XON flow control with lpr serial printing

XON flow control with lpr serial printing

Post by s.. » Mon, 20 Apr 1998 04:00:00



How does one specify that xon flow control should be used when
printing to a serial printer with lpr (and printcap)?
The (almost undocumented?) fs#/fc#/xs#/xc# printcap entries seems to
only concern the cflag and lflag structures -- not oflag.

I'm having problems printing on serial ports (through a Cyclom I/O
multiplexer) that seems to be flow control related. Neither lpr or
direct printing to the device works (long files like font downloads
gets corrupted resulting in garbage characters, and long listings gets
abruptly discontinued -- sometimes at the first page (of like 100) and
sometimes later on)

Does anybody know what the cause could be? I'll be quite desperate if
this doesn't get fixed.
I'll check if the same problems are shown when connecting directly to
the normal serial ports (instead of through the Cyclom board) and also
if printing to a terminal (pretending to be a printer) means any
difference.
Any suggestions are happily appreciated!

The OS version is Slackware Linux 2.0.30 (out of the box; I think it
was Slackware 3.2, but I'm not sure right now)

 
 
 

XON flow control with lpr serial printing

Post by Hugh McCur » Sun, 26 Apr 1998 04:00:00


[Posted and mailed]



Quote:> How does one specify that xon flow control should be used when
> printing to a serial printer with lpr (and printcap)?
> The (almost undocumented?) fs#/fc#/xs#/xc# printcap entries seems to
> only concern the cflag and lflag structures -- not oflag.

> I'm having problems printing on serial ports (through a Cyclom I/O
> multiplexer) that seems to be flow control related. Neither lpr or
> direct printing to the device works (long files like font downloads
> gets corrupted resulting in garbage characters, and long listings gets
> abruptly discontinued -- sometimes at the first page (of like 100) and
> sometimes later on)

> Does anybody know what the cause could be? I'll be quite desperate if
> this doesn't get fixed.
> I'll check if the same problems are shown when connecting directly to
> the normal serial ports (instead of through the Cyclom board) and also
> if printing to a terminal (pretending to be a printer) means any
> difference.
> Any suggestions are happily appreciated!

> The OS version is Slackware Linux 2.0.30 (out of the box; I think it
> was Slackware 3.2, but I'm not sure right now)

I haven't done anything special to support a serial printer under Linux.
XON/XOFF handshaking seems to be the default.  I have, and know people,
who have printed long documents.  

Generally, when one of my customers gets into trouble, it is because
the printer isn't setup to generate XON/XOFF.  An Okidata 320 (for
instance) doesn't generate XON/XOFF "out of the box."  It has to be
setup.

As for Cyclades, I generally have no problem with serial printing.
In fact, we have Linux and a Cyclades in the office.  The monthly
billing generates 100 or so pages.  The printer is on a Cyclades card.

However, I have run into two occasions where I've had problems printing
with a Cyclades.  In both cases the end of the report was lost.
But never the middle.  If you are having problems with the end not
printing, e-mail me for suggestions.  (If my netcom box goes down, try
the same user name at yahoo.com).  

If you do write, please let me know which printer you are using.
Oh, make sure the return data line in your cable isn't broken.
(I've experienced that once).

--
Hugh McCurdy

 
 
 

1. Serial printer, XON/XOFF flow control, anyone?

I am looking for anyone who is using a serial printer with XON/XOFF flow
control. We seem to be a distinct minority. I am wondering if it works
for anyone!

At one time I had mine working (even wrote a section in the HOWTO for
it). Since then, things have changed. While I can cat files to the port
directly with no problems, lpd seems unable to do the flow control
and I lose characters and eventually get garbage printouts. I got the
newest lpd that I could find, and upgraded to a current kernel which
was supposed to fix some XON/XOFF flow control problems (1.1.44 at the
time).

Unfortunately I print very rarely so I have no idea when things actually
stopped working. I have libc 4.5.26 and kernel 1.1.44, and the lpd was
from the NetKit-B package I believe (newest version as of about Aug. 12).

---


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