University College of Southeast Norway - home.usn.no · • Intermediate Topics in LabVIEW • Advanced Topics in LabVIEW Each tutorial may be used independently of each other. 1.1

UniversityCollegeofSoutheastNorway

http://home.hit.no/~hansha

IntroductiontoState-basedApplicationsinLabVIEW

Hans-PetterHalvorsen,2016.10.31

PrefaceStatechartsorStateDiagramsareusefulinsimplifyingthedesignofapplicationsthatusecomplexdecision-makingalgorithms.Byconstructingastatechart,youcanvisualizetheflowofacomplexdecision-makingalgorithmandachieveahigh-levelviewofanapplication.

Thisdocumentexplainsthebasicconceptsofcreatingstate-basedapplicationsinLabVIEW.

YoushouldhavesomebasicknowledgeaboutLabVIEW,e.g.,the“AnIntroductiontoLabVIEW”training.Thisdocumentisavailablefordownloadathttp://home.hit.no/~hansha/.

InadditiontoLabVIEWProfessionalDevelopmentSystem,youneedtoinstallthe“LabVIEWStatechartModule”.

iii

TableofContentsPreface......................................................................................................................................2

TableofContents.....................................................................................................................iii

1 IntroductiontoLabVIEW...................................................................................................1

1.1 Dataflowprogramming...............................................................................................1

1.2 Graphicalprogramming..............................................................................................2

1.3 Benefits.......................................................................................................................2

2 IntroductiontoSequentialControl...................................................................................3

3 IntroductiontoStateDiagrams.........................................................................................4

4 IntroductiontoSequentialFunctionCharts(SFC).............................................................5

5 State-machinewithLabVIEW............................................................................................7

5.1 WhileLoop..................................................................................................................7

5.2 CaseStructure.............................................................................................................8

5.3 ShiftRegister...............................................................................................................9

5.4 StateProgrammingArchitecture..............................................................................10

5.5 State-machine...........................................................................................................11

6 ASequentialControlexampleinLabVIEW......................................................................14

7 IntroductiontoLabVIEWStatechartModule..................................................................16

7.1 ProcedureforcreatingaStatechartapplicationinLabVIEW...................................17

7.2 StatechartEditor.......................................................................................................21

7.2.1 StatechartDevelopmentobjects.......................................................................23

7.3 UsingaCallerVItoExecuteaStatechart..................................................................25

8 Tutorial:CreateaStatechart...........................................................................................28

iv TableofContents

Tutorial: Introduction to State-based Applications in LabVIEW

9 AdvancedTopicsinLabVIEWStatechartModule...........................................................42

9.1 UsingRegionsandSubstates....................................................................................42

9.2 UsingOrthogonalRegionsandStateHistory............................................................42

9.3 SplittingandMergingTransitionSegments..............................................................43

10 WhatsNext?....................................................................................................................44

10.1 MyBlog.....................................................................................................................44

10.2 Training.....................................................................................................................44

10.3 AdditionalResources................................................................................................44

10.4 Examples...................................................................................................................44

10.5 Documentation.........................................................................................................45

10.6 LabVIEWWiki................................................................Error!Bookmarknotdefined.

10.7 LabVIEWonYouTube....................................................Error!Bookmarknotdefined.

QuickReference......................................................................................................................46

1

1 IntroductiontoLabVIEWLabVIEW(shortforLaboratoryVirtualInstrumentationEngineeringWorkbench)isaplatformanddevelopmentenvironmentforavisualprogramminglanguagefromNationalInstruments.Thegraphicallanguageisnamed"G".OriginallyreleasedfortheAppleMacintoshin1986,LabVIEWiscommonlyusedfordataacquisition,instrumentcontrol,andindustrialautomationonavarietyofplatformsincludingMicrosoftWindows,variousflavorsofUNIX,Linux,andMacOSX.VisitNationalInstrumentsatwww.ni.com.

Thecodefileshavetheextension“.vi”,whichisanabbreviationfor“VirtualInstrument”.LabVIEWofferslotsofadditionalAdd-OnsandToolkits.

ThispaperispartofaserieswithLabVIEWtutorials,suchas:

• IntroductiontoLabVIEW• DataAcquisitioninLabVIEW• ControlandSimulationinLabVIEW• LabVIEWMathScript• LinearAlgebrainLabVIEW• DataloggingandSupervisoryControlinLabVIEW• WirelessDataAcquisitioninLabVIEW• IntermediateTopicsinLabVIEW• AdvancedTopicsinLabVIEW

Eachtutorialmaybeusedindependentlyofeachother.

1.1 DataflowprogrammingTheprogramminglanguageusedinLabVIEW,alsoreferredtoasG,isadataflowprogramminglanguage.Executionisdeterminedbythestructureofagraphicalblockdiagram(theLV-sourcecode)onwhichtheprogrammerconnectsdifferentfunction-nodesbydrawingwires.Thesewirespropagatevariablesandanynodecanexecuteassoonasallitsinputdatabecomeavailable.Sincethismightbethecaseformultiplenodessimultaneously,Gisinherentlycapableofparallelexecution.Multi-processingandmulti-threadinghardwareisautomaticallyexploitedbythebuilt-inscheduler,whichmultiplexesmultipleOSthreadsoverthenodesreadyforexecution.

2 IntroductiontoLabVIEW


1.2 GraphicalprogrammingLabVIEWtiesthecreationofuserinterfaces(calledfrontpanels)intothedevelopmentcycle.LabVIEWprograms/subroutinesarecalledvirtualinstruments(VIs).EachVIhasthreecomponents:ablockdiagram,afrontpanel,andaconnectorpanel.ThelastisusedtorepresenttheVIintheblockdiagramsofother,callingVIs.Controlsandindicatorsonthefrontpanelallowanoperatortoinputdataintoorextractdatafromarunningvirtualinstrument.However,thefrontpanelcanalsoserveasaprogrammaticinterface.Thusavirtualinstrumentcaneitherberunasaprogram,withthefrontpanelservingasauserinterface,or,whendroppedasanodeontotheblockdiagram,thefrontpaneldefinestheinputsandoutputsforthegivennodethroughtheconnectorpane.ThisimplieseachVIcanbeeasilytestedbeforebeingembeddedasasubroutineintoalargerprogram.

Thegraphicalapproachalsoallowsnon-programmerstobuildprogramssimplybydragginganddroppingvirtualrepresentationsoflabequipmentwithwhichtheyarealreadyfamiliar.TheLabVIEWprogrammingenvironment,withtheincludedexamplesandthedocumentation,makesitsimpletocreatesmallapplications.Thisisabenefitononeside,butthereisalsoacertaindangerofunderestimatingtheexpertiseneededforgoodquality"G"programming.Forcomplexalgorithmsorlarge-scalecode,itisimportantthattheprogrammerpossessanextensiveknowledgeofthespecialLabVIEWsyntaxandthetopologyofitsmemorymanagement.ThemostadvancedLabVIEWdevelopmentsystemsofferthepossibilityofbuildingstand-aloneapplications.Furthermore,itispossibletocreatedistributedapplications,whichcommunicatebyaclient/serverscheme,andarethereforeeasiertoimplementduetotheinherentlyparallelnatureofG-code.

