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From: roy%cybrspc@cs.umn.edu (Roy M. Silvernail)
Newsgroups: comp.os.msdos.programmer
Subject: Serial Routine Kudos... and an addition.
Message-ID: <8BZVy3w163w@cybrspc>
Date: 16 Mar 91 05:20:06 GMT
Organization: Villa CyberSpace, Minneapolis, MN
Lines: 41

Kudos upon David Kessner for posting his serial interfacing routines
last month.  I've had occasion to directly compare them with the library
I had been using (IBMCOM.C, from SIMTEL) and David's come in about twice
as fast in character retrieval. The interface is similar enough to
IBMCOM that replacing the library was an easy task.

A couple of points, though, that didn't come through clearly in the
documentation...

The AsyncHand routine wants the whole set of flags upon invocation. At
first, I had tried AsyncHand(~DTR) to drop DTR, but soon found it didn't
work. With the 2 main control bits being DTR and RTS, AsyncHand(RTS)
drops DTR just fine, and (of course) AsyncHand(DTR | RTS) raises it once
again.

AsyncSet wants a speed and another number that represents parity, length
and stop bits. The example given is 3 for 8N1, but I had need of 7E1 and
7O1, as well. After spelunking a couple of references, I came up with
the following defines, now included in async.h:

/* Defines for Com Port Paramaters */
#define BITS_8          0x03
#define BITS_7          0x02
#define STOP_1          0x00
#define STOP_2          0x04
#define EVEN_PARITY     0x18
#define ODD_PARITY      0x08
#define NO_PARITY       0x00

This makes it simple to set up your port...

AsyncSet(2400, BITS_8 | NO_PARITY | STOP_1);

(yes, 8_BITS is more intuitive, but Turbo C chokes on it and wants an
alpha for the first character of a #define)

Again, public thanks to David! A fine piece of work he posted.
--
Roy M. Silvernail --  roy%cybrspc@cs.umn.edu - OR-  cybrspc!roy@cs.umn.edu
  perl -e '$x = 1/20; print "Just my \$$x! (adjusted for inflation)\n"'
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