Richards, Justin P wrote:
>
> Roman,
> Re LPT port, I was playing with the port and found I could get 8 outputs and
> 5 inputs.  I read that the 8 outputs could be used as inputs but read is
> best not to do this for compatibility issues.  Does this sound true
>
> Justin


Hi Justin, there are actually 3 ports but
some pins are I/O, and some are only dedicated
inputs or outputs. The MAIN port (8 pins)
is bidirectional, has been for many years,
and I prefer to use the dedicated inputs
and outputs for most stuff as you are pretty
much guaranteed compatibility on any PC, even
old ones. And obviously it's good to keep
the main 8bit port available for data use
if you need that.

In most cases you can interface to the port
with just a 220 ohm resistor from each port
pin to your PIC (or any 5v digital) pin. Port
hardware is pretty rugged, i've never fried
a parallel port in years of plugging them
live.

There is some good data on the net, try this:
http://www.beyondlogic.org/spp/parallel.htm
-Roman

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