Enabling IEEE 1588 Precision Time Protocol (PTP) on a PXI Controller for System Synchronization

Issue Details

I want to enable Precision Time Protocol (PTP), also known as IEEE 1588, on my PXI controller so that it can serve as a highly accurate reference clock source. My goal is to use this synchronized time to coordinate operations across my entire PXI system. Specifically, I would like to know if it is possible to configure the PXI controller to receive or generate PTP time and then distribute that clock signal to other PXI modules within the same chassis. Can the controller share the PTP-based clock through the PXI backplane or other synchronization lines to ensure all modules operate in sync?

Solution

While it is technically feasible to enable IEEE 1588 PTP on the PXI controller, there are several important considerations that explain why National Instruments does not recommend its use for PXI system synchronization. Please refer to the following points for further clarification:

1) PTP Support by Hardware vs. Software: 

The Intel Ethernet controller in some of the PXI controllers supports IEEE 1588 at the hardware level. However, NI has not tested or officially supported this functionality in their software stack. This means that while the hardware is capable, NI software (like NI-Sync) does not currently utilize this capability directly.

2) Third-Party Software Requirement: 

To use PTP on the PXI controller, users must rely on third-party PTP software (which is not supported by NI). This introduces complexity and potential compatibility issues, as NI does not provide support for these configurations.

3) Chassis Synchronization Limitation: 

Even if the PXI controller is synchronized to a PTP Grandmaster, the PXI chassis itself is not automatically synchronized. The PXI modules often rely on the chassis backplane clock for timing. If the chassis clock is not synchronized to PTP, modules may drift relative to the PTP time.

4) Need for a Dedicated Timing Module: 

To synchronize the entire PXI system (including the chassis and its modules) to PTP, a dedicated timing module like the PXI-6683H is required. The PXI-6683H is designed to receive PTP signals and distribute synchronized timing across the PXI backplane.

5) NI-Sync Support: 

The NI-Sync driver currently supports PTP synchronization only through the PXI-6683H. Other methods (e.g., using the Ethernet controller directly) are not officially supported, though they may be technically feasible with custom or third-party solutions.

In conclusion, while IEEE 1588 PTP can be enabled on the PXIe-8822 due to its compatible Ethernet hardware, this does not ensure full PXI system synchronization. The PXI chassis and its modules rely on the backplane clock, which remains unsynchronized unless a dedicated timing module like the PXI-6683H is used. Without this, only the controller aligns with PTP time, while the rest of the system may drift, limiting the effectiveness of PTP-based synchronization.