Thanks to everyone fo the great response, it's much appreciated!!

Darren - The host is a Win98 machine, and I'm just trying to use it
eventually for programming PIC's.  The problem is, I started building up one
of these interface circuits, and the outputs I keep getting are not what I'd
expected.  But I am just using a voltmeter to check this.  I don't have a
scope at home.

Olin - By the sound of your message, it seems that I am way off base here,
and that I won't be able to check this out without using a scope.  So the
outputs of the parallel port are not a constant high or low then?  I haven't
had a chance to read any of the links yet, nor try to implement any of the
suggestions.

Thanks,

Wade


----- Original Message -----
From: "Olin Lathrop" <olin_piclist@EMBEDINC.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, August 01, 2001 5:22 AM
Subject: Re: [EE]: PC Parallel Port -- Issues and Inquiry


> > Here's where I noticed that I'm not able to get it to work properly.  I
> > tried to connect the port to a 74LS05 (Inverter) and the output and
inputs
> > to this chip are something like 1.3V. Total garbage.  Regardless of the
> > port's state.  I do believe that the software I'm using to toggle all of
> the
> > outputs on the port is correct.
>
> Something is definitely wrong electrically if the *outputs* of the 74LS04
> are also around 1.3V.  Check the power to the chip.  What are the port
> output levels with nothing connected?  Is the LS04 oscillating?  You say
> your software to drive the port is working (although I don't know how you
> can tell given what you told us), so toggle all the bits in some pattern
and
> look at the bare outputs with nothing connected.  If that looks fine,
> incrementally add more stuff and keep following the signals to see where
> they get lost.
>
> I like to use a counting pattern for this sort of thing.  Each bit is a
> square wave with half the frequency of the next lower bit.  This makes it
> easy to identify bits and detect shorts between them.
>
>
> ********************************************************************
> Olin Lathrop, embedded systems consultant in Littleton Massachusetts
> (978) 742-9014, olin@embedinc.com, http://www.embedinc.com
>
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>

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