Data in the Analog Output buffer vanishe before generation

Hello folks!

I wish a happy new year to every one!

I'm using a National Instrument PCI-6120 (Driver NIDAQmx 9.4) with a BNC-2120, with MatLab 2010a. I'm trying to synchronize the generation of a signal with an acquisition. Easy peasy... as it should be...!! But I have an issue with the analog output (AO)! Here is how I configured AI and AO so that they are synchronized:

set(ai,'TriggerType','HwDigital')
set(ai,'HwDigitalTriggerSource','PFI0')
set(ai,'TriggerCondition','NegativeEdge')

set(ao,'TriggerType','HwDigital');
set(ao,'HwDigitalTriggerSource','PFI0');
set(ao,'TriggerCondition','NegativeEdge')

So theoretically, on a negative edge of PFI0, both AI and AO should start running, right?!

So I put some data into the AO buffer (using "pudata" function), and I execute start(ai) and start(ao) so that they get ready and wait for a trigger. But then, after having executed start(ao), and before any trigger happens, the AO returns to the initial state: no data in the buffer and AO waiting for start. I don't understand. And the most impressive thing is that if I plug a scope at the output of the AO, I don't see any signal being generated! It's like I didn't do anything! The data in the AO buffer simply vanished.

Does anybody have a clue...?

Thanks a lot in advance.

Luc

[Walter Roberson]

That's the Legacy interface, right, not the session-based interface?

[Walter Roberson]

It appears you would need R2011b to use the PCI-6120 with the session-based interface, so no point in trying to work around the problem with the session-based facilities. Ah well.

Answer 1

[Manisha]

Hi Luc,

Any chance you can upgrade to R2011b or R2012a pre-release? With session-based interface, starting 11b, your analog input and analog output channels on the same device will be synchronized automatically if added to the same session.

Thanks,

Manisha