Triggering GigE Camera with Hardware Trigger

Question

Hello,
Here is an outline of what I want to accomplish:
-LabView program starts running and waits for GigE camera to output frames
-Hardware trigger leads to GigE camera outputting frames
-Some simple arithmetic is done on each frame to generate the average pixel value--> this average value is plotted for each frame
-Repeat the above three steps
Please see the attached VI. I have successfully set my camera's settings in MAX to make it wait for an external hardware trigger. However, the output of IMAQdx Grab2.vi inside the While Loop is only a single frame (even though in MAX I have set the Acquisition Mode to MultiFrame - 255 Frames).
Any help would be appreciated!
Thank You.
Solved!
Go to Solution.
Attachments:
ImageGrab.vi ‏57 KB

Answer 1

The "problem" that you are having is the frame rate of video acquisition, which you think is about 20 Hz.  Take the very simple VI I posted and run it with your camera -- all it does is continuously take frames (and display them) -- does this have an acceptable rate?  I suspect it will.
If so, then "start with what works and add to it", rather than trying to "fix what is broken".  First, let's consider how to (better) control the Start and Stop of frame acquisition.  I like your idea of using the 6009, but I recommend (if you are using a 3V signal as the trigger) that you wire the trigger to one of the Digital I/O ports (as 0 and 3V are acceptable TTL levels for False and True).
Your Video loop will be "clocked" by the Camera at its frame rate, so you might consider using the same loop to clock the DIO.  Take a Digital sample of the line to which you've wired your TTL signal, and as long as it is True, run the loop.  [You'll need to think about how to get the loop started ...].  It should, I think, be possible to read from your USB 6009 within a 60th of a second -- if it is too slow, there are other ways of handling this with a separate parallel loop, but let's not go there until we see it is a problem.
So now, in principle, you've gone from a simple loop showing frames at 60 Hz to a loop controlled by a TTL signal showing frames at 60 Hz.  All we need now is to process those frames.
Here is where you want to use a Consumer/Producer pattern -- you don't want to do processing inside this loop (because the loop cannot run faster than all of its parts, taken together, and if you are processing incoming data, you have to get the data, then do the processing).  Instead, you have have two loops running in parallel -- the Producer loop acquiring the videos, and then "exporting" them to a Consumer loop that processes them.
Are you familiar with this pattern?  There are numerous examples around (look in File/New/From Template/Framework/Design Patterns, and at some of the Sample Projects).  It uses a Queue, with data put onto the Queue by the Producer and removed by the Consumer.  You might need to increase the number of buffers for your camera, but you should be able to do quite a bit of processing in 1/60 of a second.
Bob Schor