From: Brian May <bam@snoopy.apana.org.au>
Subject: Re: Port LPT + ADA (whta do I wrong?)
Date: Mon, 13 Dec 2004 09:25:26 +1100
Date: 2004-12-13T09:25:26+11:00 [thread overview]
Message-ID: <sa48y83qhm1.fsf@snoopy.apana.org.au> (raw)
In-Reply-To: VbKdnfKmSI1LHyvcRVn-2A@comcast.com
>>>>> "Steve" == Steve <nospam_steved94@comcast.net> writes:
Steve> Unless you're speaking about something specific to handling
Steve> of the parallel port, I can say for certain that with
Steve> serial I/O you must use OVERLAPPED I/O if you want to do
Steve> full duplex communication. This is not obvious from the
Steve> documentation, but if you dig far enough (and try it)
Steve> you'll find that this is the case.
Ok, this might be my problem I have encountered with serial I/O, where
I read from a serial port in one thread and write to it in another
thread...
I found sample code that does this (Ada Terminal Emulator at
http://www.members.optusnet.com.au/rosshigson/terminal.htm), according
to the comment:
-- 1. Windows NT is unable to read and write at the same
-- time. Attempts to do so result in one or the other
-- being blocked. Therefore, by default we use a mutex to
-- serialize read and write calls. Windows 95/98 can read
-- and write at the same time, so we can use the option
-- "/nomutex".
This seems kind of dodgy to me, and presumably means if something is
to be written it cannot be written until the read call returns.
Steve> Before using OVERLAPPED operations I found the little
Steve> ideosyncracy that if I had one thread waiting on a read,
Steve> another thread couldn't do a write until the read finished.
Steve> Using overlapped the write causes the read to wake up, the
Steve> write does it's thing. When my code detects that the read
Steve> hasn't finished, it goes back and reads again. A pain in
Steve> the butt, but it works.
Does anyone have sample Ada code that uses OVERLAPPED operations?
--
Brian May <bam@snoopy.apana.org.au>
next prev parent reply other threads:[~2004-12-12 22:25 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-03 13:56 Port LPT + ADA S�awo - MIR
2004-12-03 14:40 ` Martin Krischik
2004-12-03 15:29 ` Slawo - MIR
2004-12-03 18:46 ` Martin Krischik
2004-12-03 18:43 ` tmoran
[not found] ` <u111r0db4fsoj9u3hlkachspjt0r2vvup7@4ax.com>
2004-12-03 23:03 ` Adrien Plisson
2004-12-03 23:51 ` Slawo - MIR
2004-12-04 0:51 ` Jeffrey Carter
2004-12-04 18:05 ` Port LPT + ADA (whta do I wrong?) S�awo - MIR
2004-12-04 20:20 ` Dmitry A. Kazakov
2004-12-07 18:13 ` Slawo - MIR
2004-12-07 20:55 ` Dmitry A. Kazakov
2004-12-08 4:28 ` Steve
2004-12-08 8:27 ` Dmitry A. Kazakov
2004-12-12 22:25 ` Brian May [this message]
2004-12-14 2:41 ` Steve
2004-12-12 22:46 ` Brian May
2004-12-12 23:03 ` Adrien Plisson
[not found] ` <rt8dr09tuvgbqaeq9vmujd1pqtb72hbamv@4ax.com>
2004-12-09 8:17 ` Jerry van Dijk
2004-12-05 6:45 ` Brian May
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