Re: Broken/Fried Parallel port...

lmcgill2@xxxxxxxx wrote:
Hello all, I have been working with an interfacing project lately and I
think I have "screwed up" my parallel port. When trying to read data
from the data register (set from an A/D converter) I wasn't getting
correct results. After some "experimenting" I realized one of the pins
isn't going "high" when being supplied voltage.
Is this a data pin or a status pin on the port that you are attempting
to read?
Anyway, it seems if I
connect this pin directly to the +5 from the 7805 regulator it goes
high, but the A/D converter IC doesn't seem to se the pin high.
I would not connect the 5V direct as this will cause problems is the
device is at a low level. It is better to use a 1K resistor tied to the
5V as a pull up.
I use a
multimeter and figured that this pin needs at leats 18mA to go high
while all the others need about 2 (maybe less).
A 1K resistor to 5V is 5MA and should be sufficient. I suspect the port
is not set to input mode if you are using a data bit.
SO, my question is, is
this normal? Do specific pins on a parallel port act that differently
from eachother or have I fried something inside my laptop?
Data pins are different from Status pins and some status pins have
inverted levels.
my port still works, I just altered its functionality. So how could I
use my A/D converter to throw this malfunctioning parallel port pin
high? Could I use a transistor (2N3904?!?) somehow? Any help would be
excellent.
I don't have my chart handy, please indicate what Pin numbers you are
using.

Dave

.

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