National Instruments BridgeVIEW How Can You Use Tag Attributes to Configure HMI Indicator Attributes Programmatically?

Chapter 4 Human Machine Interface

This example illustrates the use of dataflow programming to enforce the

order of two structures that otherwise are not related by data flow. By

wiring the time interval (secs) constant through the Sequence structure and

into the While Loop, the While Loop does not begin execution until the

code in the Sequence structure has completed execution. Another way to

enforce this order of execution is to put the While Loop inside the second

frame of the Sequence structure. Both techniques are correct. The

advantage of the technique used in Figure 4-6 is that it is easy to see the

entire diagram at a glance.

How Can You Use Tag Attributes to Configure HMI Indicator Attributes Programmatically?

Use the Tag Attributes VI library to read or change specific configuration

details of a tag. Anything you have configured in the Tag Configuration

Editor can be queried programmatically using the Tag Attributes VIs. Use

these VIs when you want to control attributes programmatically for your

front panel controls or indicators, or to display configuration information

on your HMI. Setting attributes programmatically for front panel controls

and indicators is an alternative to changing attribute values for the control

or indicator through the various front panel pop-up menus or by typing into

various control and indicator fields.

Handling attributes programmatically is most useful when you use the

same indicator or control for different tags. For more information on tag

configuration, see Chapter 3, Tag Configuration. For more information

about the Tag Attributes VIs, see the section Tag Attributes VIs in

Appendix A, HMI Function Reference, and Chapter 7, Advanced

Application Topics.

Figure 4-7 shows a simple case where the scale range for all the front panel

level and temperature indicators are set to the engineering scale that is

configured for the tag. A unit string display for each L1 and Temp indicator

is initialized to the engineering unit for the respective tag. The Get Tag

Range and Units VI returns the engineering scale range information in a

form that can be wired directly to a control or indicator scale range attribute

node. The VI also returns the engineering units configured for the tag.