How Is the Timestamp of the PXI-8531 Synchronized With the Host PC?

Updated Apr 3, 2023

Reported In

Hardware

  • PXI-8531

Driver

  • NI-Industrial Communications for CANopen

Issue Details

I'm using the PXI-8531 to communicate with a CANopen device in a long duration test. After 24 hours I see a drift of 2 seconds between the Host Computer Timestamp and the PXI-8531 Timestamp when using CANopen TPDO Read VI from the NI-Industrial Communications for CANopen driver.

How is the clock of the PXI-8531 synchronized with the Host Computer?

Solution

The CANopen driver pulls the system time during initialization. After this point, the PXI-8531 has its own free-running clock, separate from the rest of the chassis. This means that the polled timestamp and the CANopen Card timestamp will be different on a long duration run. This is because any set of clocks that aren't synchronized to each other will always drift by nature of how oscillators work.

There is no possibility to link the CANopen card to any other clock, you need to restart the CANopen session periodically or get the timestamp from another source.
 

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