one control to 2 different DIO lines

[lightmiddle]

Hi there:

   I am using PXI 7833R card and Labview 8.0 for windows. FPGA 1.1 version.

I have a problem about the DIO. In a previous program I use one boolean number to control one PXI 7833R digital output line. Everything works. Then I want to use the same boolean number to control two different Digital output lines. I did not change anything else, Just add a Digital output line to the node A(the circled one is added). The program does not work any more.

I used the oscilloscope to measure the output and got the signal I want for both output!!!

Anybody knows why?

Message Edited by lightmiddle on 03-06-2006 04:57 PM

[Doug M]

lightmiddle,
When you say the program does not work anymore, what do you mean? Are you getting an error number, and if so, what is it?  I would add both Digital lines to the same Digital Output Node, rather than having two separate nodes.  This will be more efficient.

Also, I don't know how you've been able to get FPGA 1.1 to work with LabVIEW 8, you really need LabVIEW FPGA 8 to work with LabVIEW 8.

[lightmiddle]

Hi Doug:

   Actually this is only one part of my program, without the additional digital output line (the circled one), I can get the result I expect. When I add one more digital output line using the same control, the result is far away from what I expect. 

  I am wondering what affect the result, can I use one "control" to control two different digital output?
and could you explain "I would add both Digital lines to the same Digital Output Node, rather than having two separate nodes. "? How can I do this ?

Thanks.

[Doug M]

lightmiddle,

I am still confused as to what you mean by "the result is far away from what I expect".  What is actually happening? In your previous post you said "

I used the oscilloscope to measure the output and got the signal I want for both output!!!"

I am still not sure how you can be using the FPGA 1.1 module with LabVIEW 8, this should not work.  To add multiple lines to one I/O node in LabVIEW 8 you can simply drag lower edge of the I/O node downward to create more lines.  See the attached image.  I would also take a look at the shipping examples for LabVIEW FPGA module.

 

Message Edited by Doug M on 03-09-2006 06:36 PM

[lightmiddle]

Hi Doug:

   The result means I am expecting a zero at the end of my entire program, but I got a one. It might still be confusing, because I was running a complicated program. The part shown above is only very small part of it. 

   Sorry I forgot to mention I was using Labview 7.1 and FPGA 1.1.

  I think I have found the problem. when there are more lines added, the PXI 7833 R responses slower than when there is only one line. My system program is timing critical. The signal delay resulted from the additional line cause the problem.

  However new problems come out, what is the exact time delayed when you add one more line?

[Doug M]

lightmiddle,
Adding one more digital line to a single Digital Input node should not add any significant time to your possible loop rates.