Does the NI-9189 Support PTP?

Updated Apr 23, 2018

Reported In

Hardware

  • cDAQ-9189
  • cDAQ-9188

Issue Details

I have a 9189 chassis in my lab that I thought would support PTP. I have a host machine that's connected to the cDAQ, gets the time stamp, and uses the PTP time of the host to time stamp the first data element. However, I am seeing a lag in the time stamp and the time axis on the 9188. I saw that the 9189 might have better hardware to implement what I am trying to do. Does the 9189 support PTP?

Solution

The 9189 chassis supports TSN and uses 802.1AS time protocol to synchronize over the network. Because 802.1AS supports sending PTP packets, the 9189 chassis is capable of synchronizing with other devices and the host computer. There are two configurations to look out for depending on the application.

1. Daisy chain configuration
  • Daisy chaining will be the easiest implementation to synchronize your devices if you have a lower number of slaves on the network (2-6). TSN allows you to daisy chain using the ethernet ports on the chassis and you can share the tasks using channel expansion on the host. This configuration allows you to bypass a network switch and have to plugged into the computer or a network port with minimal effort.
2. Star configuration
  • If you have a larger number of slaves on the network (say 10+), you will have to incorporate an 802.1AS switch in between the devices and the computer. The 9189 chassis do not support the 1588 protocol directly yet so be sure that you are using the 802.1AS protocol when picking out the network switch to integrate into the system.

Additional Information

PTP is a package pattern between devices that falls under the 1588 time protocol umbrella. In most instances, the system will require a 1588 master, such as a switch, to dictate the network topology between all devices. Because our TSN devices don't fully support 1588 just yet, we can work with a subset of that time protocol using 802.11AS as noted in the specification sheet for the 9189 chassis. 

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