cDAQ-9178 & cRIO-9073 Eternal Triggering and Clock Synchronization

[golubovski]

Hello,

I have ordered the following hardware and look forward to its arrival:

cDAQ-9178 chassis

cRIO-9073 chassis

NI-9234 DSA modules (4)

To build a USB DAQ system and play with the cRIO. I have the following couple of questions:

1. cDAQ-9178

Besides the autonomous DAQ function it is expected that the cDAQ system would be able to integrate with our lab PXI DSA system. I was fooled by the presense of the PFO0 and PFI1 connectors and implicitely missunderstood that I have the EXT-TRIG and CLOCK-SYNC inputs required for the DSA integration of the PXI and the USB chassis. Now I see I need a DIO module present so I could route-in both sync signals. Yet, there are 4 CTRs on the cDAQ-9178. Is there a workarround to import both signals through the PFI0 and PFI1 via those 4 counters so I wouldn't waste a slot on a DIO module? Anybody done that, willing to share?

2. cDAQ-9073

Same question. I haven't noticed at all that cRIO-9073 chassi does not have an EXT-TRIG DI. Not that I need it, but how are EXT-TRIG and CLOCK-SYNC implemented here with no additional DIO module?

I apologize for wassting your time if questions are stupid.

Thanks in advance,

[Dan_N]

Hi,

Yes, you can import triggers and a sample clock into a cDAQ-9178 over the two PFI lines. You just need to specify that you will be using one PFI line for your triggering signal, and the other PFI line for your sample clock. In order to do so in LabVIEW, just wire the PFI0 or PFI1 channel to the "source" input of the DAQmx Start Trigger and DAQmx Timing VI. 

For the cRIO, which does not have PFI inputs, you will have to purchase an additional DIO module.

Best,

Dan Nelson

Applications Engineer

[golubovski]

Hello Dan,

Thank you for the prompt and clarifying response! I am happy that the cDAQ will be able to get triggered and clocked via the 2 PFI connectors WITHOUT additional DIO module.

Concerning the cRIO-9073 which lacks such PFI inputs and therefore needs a DIO module - which DIO module, with regards to DIO specifics? I expect no problem for ANY DIO C-module to sense digital trigger, however would ANY DIO C-module be able to track external clock woth regards to both the chassis capabilites and the ext-sync "speed" (kHz, MHz, ...)?

Thanks again,

[Finnabon]

Hi Dan,

Since the DSA modules use a master timebase of 13.1072 MHz, you will not be able to export this clock via the PFI line on the 9178 chassis due to a bandwith limitation of 1 MHz. However, you will be able to export the divided down Sample Clock. This will be at a maximum of 51.2 kHz, so as long as your DIO module has that bandwidth you should be fine. For example, the 9401 or 9402 would be sufficient.

Kind Regards,

[golubovski]

Hi Allie,

Thank you too! I use lowest possible sample rate (1kHz with 4472) so it is not an issue. So current status on my topics would be:

1. cDAQ-9178 - SyncClock

How do I import the divided Sample Clock? - Again through "DAQmx Timing (Sample Clock).vi"..., there is no other way to import?!

2. cDAQ-9178 - ExtTrig

I can sense START trigger on of the two PFI lines. How can I implement STOP trigger? - Is it possible to trigger it on edge? On my PXI system I START DAQ with an edge on one of the 4472s TRIG input and STOP the DAQ with a level change on a DI line on a 9713!

3. cRIO-9073 - ExtTrig

Are you discussing 9401 and 9402 for the cRIO chassis or are they mandatory equipment for the cDAQ-9178 also?

So far I have played with simulated devices since I still await the package.

Thanks in advance,

[Finnabon]

Hi again, 

1. You should explore using the DAQmx Export Signal.vi. This should allow you to route the sample clock or triggers to the PFI line.
See this DevZone: http://zone.ni.com/devzone/cda/tut/p/id/5376

2. I think what you are looking for is the Pause Trigger. You should be able to implement this the same way you did in your PXI setup. You can find the Pause Trigger in the Triggering Property node. 

3. You'll need the DIO module for the cRIO chassis to route the trigger from the PFI line on the cDAQ chassis to the cRIO.

Note that currently synchronization over multiple cDAQ chassis is not supported because of the signal degradation resulting from passing the external timebases from chassis to chassis. Your best bet may to synchronize by use of triggers alone instead of routing a clock.

Multiple synchronization of DSA across chassis' is supported on cRIOs. If you wanted to get an additional cRIOs, this can set you up.

http://zone.ni.com/devzone/cda/epd/p/id/6146

I don't personally support cRIO, but you should be able to put all of your DSA modules in the same chassis to ensure synchronization.

To synchronize modules in the same chassis you can do channel expansion, as seen here:

http://digital.ni.com/public.nsf/websearch/78E44565FD87E7D686257108007F94F8?OpenDocument

More about synchronization:

http://zone.ni.com/devzone/cda/tut/p/id/6829

Hope this helps some!

[golubovski]

Allie,

Sorry for the little delay - YES I think you helped a lot if I understand the Digital Pause Trigger correclty. I ran into this link:

https://decibel.ni.com/content/docs/DOC-12256

I understand that I can use the same PFI line of my cDAQ-9178 to both trigger by edge, and pause by level - is this correct?

In my PXI setup I use a 4472's TRIG to start DAQ and a 6713's DI to track the level change for stopping the DAQ. If that is correct than can I do the same with my PXI setup - use the TRIG line for both edge and level tracking?

Roman

[Finnabon]

Hi Roman,

If I understand correctly, I believe that will work. Worse case scenario you'll have to use one PFI line for start trig and another PFI line for the pause trig. The example you found should work for the cDAQ as well. I'm sure you've checked out the 9178 manual by now. But you can see can on page 2-8 where the pause trigger is discussed.

http://www.ni.com/pdf/manuals/372838c.pdf

Let me know if you need more information about this!

[golubovski]

Allie,

Thank you again! The hardware has arrived today and I managed to test the channel expansion already. I will try to fine dsome time off during this week to test the idea. I would like to export "sample clock" from my PXI-1006 chassis (9x PXI-4472 and 1x PXI-6713); and import it as SYNC in the cDAQ-9178 via PFI1; and import the TRIG to Start/Pause the DAQ via PFI0.

I will keep you informed :)))

Roman