Log TDMS Measurements in a Real-Time Application

DAQmx is supported in certain models of CompactRIO*, cDAQ, and PXI. Using DAQmx you can take advantage of the built-in DAQmx logging functions or create your own file handling loops.

*Please note that not all CompactRIO controllers support DAQmx. For more information consult: NI-DAQmx on the CompactRIO

• TDMS Direct Integration in NI-DAQmx Logging 
•  Writing TDMS Data from Multiple DAQmx Read Functions
• Log Multiple DAQmx Tasks in the Same TDMS File

You can use a producer-consumer architecture to acquire the samples from the Scan Engine's Shared Variables and log them into your application. Your producer loop takes data out of the Scan Engine's Shared Variables and sends them to your consumer loop, which dequeues the data and logs them into the file. You can use a Queue, RT FIFO , or RT FIFO Shared Variable to do this.

• Application Design Patterns: Producer/Consumer
• Monitor and Log Data With LabVIEW Real-Time
• Take Your First Measurement in LabVIEW Real-Time (Data Logging)

Using DCAF (Distributed Control and Automation Framework) you can have Shared Variables sending data to a TDMS file. This option also allows you to control the rotation of the measurement file, so you make sure the size of the files is adequate to your application.

• Getting Started with DCAF
• LabVIEW DCAF Github: Scan Engine Module
• DCAF TDMS Logging Module Documentatio

LabVIEW comes with a built-in template for FPGA Waveform Acquisition and Logging in a CompactRIO. Use this template as a starting architecture for your application.

• LabVIEW Real-Time and LabVIEW FPGA Sample Projects
• LabVIEW for CompactRIO Developer's Guide

You can use the FPGA waveform Library to obtain the data out of the FPGA in a similar way to a DAQmx acquisition. You can take advantage of this library to combine an FPGA acquisition with a DAQmx style of data logging.