1588 synchronization of distributed cRIO systems

[MilosR]

We need to establish 1ms synchronization on FPGA on 6 cRIO systems which are 1 - 1.5 km away from each other. All cRIO systems would be connected to gigabit ethernet network over optical fibers. My question is if this kind of synchronization can be done through IEEE-1588 protocol? I tried to search for some benchmark on ni.com but only thing I found, which gave me some information about this, was this tutorial saying that submilisecond syncronization can be achieved and image in this tutorial. Based on those, 1588 should be good enough for our needs, but I'm not sure if this refers only to systems with 1588 interface (e.g. PCI or PXI) or it is also valid for cRIO systems distributed over long distance (as in our case) with NI-TimeSync installed?

[MilosR]

I forgott to say thank you for any help you can provide 🙂

Best regards,

Milos

[drich · Accepted solution]

Hello,

I think we should be able to meet your needs. The submillisecond synchronization that was mentioned can be achieved with software 1588 using the NI-TimeSync product.

https://www.ni.com/en/support/downloads/drivers/download.ni-timesync.html

This is available for both cRIO and PXI and will work with your cRIO's. The distance and the fiber shouldn't be a problem but since all of these nodes won't be connected to the same switch, each intermediate switch/hub will add noise and jitter. This will especially be a problem if the network is very heavily loaded, as the switch/hub won't be able to immediately pass packets through. If your network isn't heavily loaded and there aren't excessive switches and hubs in between devices there shouldn't be a problem.

NI-TimeSync will set the RT system time but from you question it looks like you want to pull this time into the FPGA as well as sync'ing the RT system time. Is that right?

In that case you will also need to use the FPGA Timekeeper.

https://forums.ni.com/t5/Sync-Labs/NI-TimeSync-FPGA-Timekeeper-Getting-Started/td-p/3543895

The FPGA Timekeeper is currently only available as a NI Labs product. It allows you to keep track of time in the FPGA and derive FPGA time from the RT system time or to go the other way and derive RT system time from the FPGA. The second use case requires the custom time reference as well, but you are looking for the first use case and won't need the custom time reference.

On the page that has the FPGA Timekeeper there is a link that has an example project on how you would take RT system time and push that time into the FPGA(which is what you want).

Does that help clarify things for you?

Daniel Rich

Software Engineer

[MilosR]

Hi Daniel,

Thanks for calrifying performance doubt I had. I'm glad to hear that you think NI-TimeSync will meet our needs, and considering our network configuration I also now believe we will be able to pull out 1ms sync.

You are also right that I need this time on the FPGA as well. FPGA Timekeeper link which you've recomended is great and seems like exactly the thing I needed. I have analyzed example and it was also very usefull.

All in all, a very helpful reply.

Thank you Daniel.

Best regards,

Milos