NI-DAQ driver support for multiple cards

[alexandru gris]

Can I perform multichanell double buffered data aquisition using
LAB_ISCAN_Start from two different devices at the same time?

[Chris Matthews]

No, you can synchronize the cards with RTSI signals and you can set them up to start from the same trigger, but you can have one DAQ session running on multiple cards.

Best Regards,

Chris Matthews
National Instruments

[alexandru gris]

Here is my problem: I have 2 PC-LPM cards plugged into my computer. When my application starts, I need to start aquiring data continiously from both. I have employed 2 threads to do the job, but the OS hangs. I tried to use only one thread in a scenario like this:

iStatus = DAQ_Rate( 50000 , 0, &iSampTB, &uSampInt);

iStatus = DAQ_DB_Config( 1, 1 );
iStatus = DAQ_DB_Config( 2, 1 );

// start the conversion
iStatus = Lab_ISCAN_Start( 1, iNumChans, 0, ..
iStatus = Lab_ISCAN_Start( 2, iNumChans, 0, ..

if I comment the "DAQ_DB_Config( 2, 1 );" the code works. Otherwise, it hangs on the second call to Lab_ISCAN_Start.

Please help!

[Filipe A.]

Hello;

The best way to have multiple DAQ devices running at the same time is by using the RTSI bus to synchronize both devices with the same clock. To do that, you need to have a RTSI cable connecting both boards together.

I'm attaching an example showing how to use RTSI to synchronize the analog input with the analog output on the same board, you can extend that idea to synchronize analog input on multiple devices.

Hope this helps.
Filipe A.
Applications Engineer
National Instruments