simultaneously trigger and display two camera images with two frame grabbers

[Shahab K.]

When I try to simultaneously trigger and display two camera images, each with their own frame grabbers, Labview is only able to display one of the images at a time.

My hardware:

Two Sony XC-EU50 cameras (not in sync with each other)

NI-1410

NI-1405

My Software:

Windows XP and Labview 7.1 with IMAQ

I connect each camera to its own frame grabber.  Both frame grabbers are in the same computer.  I input a trigger into each frame grabber.  Both trigger signals are identical.  Trigger rate is only 0.2 Hz. 

I want to display and save both images at the same time.  The program i put together only displays one image at a time.  The image that is displayed alternates from one camera to the other.

Please help with any suggestions.

Thanks.

Shahab K.

[GuenterMueller]

Hi Shahab.
Without having triggered two cameras connected to two NI boards with LabVIEW yet: This shouldn't be a limitation in LabVIEW.

Updating two Image Display Indicators in one run of a while loop definitely works properly, so this cannot be the reason for the problem.

Your code uses the IMAQ Snap.vi. This VI is not reentrant, so the both instances of this VI on your block diagram cannot execute at the same time.
I could not find an appropriate example matching your scenario exactly. (Maybe someone else knows better?)
I recommend to have a look at the examples in the "IMAQ Signal IO.llb" and do some copy and paste to get a VI that satisfies your requirements.
The "Grab with two boards.VI" illustrates how to acquire images without using the not-reentrant "IMAQ Snap.VI".

Hope this helps, Guenter

P.S.: Do you know NI's Vision Forum? http://forums.ni.com/ni/board?board.id=200