LabVIEW Time Sensitive Networking (TSN)

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Using an NTP server as master time.

Hi All,

 

Is there any way to get NI-TimeSync and TSN to work with an NTP as master clock? I have two TSN compatible CompactRIOs, they need to be TSN synchronized in order for the acquisition to be correct. But then I also need the timestamp in this data to be the NTP server based time. The timestamp needs to be based on our company's time reference.

 

Would this somehow be possible? If yes, how?

 

Thanks already!

Filip.

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Re: Using an NTP server as master time.

Hi Filip,

 

On time-aware chassis, the system time and I/O time are linked so that users can specify measurement events in terms of time on the target. For NTP, this means that if system time is steered by NTP and I/O timing is not, you'll see time drift on the system clock. This behavior is described in this knowledgebase article:

 

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000015ClDSAU&l=en-US

 

Please let me know if you have questions.

Austin
Product Support Engineer
National Instruments
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Re: Using an NTP server as master time.

Well, that's not a super specific knowledgebase article regarding NTP, but it does correctly describe what happens when you set the system time on a time-aware target. Since NTP acts on the system time, the behavior you would see if NTP appearing synced, but often drifting unacceptably far from NTP time between syncs.

Austin
Product Support Engineer
National Instruments
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Re: Using an NTP server as master time.

Hi Austin,

 

To word it slightly differently then the hardware clock will always drive the system clock. If an external service changes the system clock it will get driven back to match the hardware clock.

 

Therefore NTP wont work as expected on any chassis with TSN or 1588 components (including DAQmx) installed.

 

The inclusion of DAQmx is a significant one for some of my systems. Is there a recommendation for time sync of widely distributed DAQmx enabled cRIOs? (i.e. TSN is not an option due to location or network topology)

 

Cheers,

James

James Mc
========
CLA and cRIO Fanatic
My writings on LabVIEW Development are at devs.wiresmithtech.com
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Re: Using an NTP server as master time.

Ignore that last question - I realised I already asked it here (https://forums.ni.com/t5/LabVIEW-Time-Sensitive/Interfacing-TSN-with-Other-Network-Time-Standards/gp...) and the answer is no!

 

It would still be good to use something like NTP to reduce drift to global time IMHO. The clocks on the cRIOs are 200ppm which can still mean 17s per day drift to global time if my maths is correct.

James Mc
========
CLA and cRIO Fanatic
My writings on LabVIEW Development are at devs.wiresmithtech.com
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Accepted by topic author Braggel

Re: Using an NTP server as master time.

Hi James,

 

We agree on this point. We've had several customer requests for NTP functionality or the ability to correlate time from a source besides PTP, and it's become clear that this is a need that's currently underserved with time-aware chassis. We're looking into solutions but I can't confidently give any timeline information.

Austin
Product Support Engineer
National Instruments
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Re: Using an NTP server as master time.

Thanks for the clear answer. This will mean that in my case, I'll implement some kind of clock conversion/synchronisation manually in my code. (I don't need mind blowing precision here... Precise up to some seconds is ok for me.)

 

Kind regards,

Filip.

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