Problem configuring two PCI-6534 cards for double buffering using external timing source

[JasonW]

Hello,

I am having problems configuring two pci-6534 cards for double buffering (the double buffering on port 0 is clocked from an external clock, while unstrobed ports 1-3 do not use external timing)

First of all I'm using NI_DAQ version 6.9.3 and am running under XP SP-2. 

When I follow the following procedure, only the card ID 2 will function (card ID 1 does not)

Add device 1 (add the first card)

Add group  to device 1

Configure Unstrobed on device 1 port 1-3

Add device 2 (add the 2nd card)

Add group to device 2

Configure Unstrobed on device 2 port 1-3

Set up Double Buffer on device 1 (nothing is outputed from this device)

Set up Double Buffer on device 2 (this device outputs correctly on the double buffer port)

Now if I do the following, I can get both cards working as intended

Add device 1 (add the first card)

Add group  to device 1

Configure Unstrobed on device 1 port 1-3

Set up Double Buffer on device 1

Add device 2 (add the 2nd card)

Add group to device 2

Configure Unstrobed on device 2 port 2-3

Set up Double Buffer on device 2

The problem is my test hardware does not have the external timing available when I first configure the 6534 card so I have to set up the unstrobed lines first on both cards.  Those unstrobed lines set some hardware bits that allows the external clock to be available for the double buffering, yet only device 2 will work when I try this.

Anyone offer any help?

[Otis]

Hi Jason,

You mentioned that you are using NI-DAQ 6.9.3 with a PCI-6534.

As I'm sure you know the Traditional DAQ commands are a bit older and more complicated to use.  This particular instance is a great example of just why DAQmx is such a great benefit for DAQ programmers.  If you could update to the latest version of DAQmx, then you will no longer even have to worry about how you double buffer the data because all of that is handled automatically.  You can then more easily set your ports to strobed or unstrobed and simply acquire the signals that you are looking for. 

There are even some great examples on how you can do digital operations in DAQmx. 

If you are using LabVIEW go to:
Help > Find Examples > Browse > Hardware Input and Output > DAQmx > Digital Measurements

Or if you are using Text-Based programming you can find examples here:
C:\Program Files\National Instruments\NI-DAQ\Examples\DAQmx ANSI C\Digital\Read Values

Hopefully this will make your life much simpler and it will be much easier to diagnose any other issues if you are using DAQmx.

Regards,