Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!bbn!mit-eddie!uw-beaver!rice!sun-spots-request
From: dik@uva.UUCP (Casper H.S. Dik)
Newsgroups: comp.sys.sun
Subject: Re: Sun serial port communication problem
Message-ID: <639@uva.UUCP>
Date: 28 Feb 89 07:04:24 GMT
References: <13782@bellcore.bellcore.com>
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Organization: Faculteit Wiskunde & Informatica, Universiteit van Amsterdam
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Approved: Sun-Spots@rice.edu
Original-Date: 14 Feb 89 18:46:25 GMT
X-Sun-Spots-Digest: Volume 7, Issue 170, message 10 of 12
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quasar@ctt.bellcore.com (Laurence R. Brothers) writes:
>I'm writing a little application to read stuff coming in over my sun's
>serial port (Sun-4/260, though it shouldn't make much difference).
>
>Since I don't yet have the OGM (Obsolete Garbagey Machine) that will be
>supplying the RS232 chatter, I'm faking it by connecting a null modem from
>ttya to ttyb, writing to a, and reading from b.

This is what I think happens:

You write a character to a
It travels to b

It gets echoed by the tty driver at b. (and read by your program)

It travels back to a

It gets echoed by the tty driver listening to port a

It gets back to b. (read again by your program)

... ad infinitum

So switching of echoing on port a and b should do the trick.

This also accounts for doubled line-terminators.  If you output a newline
on port a it gets converted to nl-cr on output.  Port b then finds two
line terminators.

Your best bet is raw & noecho.

Hope this helps,
--cd

Casper H.S. Dik
University of Amsterdam     |		      dik@uva.uucp
The Netherlands             |                 ...!uunet!mcvax!uva!dik