How can I detect a trigger missed (i.e. 2nd trigger arrives before the task completes)

Is it possible to know if a trigger pulse has been failed, because the device is busy?

To give a specific example:

I use a NI4462 Board with digital triggers of falling on the PFI0 entry point.

I have an external clock, exactly the 1 kHz square wave.

On each falling edge of the clock, I (re) start a task than 200 times, samples (200 kHz).

Normally, it works well (as long as I take care to keep the task, stop and start the task in a tight loop and not make too much treatment in 5 ms, which remains after the last sample).

BUT, if something went wrong (think of the external clock running too fast 1%), the 2nd trigger would happen during the running task (say, on the sample of 198).

The NI4462 (I think) simply ignore this trigger, because the task is still running, and I would miss out on a framework for data set, getting only the 1st and 3rd groups of 200,

Is it possible to detect when this has happened and raise at least one error?

Thanks for your help.

P.S. I also worry about the 63-sample-delay filter: is there a better solution than post processing to cut the beginning of a group and on the end of the previous 63 samples? This works well, but it incorporates a timing glitch after the 63rd sample.

Hello

I can't imagine a way to solve this problem in your task to the DAQmx. This should be relatively simple in FPGA or maybe even in real time. I'll come if I invent something.

You could check your trigger with a counter clock (just carry your meter with your signal of 1 kHz) and throws an error if it derives.

Perhaps I could ask a little more of the context of this question - why do you need this architecture? I don't know why you cannot acquire just streaming samples - this can lead us to a different solution!

I will mention that your schedules are very tight, as this 5 spare part is at best because I don't think that your sample clock is synchronized with the clock of your relaxation.

In response to your question about the delay, can preload you the filter before your main acquisition to lose the delay?

A bit like the solution described in this KB (http://digital.ni.com/public.nsf/allkb/F989B25FF6CA55C386256CD20056E27D?OpenDocument), of course you would have to set up your triggers properly. A trigger of reference might use with a size of pre-triggersample of 63.

I hope this is a help - let me know how you go.

Best regards

Tags: NI Hardware

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