1.3 BenefitsOnebenefitofLabVIEWoverotherdevelopmentenvironmentsistheextensivesupportforaccessinginstrumentationhardware.Driversandabstractionlayersformanydifferenttypesofinstrumentsandbusesareincludedorareavailableforinclusion.Thesepresentthemselvesasgraphicalnodes.Theabstractionlayersofferstandardsoftwareinterfacestocommunicatewithhardwaredevices.Theprovideddriverinterfacessaveprogramdevelopmenttime.ThesalespitchofNationalInstrumentsis,therefore,thatevenpeoplewithlimitedcodingexperiencecanwriteprogramsanddeploytestsolutionsinareducedtimeframewhencomparedtomoreconventionalorcompetingsystems.Anewhardwaredrivertopology(DAQmxBase),whichconsistsmainlyofG-codedcomponentswithonlyafewregistercallsthroughNIMeasurementHardwareDDK(DriverDevelopmentKit)functions,providesplatformindependenthardwareaccesstonumerousdataacquisitionandinstrumentationdevices.TheDAQmxBasedriverisavailableforLabVIEWonWindows,MacOSXandLinuxplatforms.

3

2 IntroductiontoSequentialControl

Sequentialcontroliscrucialinmanycontrolapplications,asinchemicalbatchprocesses.Asequentialcontrolprocedurecanberepresentedgraphicallybye.g.oneofthefollowingtwomethods:

• AStatediagram,alsodenotedaStatemachine• ASequentialfunctionchart(SFC)

StatediagramsandSFCarequitesimilar,astheyhavethesamebasicelements:

• Stateswithactionstobeexecutedwhenthestateisactive• Transitionsfromoneactivestatetoanother

SequentialcontrolcanbeimplementedusinggraphicalprogrammingofstatediagramsorSFCsinproperprogrammingtools.Forexample,statediagramsaresupportedbytheLabVIEWStatechartModule.DifferentPLC(ProgrammableLogicController)toolssupportSFC.

4

3 IntroductiontoStateDiagrams

Statediagramshavestateswithactionstobeexecutedwhenthestateisactive.Theyhavetransitionsfromoneactivestatetoanothertakingplaceifthetransitionconditionislogicallytrue.

Belowweseeatypicalstatediagram:

ByFredtheOyster,CCBY-SA4.0,https://commons.wikimedia.org/w/index.php?curid=35221177

Astatediagramrepresentsastatemachine.Statesofastatemachineareeitheractiveorpassive.Onlyonestateisactiveatatime.Thestatemachinealwaysstartsinaparticularstatedefinedastheinitialstate,anditends(stops)afterthefinalstate.Specialsymbolsorcolorsmaybeusedfortheinitialstateandthefinalstate.SeetheFigureabove.

5

4 IntroductiontoSequentialFunctionCharts

SequentialFunctionChartsdescribecontrolsequencesingraphicalform.StateDiagramsandSequentialfunctioncharts(SFC)techniquesareverysimilar.Theyhavestates/steps(inSFCthetermstepsisused)withactionstobeexecutedwhenthestateisactive.Theyhavetransitionsfromoneactivestatetoanothertakingplaceifthetransitionconditionislogicallytrue.

Sequentialfunctionchart(SFC)isagraphicalprogramminglanguageoftenusedforPLCs(PLC-ProgrammableLogicController).

BelowweseeatypicalSFCchart:

[Figure:http://www.plcdev.com/sequential_function_charts_all]

The Sequential Function Charts break a sequential task down into Steps, Transitions andActions.Thesearedrawngraphicallytodescribeasequenceofinteractionsasseenabove.Steps:

• Everystepcanexecuteoneormoreactions.• A step can be either active or inactive. When it becomes active, it's actions are

executed

6 IntroductiontoSequentialFunctionCharts


Transitions:

• Therearetransitionsbetweeneverystep.• WhenaStep is activeand the following transitionbecome true the successor step

becomesactiveandtheprecedingstepbecomesinactive.• Eachtransitionhasassociatedeventswhicharecalledtransitionconditions.• ThetransitionconditionsmustcombinetomakeasimpleBooleanresult,TrueorFalse.

StepActions:

• Every action is associated with a step. The step can have none or several actionsassociated.

• Ifthereisnoassociatedactiontothestep,itwillbeconsideredasaWAITfunction. • Eachstep/actionassociationshallhaveanassociatedactionqualifier.

TheProgramFlowisasfollows:• Astepbecomesactivewhenitsprecedingtransitionactivates(thatisthetransitionis

true,whilethestepbeforethattransitionisactive.)• Astepbecomesinactivewhenit'ssubsequenttransitionbecomestrue• InParallelbranches,alltheinitialstepsbecomeactivewhentheprecedingtransition

activates• Aparallelbranchendwhenallthestepsbeforethebranchendarebeactive,andthe

subsequenttransitionbecomestrueManysystemshavesequentialoperationrequirementsandSequentialFunctionCharts(SFC’s)have become a popularmethod of accurately specifying sequential control requirements.SFC’shavemanyadvantagesforsoftwaredevelopmentbothinthedesignstageaswellastheimplementationandtesting,maintainingandfaultfindingstages,suchas:

• DesignStageo Detailedcleargraphicalspecificationo Nonsoftwarepeoplecanspecify/verify

• Implementationo Straightforwardconversionfromspecificationtocodeo Structuredtesting/debugging

• MaintenanceofSoftwareo Readilyunderstoodbyengineermodifyingsoftware

• MachineMaintenanceo Allowsquickaccuratefaultdiagnosis

7

5 State-machinewithLabVIEW

TheStateMachineapproachinLabVIEWusesaCasestructureinsideaWhilelooptohandlethedifferentstatesintheprogram,andthetransitionsbetweenthem.TheShiftRegisterisusedtosavedatafromandbetweenthedifferentstates.

BelowweshortlyrepeattheWhileLoop,theCasestructureandtheShiftRegisterbeforewedigintotheprinciplesofthestate-machine.

FormoredetailsaboutbasicLabVIEWprogrammingtechniques,refertothetutorial“IntroductiontoLabVIEW”.Thetutorialisavailablefordownloadfrom:http://home.hit.no/~hansha.

