'OldVal' Property Returns an Incorrect Value Using Embedded UI

Updated Jan 3, 2018

Reported In

Software

  • LabVIEW Real-Time Module

Operating System

  • NI Linux Real-Time

Issue Details

I am interactively running a LabVIEW Real-Time VI on a target with Embedded UI enabled. Why does the OldVal property in my Value Change Event Structure return an incorrect value?

Solution

This is a documented known issue with using NI Linux Real-Time with Embedded UI in LabVIEW 2014 or 2015. You can work around this by using a shift register to access the old value instead of the OldVal property node. The code snippet below illustrates this work around. 
 

Note: You will not experience this behavior if you use a Real-Time executable, rather than an interactive VI on the target.
 

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