Writing to the parallel port (Mem 0x378) when runnning

John Benson jsbenson at bensonsystems.com
Sat Dec 6 18:41:26 CET 2003


Regarding the appended thread below:

Doing hard real-time tasking on Windows sounds like a doomed task. I just
wanted to point out that there's a line of microcontrollers put out by
Z-World (www.zworld.com) that are serial-, parallel- and Ethernet-enabled
and programmable in C that are a good choice for offloading that kind of
job. I used them a few years ago and they were a whole lot of fun to work
with. Since a lot of Pythonistas have some C background, I just wanted to
throw this observation into the mix. Another solution might be a
communications coprocessor board to handle the time-critical signalling.

begin quote of previous thread:

Message: 12
Date: Sat, 06 Dec 2003 08:31:21 GMT
From: Dennis Lee Bieber <wlfraed at ix.netcom.com>
Subject: Re: Writing to the parallel port (Mem 0x378) when runnning
WinXP or Mandrake 9.2
To: python-list at python.org
Message-ID: <ig98a1-o03.ln1 at beastie.ix.netcom.com>
Content-Type: text/plain; charset=us-ascii

Derrick 'dman' Hudson fed this fish to the penguins on Friday 05
December 2003 13:34 pm:

>
> If you are trying to interact with some other parallel port device,
> then some abstraction layer like the recommended PyParallel would be
> better for production.
>
        Not that I'm involved in this query, but just for an example: My
last
assignment (and if the company doesn't find anything else to do, "last"
as in pre layoff) had me producing three "lines" of RS-422 compatible
signals, synchronized to transitions of an external clock sensed via
the printer busy line.

        W98 system. It works, but I've not been able to track down and
prevent
some OS preemption problem that occurs between 200 and 250 milliseconds
into a stream of output data. This is with the process upped to
REALTIME class, and the port "driver" thread upped to TIME_CRITICAL (a
combination that should have the thread running at priority 31!)

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