5.1 WhileLoopAWhilelooprepeatsthesubdiagraminsideituntiltheconditionalterminal,aninputterminal,receivesaparticularBooleanvalue.TheBooleanvaluedependsonthecontinuationbehavioroftheWhileLoop.Right-clicktheconditionalterminalandselectStopifTrueorContinueifTruefromtheshortcutmenu.Youalsocanwireanerrorclustertotheconditionalterminal,right-clicktheterminal,andselectStoponErrororContinuewhileErrorfromtheshortcutmenu.Note!TheWhileLoopalwaysexecutesatleastonce.

BelowweseeanemptyWhileloop:



AfteryoucreateaWhileLoop,youcanuseshiftregisterstopassvaluesfromoneiterationtothenext.IfyouwireanarraytoaWhileLoop,youcanreadandprocesseveryelementinthatarraybyenablingauto-indexing.Seexamplebelow.

InordertoconvertaWhileLoopintoaForLoop,right-clicktheWhileLoopandselect“ReplacewithForLoop”fromtheshortcutmenu.ToconvertaWhileLoopintoaTimedLoop,right-clicktheWhileLoopandselect“ReplacewithTimedLoop”fromtheshortcutmenu.

5.2 CaseStructureTheCaseStructurehasoneormoresubdiagrams,orcases,exactlyoneofwhichexecuteswhenthestructureexecutes.ThevaluewiredtotheselectorterminaldetermineswhichcasetoexecuteandcanbeBoolean,string,integer,orenumeratedtype.Youmayright-clickthestructurebordertoaddordeletecases.UsetheLabelingtooltoentervalue(s)inthecaseselectorlabelandconfigurethevalue(s)handledbyeachcase.

BelowweseeanemptyCasestructure:



BelowweseeanexampleofaCasestructurewith2cases,a“True”caseanda“False”case.DependingoftheBooleaninputvalue,theNumeric1andNumeric2iseitherAddedorSubtracted.

Youmayalsoconnectanerrorclusterdirectlytoacasestructure,likethis:

Thecasestructureautomaticallyswitchestoa“NoError”caseandan“Error”case.

5.3 ShiftRegister



UseshiftregistersonForLoopsandWhileLoopstotransfervaluesfromoneloopiterationtothenext.Shiftregistersaresimilartostaticvariablesintext-basedprogramminglanguages.Ashiftregisterappearsasapairofterminals,directlyoppositeeachotherontheverticalsidesoftheloopborder.Therightterminalcontainsanuparrowandstoresdataonthecompletionofaniteration.LabVIEWtransfersthedataconnectedtotherightsideoftheregistertothenextiteration.Createashiftregisterbyright-clickingtheleftorrightborderofaloopandselectingAddShiftRegisterfromtheshortcutmenu.

Ashiftregistertransfersanydatatypeandautomaticallychangestothedatatypeofthefirstobjectwiredtotheshiftregister.Thedatayouwiretotheterminalsofeachshiftregistermustbethesametype.

Toinitializeashiftregister,wireanyvaluefromoutsidethelooptotheleftterminal.Ifyoudonotinitializetheshiftregister,theloopusesthevaluewrittentotheshiftregisterwhenthelooplastexecutedorthedefaultvalueforthedatatypeiftheloophasneverexecuted.

UsealoopwithanuninitializedshiftregistertorunaVIrepeatedlysothateachtimetheVIruns,theinitialoutputoftheshiftregisteristhelastvaluefromthepreviousexecution.UseanuninitializedshiftregistertopreservestateinformationbetweensubsequentexecutionsofaVI.Aftertheloopexecutes,thelastvaluestoredintheshiftregisterremainsattherightterminal.Ifyouwiretherightterminaloutsidetheloop,thewiretransfersthelastvaluestoredintheshiftregister.Youcanaddmorethanoneshiftregistertoaloop.Ifyouhavemultipleoperationswithinaloop,usemultipleshiftregisterstostorethedatavaluesfromthosedifferentprocessesinthestructure.

ShiftRegisterExample:

CreateandRunthisexampletoseewhathappens.

5.4 StateProgrammingArchitecture



CreatingVIsusingtheStateMachineapproachisveryusefulwhencreating(large)applications.

Ingeneral,astatemachineisamodelofbehaviorcomposedofafinitenumberofstates,transitionsbetweenthosestates,andactions.Itissimilartoa"flowgraph"wherewecaninspectthewayinwhichthelogicrunswhencertainconditionsaremet.

[Wikipedia]

Sometimes,youmaywanttochangetheorderofthesequence,repeatoneiteminthesequencemoreoftenthantheotheritems,stopasequenceimmediately,orhaveitemsinthesequencethatmayexecuteonlywhencertainconditionsaremet.Althoughyourprogrammaynothaveanysuchrequirements,thereisalwaysthepossibilitythattheprogrammustbemodifiedinthefuture.Therefore,astateprogrammingarchitectureisagoodchoice,evenifasequentialprogrammingstructureissufficient.Thefollowinglistdescribesmorecomplexprogrammingrequirementsthatjustifytheuseofastateprogrammingarchitectureforanapplication.

• Youneedtochangetheorderofthesequence• Youmustrepeataniteminthesequencemoreoftenthanotheritems• Youwantsomeitemsinthesequencetoexecuteonlywhencertainconditionsare

met

5.5 State-machineTheStateMachineapproachinLabVIEWusesaCasestructureinsideaWhilelooptohandlethedifferentstatesintheprogram,andthetransitionsbetweenthem.TheShiftRegisterisusedtosavedatafromandbetweenthedifferentstates.

BelowweseeexamplesofastatemachineprincipleimplementedinLabVIEW.



SimpleStateMachineprinciple

StateMachinewithmultipletransitionsdependingontheState:

MoreadvancedStateMachineusingShiftRegisters:



TemplatesforState-machinesinLabVIEWareavailablefordownloadat:http://home.hit.no/~hansha

14

6 ASequentialControlexampleinLabVIEW

Thisexampleillustrateshowwemayusethestate-machineprincipleinLabVIEWtocreateasequentialcontrolapplication.

Thisexampleusesastatemachineforsequentialcontrolofthepositionofabicycle.

Thestate-machineisimplementedwith:

• AnoverallCase-structurewhichdefinesthestatesandcontainstheactionsofeachstate

• AShift-registerwhichrememberswhichstateistheactivestate• AninternalCase-structureinsideeachstate(CaseintheoverallCase-structure)

togetherwithproperBooleancomparisonfunctionsimplementingthetransitionconditions.

Thestate-machinecontrolsasimulatedprocess(bicycleposition)givenbythefollowingdynamicmodel:

𝑑𝑥𝑑𝑡 = 𝑣

Wherexispositionandvisspeed.Thespeedismanipulatedbythestate-machine.

ThismodelisimplementedinaSimulationLoopwhichrunsinparallelwiththeWhileloop.Data(variables)areexchangedbetweentheseloopsusinglocalvariables.

