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