mgetty-docs 1.1.36-3.1 / usr / share / doc / mgetty / contrib / readme.supra

From sashimi.wwa.com!pshrink!veck Sat Jul  9 21:16:51 1994
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Date:	Sat, 9 Jul 1994 11:55:12 +0200
From:	"Steven King [Really!]" <veck@pshrink.chi.il.us>
Subject: Re: MGETTY: Can't do RTS/CTS?
To:	Gert Doering <gert@greenie.muc.de>
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On Fri, 1 Jul 1994, Gert Doering wrote:
> Should do. I'm using it with a ZyXEL and H/W flow control, and it works.

I found my problem with mgetty not playing nicely with my Supra.  Turned 
out to be a Supra problem.  (Oooh, big surprise there!)  Here's the 
synopsis I posted to comp.os.linux.help.  Since there *is* a work-around 
possible in mgetty, I figured you might want to consider it for future 
releases.

Thanks for your help!  (And your excellent program!)


Newsgroups: comp.os.linux.help
From: veck@pshrink.chi.il.us (Steven King [Really!])
Subject: Re: MGETTY: Can't do RTS/CTS?
Message-ID: <1994Jul9.154954.547@pshrink.chi.il.us>
Date: Sat, 9 Jul 1994 15:49:54 GMT

veck@pshrink.chi.il.us publicly declared:
>Well, one problem.  I just discovered that mgetty doesn't enable RTS/CTS
>handshaking properly.  This is most noticable when a low-speed modem dials
>in to my Supra 14k4 modem.  I do an "ls -l" and the whole thing is sent to
>the Supra at 38400 bps.  Unfortunately, the Supra is only spooling out to
>the remote modem at 2400 bps, and the text gets very garbled. 

I found the problem.  You're gonna love it.

First, after mgetty initted the modem, I connected with kermit and checked
the settings. AT&V showed me that RTS/CTS was turned off, despite the fact
that it's turned on in the non-volatile RAM and I set mgetty's init string
to just "ATZ" to load the stored settings.  So I cranked up mgetty's
debugging level to the point where I could see everything it sent to the
modem.  No obvious problems.  It sent the "ATZ" then a bunch of fax 
commands.  Howinthehell did flow control get nuked?

I connected with kermit again and started issuing the commands one by 
one, just as mgetty did.  In between I checked the settings to see where 
I lost flow control.

    ATQ0V1H0       Hard-coded into mgetty to make sure it can talk
                       to the modem, no problems here
    ATZ            Okay, &K3 is set, we have flow control
    AT+FCLASS=0    Bingo!  A side effect is that this turns off flow
                       control, as shown by AT&V reporting &K0.

So, apparently Supra modems (both my 14k4 and my 28k8 models have this 
behavior) turn flow control *OFF* as a side-effect of "AT+FCLASS=0".  
Supra probably thinks this is a feature of some sort.  Who know what evil 
lurks in the hearts of firmware programmers?

The fix was too easy.  Now that I knew where flow control was being 
disabled, it was simply a matter of hacking a line into mgetty to 
re-enable it.  Thanks to Gert's fine programming this simply meant adding 
a single line to mgetty.c.  After line 65, add

     65                             "AT+FDCC=1,5,0,2,0,0,0", "OK",
>>>> 66                             "AT&K3", "OK",

as the last fax init string.  A simple fix, but hard-coded for Supra 
modems.  If your modem isn't a Supra this may not be the proper command.  
(But if your modem isn't a Supra you probably don't have this problem, eh?)

-- 
----------------------------------------<Steven King, veck@pshrink.chi.il.us>--
"What if there were no beer?"
Yep, that's about the only time I'd order a Zima, all right.