How can I synchronize the PXI RT system time with a Host PC in a range less 10ms

[JoergLee]

How can I synchronize the system time from a RT PXI target with a host PC or time server in the network with a limit <10ms.

If I use the RT utility 'RT Set Time and Date.vi' I have an error till 500ms because I can only set seconds, but no milliseconds.

Is there a command under PharLab that I can connect the time server inside my company intranet, like the command w32tm.exe under Windows?

Best Regards

Joerg Koch

[Ken_Tobler]

Hello!

At the time on Pharlab its not possible to set Time in software with a higher resolution of a second.
It means that you can only set with the "RT Set Time and Date.vi" the timing of you RT Controller.

It means that to check the synchronisation of the RT Target and the PC you should run the RT Target
and the host PC and make a comparison of the two timestamps.
Ifa after 100Seconds the PXI Timestamp is always the same with the PC Timestamp, then you can assume
that the both system are running with a synchronised clock <10ms.
Sure, this workaround is not for a simultaneous start of both clock <10ms.

Best regards
Ken

[Peter-R]

This is good - is there any updated information that describes best practices for syncronizing timing between the Host PC and RT targets?

[Bob_Schor]

I've always assumed (without proof, so I could be totally wrong) that "Time" reported by the PXI would be precise, but possibly not accurate (meaning if it said 20 ms elapsed, then this is correct, but if it says that the time is 11:01, it might really be 11:02), while the PC is more likely to be accurate (because it can sync with a Time source) but not precise (because of Windows, largely).  Hence I use the PXI and its clock for all the "delta-time" measurements, and if I need Absolute Time, I take a single reading on the PC at a known point in the program (say, when I start the PXI) and call this "Time Zero".

Theire are "Time Synchronization" tools that can be installed in MAX -- I've not really studied them, so don't know if they'll help.

It seems to me that if we assume that the PXI and PC clocks run at the same speed, then if we accurately know the time offset between them, we can use either clock (as appropriate) and add/subtract the offset to standardize the time measurements.  So it may come down to how to get both platforms to accurately "respond" to a request to get the time.  If you could do a round-trip "message exchange" between the two that was sufficiently rapid, you could use that, I suppose.  Something we used a long time ago was to toggle a bit on the parallel port (what's that, Grandpa?) on the PC, read this into a DIO port on the PXI, and record the transition time ...

I'll be interested to see how you resolve this.

BS

[JamesB.]

NI offers several options for synchronizing systems and devices. As an introduction, it may be helpful to review the Synchronization white papers.

Bob_Schor mentioned the "Time Synchronziation" tools, by which I think he is referring to NI-TimeSync. NI-TimeSync is a software-only product that runs on RT targets. It comes with a couple of plugins that support different synchronization protocols, including one for the IEEE-1588 Precision Time Protocol; beta versions of some other plugins are also available in Sync Labs, including the SNTP and FPGA timekeeper plugins.

P.S. The RT platform is correctly spelled "PharLap."