read 16-bit digital port using strobed input and Start/Stop trigger

[vickykld]

Hi,

I have the NI-6025E Card, Labview 7.1. and DAQmx 7.2.

I want to read digital data through Ports A and B (16-bit), using the STROBE Input signal (Handshaking mode). So far I have this working.
But now I also want it to begin reading and stop reading when it recieves two different signals (Start and Stop signals).

I looked into using the DAQmx Start Trigger.vi, but I can't seem to make it work.

I need help on how to do this.

Thanks,
Victor

[Abhinav T]

Hi Victor,

It sounds like you are trying to perform a start and stop trigger. 

Hope this helps!

[vickykld]

Hi Abhinav,

Thanks for the response. I loked into the example, and it does not load completely because it's missing "DAQmx Start Trigger (Digital Pattern).vi" and "DAQmx Reference Trigger (Digital Pattern).vi" . I looked at the options the Start Trigger and Refeence Trigger VIs have, and they are: NONE, DIGITAL EDGE, ANALOG EDGE, ANALOG WINDOW.

It seems like it is missing the DIGITAL PATTERN option.

Additionally, it uses the sample clock to read the samples, I want to use the Strobe Input (Handshaking). I'll modify this vi and try to see if it works. Do you think it will?

Thanks,

Victor

[vickykld]

Hi Abhinav,

I just tried to run the vi, taking out the pattern options that were creating compile errors.

Now it allows me to run the VI, but as soon as I click the Run button it gives me an error in the timing VI, saying that the Sample Clock is not a valid option.

I'm attaching a screenshot so you can look at.

Thanks,

Victor

[Abhinav T]

Victor,

You just need to change the DAQmx Timing VI's poly-morphic instance to Handshaking:

You can do this by click on the drop-down box below the Timing VI.

Message Edited by Abhinav T on 06-21-2007 09:24 AM

[vickykld]

Abhinav ,

I tried this and it does not work. I tried it before the e-mail I sent you yesterday. I did not mention it because It involved a modification to the example you told me would work and did not. Shouldn't I have been able to run the VI just as I downloaded it form the Internet?

I'm sending you the vi so you can look at and see what I'm doing wrong.

I took out the options for the digital pattern (two case items for each trigger)

I selected PFI0 as the start trigger and PFI2 as the stop trigger.

Selecting Handshaking it is giving me a Start Trigger error now.

Thanks,

Victor

[Ed W]

Hi Victor,

Abhinav may have overlooked the fact that you’re using an E Series device.  These devices do not support correlated digital I/O.  This means that you can only perform software timed digital I/O triggering.  You can read off of the triggering lines and setup logic within LabVIEW to stop the digital task, but the triggering will not be hardware timed. Post back if you have further questions.

Regards,

Ed W.

Applications Engineer

National Instruments

[vickykld]

Hi Ed W.,

Thanks  for your help.

I was able to sort of achieve what I needed with the sequence structure, triggering a dummy analog sample in the first frame.

Regards,

Victor