ThearrowonaVerticalPointerSlideisreplacedwithapictureofabicycle.TheproceduretosubstituteanygraphicalpartofanindicatororcontrolontheFrontpanelisasfollows:Right-clickontheitem(graphicalpart),e.g.thearrowofaVerticalPointerSlide.SelectAdvanced/Customizeinthemenuthatisopened.ClicktheToolbuttoninthetoolbarofthenewwindowthatisopened.Right-clickonthearrowontheslider,andselectthepictureyouwant.Etc.

Howtouseit?

UsethisVIasatemplateforyourownstate-machinecontrollerforanysimulateddynamicsystem.Tocontrolareal(physical)processinstead,justsubstitutethesimulatedprocesswithreadand/orwritefunctionsforanalogand/ordigitalI/O(input/output).

15 ASequentialControlexampleinLabVIEW


TheFrontPanellookslikethis:

TheBlockDiagramlookslikethis:

Inordertogetthefeelingwithstatemachines,whileloops,casestructuresandshiftregisters,trytoreproducetheexample.

TheexampleiscreatedbyFinnHaugen,UniversityCollegeofSoutheastNorway.

16

7 IntroductiontoLabVIEWStatechartModule

TheNILabVIEWStatechartModuleprovidesaprogrammingmodelthatyoucanusetodesignapplicationsatahigherlevelthanwaspreviouslypossible.WiththeLabVIEWStatechartModule,youcandevelopstatechartdiagrams,definebehaviorswithLabVIEWdataflowprogramming.

Statechartsexpandtheclassicstatediagramwiththeadditionalfeaturesofhierarchy,concurrency,andcomprehensiveactions.

LabVIEWstatechartsareespeciallyusefulforprogrammingevent-responseapplicationssuchasintricateuserinterfacesandadvancedstatemachinesusedtoimplementdynamicsystemcontrollers,machinecontrollogic,anddigitalcommunicationprotocols.

UsingtheLabVIEWStatechartModuleinvolvesthefollowingtwosteps:

• UsingtheStatechartEditorwindowtobuildastatechart. • CreatingaVIthatexecutesthestatechart.ThisVIalsosendsinformationto,and

receivesinformationfrom,thestatechart.

BuildingaStatechart

Buildingastatechartinvolvesdefiningthefollowingitems:

• States • Actionsandstaticreactionsthesestatesexecute • Transitionsbetweenstates • Actionsthesetransitionsexecute • Triggers

Whenyoubuildastatechart,youdefineuniquestatesinwhichthestatechartcanbe.Youalsodefinetransitionsbetweenthesestates,whenthestatechartcantakethesetransitions,andwhatactionsthesetransitionscantake.Youthendefinetriggersthatcausethestatecharttobeginevaluatingacertaintransition.Forexample,considerastatechartthatyouusetocontrolachemicalprocess.YoucanspecifythatthestatechartmovesfromState1toState2afterreceivingtheValveOpentrigger.Statesandtransitionsalsohave



associatedactions,whichyouusetomodifyoutputandstatedataassociatedwiththestatechart.

CreatingaVIthatExecutestheStatechart

Afteryoudefinethevalidtriggersandconfigurethestatecharttoreacttothosetriggers,youmustsendthosetriggerstothestatechart.YousendtriggerstothestatechartbycreatingaVI,knownastheCallerVI,tosendtriggersataspecifictime.Forexample,youcanconfigurethecallerVItosendtheStoptriggerafteryouclicktheStopfrontpanelbutton.

ThecallerVIalsosendsinputdatatothestatechartsothestatechartcanactonthatdata.ThecallerVIreceivesdatathatthestatechartmodifiesasaresultofastateortransitionaction.YouthencanusethisdatainotherpartsofthecallerVIorsendthisdatatootherVIs.

ThefollowingfigureshowshowacallerVIinteractswithastatechart.

ThefigureaboveshowshowthecallerVIsendsdatatothestatechart,whichreturnsoutputdatatothecallerVI.Ifthestatechartisasynchronous,thecallerVIalsomightsendatriggertothestatechart.Sendingatriggertothestatechartcausesthestatecharttobeginexecuting.

7.1 ProcedureforcreatingaStatechartapplicationinLabVIEW

TheprocedureforcreatingastatechartapplicationinLabVIEWwiththeLabVIEWStatechartModuleisasfollows:

Step1:IntheNewdialogselect“Statechart”.



Step2:NametheStatechart

Step3:TheProjectExplorerfortheStatechartapplicationappears:



Asyousee,theLabVIEWStatechartModuleautomaticallygeneratesasetofVisandControls.

LabVIEWStatechartPalette:

LabVIEWStatechartModuleoffersthefollowingFunctionsandObjectsintheStatechartpalette:

StatechartCommunicationFunctions:

UsetheStatechartCommunicationfunctionstoexecuteastatechart,sendtriggerstoastatechart,anddeterminewhetheraparticularstateisactive.Youcanplacethesefunctionsonablockdiagram.

StatechartCommunicationpalette:



RunStatechartExecutesaninstanceofthelinkedstatechart.YoutypicallyplacethisfunctioninsidealoopinthecallerVI.

Example:

SendExternalTriggerSendsatriggertotheexternalqueueofaninstanceofthelinkedstatechart.YoucanusethisfunctioninthecallerVIorinaVIthatrunsparalleltothecallerVI.Seexampleabove

IsInDetermineswhetherthespecifiedstateisactive.Anactivestateisonethatastatechartiscurrentlyin.Youcanusethisfunctioninaguard,anaction,orasubVIthataguardoractioncalls.

SendInternalTriggerSendsatriggertotheinternalqueueofthestatechart.YoucanusethisfunctionwithinonlyanactionorinasubVIthatanactioncalls.



StatechartDevelopmentObjects:

UsetheStatechartDevelopmentobjects,consistingofstates,regions,“pseudostates”,andconnectors,toconstructstatecharts.Note!Youcanplacetheseobjectsonlyonastatechartdiagram.

StatechartDevelopmentpalette:

Thedifferentobjectsareexplainedbelow.

7.2 StatechartEditorYouusetheStatechartEditorwindowtoeditastatechart.YoucandisplaytheStatechartEditorwindowinoneofthefollowingways:

• Double-clickthe“Diagram.vi”itemintheProjectExplorerwindowofthestatechart. • Right-clickthe“Diagram.vi”itemandselectOpenfromtheshortcutmenu. • Right-clickaRunStatechartfunctionthatlinkstothestatechartandselect

View»StatechartDiagramfromtheshortcutmenu.

