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parallel port confusion

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Hi,

I have the professional development version of LabView 61 installed in my Windows NT machine. I have used the attached vi for sending signal to my parallel port. Upon sending this signal, the LED, that is connected to pin 2 (pin 25 grounded) should turn on. It works fine. However, when the vi is not running, I noticed that when I connect the positive of the LED to pin 2 and grounded pin 25, the LED does not turn on (note: the labview prog. is not running at this time and the LED is turned off.) So I send a signal using my vi and turn on the LED.

When I connect this LED to another PC (on Win NT), the LED continues to be in the on state, even if the LV program is not running. I created the executable of this vi and installed in an
other PC (on Win NT) and could not send turn the LED off.

Can someone please explain why this is going on?
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Just a wild guess, but are the parallel port modes (ECP, EPP etc) set the same on these 2 computers? I don't know much about the different modes, but it's something to do with the port being bi-directional or not... This may explain why the LED turns off when LV stops driving it, as the port maybe going into a tri-state condition...
Of course, I could be talking complete gibberish...
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hi kmoorthy.....,

who is this stupid guy, called slaine, who writes a lot of rubbish on Natinst website....? Back to your problem: WinNT and W2k need the hardware-access to paraport (workaround for security layer). You will find it on:
http://zone.ni.com/devzone/explprog.nsf/webmain/49664743DED6F1DA862564BC004E3A7F?opendocument&node=DZ52058_US

1st:You have to install accesshw on your NT-machine. 2nd:substitute the system.llb in C:\ProgramFiles\NationalInstruments\LabVIEW6.1\vi.lib\platform\system.llb by the system.llb I attach herewith.

If you do not trust: save your version before substitution...... Then you can use the "Out Port.vi" and "In Port.vi" like with Win98 (but slower perfomance)

still open questions? - write to: werner.hasche@web
.de

regards
wha
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I think wha@atmel's comment about slaine was uncalled for. This is a public forum, please try to be civil. Besides, as I understood the question; kmoorthy76107 wanted to know why the data lines sometimes remain high even if his LabVIEW program is not running and why it didn't work on the other system. He didn't mention anything abouth the "Capability not supported" error that results from not having the accesshw kernel level driver on NT. He might be using serial I/O instead of port I/O.

kmoorthy, care to elaborate a little on how you are doing things?
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Hi everyone,

Thank you all for your efforts and patience to clear my doubts. I am reiterating my situation. I have connected a LED to the parallel port of my PC. One end of the lED goes to pin 2(data line) of my parallel port and the other end goes to pin 25 (ground). The ideal condition that I am looking for is that the LED should be in the off state when I connect it as mentioned above. Now, I run my Labview code(as shown in the attachment earlier) and i should be able to turn on and off the LED when I send the signal thru the LV code to the Parallel port pin 2 through 9. WHat I have noticed so far is that when I connect the LED to the parallel port in my machine (which has Win NT and another machine with Win 98), the LED is in the off s
tate . So when I run my LV code, i am able to turn on the LEd and turn it off using my LV code.

HOwever, when the LED is connected to another Win NT or Win 2000 machine to the same parallel port pin numbers, the LED always remains on. So i am not able to use my Executable LV code on that machine bcos the light always remains on.

MY question is that why is the led initially on in certain machines (even when the LV is not running) and why is it initially off in my machine and the other Win 98 machine?

I am thinking that the OS in those machines is sending a high signal to the port when the machine is turned on. If that is the case, can i programmatically reset the port so that it is the low state and the light is off initially?

Thanks in advance.
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kmoorthy76107 wrote in message news:<50650000000500000021690000-1012609683000@exchange.ni.com>...
> Hi everyone,
>
> Thank you all for your efforts and patience to clear my doubts. I am
> reiterating my situation. I have connected a LED to the parallel port
> of my PC. One end of the lED goes to pin 2(data line) of my parallel
> port and the other end goes to pin 25 (ground). The ideal condition
> that I am looking for is that the LED should be in the off state when
> I connect it as mentioned above. Now, I run my Labview code(as shown
> in the attachment earlier) and i should be able to turn on and off the
> LED when I send the signal thru the LV code to the Parallel port pin 2
> through 9. WHat I have noticed so far is that when I connect the LED
> to the parallel port in my machine (which has Win NT and another
> machine with Win 98), the LED is in the off state . So when I run my
> LV code, i am able to turn on the LEd and turn it off using my LV
> code.
>
> HOwever, when the LED is connected to another Win NT or Win 2000
> machine to the same parallel port pin numbers, the LED always remains
> on. So i am not able to use my Executable LV code on that machine bcos
> the light always remains on.
>
> MY question is that why is the led initially on in certain machines
> (even when the LV is not running) and why is it initially off in my
> machine and the other Win 98 machine?
>
> I am thinking that the OS in those machines is sending a high signal
> to the port when the machine is turned on. If that is the case, can i
> programmatically reset the port so that it is the low state and the
> light is off initially?
>
> Thanks in advance.

I hope I can help. I don't know how you are sending data to the
parallel port in Labview. If you use the Out Port, then you can always
send data to the data lines. If you are using vISA you first have to
clear the buffer. And then you can send data again, otherwise the data
from the first "sending" remains on the pins.

I hope you understand what I've written.

Greetz,
JJ
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Hi all,

sorry for my "bad words" - it will not happen again....
But as an engineer I cannot distribute wild guesses. It would be one of my last days in my company, if I tell this kind of answers to my boss.
Next: The different bahaviour of PC's during power on/reset is for sure a result of BIOS and the use of different chips for handling parallel and serial port on motherboard. If you need to be "clean" - no LED ON at startup - you have to use some simple logic (Latch).
But this will reduce your performance.

Regards
wha
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