NIWeek 2011: Beyond State Machines / Building Modular Applications in LabVIEW (JKI)

Justin GoeresSenior Engineer & Product Marketing ManagerJKI

PUSHING THE LIMITS OF LABVIEW

Beyond State Machines:Building Modular Applications in LabVIEW Using Public & Private Events

Monday, August 8, 11

1. Vote with your feet.

2. Please turn on your smartphones.

PUSHING THE LIMITS OF LABVIEW | JKI CONFIDENTIAL

Rules

@JustinGoeres is going Beyond State Machines at #niweek!

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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.

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A Public & Private Events Framework

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Agenda

What is it?

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Agenda

What is it?How does it work?

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Agenda

What is it?How does it work?What’s it good for?

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Agenda

What is it?How does it work?What’s it good for?What’s it bad at?

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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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What is it?

A “module” has: Statefulness / private data Asynchronous process(es) Public API Public Events

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Key Benefits

Module knows nothing about who’s consuming the data it producesLightweight & easy to useCompatible with by-ref and by-val architectures

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Client Code is Simple

Start Process & register for Public

EventsInvoke Public API

as neededExit Modulewhen done

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How Does it Work?

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Process VI & Public Events

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Shift register for private module data(“State”)

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Shift register for private module data(“State”)

Generate a “Public Event” when “something happens”

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Public Events: Sending Information OUT

Process VI generates a Public Event...

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...which is received by any other Event Structure that’s registered for

it.

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Public Events: One to Many


...that can be received by any number of consumers!

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The Public API

Public API VIs...

...generate Private Events...

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The Public API

Public API VIs...

...generate Private Events...

...that are handled by the asynchronous Process VI

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Public API / Private Events

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Only our Process VI can receive thisPRIVATE event

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Process VI registers for“Private Events” at initialization

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When the Process VI receives a Private Event, it responds

appropriately.

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Putting it All Together

Client code invokes Public API

Client code registers for Public

Events

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Putting it All Together

Start Process & register for Public

EventsInvoke Public API

as neededExit Modulewhen done

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MainApp


Everything is a Module

AnalogInput

MotorController

LeakDetection

EKGAnalysis

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MainApp



AnalogInput

MotorController

LeakDetection

EKGAnalysis

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MainApp



AnalogInput

MotorController

LeakDetection

EKGAnalysis

MainApp UI

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Extensions & Tweaks

Use with by-value & by-ref objectsCommunity & Protected EventsDynamically unregister / reregisterSynchronous communication

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Things That Suck

Most annoying bug ever. Fixed in LV2011!No Event queue management or introspectionNo Notifier-like behavior (“ignore previous”)

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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.

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The End!

Discussion!

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NIWeek 2011: Beyond State Machines / Building Modular Applications in LabVIEW (JKI)

Technology

public api public api

public eventsshift

public api private eventsonly

public eventsclient

public api exit moduleregister

private module datastate

simple start process

straight user events