StatechartEditorWindow:



TheStatechartEditorwindow,whichdisplaysastatechartdiagram,issimilartotheLabVIEWwindowthatdisplaysablockdiagram.Inbothofthesewindows,youcanplaceobjectsfromtheFunctionspaletteonthediagram,usetheLabVIEWtoolstomanipulateobjects,andconnectobjectstogether.However,theStatechartEditorwindowisdifferentfromtheLabVIEWwindowinthefollowingways:

• YoucanplaceonlyStatechartDevelopmentobjectsonastatechartdiagram.YoucannotplaceLabVIEWVIs,functions,orstructuresdirectlyonastatechartdiagram.

• TheLabVIEWblockdiagramwindowdisplaystheRunbuttononthetoolbar.The

StatechartEditorwindowdisplaysthe“GenerateCode“button onthetoolbar.Clickingthisbuttongeneratescodeforthestatechart.



• TheLabVIEWblockdiagramhasafrontpanelwindow.TheStatechartEditorwindowdoesnothaveafrontpanelwindow.

• OntheLabVIEWblockdiagram,youusethewiringtooltocreatewiresbetweenVIsandfunctions.IntheStatechartEditorwindow,youusethewiringtooltocreatetransitionsbetweenstatesandotherobjects.

• TheLabVIEWblockdiagramprovidesoptionsfordebuggingVIs.TheStatechartEditorwindowdoesnotprovideanydebuggingoptions.Youdebugstatechartsbyusingaseparatewindowthatyoucanaccesswhilethestatechartisrunning.

• TheStatechartEditorwindowdisablesmanyLabVIEWpull-downmenuitemsthatdonotapplytostatecharts.

7.2.1 StatechartDevelopmentobjects

UsetheStatechartDevelopmentobjectstoconstructstatecharts.Youcanplacetheseobjectsonastatechartdiagram.

TheStatechartDevelopmentobjectsconsistofstates,regions,andconnectors.

TheStatechartDevelopmentpalette:

TheStatechartDevelopmentobjectsareasfollows:

StateDefinesastate,whichisauniqueconditioninwhichthestatechartcanbe.Youmustplaceallstateswithinaregion.Note!Thetop-levelstatechartdiagramrepresentsaregion.Allstatesmusthaveatleastoneincomingtransition.



InitialSpecifiesthefirststatethattheenclosingregionenterswhenthestatechartentersthatregion.Tospecifythisstate,createatransitionfromtheInitialpseudostatetothestatethatyouwanttoenterfirst.Youcanplacethispseudostatewithinonlyaregionoratthetoplevelofastatechartdiagram.EachregionmusthaveoneandonlyoneInitialpseudostate.

TerminalSpecifiesastatethatcanterminatetheexecutionoftheenclosingregion.Tospecifythisstate,createatransitionfromastatetoaTerminalpseudostate.Youcanplacethispseudostatewithinonlyaregion.YoucanplacemorethanoneTerminalpseudostateinaregion.

JunctionConnectscommonelementsofmultipletransitionstogether.Forexample,youcanuseaJunctionconnectortospecifythatmultipletransitionsusethesameaction,eventhougheachtransitionmighthaveadifferenttrigger.Youcanplacethisconnectoronlyinaregion.

RegionDefinestheareainwhichyoucanplacestatesandpseudostates.EachregionmustcontainanInitialpseudostateandatleastonesubstate.Note!Thetop-levelstatechartdiagramrepresentsaregion.Youcanplaceregionswithinonlyastate.

ForkSplitsoneincomingtransitionsegmentintomultipleoutgoingsegments.Youcanplacethisconnectorwithinonlyastate.

JoinMergesmultipleincomingtransitionsegmentsintooneoutgoingsegment.Youcanplacethisconnectorwithinonlyastate.



PortIndicateswhereatransitionleavesastateorconnector.Portsalsoindicatewhereatransitionpassesthrougharegion.Whenyouareeditingastatechart,portsappearautomaticallyasyoucreatetransitions.Youcanplaceportsmanuallyonlywhenyouareviewingastateasasubdiagram.

ShallowHistorySpecifiesthat,whenthestatechartleavesandthenreturnstoaregion,thestatechartentersthehighest-levelsubstatesthatwereactivewhenthestatechartlefttheregion.TousetheShallowHistorypseudostate,placethispseudostateinaregionandthencreateatransitionfromastatetothispseudostate.

DeepHistorySpecifiesthat,whenthestatechartleavesandthenreturnstoaregion,thestatechartentersthelowest-levelsubstatesthatwereactivewhenthestatechartlefttheregion.TousetheDeepHistorypseudostate,placethispseudostateinaregionandthencreateatransitionfromastatetothispseudostate.

7.3 UsingaCallerVItoExecuteaStatechartThecallerVIistheVIyoucreatethatcontainsa“RunStatechart”function.Thisfunctioncreatesandexecutesaninstanceofastatechart.Executingastatechartmeanssendinginputdatatoastatechart.YoualsocanusethecallerVItosendtriggerstoastatechart.

ThecallerVIhasadifferentstructuredependingonwhetherthestatechartisasynchronousorsynchronous.Thefollowingsectionsprovideinformationaboutthesedifferences.

Executingasynchronousstatechartsinvolvesthefollowingtwoprocesses:

• Executingthestatechartbyusingthe“RunStatechart”function. • Sendingtriggerstotheexternalqueuebyusingthe“SendExternalTrigger”function.

Inthissituation,theVIthatcontainsthe“RunStatechart”functionisthecallerVI.YoucansendtriggerstotheexternalqueuefromanotherVIoraparallelloopinthecallerVI.ThefollowingfigureshowsacallerVIthatbothexecutesanasynchronousstatechartandsendstriggerstotheexternalqueue.



Inthefigureabove,theStatechartLoop,whichisaWhileLoop,executesthestatechart.TheInputscontrolcontainsanyinputdataofthetypesthatyoudefined.TheOutputsindicatorreturnsoutputdatafromthestatechart.TheInstanceNameconstantspecifiesStatechart1asthenameofthestatechartinstance.

TheTriggerLoop,whichcanexecuteinparallelwiththeStatechartLoop,containsanEventstructure.ThisEventstructurehandleseventsthatoccurwithintheVI.Inthiscase,aneventoccurswhenyouclicktheButtonfrontpanelcontrol.Whenyouclickthiscontrol,theEventstructuredetectsthiseventandtheSendExternalTriggerfunctionsendstheTrigger1triggertotheStatechart1statechartinstance.

Note!ThisexampleusesthecallerVItosendtriggerstoanexternalqueue.However,aslongasthecallerVIisrunningandthestatechartisinmemory,youcanuseanyVItosendtriggerstoanexternalqueue.ThisbehaviormeansthatyoucanplacetheTriggerLoopandStatechartLoopinseparateVIs.

StatechartEditor:

OpentheStatechartDiagram(intheStatechartEditor)asfollows:

Right-clickonthe“RunStatechart”VIandselectView→StatechartDiagram.



ProjectExplorer:

OpentheProjectExplorerasfollows:

Right-clickonthe“RunStatechart”VIandselectView→Statechart.

