1. National Instruments Leadership Seminar
April, 2002
The Art of Creating Dynamic, Flexible LabVIEW Applications
Norman Kirchner CLD, CPI – Texas Instruments
Gerald Albertini CLD – Texas Instruments
August 10, 2006
As LabVIEW has grown into a much more dynamic programming language, so have the demands from the end-users for more dynamic programs and displays. This session will cover those techniques necessary to take those creative concepts to their implementation in the code you create.
By understanding the tools available within the LabVIEW API, such as: Dynamic Events, VITs and their use during runtime, Sub-Panels and Plug-in Architectures; Programmers basic and advanced can create code that will result in dynamic displays and code abstraction.
Examples and demonstrations will show how little code is needed to accomplish some eye-opening and dynamic tasks.
National Instruments CONFIDENTIAL

2. ‘Dynamic’ in LabVIEW – Going N+1
National Instruments Leadership Seminar
April, 2002
‘Dynamic’ in LabVIEW – Going N+1
What does ‘Dynamic’ mean to us?
Ability to have software change and grow based upon customizable configurations and user inputs
Ability to transfer data and control, without the need of additional wiring
Why use it?
How do We Accomplish it?
How does it differ from traditional meaning in SW
High level advantages ‘saves time later’
National Instruments CONFIDENTIAL

3. Measurement Library – Adding Instrument
National Instruments Leadership Seminar
April, 2002
Measurement Library – Adding Instrument
Done Once
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4. National Instruments Leadership Seminar
April, 2002
The Art at Work
Test Module
Universal Instrument Configuration & Control
Drop-In “Brat Code”
Daemon – Background Engine
Calling into Other VIs
VIt Usage
Plug-in Architecture
Sub-panel
Callback
Sub-Panel
Config.vit
Data
Instrument
Configuration
Instrument
Configuration
Instrument Driver
Instrument Driver
Instrument
Configuration
Instrument Driver
National Instruments CONFIDENTIAL

5. Advanced VI Server Techniques
National Instruments Leadership Seminar
April, 2002
Advanced VI Server Techniques
Drop-In ‘Brat Code’ & Extrapolation
What Happens When Children Control the Parent
Calling VI’s From Anywhere
Reach Out and Run Someone
Utilizing the VIt
These ain’t your fathers templates
Extrapolation From Self:
Smart code, allows your program to grow and change w/out needing to re-work your code
Extrapolation from Predecessors:
Allows independence from caller
Self Operation
A VI operates on its own properties and/or objects Example: Customize appearance based on information saved in an .ini file (size, color, logo, visible objects,…)
Operation on other VIs
Open a reference to a LabVIEW instance
Open a reference to a VI
Operate on properties/methods
Close references after use
National Instruments CONFIDENTIAL

6. Drop-In ‘Brat Code’ & Extrapolation – The What
National Instruments Leadership Seminar
April, 2002
Drop-In ‘Brat Code’ & Extrapolation – The What
Code that can “look up to” and operate on the code it’s placed inside
Stupid about the code around it
Smart enough to function w/ little to NO input
National Instruments CONFIDENTIAL

7. Drop-In ‘Brat Code’ & Extrapolation – The Why
National Instruments Leadership Seminar
April, 2002
Drop-In ‘Brat Code’ & Extrapolation – The Why
Achieve Complex Operations w/ Little to No Wiring
Very Modularized
Fosters Re-use
Enables Plug & Play Code (or Drop & Run)
“The scope of the code does not depend on pre-defined limitations.
It adapts to the code it’s in.”
DO DEMO after this slide then show how
“The scope of the code does not depend on pre-defined limitations, rather, it changes depending on the code it’s in.”
National Instruments CONFIDENTIAL

8. Drop-In ‘Brat Code’ & Extrapolation – The How
National Instruments Leadership Seminar
April, 2002
Drop-In ‘Brat Code’ & Extrapolation – The How
Get a reference to the high level object of interest
Front Panel Ref
Application Ref
Path
Scan results to get items
Utilize unused/hidden fields to flag items
Perform extraction or operation
No Passing of Data Needed
Traverse Ref – Find all references of specific ClassName
vi.lib\Utility\traverseref.llb\TRef Traverse for References.vi (8.0)
Call Chain
Find where current VI resides in hierarchy
VI.Callees
Find everyone who is using specific VI
Panel Properties – Filter array for item of interest
National Instruments CONFIDENTIAL

9. Daemons – Drop-in Engines
National Instruments Leadership Seminar
April, 2002
Daemons – Drop-in Engines
Adds Complex Functionality by the Addition of 1 VI
Self Managed or ‘Lite’ Interaction
Similar to Windows Services
Utilizes Multi-Processing CPU
Does not come free – Debugging difficulty
Encapsulate Complexity Within Engine
Clean Code = Happy Code
National Instruments CONFIDENTIAL

10. Invoking VI’s from others – The What
National Instruments Leadership Seminar
April, 2002
Invoking VI’s from others – The What
Running Code Not Placed as SubVI
“Dynamically” call a VI
Load VI | Pass parameters | Run VI | Read Result | Close
In LV, EXE, Across PC, Around World
National Instruments CONFIDENTIAL

11. Invoking VI’s from others – The Why
National Instruments Leadership Seminar
April, 2002
Invoking VI’s from others – The Why
Improve performance (memory usage)
Make design more modular
Ability to share work among team members
Increase scalability of the application
Create distributed applications
Enable recursion in G
Also…very useful for “release tools” builder
VI analyzer is a good example
Your Programs are No Longer Limited by Software and Physical Boundaries
National Instruments CONFIDENTIAL

