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'[EE]: Could PC Parallel port drive a device that n'
2005\10\19@144606 by John Waters

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Hi All,

I have a equipment whose operation invloves being triggered by a continuous
pulse train of 1 Hz at TTL level. Currently I'm using a funtion generator
with TTL o/p for doing that, but I want the operation be more automatic, so
I'm considering using the parallel port of a PC to replace the function
generator. However I wonder if the parallel port of a PC is TTL compatible.
Could anyone give some comments?

Thanks in advance!

John


2005\10\19@154217 by Herbert Graf

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On Wed, 2005-10-19 at 11:45 -0700, John Waters wrote:
> Hi All,
>
> I have a equipment whose operation invloves being triggered by a continuous
> pulse train of 1 Hz at TTL level. Currently I'm using a funtion generator
> with TTL o/p for doing that, but I want the operation be more automatic, so
> I'm considering using the parallel port of a PC to replace the function
> generator. However I wonder if the parallel port of a PC is TTL compatible.
> Could anyone give some comments?

Most are TTL compatible. Some will only be 3.3V (i.e. laptops), which
might still work fine with TTL hardware, but I wouldn't count on that.

A bigger problem is how accurate do you need that 1Hz to be. If you're
running just DOS you can get it pretty close, but in Windows expect that
1Hz to glitch every once in a while.

TTYL

-----------------------------
Herbert's PIC Stuff:
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2005\10\20@072303 by Michael Rigby-Jones

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{Quote hidden}

Not just laptops either, many modern desktop machines have 3.3volt logic levels on the parallel port.

>A bigger problem is how accurate do you need that 1Hz to be.
>If you're running just DOS you can get it pretty close, but in
>Windows expect that 1Hz to glitch every once in a while.

Indeed.  A 555 timer is likely to offer far better short term stability and costs pennies.  A 32.768kHz watch crystal and binary divider costs litrle more, and gives you excellent accuracy and stability.

Regards

Mike

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2005\10\23@061442 by Bill & Pookie

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This looks like a job for "Simple Pic".  Just program one to put out the
signal and be controlled by the parallel port of the pc.  Even simpler, use
something from the other device or even have it to supply power to the pic
to start the oscillator, or in conjunction with the parallel port.

Instead of the parallel port, the serial port could be used to turn pic on
and off.  use the timing of the pulse width when sending a hex 80 and a hex
FF to signal the pic to start /stop oscillator.   Wouldn't need a fancy
RS232 interface on pic, just look at the data pulse and measure time for
control.

Bill

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