IRIG-B with NI 9467

[IgorE]

Hello,

I have a question on using a NI 9467 (GPS Timestamping and Synchronization Module).

Based on its description http://sine.ni.com/nips/cds/view/p/lang/ru/nid/210834, I can conclude there is only one input used to connect a GPS antenna. But what if I already have a GPS clock streaming time info in the standard IRIG-B format? Can the NI 9467 be connected to such a GPS clock? I assume the answer is no but wanted to make sure I understand what happens.

Also, could anyone tell me if a NI 9467 is suitable for ALL cRIO platforms including cRIO-9074: http://sine.ni.com/nips/cds/view/p/lang/ru/nid/203964.

Thank you,

Igor.

[AndyCandy · Accepted solution]

Hi Igor,

Yes, I believe you are correct.  Based on all the documentation my colleagues and I can discover, the 9467 does notn support streaming time info in the standard IRIG-B format, so would not be compatible with that form of GPS clock.  

Also, according to the following article, the 9467 is compatible with all cRIO platforms--http://www.ni.com/product-documentation/8136/en/

[IgorE]

Hi Andy,

Thank you for your quick reply.

Could you please also tell me if there is any platform produced by NI that does have support for IRIG-B? Is using NI 9467 embedded into a cRIO chassis together with a GPS antenna the only option to make the internal clock synchronized with an external GPS-based time source?

Here - http://sine.ni.com/nips/cds/view/p/lang/en/nid/210834 - under the overview tab, there is a note about the FPGA Timekeeper saying that this is "LabVIEW FPGA IP designed to integrate the CompactRIO onboard FPGA clock with external timing sources such as SNTP, IRIG-B, and GPS". That makes me believe IRIG-B would not be mentioned without some built-in support for it.

Thank you,

Igor.

[AndyCandy]

Hi Igor,

Glad to be of assistance.  Unfortunately it doen't look like there is a module that directly supports IRIG-B.  This article sums it up pretty well--https://lavag.org/topic/18868-ni-fpga-timekeeper-and-irig-protocol/

This post within the article gives good insight into the FPGA Timekeeper--"The FPGA timekeeper is timing source independent. It's like the backend, you give it a time and it will synchronise to it, the main benefit is it will manage servoing the time, so rather than one big step change, any difference is corrected gradually."

So the Timekeeper description mentions it supports IRIG-B, but you'd have to do some decoding of the protocol.  NI doesn't recommend IRIG-B for synchronization in the first place, however.  If possible I'd suggest moving toward another protocol like GPS.

Unfortunately there aren't a plethora of options available for time-sychronizing cRIO systems.  The 9467 is the only module that supports GPS synronization.  

[IgorE]

Hi Andy,

Ok, I got the idea. Thank you very much!

Igor.

[Be11]

Hi Andy,

I had the same question. Thanks for the info and the link.

If I have to use IRIG-B ( or even ethernet IEEE 1588), do you have sugegstions/recommendations on how to do the encoding for it? Can the encoding be done in LabView and be compiled on the FPGA? Or a seperate IRIG-B encoding module is required?

THansk,

Behnoosh

[AndyCandy]

Hi Behnoosh,

Are you referring to decoding the IRIG-B signal?  If so, this link may prove useful--http://www.ni.com/example/28396/en/.  The link I sent previously also has some relevant information.  The coding should be able to implemented in LabVIEW FPGA, rather than an external module/toolkit.

Hope this helps!

[Be11]

Great, thanks Andy, (yes decoder, not encoder) I beleive I undesrtand it better now. To sum it up:

I don't want to use GPS module (NI 9467). I already have an external GPS which streams timing info in IRIG-B format. I can use the IRIG-B decoder implemented in LabVIEW FPGA VI (my time source). Then this time source can be feed to FPGA timekeeper?

How about if I need to use ethernet based protocols ( PTP,SNTP, IEEE 1588)? Is there a decoder for these as well?

Thanks,

Behnoosh

[AndyCandy]

Behnoosh,

Yes, that is correct.  You should be able to use FPGA timekeeper after decoding the IRIG-B signal.

Here are some resources to get you started with ethernet based protocols--

https://decibel.ni.com/content/docs/DOC-14480

http://forums.ni.com/t5/Real-Time-Measurement-and/1588-synchronization-of-distributed-cRIO-systems/t...

http://www.ni.com/newsletter/51018/en/

[LindsW]

Hi All,

Just wanted to clarify something on Andy's latest post. The third link mentions a IEEE 1588 software beta program. This driver has been released since the posting of this article, and is NI-TimeSync, the latest version of which can be downloaded here.

NI-TimeSync provides a way to synchronize system time on RT controllers via IEEE 1588. To synchronize the FPGA time as well, you can use the FPGA Timekeeper in addition to NI-TimeSync.