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Global Data and Properties in Point Value Maps

NI InsightCM™ SDK Help

Edition Date: July 2017

Part Number: 375191C-01

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Parent Topic: Device Software Fundamentals

Processes commonly need to read properties that other processes write. For example, various processes need to read the current operating state of a data group. Rather than each process querying for the same value, the NI InsightCM SDK provides an API to create point value maps to store properties and data in a global context. Maps contain points, which work like variables that store only the latest value written to them. In other words, point value maps are repositories of information that any process can read and write at run time.

In the example of reading the current operating state, processes do not require knowledge of every change in operating state that occurs, but rather, only the current state. Point value maps are designed for this use case, where the device software must store a value in memory that readers and writers can access with no flow control.

Map Implementation

To create and access maps and points, use the Point Value Map API. LabVIEW maintains maps internally, and any process can access a map or map point by calling the API and specifying the map or point name. Therefore, you do not need to pass references to these items throughout your code.

Map Format

  • Maps and map points persist until the device code restarts. In other words, maps and points created before a restart no longer exist in memory after the restart.
  • Map points consist of a key-value pair.
  • Each map can contain multiple points, which are identified by name.
  • Multiple maps can exist simultaneously, each of which is identified by name.
  • Points support values whose data type is string, double, integer, Boolean, or variant.
  • Points support a few types of attributes: a property that indicates whether the point value is valid, a timestamp that indicates when the value was written, and generic user-defined attributes.

Related Information

Reading and Writing Point Value Maps

Differences between Point Value Maps and Configuration Files

Processes also commonly require a different type of property data to operate: configuration properties. Unlike run-time properties that processes write to point value maps, configuration properties are static values set outside the device software. For example, consider the user-defined sample rate set in the InsightCM web application. NI InsightCM Server sends these configuration properties to devices in a series of JSON files.

Related Information

Reading and Writing Point Value Maps


 

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