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From: baxter@zola.ICS.UCI.EDU (Ira Baxter)
Newsgroups: comp.unix.i386
Subject: ISC 2.0.2, How to set baud rate on serial ports?
Message-ID: <9008280005.aa24338@PARIS.ICS.UCI.EDU>
Date: 28 Aug 90 07:05:17 GMT
Lines: 28


I have 3 serial ports, /dev/tty00, tty01, tty02 under ISC 2.0.2.  I
want to use /tty02 as a simple serial I/O device to move files to/from
an ancient Z80 CP(shudder)M system at 9600 baud.  I assume that UNIX
on my 20Mhz 386 can catch any stream of characters I pitch at it
without losing anything [if it can't, I'll just lower the baud rate
some] and am hoping to do a simple "cat /dev/tty02 > FILENAME" to
capture a file from the Z80.

The tty manager under SYSADM thinks that tty02 is "disabled", i.e.,
not a user, but that its default baud rate is 9600.
Trying "stty -a < /dev/tty02" tells me the baud rate is 300 baud.
Why is that inconsistent with what SYSADM tells me?

Trying "stty 9600 < /dev/tty02 & stty -a /dev/tty02" also tells
me the baud rate is 300, but "stty 9600 < /dev/tty02 & cat FILENAME /dev/tty02"
moves FILENAME to the Z80 at 9600 baud.
Par for the course is that "stty 9600 < /dev/tty02 & cat /dev/tty02"
seems to pick up garbage when the Z80 transmits at 9600;
I'm guessing, but I highly suspect the "cat" is reading at 300 baud.
TFM says that stty sets the line characteristics, but it doesn't say
how long they stay set; it implies that after *every* open, the baud rate
is set to 300 baud.   This is confusing, to say the least.

How should I go about this task?

IDB
(714) 856-6693  ICS Dept/ UC Irvine, Irvine CA 92717