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Analog Start Trigger does not work for Analog Output tasks

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Hi there. I am wondering anyone has tested the Analog Start trigger mode for Voltage - Continuous example found under Hardware Input and Output -- Analog Output folder in the Labview.

My device is PXIe 6358 which has two APFI lines and supports analog triggering. Although it is very difficult to find information about using Analog Triggering for Analog output tasks, what I have learned so far is to wire the interested analog trigger signal (an external sound for example) to both the AI channel that is used as a trigger source (ai0 in my case) and to an APFI channel (APFI0 in my case).

While testing the above example vi, no matter what trigger level that I set (even with 0), the output task did not work at all. No error message is returned either. Just for your information, I am doing physical tests, not just software simulation, so no signal means no signal.

Any help is appreciated!


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Message 1 of 9

Just to push it up to get some attention. Problem ansolved!

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Message 2 of 9

I don't believe that the AO system uses a Start Trigger.  I think you call the DAQmx Start Task, and it starts to run.  I do not have this board, but I did look at its manual and find no indication that AO uses a Trigger.  Note that if noone replies to contradict me, it doesn't prove that I'm correct, but it doesn't disprove it, either ...


I hope this is helpful.


Bob Schor

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Message 3 of 9

You shouldn't have to wire the signal into both the APFI line and the AI line. If you want to monitor the signal as well as use it as a trigger, then you will need to wire it into both places but if you want to just use it as the source for an analog trigger then you should only have to wire it into the APFI line. 


Have you tried simply observing your signal to ensure that you are reading the signal in correctly or that the signal is such that it will set off the trigger that you have set up?

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Message 4 of 9

Dear Bob,

    The X series user manual does state that analog output task can be triggered by analog input signal, see 5-4 to 5-7 (Chapter 5, page 4 to page 7). Unfortunately, it is not detailed. The example vi that I mentioned also have the option of analog start trigger. But I just could not figure it out. I believe very few people have ever test it.

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Message 5 of 9

Dear Charles,

    I had a test of your suggestion of only wiring the trigger signal to APFI0. Unfortunately, it does not work either. I also tried to only wire the trigger signal to ai0, similarly the result is negative.

    I can clear your concern that I might have made a mistake with the level of the trigger signal. I have used the same trigger signal to initialize analog sound recording and it works fine. In other words, there is no problem of doing analog input tasks with analog start trigger. 

    I am in contact with NI engeneer since yesterday. The engeneer is working on my problem and gave me several options. As he did not offer me a specific solution, I guess that he did not have the right hardware or opportunity to test the example vi. Up to now, I have tested all these suggestions, again, it did not work. In short, it must be an unsual problem that has not get the attention of NI itself.

    I will continue to search for solutions and alternative programing ideas to get around my problem.

    Any suggestion is welcome and I can directly test it.

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Message 6 of 9

I'm glad to hear you are working with NI support on this issue. If you happen to find the solution feel free to post it here for others to see.

Brandon Grey
Certified LabVIEW Architect

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Message 7 of 9

Sure, once I get a solution.

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Message 8 of 9
Accepted by topic author luojh135

Here I sumarize the solutions to this question, just mean to say thanks to all the people who helped me with this topic.

To use analog trigger for analog output tasks, make sure the trigger signal (ai input) is connected to APFI0. There is no need to connect the same trigger signal to ai0 if you don't want to record the trigger signal. However, if you do want to record the trigger signal, connect the trigger signal to both ai0 and APFI0 with a signal splitter. In the latter case, the ai task don't have to take the same trigger as the ao task. This means that you can start your recording with or without a trigger, while let the ao task wait for a certain trigger signal. This is helpful in a situation that you only want to generate ao task to a certain trigger event, such as when a sound signal reaches a certain sound pressure level.


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Message 9 of 9