Re: [PARPORT] Lost characters again

David Campbell (
Sun, 4 Oct 1998 08:09:18 +0800

Date sent: Sat, 3 Oct 1998 12:49:11 +0100 (BST)
From: Tim Waugh <>
Subject: [PARPORT] Lost characters again

> Hi guys,
> I think the lost characters bug might still be there, but I don't know for
> sure. Here's what I did:
> - printer is off
> - ghostscript | lpr
> - turn printer on
> - garbage on paper

*nod knowingly*

Under certain circumstances the lp driver will quite happily "eat" a print job
when the printer is disconnected/power off. I tried once to fix this but it the
"paranoia (tm)" checking of the printer port slowed the process down.

> - turn printer off
> - remove print job
> - turn printer on again
> - ghostscript | lpr as before
> - correct output on paper

> Another possibility is that the Zip drive is swallowing data by accident -
> it sits between the printer and parallel port.

*cough quietly*

Unlikely to be the cause, it is more likely that the lp driver released the
parport before the printer ack'd the byte. In which case it is an lp driver

> I don't really have time now to see if I can reproduce it. Does anyone
> feel like trying to find possible data lossage in lp.c?

I know that my DJ500 when connected (but off) will cause the lp driver to
process the job. Does anyone have the formal specs for the centronics
printer port (timing diagrams etc)?

The IEEE 1284 spec may have some info (need to check)

David Campbell

Current project list:
a) Maintain Linux ZIP drivers
b) Create Linux chipset specific parport drivers
c) Start on ParSCSI drivers
d) Boot proms for parport devices (socket onto NE2000 cards)

Any assistance to clearing this list most welcome

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This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:18:29 EST