Dot matrix printer on OpenBSD
reddit / BSD

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ttlaxia · 2023-06-21 00:01

I have an old Core 2 Duo machine with a parallel port running recent
OpenBSD and I am trying to connect a much older Star Micronics
Gemini-10x dot matrix printer to it. I've gotten as far as the word
"root" being printed with some random-looking garbage below it -- I
assume it's a burst page. But nothing else. lpd runs and when I do
something like `lpr -Plp file.txt` what looks like a print job shows
up in /var/spool/output/lpd but nothing prints.

I have these in /dev/ :   lpa0, lpa1, lpa2, lpt0, lpt1, and lpt2. I
think lpa0 is the correct one, but I'm not sure how to find out for
sure.

If I do `cat file.txt > /dev/lpa0` I get "device busy".

My /etc/printcap looks like this:

    lp|Local Line Printer:\
:lp=/dev/lpa0:SD=/var/spool/output/lpd:lf=/var/log/lpd-errs

The permissions for that spool output directory look like rwxr-xr-x.

Does anyone have any thoughts about what I may have missed? I've never
tried setting something like this up and I don't know if I'm missing a
driver, or the computer is sending UTF-8 or... what. The computer is
not on a network so it would be a bit of a pain to get drivers onto
it, really.

[Edit: I've gotten it to print a couple of times now, but I haven't
figured out what combination of printing as root, resetting the
printer, command line switches made it work. The printer always stops
being in Ready status as soon as I submit a job, whether it prints or
not. Sometimes after I reset it it will print the first few characters
of the previous job. Maybe the printer is just broken...]

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gumnos · 2023-06-21 02:10

Not sure why this got updated, it's an interesting problem. My first
question would be whether your file has form-feeds (0x12) in it to
tell the printer to eject the current page. Though that's usually more
a problem for things like inkjets and laser printers rather than for
dot-matrix & line-printers (where you usually get the characters
printed as they're streamed to the hardware. I *would* check for
strange characters such as non-ASCII characters (such as Unicode or
other code-blocks of 1-byte character-sets), as well as control
characters.

On a reset printer, streaming the text bytes to the printer *should*
print them directly.  I'm not sure how the Gemini handles long lines,
so you might need to [`fmt(1)`](https://man.openbsd.org/fmt.1) them
first like

    fmt -79  /dev/lpa0

or possibly pipe it to [`lpr(1)`](https://man.openbsd.org/lpr.1)
instead

    lpr < file.txt

Maybe testing known-good text with something like

    printf 'hello\n\f' | lpr

or try [`lptest(1)`](https://man.openbsd.org/lptest.1)

Additionally, something feels strange about `/dev/lpa*` where I'm used
to parallel printers showing up at `/dev/lpt*`.  Having the wrong
device-name could manifest with your "it queues but doesn't print"
behavior. So I'd also lean strongly toward testing `/dev/lpt0`

It's been more than a decade since I had to directly shovel printer
control-codes down the wire, so I might be amiss, but I did write some
custom printer-interface drivers/libraries (this was for thermal
printers, printing from PocketPC handhelds, so a slightly different
world; and before that, dot-matrix printers from Apple ][ and old
286/386/486 hardware) so I'm not totally unfamiliar.

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ttlaxia · 2023-06-21 03:31

Thank you! I think the device name was the issue, even though I
thought I'd tested lpt0 already. I found some NetBSD docs that say
that lpa0 is the "polled" driver, and lpd0 is the "interrupt driven"
driver. And I gather lpt0 just dumps data directly to the port. (?)
Anyway, when I changed it to lpt0 it started working.