Date: Tue, 30 Aug 2005 15:10:13 GMT From: garys@opusnet.com (Gary W. Swearingen) 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: <200508301510.j7UFADd8050921@freefall.freebsd.org>
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The following reply was made to PR docs/85355; it has been noted by GNATS.
From: garys@opusnet.com (Gary W. Swearingen)
To: jpeg@thilelli.net
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 08:01:44 -0700
"Julien Gabel" <jpeg@thilelli.net> writes:
> Ok. Is it worth to mention a specialized book ("RS-232 Made Easy",
> for example) or not?
I first wrote "not". Too few people could find the old book in time
for their need. But it does have the important benefit of giving
readers some reason to select the alternate design and thus justify
the added paragraph's existance and discourage it's removal. See
below.
> Note: there are two versions of the patch. One with a reference to
> the "RS-232 Made Easy" reference book, one without it.
The first two paragraphs look OK to me, as-is. But what you copied
into the last para from my informal comments could be improved. For
example, I was wrong to have "generic null-modem"; there is no such
thing. I'll also comment on the first two paras, for kicks.
+ <para>If you prefer making your own cables (for quality purpose for
+ example), you can construct a null-modem cable for use with terminals.
I would omit the (...); else, use "(for quality purposes, for example)"
or "(e.g., for quality purposes)"). On second though, I would change
it to simply "You can [...] with many serial devices".
+ DB-25 connector. A warning though: the standard also calls for a
I would omit "A warning though:" or at least "though".
+ straight-through pin 1 to pin 1 <quote>protective ground</quote>
IIRC, that should be "<emphasis>", or something like that, so it
could, for example, be rendered into italics.
For the record: If this gets overhauled later, it should get a 9-pin
version, which is more common these days (and which doesn't even have
a protective ground pin). Also: The design(s) _could_ be presented
once in terms of signal names (eg, SG), and then the association of
signals with pins given for 25-pin and 9-pin connectors.
+ <para>If the proposed design seems to be the most popular, others tend
+ to prefer a generic null-modem design like that, except it has pins 4
+ and 5 going to pin 8 and vice versa.</para>
<para>The proposed design seems to be the most popular. In one
variation (explained in the book <emphasis>RS-232 Made
Easy</emphasis>) the note doesn't apply and at each end pins 4 and
5 connect only to each other and to pin 8 at the other end.</para>
The few who want to look for the book can start with a WWW search.
Maybe someone can double-check my "replacement explanation".
The book's diagram is something like this:
1 -- 1 (No need to mention further, IMO)
7 -- 7
2 -- 3
3 -- 2
4+5 -- 8
8 -- 4+5
6 -- 20
20 -- 6
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