Using NI-9469 to Synchronize Two cDAQ Chassis

Updated Apr 28, 2023

Environment

Hardware

NI-9469
cDAQ-9178
cDAQ-9179
NI-9229

Software

LabVIEW
Measurement & Automation Explorer (MAX)

In this document, you will find the instructions to synchronize two chassis cDAQ-9178/9179 using the NI-9469.

Each chassis must have one NI-9469 to be installed, so two NI-9469 are required in this case.
Check the module datasheet to ensure that these modules allow synchronization.
- Modules that accept an external master time bases are one example of the criteria.
Plug in power of each chassis cDAQ-9178/9179.
Use USB cables to connect two cDAQ-9178/9179 to the same host computer.
Install one NI-9469 on each cDAQ-9178/9179.
According to NI-9469 Getting Started Guide, CAT 5e (Shielded Twisted Pair) wire should be used to connect two NI-9469.
- Some CAT 5e wire engrave words "CATEGORY 5E PATCH CABLE"
Select any topology based on application and timing requirements. In this example, star topology is selected because it can reduce skew and delay due to shorter cables.
- Refer to NI-9469 Getting Started Guide >> Topologies section for more details.
- Open NI MAX to configure the NI-9469.
Refer to Synchronization Explained, design a LabVIEW VI programming code by focus criteria below:
- Master & slave: The slave device should start the task before the master device.
- Trigger: It's recommended to share the same trigger between the 2 chassis.
- Share same time base: NI-9469 can provide a reference clock at 13.1072 MHz or 12.8 MHz.
Refer to Example section for more information on LabVIEW synchronization code.

Verify two chassis whether are synchronized or not by referring t0 (time acquired of first data) in the timestamp.
If both devices' task t0 are equal, it means both chassis are synchronized.

In DAQmx Read.vi, select Analog >> Multiple Channels >> Multiple Samples >> 1D Waveform (Duration).
In the output, Right-click at data >> Create indicator.
Compare t0 for both devices.