Multiple task in LabWindows for 6723

[yogeesh]

Hi All,

A trivial doubt.

Is it possible to have multiple tasks for PCI 6723 in LabWindows, each configured differently?

Basically, two types of signals are required to be generated via 6723: Frequency and DC. Frequency signals require clock sampling where as DC doesn't require one.

Please reply ASAP.

Thanks and regards,
Yogeesh

Message Edited by yogeesh on 04-10-2006 07:08 AM

[Graziano]

Hi Yogeesh!
  It's not a trivial doubt at all!

   In general, for the same type of task (i.e. analog out, or analog in, or Digital in....) you use a single task for different channels.  If I'm rigth NI encourages to do so. 

   Of course I know you can't use the same task for, say, digital in and digital out.  But actually, I don't know if you are even forced to configure a single task for 2 such different signals.

   Please, let me know if you find a solution for your task! I hope this can help.....

graziano

[Jarrod_B.]

Hi Yogeesh,

To add to the information provided by Graziano, in order to generate both a waveform and a DC value on two separate analog output channels, you would simply create one analog output task, fill the output buffer with a predefined number of samples for each channel, and then clock the task at the rate necessary to generate your waveform at the correct frequency.  In order for this to work properly, you have to fill your buffer with the same number of samples for each channel.  Once this is done, both channels will be updated at the same rate, but the DC channel will just output the same value every time. 

The attached example demonstrates how to do this.  I hope this information helps!

Best regards,

[Graziano]

So I was right!!!!

[yogeesh]

Hi Jarrod,

Thanks for your help.

Unfortunaltely, I couldn't open the example.

Could you post LabWindows project in a zip? This would be of great help..

Thank you Jarrod.

Also Thank you Graziano..

[Jarrod_B.]

Hi yogeesh,

Sorry about that.  You were not able to open this file because it is a LabVIEW program.  I wasn't thinking when I posted it.  Unfortunately, I don't have a similar example that does this in CVI, but you can just use any of the analog output examples, specify two channels when you create your task, and then write the necessary values to your output buffer. 

You may want to look at the following examples for a template to start from.  Although these aren't written to produce a DC output, you could easily modify them to do that:

NI-DAQmx: Continuous Multi-Channel Analog Output Example in CVI

Multiple Channel Analog Output of Different Frequencies - CVI

Hope this helps you to get started on your application.  Good luck!

Best regards,

[yogeesh]

Thanks Jarrod..

I'll let you know the results..

[yogeesh]

HI,

 I just tried with creating one task for both DC and Frequency signals but couldn't succeed.

Please find the attached file for your reference.

Regards
Yogeesh

[Jarrod_B.]

Hi Yogeesh,

If you are getting a particular error or have some specific questions about certain parts of your code, please let me know and I would be glad to help.  It would be difficult for anyone to help you troubleshoot without some more detailed information.  I tried running the code once just to see what was happening, and I got the error shown in the attached picture.  If you give some more detailed description of the exact problem you are having, we can try to narrow it down.

Best regards,