12. Invoking VI’s from others – The How
National Instruments Leadership Seminar
April, 2002
Invoking VI’s from others – The How
VI server Method “Run VI”
Passing parameters through “Set” and “Get” methods (Invoke Nodes)
Ability to run asynchronously : “Wait Until Done”
VI server Method “Call by Reference”
Passing parameters is direct
Runs synchronously – like a subVI would
Pay Attention to Error Handling
National Instruments CONFIDENTIAL

13. Utilizing the VIt – The What
National Instruments Leadership Seminar
April, 2002
Utilizing the VIt – The What
Running Multiple Instances of a Same VI…asynchronously
Dynamic calls to a VIt
Example:
an application controlling N similar devices
Pseudo “MDI” Applications
National Instruments CONFIDENTIAL

14. National Instruments Leadership Seminar
April, 2002
Utilizing VIt – The Why
Write once, reuse over and over and over …
Maintenance and growth made simple
Easily expandable to “N+1”
Maximizes Code Reuse
MDI
Easy and elegant…No need to duplicate VIs
National Instruments CONFIDENTIAL

15. National Instruments Leadership Seminar
April, 2002
Utilizing VIt – The How
It’s just VI Server…
“VI Path” Points to a VIt
Keeping Track of Instances References
New instances dynamically created are named “<VITNAme>1, <VITNAme>2, …<VITNAme>n ” so that the calling VI needs a way to keep track of running instances references for subsequent operations on a specific instance
Windowing operations could be embedded in the VIT itself or operated at the calling VI level.
National Instruments CONFIDENTIAL

16. Plug-in Architecture – The What
National Instruments Leadership Seminar
April, 2002
Plug-in Architecture – The What
Connector Pane
Directory structure
Naming Conventions
Software Calls Into Dynamic Framework
Plug-ins Must Match Rules of Framework
Automatically recognized by the software
Drop new “Plug-In” in a specific directory to make it available to the application
Program Extension
Add new features without rebuilding program
Enum b4
Enum aftr
Dirs b4
Dirs aftr
Going N+1 – Transparently adding one more to <whatever>
Signal processing
Algorithms
Adding functionality
New Camera – Imagine MAX needing to be re-written for a new camera
New SourceCodeControl Provider (%LV%\vi.lib\SourceControl\Providers)
National Instruments CONFIDENTIAL

17. Plug-in Architecture – The Why
National Instruments Leadership Seminar
April, 2002
Plug-in Architecture – The Why
SCALABILITY !
Easily deploy new features
Make Code More Modular
Examples:
Adding signal processing algorithms to an analysis SW
Adding support for a new instrument in the “Universal Capture” module presented earlier
ShowCase LV SCC providers
National Instruments CONFIDENTIAL

18. Plug-in Architecture – The How
National Instruments Leadership Seminar
April, 2002
Plug-in Architecture – The How
Call By reference Node + Strictly typed refnums
Connector assignment MUST be clearly specified (all plug-ins use the same!)
“Plug-in” directory(ies) so that the SW can automatically scan available modules
National Instruments CONFIDENTIAL

19. Event Registration & Encapsulation – The What
National Instruments Leadership Seminar
April, 2002
Event Registration & Encapsulation – The What
Defining Events External to Event Structure
Handling Events Inside of SubVIs
Change What is Registered During Run-Time
Concept of Registration
Encapsulation in Sub-VI’s
Why – So you don’t have to add to your event structure every time you do <whatever>
Utilizing User Events
Initialization
Great for fully event driven software
Bad for replacing queues
National Instruments CONFIDENTIAL

20. Event Registration & Encapsulation – The Why
National Instruments Leadership Seminar
April, 2002
Event Registration & Encapsulation – The Why
More reactive code
Prevents “Bloated” Case Selectors
Promotes Re-use
Reduces need for wiring
Re-use event action w/out needing to code it into your event structure every time!
Your Code
Event
Event handler
National Instruments CONFIDENTIAL

21. Event Registration & Encapsulation – The How
National Instruments Leadership Seminar
April, 2002
Event Registration & Encapsulation – The How
Define objects of interest
Get reference to object(s) & wire to registration node
Handle events in same VI or pass registration node ref to sub-VI
SideNote: Sub-VI may grab object ref from caller
MAKE EXAMPLE THAT SIMPLY HAS THE CASE STRUCTURE WITHIN THE EVENT STRUCTURE
National Instruments CONFIDENTIAL

22. National Instruments Leadership Seminar
April, 2002
Utilizing Sub-panel
Everyday unseen Example : LV Options window
Multiple views of same information (Tabular / Pie / Chart)
Reduction of code space & data space
Single window / Multiple Displays
When switching between multiple windows just won’t do
National Instruments CONFIDENTIAL

23. National Instruments Leadership Seminar
April, 2002
Caveats and Pitfalls
Complexity Up Front
Harder to Troubleshoot
Document Paradigm, Not Just Code
Need Clear Vision of the Future (no crystal ball, just binoculars)
National Instruments CONFIDENTIAL

24. National Instruments Leadership Seminar
April, 2002
Conclusion
Spend Time Now and Save a Lot of Time Later
Saves Room on BD and Time Spent Coding
Saves Memory
Lets You Create Dynamic / Flexible Displays
SMRS ( scaleable, modular, reusable, simple)
Always Think
“What If I Need to Add 1 More”
National Instruments CONFIDENTIAL

25. Questions? Maybe answers…
National Instruments Leadership Seminar
April, 2002
Questions? Maybe answers…
National Instruments CONFIDENTIAL