trigger 9074

[MaxXx]

Hello,

I have an NI cRIO-9074 with several modules, namely 9215, 9203, 9213, and 9211. I have various inputs connected to these modules to record data for a flow (temperature, velocity, etc.) . I have a high speed camera that I need to sync the recording with the data. The camera will be taking pictures at 15 times per second. I have been reading and trying to figure out if it's possible to have an external trigger from the camera into the 9074 that will trigger the data recording of the sub-modules? So far it seems like it's not possible according to this document http://digital.ni.com/public.nsf/allkb/C11571D3F53DAC6C862574C9004C1A3C?OpenDocument . Are there any other ways around this?

Thanks,
Max

[nturley]

Let me make sure I understand.  You have a camera that sends out a signal whenever it takes a picture and four c series modules that are being used as sensors.  You would like to synchronize the approximate time that data was collected with the time the cameras picture was taken.  At first, I thought you meant you wanted to take some data from all four modules whenever the camera takes a picture, but it looks like the 9211 can only take 14 samples per second whereas the camera is taking 15 pictures per second, so that's not going to be possible. So I'm going to assume that instead, you are going to have the modules start collecting data as soon as the camera takes it's first picture and they will just chug out their data as fast as they can, independent of the speed of the pictures. If your start time is synchronized, then you can get the sample rate from the number of samples and the end time or you can solve for the end time from the number of samples over how long it was running.

The first question to ask yourself is how much latency is acceptable or in other words how close in time does the first sample need to be to the first picture?  The second question is how much jitter is acceptable or how important is it that it takes the same amount of time in between the first picture and the first sample every time you run your application?  If you need low latency and low jitter, then you should to get a parallel digital input module and connect your camera signal to it.  Your latency will be extremely low because the signal will go straight into the FPGA which can immediately trigger your input modules.  If you don't really care about latency and jitter and you'd rather not fuss with compiling FPGA designs, then you can connect your camera signal to the SMB connector, put the FPGA in scan mode and in your RT VI you'll need to get it to start pulling data from the modules the first time the camera signal goes high. I've never personally used the SMB connector, but the white paper you referenced seems pretty straight forward.

Good luck!

Neil Turley
RIO Software Engineer