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'[PIC]:parallel port? FPP programmer help'
2002\05\15@004605 by Jim

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Well after pulling my hair out for a while I found that my parallel port put
out 3v for a high is this normal.
I'v been looking around the web at parallel port spec's nad didn't find
anything about voltages on the
parallel port so I am assuming that it's suppost to be 5v for a high. Can
anyone tell me if 3v is correct
for a high?.

Thanks
Jim
{Original Message removed}

2002\05\15@110449 by Rex Byrns

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Yeah dude, this is very common.  I myself have to use my new desktop to
program with my noppp.  My laptop puts out just under 4 volts.  I could use
different diodes and get it to work, but Radio Shack no longer carries
1n34's and I don't need to order anything else.

Sometimes buying an extra lpt card will help if you are using a desktop (or
if you are like me and like to hook up dangerous stuff to our puter).

{Original Message removed}

2002\05\15@111529 by Roman Black

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Rex Byrns wrote:
>
> Yeah dude, this is very common.  I myself have to use my new desktop to
> program with my noppp.  My laptop puts out just under 4 volts.  I could use
> different diodes and get it to work, but Radio Shack no longer carries
> 1n34's and I don't need to order anything else.
>
> Sometimes buying an extra lpt card will help if you are using a desktop (or
> if you are like me and like to hook up dangerous stuff to our puter).


I have a solution for this, stick some 1k resistors
(even 680 ohm) from the par port output pins to
+5v. Most par port chips are TTL and only give about
3.5v high, with the pullup you can get almost 5v.
Been there, done that! :o)
-Roman

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2002\05\15@124707 by Alan Shinn

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Jim,
Some parallel ports are open collector. Try pullup resistors to 5V.


Date:    Tue, 14 May 2002 09:07:29 -0700
From:    Jim <.....james3162KILLspamspam@spam@WORLDNET.ATT.NET>
Subject: Re: [PIC]:parallel port?   FPP programmer help

Well after pulling my hair out for a while I found that my parallel port put
out 3v for a high is this normal.
I'v been looking around the web at parallel port spec's nad didn't find
anything about voltages on the
parallel port so I am assuming that it's suppost to be 5v for a high. Can
anyone tell me if 3v is correct
for a high?.

Thanks
Jim
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2002\05\15@130356 by Jim

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THanks guys
I just tryed pullup resistor worked great for the high level but then the
low level was 3v I tryed greater resistance
with the same result oh well I just tryed a 74hc buffer and got good
results. I think I'll just rebuild the programmer.

Jim



{Original Message removed}

2002\05\15@223305 by Byron A Jeff

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On Tue, May 14, 2002 at 09:07:29AM -0700, Jim wrote:
> Well after pulling my hair out for a while I found that my parallel port put
> out 3v for a high is this normal.

Yup. The parallel port is TTL which means that a high only needs to be
above 2V. The PIC needs 0.8Vdd for a high, which usually is 4V.

> I'v been looking around the web at parallel port spec's nad didn't find
> anything about voltages on the
> parallel port so I am assuming that it's suppost to be 5v for a high.

Nope. 2V is all that is guaranteed for a high.

> Can
> anyone tell me if 3v is correct
> for a high?.

Yes. Many parallel port will output 3.3V for a high.

BAJ

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2002\05\15@223522 by Byron A Jeff

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On Tue, May 14, 2002 at 10:04:26PM -0700, Jim wrote:
> THanks guys
> I just tryed pullup resistor worked great for the high level but then the
> low level was 3v I tryed greater resistance

That's because the parallel port output is run through a dampening resistor
and your pullup is cauding a voltage divider.

> with the same result oh well I just tryed a 74hc buffer and got good
> results. I think I'll just rebuild the programmer.

I'm came to the same conclusion with my Trivial LVP programmer. It's here:

http://www.finitesite.com/d3jsys

BTW HCT is better than HC because HCT allows for TTL inputs while HC still
may flake out on TTL input.

BAJ

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2002\05\16@020144 by Jim

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ahh many Thanks.
I saw your web site months ago thats where I got the idea of using the
buffer. The one buffer that I had lying
around was a 74hct (lucky me) I did try a 74ls schimtt nand and got 4v then
with a diode on the output to prevent  r/w confilicts it was down to +/-3v
again. the board is in the bath now hope it works the first time haha
well it happens.
Thanks Byron

BTW Thank you David Tait I have built several of your programmers and I love
the fpp configerable software.

Jim




{Original Message removed}

2002\05\16@022430 by innoelec

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hi all
No I don't think is normal, if you have any load on the pin try to remove it
before testing volt.
and try to work with data pins (2-9  usually port 378$)
have you tried to see the signal using oscilloscope..? because some
multitasking programs may are using the port at the same time and you may
have a clock output (switch between input and output), and using only volt
meter would then show you a 3V DC signal
finally try to start your PC in Dos and use any old language like turbo
Pascal 7 (under dos ) to really get full control of port without an
interrupts
I have a little article of simple control of lpt port with pins details I
hope it would help try it http://www.innoelec.com
I have done allot of projects using lpt it usually works with different PC's


Nouman Al-Mounajed
ownerspamspam_OUTinnoelec.com



{Original Message removed}

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