Controlling external hardware via lpt0
Fernando Gleiser
fgleiser at cactus.fi.uba.ar
Tue Aug 3 09:04:52 PDT 2004
First, I apologize if this isn't the right place for asking this things
I need to control some external hardware with a small program in
FreeBSD. I thought about using the 8 data bits of the parallel port
for sending the control bits to the hardware.
The hardware is a very simple combinational logic, triggered by level,
I don't need any flow control or such.
The soft opens /dev/lpt0 and then writes whatever value is needed (i.e,
if I need the 2 lsb to be high and the rest low, I write 0x3)
The problem is, I can't even open the paralel port for writing, it
always fails with EBUSY.
on the parallel port I attached a DB-25 wired as a "dummy printer", that
is: strobe->/ack, busy, paper end and select inh, wired together and
then sent to pin 18 (GND).
Is there anything I'm missing? Are there a "programming and using the
parallel port in FreeBSD" guide?
Thanks in advance
Fer
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