VISA output to LPT1 fails on one computer

[JamesMcLean]

I need to send information to hardware via LPT1.  I have a VI which successfully does this using the VISA interface -- on all the computers in my lab except the one on which it is required.

On the problem computer, the VI runs with no errors, but the data never comes out the parallel port.

Nominally, all these computers are the same except for the fact that the problem computer has NI-IMAQ v.3.4 installed.  Obviously, there is some difference causing the probelm, but I can't for the life of me figure out what it is.  Everything looks the same and proper in MAX, for instance.

Any suggestions on where to look?  Is it conceivable that IMAQ is causing the problem (seems unlikely to me).

[Steven_T]

Hello James,

You may want to check how the parallel port is set up in the bios.  Make sure that your problem computer has matching settings with one of the computers that communicates through the parallel port.

It is strange that the one computer with IMAQ installed does not allow the communication.  However, I do not think this could be the problem.  You can test this by uninstalling the IMAQ from one machine and installing it on another to see if the behavior changes.

Steven T

[JamesMcLean]

Update: the presence of IMAQ was definitely not the problem.  We physically swapped two computers, installed IMAQ on the new one, and everything is working there.
I'd still like to resolve the parallel port issue on the other computer.  I'll check the BIOS....

[Dynamik]

Hi James,

In case it helps, came across this while trying to use a parallel-port under 7.1 on a Win2K machine.

http://zone.ni.com/devzone/conceptd.nsf/webmain/72C6FC6CE4AD4D1386256B1800794596

Eventually I gave-up on using VISA and went with OutPort (which worked.)

If yours is a Win2K machine and you get the VISA/parallel-port working, I hope you'll post the solution!

Cheers.

[JamesMcLean]

Thanks for the reference; I had seen it before, but it's a good page!

It happens that this is a WINXP(sp2) machine.  I think that I have successfully used VISA for the parallel port under Win2k, but I don't remember for sure.  One definite key is that for this application I only need access to the 8 Data lines.  In another application, I had to control some of the other lines, and for that I definitely had to turn to OutPort and InPort.

At this point I'm suspecting that I am actually dealing with a problem in the port hardware; I can't find any software difference between a working computer and the malfunctioning one (I even checked the BIOS, as suggested above).

You have just given me the idea that I can test everything at a lower level with OutPort.  I'll try that...