Repeat outputs with analogoutput without requiering to use putdata repetadly

Hi all!

I've got my analogoutput channel working as I want. When it receives a digital trigger on line PFI1 it starts the function that I loaded.

ao_Ref = analogoutput('nidaq','Dev1');
addchannel(ao_Ref, [1]);
set(ao_Ref,'TriggerType','HwDigital')
set(ao_Ref,'HwDigitalTriggerSource','PFI1');
putdata(ao_Ref, xt);
start(ao_Ref)

However once its started (and finished) the "buffer" on the nidaq card is empty. Triggering again doesn't do anything. Currently, I need to reload the data on the card by repeating the whole code.

Surely there is a much more efficient way to make it output the same data every time the trigger is activated.

Thanks,

Michael

Answer 1

[Walter Roberson]

No there isn't, not unless your hardware supports storing a buffer of data and sending the buffer on request. Which some hardware does, but most does not.

[Michael Leung]

Thanks Walter. I guess for now I'll just put the digital trigger line to a function generator, and use the "burst" function from that.

[Michael Leung]

Hi Walter, apparently it's possible.

http://zone.ni.com/devzone/cda/epd/p/id/4787

Would you happen to know what flags I need to trigger to enable this option?

[Walter Roberson]

I would need to research that; I am not familiar with how to program those devices, such as to construct the waveform buffer.

Which model device are you using?

[Michael Leung]

NI 6259.

I never managed to get it to work, so I moved this part of the code to a micro controller.

Answer 2

[Manisha]

Hi Micheal,

Have you looked at the property TriggerRepeat?

Regards, Manisha

[Michael Leung]

No, I have not. I was hoping that something like this would exist. I'm getting an error message now.

(I placed this line of code after the HwDigitalTriggerSource)

??? Error using ==> daqdevice.set at 261

Invalid property: 'TriggerRepeat'.

Error in ==> Ramp at 26

set(ao_Ref,'TriggerRepeat',10)

[Michael Leung]

http://www.mathworks.com/help/toolbox/daq/ref/triggerrepeat.html

Hmm it seems its only applicable to AI (Analog Input) channels.

I'd need it for Analog Output

Answer 3

[signal]

set(ao_Ref,'RepeatOutput',num)

where num is an integer or inf for continuous output.