simultaneous read

[iturriamiren]

Dear all!

I'm using the following vi in order to read data from two devices (two USB-6009 adquisition boards) and a channel I myself have built.

Although I have managed to synchronize both DAQ boards in order to start reading data from both devices at the same time (I have used a stacked sequence structure including the two start task.vi-s), I'm not sure how could I mange to start the loop that reads the boolean control channel with the other two loops at the same time.

Could somebody help me? I would be very pleased.

Thank you very much in advance,

Miren

[DavidOna]

Hi Miren,

    There is no synchronization between your analog acquisitions, since you are not using the same clock signal to perform the acquisition. The only thing you are doing is starting the tasks at the same time, which could be interpreted as sending a "kind of software trigger" to start the tasks at the same time (this is not strictly true as detailed in the follwing document). Since the DIOs in the USB-6009 are not correlated, it does not have much sense synchronizing the associated task with the other two. Anyway, you can give a try and include the "DAQmx Read" VI for the digital lines in one of the loops related to the analog input operation.

Regards,

[iturriamiren]

Dear David,

Thank you very much for your answer but I don't really understand one of your suggestions.

"Anyway, you can give a try and include the "DAQmx Read" VI for the digital lines in one of the loops related to the analog input operation."

Which are the digital lines you are refering to? Do you mean the boolean channel I myself have built? As far as I'm concerned, I'm not using any digital input from the USB-6009 to acquire this information.

I have also read your documents and I had some doubts about them. In case I would be using an Externally Powered USB M Series device, how could I manage (in the previously attached example) to send a trigger signal to the boolean channel in order to start reading the samples?  

Looking forward to hearing from you,

Miren