Data acquisition from NI 9215 with external trigger signal sync

[mcduff]

Other possibilities, note I have not tried all of these.

1. You can sync the chassis to an external time signal through the Ethernet port, either 802.1AS-2011 or 1588-2008. You can sync this and instead of getting an array of points get an array of waveforms that contain the timestamp.
2. Use an external GPS that can output a pulse train at a set rate. I have done this with some GPS modules. The pulse train is locked to the GPS; you can use this pulse train as your TTL trigger. It may be possible to output your pulse train from the GPS at a specific time, thus you can later backfill the timestamps. NI has PXI modules that can do this, but Trimble at other GPS manufacturers may also have the capability.

[Kevin_Price · Accepted solution]

I don't what "rackDAQ" might be, but I would first suggest you right-click the DAQmx channel constant that specifies your counter channel and select I/O Name Filtering...    Then check the box to include internal channels.   Look for counters with a leading underscore in the name, similar to "cDAQ9185/_ctr0".  Those would be the internal counters I'd hoped you could find back on your original chassis.

-Kevin P

[DanFreeze]

Thank you all for the input! I think I have exactly what I need now and learned a lot in the process.

Including the internal channels in the I/O Name Filtering did the trick and I was able to access the counters on the cDAQ.

I attached the final VI in case someone else is interested in this.

[Kevin_Price]

Some things are easier done than said.

I think you'll find that this isn't quite your final version after all.  Attached are some mods that should get you closer, along with several cyan-colored comments I added.

There are still at least a couple things to address.

1. To *really* sync up your timestamps with your AI samples, you need to carefully work out the implications of some things I mentioned back in msg #9.  Remember that the end of the 1st full period is the same point in time that you're capturing your 2nd AI sample.  There's a built-in "off by 1" problem to deal with.  Depending on your hardware, the 1st full period may end at either the 1st or 2nd value in your timestamp array.  You need to figure out which, and then you can prepend a t=0 value in front of that 1st full period.

-Kevin P