Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/5/84; site mordor.UUCP
Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!harpo!decvax!genrad!grkermi!panda!talcott!harvard!seismo!ut-sally!mordor!jdb
From: jdb@mordor.UUCP
Newsgroups: net.micro.mac
Subject: serial port I/O
Message-ID: <2238@mordor.UUCP>
Date: Tue, 11-Jun-85 15:53:15 EDT
Article-I.D.: mordor.2238
Posted: Tue Jun 11 15:53:15 1985
Date-Received: Fri, 14-Jun-85 00:16:26 EDT
Distribution: net
Organization: S-1 Project, LLNL
Lines: 26

I've been trying to put together an application which will use the
modem port to talk to a standard RS-232C device (modem or VAX).
I was able to get it to work, but I've run across a couple of
unexpected software problems.  I am using the Megamax C compiler.

My first problem is that a number of the routines (OpenDriver,
SerSetBuf, SerReset) are returning a positive "error code".  I
interpreted *IM* to say that a successful driver call will return
0 and an unsuccessful one will return a negative error code.  The
functions I call appear to work, so I now ignore the error code
unless it is negative.  (Before I had this code debugged I would
occasionally see a negative error code, and they were always
meaningful.)  Does the positive number have any meaning?

My second problem concerns the function "SerGetBuf", which is
supposed to return the number of bytes which are available for
reading.  According to *IM* this is implemented as status call #2.
As far as I can tell (thanks to the misplaced Sound Driver pages
in the *IM* "phone book") it is only supposed to return the
count as a longword.  However, it is definitely returning more
than 32 bits of information.  What are these extra words/longwords
supposed to mean?
-- 
  John Bruner (S-1 Project, Lawrence Livermore National Laboratory)
  MILNET: jdb@mordor.ARPA [jdb@s1-c]	(415) 422-0758
  UUCP: ...!ucbvax!dual!mordor!jdb 	...!decvax!decwrl!mordor!jdb