Resynchronizing C-Series XNET CAN Modules

[RHryniowski]

Hi community,

I'm using a C-Series XNET NI-9860 to collect CAN data, I start the session on Monday and by Friday the timestamps of the signals have drifted by ~1 second relative to the system clock and can't be trusted anymore.

I've read over some KB articles 

https://www.ni.com/docs/en-US/bundle/ni-xnet/page/nixnet/propertysessioninterfacesourceterminalstart...

https://www.ni.com/docs/en-US/bundle/ni-xnet/page/nixnet/synchronization.html

https://www.ni.com/docs/en-US/bundle/ni-xnet/page/nixnet/propertysessioninterfaceoutputstreamtiming....

But I don't understand how to synchronize the HW Clock to my system clock, and since it takes 4 days for the issue to return it's hard to trial.

If I stop then restart the session does this force the clocks to resync?  Or do I need to include a timing frame first?

Thanks,

[ZYOng · Accepted solution]

Regardless of which API is used, XNET will querry the host OS for the current system time when a Interface is started. At that point, the current time is placed into a interface specific timestamp regiseter on the XNET device. The timestamp register will then increment with every tick of the master timebase clock. When a CAN frame is acknowledged, a copy of the timestamp register is attached to the frame and placed into the receive buffer to be read by the XNET API.

Reference: Solved: Re: XNET Timestamp and Windows Timestamp Synchronization

So restarting the interface will force the hardware the query the OS time again.

[RHryniowski]

Thanks ZYOng,

The wording in the linked article is a little ambiguous, the commands I am using stop and start the session, the article uses the word interface.

This is the solution I went with, and I'll be watching for a few days to make sure it sticks, but is there a cleaner way?  Stopping and starting the session on the computer I have this deployed to takes ~4 seconds, (a lifetime in production) 😏.

[ZYOng]

An XNET interface can have more than one session. I am not sure if simply restarting the session will help.

There is a property that allows you to adjust the time without restarting the interface. However, I think it is only supported on PXI/PXIe module.