28

8 Tutorial:CreateaStatechart

InthisTutorialyouwilllearnhowtocreateastatechartfromscratch.Inthisexamplewewillcreatethefollowingapplication:

Whenyoupushthedifferentbuttons,thecurrentstatewillbedisplayedinthe“CurrentActivity”indicator

ThisTutorialgoesthroughthefollowingsteps:

• Step1:CreatingandConfiguringtheStatechart• Step2:DefiningStates• Step3:CreatingaTransition• Step4:CreatingaTriggerandConfiguringaTransition• Step5:CreatingandConfiguringtheTerminalTransitions• Step6:CreatingandConfiguringtheInitialpseudostateandTransition• Step7:DefiningtheTypeofOutputData• Step8:DefiningtheTypeofStateData• Step9:ConfiguringaStateEntryAction• Step10:ConfiguringtheActionofaTransition• Step11:DuplicatingtheTransitionNode• Step12:GeneratingCodefortheStatechart



• Step13:CreatingtheCallerVI• Step14:Debugging

Let’sstarttheTutorial:

Step1:CreatingandConfiguringtheStatechart

Completethefollowingstepstocreateandconfigurethestatechart.

1. LaunchLabVIEWanddisplaytheGettingStartedwindow. 2. SelectFile»NewtolaunchtheNewdialogbox. 3. SelectOtherFiles»StatechartfromtheCreateNewtree.

4. ClicktheOKbutton.LabVIEWpromptsyoutosavethestatechart. 5. Enterthename“Tutorial”asthenameofyourstatechart(Note!Ithastheending

.lvsc)andsavethestatechartinaconvenientlocationondisk. 6. LabVIEWdisplaysaProjectExplorerwindowthatcontainsthenecessarysupport

files.Thisprojectitemrepresentsthe“Tutorial.lvsc”fileinwhichLabVIEWstoresstatechartinformation.

7. Right-clickthe“Tutorial.lvsc”itemandselectProperties.LabVIEWlaunchesthePropertiesdialogbox.



8. Selectthe“StatechartCodeGeneration”itemfromtheCategorylist.LabVIEWdisplaysoptionsrelatingtostatechartcodegeneration.

9. SelectAsynchronousfromtheUsagepull-downmenu.Thisactionspecifiesthatthestatechartisasynchronous.

10. ClicktheOKbuttontosavechangesandreturntotheProjectExplorerwindow.

Step2:DefiningStates

Thenextstepiscreatingthestatesthatcomprisethestatechart.Astateisauniqueconditioninwhichthestatechartcanbe.

Thisstatechartconsistsofthreestates:Menu,Play,andPause.Completethefollowingstepstocreatethesestates.

1. IntheProjectExplorerwindow,double-clicktheDiagram.viitemtolaunchtheStatechartEditorwindow.Thiswindowdisplaysthestatechartdiagram.Youbuildastatechartbyplacingstatechartobjectsonthestatechartdiagram.

2. IfyoudonotseetheFunctionspalette,selectView»FunctionsPalettetodisplaythispalette.



3. Onthispalette,selectStatechart»StatechartDevelopmenttodisplaytheStatechartDevelopmentpalette.

4. ClicktheStateobject. 5. Movethecursoroverthestatechartdiagram.Clicktoplacethetopleftcornerofthe

state,dragthecursordiagonallytoestablishthesizeofthestate,andclickagaintoplacethestateonthestatechartdiagram.

6. NoticethestateislabeledState.Double-clickthislabeltoenabletexteditingandenter“Menu”asthenewlabel.

7. MovethecursorovertheblackborderoftheMenustateuntilthecursorchangestothePositioningtool.

8. Pressthe<Ctrl>keyandclickanddragthecursortotherightoftheMenustate.Thisactioncreatescopyofthestate.

9. Labelthisnewstate“Play”. 10. Createanothernewstatelabeled“Pause”.PlacethisstatetotherightofthePlay

state. 11. ReturntotheStatechartDevelopmentpaletteandplacea“Terminal”pseudostate

belowthePlaystate.

Thediagramshouldlooklikethis:

Step3:CreatingaTransition

Thenextstepisdefiningthewaysinwhichthestatechartcanmovebetweenstates.Todefinethisbehavior,youusetransitionstoconnectonestatetoanothervisually.Completethefollowingstepstocreatetransitionsbetweentwostates.



1. MovethecursorovertherightborderoftheMenustateandchangethecursortotheWiringtool.

2. Clickthestateborder.Asyoumovethecursoracrossthestatechartdiagram,LabVIEWdrawsadottedlinebetweenthestateandtheWiringtool.

3. MovethecursorovertheleftborderofthePlaystate.Agrayboxappearsunderthecursor.

4. Clickthebordertofinishthetransition.LabVIEWcreatesatransitionbetweenthetwostates.

Thestatechartdiagramshouldlooklikethis:

Step4:CreatingaTriggerandConfiguringaTransition

Thenextstepisspecifyingthatthestatecharttakesthetransitiononlyafterreceivingaspecificevent,alsocalledatrigger.Bydefault,transitionsareconfiguredtoreacttotheNULLtrigger.However,thecallerVIthatexecutesthisstatechartdoesnotsendtheNULLtrigger.Therefore,youmustconfigurethistransitiontoreacttoadifferenttrigger.

Eachstatecharthasalistoftriggersfromwhichyoucanchoosewhenconfiguringatransition.Configuringatransitioninvolvescreatingatriggerandthenassociatingthattriggerwiththetransition.Completethefollowingstepstoconfigurethetransition.

1. Double-clickthetransitionnodebetweentheMenuandPlaystates.ThisactionlaunchestheConfigureTransitiondialogbox.Youusethisdialogboxtoconfiguretransitions.ThefirsttabinthisdialogboxistheTriggers/Groupstab.NoticethattheNULLtriggerisselectedbydefaultintheTriggersandGroupslist.Everystatecharthasthistriggerbydefault.



2. Clickthe“EditTriggersandGroups”buttontolaunchtheEditTriggersandGroupsdialogbox.Youusethisdialogboxtocreateandmodifytriggers.

3. ClicktheCreateTriggerbuttontocreateanewtrigger,whichappearsintheTriggersandGroupslist.

4. Enter“Play”asthenewtriggername. 5. ClicktheOKbuttontosavechangesandreturntotheConfigureTransitiondialog

box.NoticethenewtriggerappearsintheTriggerslist. 6. IntheTriggers/Groupslist,placeacheckmarkinthePlaycheckboxtospecifythatthis

triggercausesthestatecharttotakethetransition. 7. RemovethecheckmarkfromtheNULLcheckbox. 8. ClicktheOKbuttontosavechangesandreturntothestatechartdiagram. 9. SavethestatechartbyselectingFile»SaveintheStatechartEditorwindow.Youalso

canpressthe<Ctrl-S>keys.

