Slides for presentation given by Justin Goeres at NIWeek 2011. Learn about a template for inter-process communication that’s easy enough for Intermediate developers, but powerful and flexible enough for CLAs. Nearly every significant LabVIEW-based application uses multiple loops and multiple pieces of hardware. Without a clear design pattern, coordinating all these moving pieces is a recipe for spaghetti code. In this presentation, we introduce an elegant, powerful, and easy-to-use template for inter-process communication based on the concept of “Public” and “Private” events.

1. PUSHING THE LIMITS OF LABVIEW
Beyond State Machines:
Building Modular Applications in LabVIEW Using
Public & Private Events
Justin Goeres
Senior Engineer & Product Marketing Manager
JKI
Monday, August 8, 11

2. Rules
1. Vote with your feet.
2. Please turn on your smartphones.
@JustinGoeres is going Beyond
State Machines at #niweek!
PUSHING THE
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LIMITS OF LABVIEW
Monday, August 8, 11

3. Let’s Get This Straight
User Events are a very easy-to-use feature with a lot
of cool functionality.
They form the basis of JKI’s primary application
frameworks & templates.
If we could get a couple things fixed/added to
LabVIEW, we could do even better.
PUSHING THE
3 | JKI CONFIDENTIAL
LIMITS OF LABVIEW
Monday, August 8, 11

4. A Public & Private Events Framework
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5. Agenda
What is it?
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6. Agenda
What is it?
How does it work?
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LIMITS OF LABVIEW
Monday, August 8, 11

7. Agenda
What is it?
How does it work?
What’s it good for?
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5 | JKI CONFIDENTIAL
LIMITS OF LABVIEW
Monday, August 8, 11

8. Agenda
What is it?
How does it work?
What’s it good for?
What’s it bad at?
PUSHING THE
5 | JKI CONFIDENTIAL
LIMITS OF LABVIEW
Monday, August 8, 11

9. Agenda
What is it?
How does it work?
What’s it good for?
What’s it bad at?
How can you use it in your projects?
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Monday, August 8, 11

10. What is it?
A “module” has:
 Statefulness / private data
 Asynchronous process(es)
 Public API
 Public Events
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11. Key Benefits
Module knows nothing about who’s consuming the
data it produces
Lightweight & easy to use
Compatible with by-ref and by-val architectures
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12. Client Code is Simple
Start Process &
Invoke Public API Exit Module
register for Public
as needed when done
Events
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LIMITS OF LABVIEW
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13. How Does it Work?
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14. Process VI & Public Events
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15. Process VI & Public Events
Shift register for private module data
(“State”)
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LIMITS OF LABVIEW
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16. Process VI & Public Events
Shift register for private module data
(“State”)
Generate a “Public Event”
when “something happens”
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17. Public Events: Sending Information OUT
Process VI generates a Public Event...
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Monday, August 8, 11

18. Public Events: Sending Information OUT
Process VI generates a Public Event...
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LIMITS OF LABVIEW
Monday, August 8, 11

19. Public Events: Sending Information OUT
Process VI generates a Public Event...
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LIMITS OF LABVIEW
Monday, August 8, 11

20. Public Events: Sending Information OUT
Process VI generates a Public Event...
PUSHING THE
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LIMITS OF LABVIEW
Monday, August 8, 11

21. Public Events: Sending Information OUT
Process VI generates a Public Event...
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LIMITS OF LABVIEW
Monday, August 8, 11

22. Public Events: Sending Information OUT
Process VI generates a Public Event...
...which is received by any other
Event Structure that’s registered for
it.
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23. Public Events: One to Many
Process VI generates a Public Event...
...that can be received by any number of consumers!
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24. The Public API
Public API VIs...
...generate Private Events...
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25. The Public API
Public API VIs...
...generate Private Events...
...that are handled by the
asynchronous Process VI
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26. Public API / Private Events
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27. Public API / Private Events
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28. Public API / Private Events
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29. Public API / Private Events
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30. Public API / Private Events
Only our Process VI
can receive this
PRIVATE event
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LIMITS OF LABVIEW
Monday, August 8, 11

31. Public API / Private Events
Process VI registers for
“Private Events” at initialization
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32. Public API / Private Events
When the Process VI receives a
Private Event, it responds
appropriately.
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33. Putting it All Together
Client code
registers for Public
Events
Client code invokes
Public API
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LIMITS OF LABVIEW
Monday, August 8, 11

34. Putting it All Together
Start Process &
Invoke Public API Exit Module
register for Public
as needed when done
Events
PUSHING THE
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LIMITS OF LABVIEW
Monday, August 8, 11

35. Everything is a Module
Main
App
EKG Leak
Analysis Detection
Analog Motor
Input Controller
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LIMITS OF LABVIEW
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36. Everything is a Module
Main
App
EKG Leak
Analysis Detection
Analog Motor
Input Controller
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LIMITS OF LABVIEW
Monday, August 8, 11

37. Everything is a Module
Main
App UI Main
App
EKG Leak
Analysis Detection
Analog Motor
Input Controller
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38. Extensions & Tweaks
Use with by-value & by-ref objects
Community & Protected Events
Dynamically unregister / reregister
Synchronous communication
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39. Things That Suck
Most annoying bug ever. Fixed in LV2011!
No Event queue management or introspection
No Notifier-like behavior (“ignore previous”)
PUSHING THE
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LIMITS OF LABVIEW
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40. Take Home Point
User Events are a very easy-to-use feature
with a lot of cool functionality.
They form the basis of JKI’s primary application
frameworks & templates.
If we could get a couple things fixed/added to
LabVIEW, we could do even better.
PUSHING THE
24 | JKI CONFIDENTIAL
LIMITS OF LABVIEW
Monday, August 8, 11

41. The End!
Discussion!
PUSHING THE
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LIMITS OF LABVIEW
Monday, August 8, 11