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Date: Mon, 21 Nov 2011 15:26:48 +0100
Subject: Re: Non-POSIX parity (mark/space) with Python-Serial on Linux.
From: Nizamov Shawkat <nizamov.shawkat@gmail.com>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:16009

2011/11/21  <mlenz@nocturnal.org>:
> I'm working on a project where I need to communicate with some devices vi=
a modem which have the possibility of using MARK and SPACE parity. =A0These=
 are not defined by POSIX and therefore are not directly supported under Li=
nux.
>
> I've found the following discussion on the topic:
>
> http://www.lothosoft.ch/thomas/libmip/markspaceparity.php
>
> and I have been trying to use this information (since the TERMIOS module =
is available) to proceed with the communication.
>
> I was able to use minicom to determine that the first device I started te=
sting with uses 7M1 but cannot figure out how to implement the solution des=
cribed by the author above.
>


"The modes 7M1 (7 data bits, MARK parity, 1 stop bit) and 7S1 (7 data
bits, SPACE parity, 1 stop bit) can easily be emulated using 8N1 (0
data bits, NO parity, 1 stop bit) and setting the 8th data bit to 1
resp. 0. This is relatively simple to implement and cannot be
distinguished by the receiver."

It means that 7M1 =3D=3D=3D 8N1. Set 8N1 mode on your side and 7M1 on the
other side. I really do not understand what is the reason to have
dedicated 7M1 or 7S1 mode - it is no different from regular 8 bit mode
from the hardware point of view. From the software point of view it is
just the matter of the definition of the highest bit. In other words,
7M1/7S1 are two complementary subsets of a single 8N1 set.

HTH