Noticethebluerectangleonthetransitionnode.Thisrectangleindicatesthatyouhavespecifiedanon-NULLtriggerforthetransition.Ifyoumovethecursoroverthetransitionnode,theContextHelpwindowdisplaysthepropertiesofthetransition,includingthetrigger.IfyoudonotseetheContextHelpwindow,pressthe<Ctrl-H>keystodisplaythiswindow.

Createandconfigurethefollowingtransitionsandtriggers.RememberalsotodeselecttheNULLtriggerforeachtransition.



• Fromthe“Play”statetothe“Menu”state.Configurethistransitiontoreacttothe“Menu”trigger.

• Fromthe“Pause”statetothe“Play”state.Configurethistransitiontoreacttothe“Play”trigger.

• Fromthe“Play”statetothe“Pause”state.Configurethistransitiontoreacttothe“Pause”trigger.

Thestatechartshouldlooklikethis:

Step5:CreatingandConfiguringtheTerminalTransitions

Createatransitionfromthe“Menu”statetothe“Terminal”pseudostate.Configurethistransitiontoreactonlytoanewtrigger,Stop.ThistransitionspecifiesthatifthestatechartisintheMenustateandreceivestheStoptrigger,thestatechartterminates.

Tip!Right-clickthetransitionnodeandselecteitherRotateorReversetoensurethenodefacestheproperdirection.

Then,savethestatechartbypressingthe<Ctrl-S>keys.

Thestatechartdiagramshouldnowlooklikethis:



Step6:CreatingandConfiguringtheInitialpseudostateandTransition

PlaceanInitialpseudostate,locatedontheStatechartDevelopmentpalette,totheleftofthe“Menu”state.

Createatransitionbetweenthispseudostateandthe“Menu”state.NoticetheGenerateCodebuttonnolongerisbroken.

Thestatechartshouldlooklikethis:

Step7:DefiningtheTypeofOutputData

Ifyouwantthestatecharttomodifydata,youfirstmustdefinethetypeofdata.Thisprocessinvolvescreatingthecontrolsand/orindicatorsthatrepresentthestatechartdata.

Completethefollowingstepstodefinethestatechartoutputdata.Laterinthispartofthetutorial,youconfigurethestatecharttomodifythisdata.

1. Double-clicktheOutputs.ctlitemintheprojectExplorer.LabVIEWdisplaystheControlEditorwindowforthistypedefinition.

2. NoticethenumericcontrolNumericinsidetheOutputscluster.Right-clickthiscontrolandselectChangetoIndicatortochangethiscontroltoanumericindicator.

3. Right-clicktheNumericindicatorandselectReplace»StringIndicator.Thisactionreplacesthenumericindicatorwithastringindicator.

4. Double-clicktheStringlabelandenterCurrentActivityasthenewlabel. 5. Pressthe<Ctrl-S>keystosavethistypedefinition. 6. ClosetheControlEditorwindowtoreturntotheProjectExplorerwindow.



Step8:DefiningtheTypeofStateData

Statedataisdifferentfromoutputdata.Statedataisaccessiblefromonlythestatechart,whereasoutputdataalsoisaccessiblefromaVIthatcallsthestatechart.UsestatedatatodefinedatatypesthatotherVIsdonotneedtoaccess.

Completethefollowingstepstodefinethestatechartstatedata.

1. IntheProjectExplorerwindow,double-clicktheStateData.ctlitem. 2. Right-clicktheDatacontrolandselectChangetoIndicator.Thisactionreplacesthe

numericcontrolwithanumericindicator. 3. Double-clicktheDatalabelandenterCounterasthenewlabel. 4. Pressthe<Ctrl-S>keystosavethistypedefinition. 5. ClosetheControlEditorwindowtoreturntotheProjectExplorerwindow.

Step9:ConfiguringaStateEntryAction

ThenextstepisconfiguringeachstatetomodifytheCurrentActivityindicatorthatyoudefinedearlier.Youaccomplishthistaskbydefininganentryactionforastate.AnentryactionisLabVIEWblockdiagramcodethatthestatechartexecutesimmediatelyafterenteringastate.



CompletethefollowingstepstoconfiguretheMenustatetoupdatethisindicator.

1. Double-clicktheDiagram.viitemtodisplaytheStatechartEditorwindow. 2. Double-clicktheborderoftheMenustate.ThisactionlaunchestheConfigureState

dialogbox.Note!Whenyouconfigureastate,awrenchicon appearsonthestate()intheStatechartEditorwindow.Thestatealsochangescolor.

3. NoticetheOutputsclusterelementontherightsideofthisblockdiagram.ClickthisclusterelementandselectOutputs»CurrentActivity.ThiselementnowdisplaysOutputs.CurrentActivity,whichindicatesyoucanwritetothevalueofthetypedefinitionyoudefined.

4. MovethecursorovertheinputofthisclusterelementuntilthecursorchangestotheWiringtool.

5. Right-clicktheinputandselectCreate»Constant.LabVIEWplacesastringconstantontheblockdiagram.

6. EnterMenuasthevalueoftheconstant.



7. Thisentryactioncodemeansthat,immediatelyafterenteringtheMenustate,thestatechartchangestheCurrentActivityindicatortoreadMenu.Laterinthistutorial,youwilldisplaythevalueofthisindicatorintheVIthatcallsthestatechart.

8. ClicktheOKbuttontosavechangesandreturntothestatechartdiagram. 9. Thenextstepisdefiningthe“Play”and“Pause”statestoupdatetheCurrentActivity

indicatorappropriately.ConfiguretheEntryActionforeachstatetoupdatethisindicatorto“Playing”or“Paused”,respectively.

10. Savethestatechart.

Step10:ConfiguringtheActionofaTransition

Thetransitionfromthe“Menu”statetothe“Terminal”pseudostatealsocausesachangeintheactivityofthestatechart.Completethefollowingstepstoconfigurethistransition.

Double-clickthetransitionnodeinbetweenthe“Menu”stateand“Terminal”pseudostate.ThisactionlaunchestheConfigureTransitiondialogbox.

ClicktheActiontab.

Writetheblockdiagramcodethatchangesthevalueofthe“CurrentActivity”indicatorto“Stopped”.

ClicktheOKbuttontosavechangesandreturntothestatechartdiagram.

Note!Thetransitionnodeyoujustconfigurednowdisplaystwobluerectangles.Thesecondbluerectangleindicatesthetransitionhasaspecifiedaction.

Step11:DuplicatingtheTransitionNode

ThenextstepiscreatingtransitionsfromthePlayandPausestatestotheTerminalpseudostate.Insteadofconfiguringadditionaltransitionnodes,youcanduplicatethetransitionnodeyouconfiguredalready.Completethefollowingstepstoduplicatethistransitionnode.

