Event Structure --- Using UserEvent

In LV6.1, LabVIEW introduced event structure. Event-driven is the basic design concept of popular programming languages ​​such as VB and VC. The introduction of LV+EVENT STRUCTURE is a great improvement for LabVIEW. It may be that the user events and dynamic registration events added in 7.1 are eagerly awaited by engineers who used to program in VC language.

Anyone familiar with VC knows that WM_USER is a message reserved by Microsoft specifically for users, through which various commands and data can be sent to the main window.

Now, LABVIEW also has this capability. I wonder if you have used it.

If a project controls several devices and they work in parallel, how do the parallel control loops exchange data with the main loop? You can do this through global variables, shared variables, control references, and queues.

Today I'll introduce a new method to make full use of USER EVENT.

 

First, use Custom Control to create a strict type def cluster. The example I gave is to simulate a WINDOWS message, but it can actually be of any type. Using variant data may be more appropriate.

 

Here I define 50 kinds of messages

The information that each event needs to pass is:

1. Message number (50 types, which can be understood as 50 commands)

2. String, used to transmit information

3.4 are two data, simulating wParam and lParam of WINDOWS

The next step is to use the Action Engine method to encapsulate all operations in a SUBVI

First, a user event is generated in First call=TRUE, and a reference is returned and stored in SHIFT REGISTER.

 

 

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There are three commands defined here: GetRef (get reference) Fire (generate event) Release (release)

 

Such a complete AE is formed, and the specific calling method is as follows:

 

Specific effect demonstration: