Synchronize Multiple cDAQ or cRIO Chassis Using the NI-9469 Module

To perform multiple DAQ tasks across different CompactDAQ (cDAQ) or CompactRIO (cRIO) it is necessary to synchronize the chassis. The 9469 is a synchronization device that works by physically sharing timing and triggering signals in a master-slave configuration. 

To use the NI-9469 modules, NI-DAQmx 9.6.0 or later needs to be installed. Because NI-9469 synchronization is module-determined, they also work in cDAQ-chassis featuring TSN (Time-Sensitive Networking). The 9469 can only be used to share signals slower than 1MHz or at the two specific Oversample clock rates (12.8MHz and 13.1027MHz).

This guide explains how to implement this synchronization with LabVIEW using NI-DAQmx API in 3 steps:

1. Wiring the Modules
2. Configuring the NI 9469 in NI Measurement & Automation Explorer (MAX)
3. Using synchronization in LabVIEW

Wiring the modules

First, you need to wire the modules in one of the supported patterns to allow them to recognize each other and communicate properly. To achieve this, there are two basic configurations, star, and daisy-chain.
Please note that on the NI-9469 modules, port 0 is an input, while ports 1 and 2 are outputs.

Daisy-chain configuration	STAR configuration

Configuration in NI-MAX

Please refer to Configuring the NI 9469 in NI Measurement & Automation Explorer (MAX)
 

Using synchronization in LabVIEW

After setting the synchronization properties as described above, you can start developing your LabVIEW DAQ project. Before configuring your DAQmx modules it is necessary to use the DAQmx Auto-Configure cDAQ Sync Connections VI

• Palette: Measurement I/O >> DAQmx - Data Acquisition >> DAQmx Advanced >> DAQmx System Setup >> DAQmx cDAQ Sync

Please refer to the code section below for examples of synchronized Tasks.
 

Example 1 - Synchronized Digital Waveform Output with common sample rate

Note: This image is a LabVIEW snippet, which includes LabVIEW code that you can reuse in your project. To use a snippet, right-click the image, save it to your computer, and drag the file onto your LabVIEW diagram.  

Example 2 - Synchronized Digital Output and Analog Input Tasks with different sample rates

Note: This image is a LabVIEW snippet, which includes LabVIEW code that you can reuse in your project. To use a snippet, right-click the image, save it to your computer, and drag the file onto your LabVIEW diagram.  

Example 3 - Programmatic synchronization setup via LabVIEW

Instead of using configuration via MAX or using Auto-Configure VI, you can also set up the synchronization options via LabVIEW. The order of the connection port strings within the string array is not important. The example below shows a While loop that retries the setup until the connection succeeds.

Note: This image is a LabVIEW snippet, which includes LabVIEW code that you can reuse in your project. To use a snippet, right-click the image, save it to your computer, and drag the file onto your LabVIEW diagram.