1. Pressthe<Ctrl>keyandclickanddragthetransitionnodeyoujustconfigured. 2. MovethisnodeunderthePlaystate. 3. ClickthebottomborderofthePlaystatetoinitiateatransitionsegment. 4. MovethecursorovertheincomingtunnelofthetransitionnodeuntilLabVIEW

displaysatipstripthatreadsSegmentIn. 5. Clickagaintocompletethetransitionsegment. 6. CreateatransitionsegmentfromtheothersideofthisnodetotheTerminal

pseudostate. 7. Right-clickthetransitionnodeandselecteitherRotateorReversetoensurethenode

facestheproperdirection.



Repeatsteps1–7tocreateanadditionaltransitionnodefromthePausestatetotheTerminalpseudostate.AllthreestatesnowhaveatransitiontotheTerminalpseudostate.

Savethestatechart.

Step12:GeneratingCodefortheStatechart

Thenextstepisgeneratingcodeforthestatechart.ThiscodeiscontainedinasingleRunStatechartfunctionthatyouplaceontheblockdiagramofthecallerVI.Completethefollowingstepstogeneratecodeforthisstatechart.

1. DisplaytheStatechartEditorwindow.

2. Clickthe“GenerateCode”button ,whichislocatedonthetoolbarofthiswindow.

3. ClosetheStatechartEditorwindow.

Note!Youalsocangeneratecodebyright-clickingthe.lvscfileintheProjectExplorerwindowandselectingGenerateCodefromtheshortcutmenu.

Step13:CreatingtheCallerVI

ThenextstepistocreatethecallerVItoexecuteandsendtriggerstothestatechart.ThisVIcontainstwofunctions,RunStatechartandSendExternalTrigger,thatyoumustlinktothestatechart.

RunStatechartExecutesaninstanceofthelinkedstatechart.YoutypicallyplacethisfunctioninsidealoopinthecallerVI.

SendExternalTriggerSendsatriggertotheexternalqueueofaninstanceofthelinkedstatechart.YoucanusethisfunctioninthecallerVIorinaVIthatrunsparalleltothecallerVI.

Completethefollowingsteps.

1. SelectFile»NewVIfromtheProjectExplorerwindow2. Create2WhileLoopscalled“StatechartLoop”and“TriggerLoop”3. Addthe“RunStatechart”VIinthe“StatechartLoop”4. Add“SendExternalTrigger”functioninthe“TriggerLoop”



5. Link“RunStatechart”and“SendExternalTrigger”tothestatechart.Right-clickandselect“Linktostatechart…”

6. FinishtheCallerVIsoitlookslikethis:

7. TheFrontPanelshouldlooklikethis:



8. Pressthe<Ctrl-R>keystorunthecallerVI.ClickthefrontpanelbuttonsandnoticehowtheCurrentActivityindicatorschangesaccordingtothestate.

Step14:Debugging

Right-clicktheRunStatechartfunctionandselect“DebugStatechart…”.ThisactiondisplaysthestatechartintheStatechartDebuggingwindow.

Clickthe“HighlightExecution”button ,locatedonthetoolbaroftheStatechartDebuggingwindow,toenablestatechartexecutionhighlighting.

RuntheCallerVIandseehowthedebuggingworks.

42

9 AdvancedTopicsinLabVIEWStatechartModule

InthischapterwewillmentionsomeofthemoreadvancefeaturesintheLabVIEWStatechartModule.

9.1 UsingRegionsandSubstatesWerecallthefollowingobjectsfromtheStatechartDevelopmentpalette:

RegionDefinestheareainwhichyoucanplacestatesandpseudostates.EachregionmustcontainanInitialpseudostateandatleastonesubstate.Thetop-levelstatechartdiagramrepresentsaregion.Youcanplaceregionswithinonlyastate.

PortIndicateswhereatransitionleavesastateorconnector.Portsalsoindicatewhereatransitionpassesthrougharegion.Whenyouareeditingastatechart,portsappearautomaticallyasyoucreatetransitions.Youcanplaceportsmanuallyonlywhenyouareviewingastateasasubdiagram.

9.2 UsingOrthogonalRegionsandStateHistory

WerecallthefollowingobjectsfromtheStatechartDevelopmentpalette:

ShallowHistorySpecifiesthat,whenthestatechartleavesandthenreturnstoaregion,thestatechartentersthehighest-levelsubstatesthatwereactivewhenthestatechartlefttheregion.TousetheShallowHistorypseudostate,placethispseudostateinaregionandthencreateatransitionfromastatetothispseudostate.

DeepHistorySpecifiesthat,whenthestatechartleavesandthenreturnstoaregion,thestatechartentersthelowest-levelsubstatesthatwereactivewhenthestatechartleft

43 AdvancedTopicsinLabVIEWStatechartModule


theregion.TousetheDeepHistorypseudostate,placethispseudostateinaregionandthencreateatransitionfromastatetothispseudostate.

9.3 SplittingandMergingTransitionSegmentsWerecallthefollowingobjectsfromtheStatechartDevelopmentpalette:

ForkSplitsoneincomingtransitionsegmentintomultipleoutgoingsegments.Youcanplacethisconnectorwithinonlyastate.

JoinMergesmultipleincomingtransitionsegmentsintooneoutgoingsegment.Youcanplacethisconnectorwithinonlyastate.

44

10 WhatsNext?

10.1 MyBlogFormoreinformationaboutLabVIEW,visitmyBlog:http://home.hit.no/~hansha/

10.2 TrainingThisTutorialisapartofaserieswithotherTutorialsIhavemade,suchas:

• IntroductiontoLabVIEW• DataAcquisitioninLabVIEW• ControlandSimulationinLabVIEW• LabVIEWMathScript• LinearAlgebrainLabVIEW• DataloggingandSupervisoryControlinLabVIEW• WirelessDataAcquisitioninLabVIEW• IntermediateTopicsinLabVIEW• AdvancedTopicsinLabVIEW

TheseTutorialsareavailablefordownloadfrommyblog:http://home.hit.no/~hansha

10.3 AdditionalResourceswww.ni.com

10.4 ExamplesIntheNIexampleFinder(Help→FindExamples…)youfindlotsofusefulexamplesthatyoucanplaywithoruseasastartwhencreatingyourownapplications.

45 WhatsNext?


10.5 DocumentationAspartoftheLabVIEWinstallationthereislotsofusefuldocumentation.

46

QuickReference

47 QuickReference


Hans-PetterHalvorsen,M.Sc.

E-mail:[email protected]

Blog:http://home.hit.no/~hansha/

UniversityCollegeofSoutheastNorway

www.usn.no

Documents

University College of Southeast Norway - home.usn.no · • Intermediate Topics in LabVIEW • Advanced Topics in LabVIEW Each tutorial may be used independently of each other. 1.1