1. User Events in LabVIEW RT
Colorado ALARM User Group
17 November 2011
STEVE SOLGA | ELECTROMECHA LLC

2. Event Structure under LabVIEW RT
RT TARGETS ONLY SUPPORT USER EVENTS
Event structures on RT targets do not support events associated with user interface objects, such as VI panels or controls (i.e. no Value Change or Mouse Down type events)
The options for associating the Value Change event with a control still exist in LabVIEW RT but they have no effect

3. Inter-Process Communication Mechanism
AN ALTERNATIVE RT COMMUNICATION MECHANISM
User Events in LabVIEW RT are another way to communication between parallel processes
More common communication mechanisms include Queues, RT-FIFO’s, and Shared Variables
RT SOFTWARE
STANDARD METHODS
ALTERNATIVE METHOD

4. Moving from Windows UE’s to RT UE’s
MULTIPLE TASK (MULTIPLE CONTROL LOOP) COMMUNICATION METHOD
In many applications, the RT controller runs multiple control processes that need to communicate with each other
This presentation demonstrates a general state machine architecture which uses a Cluster of State Command Enum and Variant for the State Queue, User Event [UE], and Notifier data types
WINDOWS CODE QUICKLY PORTS TO RT
Code transfers nicely from Windows to LabVIEW RT when control Value Change Events are converted to User Events.
Each User Event can then have a dedicated State to handle required logic
GOOD FOR QUICK PROTOTYPING
Using Networked Shared Variables (NSV) to communicate between the Host PC and the RT simplifies basic communication and utilizes existing communication methods (User Events) already existing in software architecture
Host modules (Touch Panels, Tables, Windows PC Hosts) can fire User Events on the RT in a round-about way using Network Shared Variables

5. SYSTEM ARCHITECTURE Host Communicates with RT Hardware via Networked Shared Variables RT Asynchronous Processes Communicate via RT User Events
RT HARDWARE
HOST INTERFACE
Module A UE API
SHARED VARIABLES
Module B UE API

6. RT CONTROLLER MODULE Low priority loop in RT Controller Module polls Network Shared Variable for State and Data Commands from Host. New State Commands fire User Events on the RT Controller Module
RT CONTROLLER MODULE
Poll ‘RT Cmd’ NSV for States other than ‘Idle’. Fire associated State | Data Command as RT User Event

7. Fundamentals Components of a Module
The general state machine architecture uses a State Command Enum and a Variant data for both the State Queue and User Event [UE] data types.
Type Defined Cluster of Command | Data
Mechanism for sharing the Created User Event to other Modules
User Event
UE Publishing Mechanisms
Global
Shared Variable
Command Queue for Module State Machine
LV2 Functional Global
Notifier
Type Defined Main Cluster for data internal to the Module
Single Element Queue

8. UE handling in a Module
A Module’s State Machine handles the specific State Command sent to the Module via the User Event. Variant Data is converted back to the LabVIEW data type for further processing
Need to know the original data type in order to convert the variant data back to LV data type properly
Specific States type defined in the Command Enum can be used to handle any number of unique User Events
Use Type Defined Controls for Complex Data Types
Convert Variant to LabVIEW data type and process accordingly

9. Sending a UE to a Module
Modules are ideally standalone processes that are often required to be command remotely or may need to patched into a higher level controller using sub panels.
Only sending one type of Registered User Event, a cluster of Command Enum and Variant Data
Each Module has an API that provides access to it’s registered user events
Other modules can use the API to send User Events to the specific Module

10. User Event API for a Module
Provides access to the Dynamic Event registered for a Module
Incorporates a Notifier that can be used for confirmation of commanded User Event

11. Run Demo Run Demo code on cRIO-9075 embedded controller
Run Host Module and send commands to RT Controller Module which in turns commands Modules A and B via RT User Events

12. More Potentially Useful Information
Alternative Host – RT Communication Mechanisms
TCP/IP
UDP
Data Socket
Network Streams (LV ≥ 2010)
Serial 232, 484, CANbus, GPIB
Real-time VI to Host VI Communication Knowledgebase
NI’s cRIO DEVELOPER GUIDE
Questions
Thanks!