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I am having synchronization problems with a PXI system using 3 6071E boards – the master board is in slot 3 and acquires differential signals and the slave boards are in slots 1 and 2 and acquire referenced single ended signals.

The master board triggers and acquires data and when it is finished, the first slave board triggers and then 0.1 seconds later the second slave board triggers.
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Message 1 of 12
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I can't look at your VI--it gives me an error. Can you try reposting it?

Is the timing you mentioned in your question the timing you wish to have, or you want them all to simultaneously trigger, but the timing above is what you are seeing?

Mark
Message 2 of 12
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The timing that I mentioned is what I have. What I want to do is trigger the boards simultaneously and then sync the scan clocks using the master board to drive the slave boards. The master board collects 15 differential channels and each of the slave boards collect 48 referenced single ended channels. I am reposting the VI. I have also been working on a Stat - Machine to accomplish the same goal. I am posting that as well. Thanks for you help.
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Message 3 of 12
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Brian,

In your "regular DAQ" that you posted, I can see that you've combined two examples together, one for synching up the clocks, and one for synching up the start triggers. The way you have done this seems to be correct, except for one small thing.

If you dig a little deeper into the example on synching up the start trigger, you'll see that you have to tell the Trigger Config VI that you want to turn the trigger ON; therefore, when you call this VI and wire the RTSI1 for the trigger line, there's also an input to the Trigger Config VI called "Mode"--you must wire an "on" to this. (Do this for both slave boards.)

Try that first.

Mark
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Mark,

I made the correction, however, it did not change the performance of the program. If, for example, I set the sample rate to 50 Hz and collect 1000 samples, the difference in start times (based on the waveform time stamp) between the master board and the first slave is 19.999 seconds. The difference between the first and second slave board is 0.11 seconds. I am also getting an AI Control Warning 10694 that says my scan rate is either above the maximum or below the minimum for the hardware.

Thanks,
Brian
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Message 5 of 12
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Hello;

I can't open your VI. It keeps giving me an error. I believe it is something in your VI that is causing that extra delay. You can meanwhile take a look on how to program multiple devices in Labview, through its shipping examples.

Regards
Filipe A.
Applications Engineer
National Instruments
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Message 6 of 12
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Filipe,

Thanks for the interest. I will look at the shipping examples for multiple boards. I used NI examples from the web to write the code. I am trying to use a master board (in this case board #3) to trigger and sync data acquisition for two slave boards (boards #1 and #2). The master board collects 15 differential signals and each slave board collects 48 signals that are referenced single ended. They are all in a PXI 1000B chassis with the master board being in slot #3.

Thanks for your help.
Brian
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Message 7 of 12
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Brian,

I don't see anything that is intuitively obvious. Have you tried the included examples, specifically
1) 2 E-series shared digital trigger,
2) 2 E-series shared scanclk?

See if you can get either of these to work independent. Maybe we can narrow it down that way.

Mark
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Message 8 of 12
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Mark,

I went back and tried both examples. The 2 E-Series shared digital trigger performs correctly. The two boards are triggered with a couple thousandths of a second. However, when I tried the 2 E-Series shared scanclk example the performance was the same as my VI. The master board finishes its data acquisition before the slave board starts. In addition, this is the behavior independent of which board I select as the master and which on I select as the slave.

Brian
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Message 9 of 12
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Something seems fishy. I happen to have a PXI chassis with 2 E-series boards in them, so I'll try them as well. I've done synchronization before, and even a couple of thousandths of a second seems long for synching up. I'll get back to you here.

Mark
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Message 10 of 12
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