Date: Tue, 30 Aug 2005 09:50:26 GMT From: "Julien Gabel" <jpeg@thilelli.net> To: freebsd-doc@FreeBSD.org Subject: Re: docs/85355: [patch] Error in the pin numbers of the described connector in the Handbook (serial). Message-ID: <200508300950.j7U9oQ2H002727@freefall.freebsd.org>
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The following reply was made to PR docs/85355; it has been noted by GNATS.
From: "Julien Gabel" <jpeg@thilelli.net>
To: "Gary W. Swearingen" <garys@opusnet.com>
Cc: "Yar Tikhiy" <yar@comp.chem.msu.su>,
bug-followup@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 resource, which is likely to become incomplete, outdated, or down.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.
--
-jpeg.
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