without it.

 --
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