CLADStudyGuidePreparedbyLabVIEWStudentAmbassadors:

JulianFerrerRiosKristenHeck

FrancescaRamadoriKelvinTang

TableofContentsSection 1: LabVIEW Programming Concepts...........................................................................................2Section 2: LabVIEW Environment............................................................................................................6Section 3: Software Constructs in LabVIEW............................................................................................9Section 4: Programming Vis and functions..............................................................................................16Section 5: Data Communication and Synchronization VIs and Functions..............................................18Section 6: VI Server and Functions.........................................................................................................21Section 7: Errors handling VIs and Functions........................................................................................26Section 8: VI Design Patterns..................................................................................................................29Section 9: SubVI Design..........................................................................................................................37Section 10: Debugging VIs.....................................................................................................................39Section 11: VI Design and Documentation..............................................................................................43Section 12: Memory, Performance, and Determinism.............................................................................45

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Section1:LabVIEWProgrammingConcepts

DataFlow

LabVIEWfollowsadataflowmodelforrunningVis.

Ablockdiagramnodeexecuteswhenallitsinputsareavailable.Whenanodecompletesexecution,itsuppliesdatatoitsoutputterminalsandpassestheoutputdatatothenextnodeinthedataflowpath.

VisualBasic,C++,JAVA,andmostothertextbasedprogramminglanguagesfollowacontrolflowmodelofprogramexecution.Incontrolflow,thesequentialorderofprogramelementsdeterminestheexecutionorderofaprogram.

Considertheblockdiagramabove.Itaddstwonumbersandthenmultipliesby2fromtheresultoftheaddition.Inthiscase,theblockdiagramexecutesfromlefttoright,notbecausetheobjectsareplacedinthatorderbutbecauseoneoftheinputsoftheMultiplyfunctionisnotvaliduntiltheAddfunctionhasfinishedexecutingandpassedthedatatotheMultiplyfunction.Rememberthatanodeexecutesonlywhendataareavailableatallofitsinputterminals,anditsuppliesdatatoitsoutputterminalsonlywhenitfinishesexecution.Inthesecondpieceofcode,theSimulateSignalExpressVIreceivesinputfromthecontrolsandpassesitsresulttothegraph.

Youmayconsidertheaddmultiplyandthesimulatesignalcodetocoexistonthesameblockdiagraminparallel.Thismeansthattheybeginexecutingatthesametimeandrunindependentlyofoneanother.Ifthecomputerrunningthiscodehadmultipleprocessors,thesetwopiecesofcodecouldrunindependentlyofoneanother(eachonitsownprocessor)withoutanyadditionalcoding.

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Polymorphism

Aprogramminglanguagefeaturethatallowsvaluesofdifferentdatatypestobehandledusingauniforminterface.

InLabVIEW:theabilityofVIsandfunctionstoautomaticallyadapttoacceptinputdataofdifferentdatatypes(i.e.NumericFunctions);Usefulwhenperformingthesameoperationondifferentdatatypes

Section1PracticeQuestions

1. YoudevelopaSubVIthatonlyoutputsavalueandneedtousethisSubVIina(calling)VI.WhichofthefollowingisthebestwaytoenforcedataflowtocontroltheexecutionoftheSubVI?

a.UsetheSubVIinaSequencestructureb.ModifytheSubVItohavedummyinputsthatcanbeusedfromthecallingVIc.ModifytheSubVItohaveErrorclustersthatcanbeusedfromthecallingVId.ModifytheSubVItohaveaglobalvariableanduseitfromthecallingVI

2. Whichofthefollowingdoesnotconformtodataflowprogrammingparadigm?

a.ShiftRegistersb.Tunnelsc.SubVIsd.LocalVariables

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3. Inthefigurebelow,whatwillResultequalwhenthiscalculationisexecuted?

a.55b.70c.65d.Indeterminate

4. WhatisthevalueinXORResultafterthefollowingcodehasexecuted?

a.0b.1c.Trued.False

5. WhatdeterminestheprogramorderofexecutionofcodeinLabVIEW?

a.Thetimewhenyouenteredthecodeb.Itgoesfromlefttoright.c.Thedataflow

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6. InthefollowingVI,whatwillbetheexecutionorderoffunctions?

a.

b.

c.

d.

Section1Answers1.C2.D3.B4.B5.C6.C

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Section2:LabVIEWEnvironment

LabVIEWprogramsarecalledvirtualinstruments(Vis).Controlsareinputsandindicatorsareoutputs.

EachVIcontainsthreemainparts:

FrontpanelHowtheuserinteractswiththeVI

BlockdiagramThecodethatcontrolstheprogram

Icon/connectorThemeansofconnectingaVItootherVis

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InLabVIEW,youbuildauserinterfacebyusingasetoftoolsandobjects.Theuserinterfaceisknownasthefrontpanel.Youthenaddcodeusinggraphicalrepresentationsoffunctionstocontrolthefrontpanelobjects.Theblockdiagramcontainsthiscode.Insomeways,theblockdiagramresemblesaflowchart.

Youinteractwiththefrontpanelwhentheprogramisrunning.Youcancontroltheprogram,changeinputs,andseedataupdatedinrealtime.Controlsareusedforinputssuchasadjustingaslidecontroltosetanalarmvalue,turningaswitchonoroff,orstoppingaprogram.Indicatorsareusedasoutputs.Thermometers,lights,andotherindicatorsdisplayoutputvaluesfromtheprogram.Thesemayincludedata,programstates,andotherinformation.

Everyfrontpanelcontrolorindicatorhasacorrespondingterminalontheblockdiagram.WhenyourunaVI,valuesfromcontrolsflowthroughtheblockdiagram,wheretheyareusedinthefunctionsonthediagram,andtheresultsarepassedintootherfunctionsorindicatorsthroughwires.

ControlsPalette

UsetheControlspalettetoplacecontrolsandindicatorsonthefrontpanel.TheControlspaletteisavailableonlyonthefrontpanel.Toviewthepalette,selectViewControlsPalette.YoualsocandisplaytheControlspalettebyrightclickinganopenareaonthefrontpanel.TackdowntheControlspalettebyclickingthepushpinonthetopleftcornerofthepalette.

FunctionsPalette

UsetheFunctionspalettetobuildtheblockdiagram.TheFunctionspaletteisavailableonlyontheblockdiagram.Toviewthepalette,selectViewFunctionsPalette.YoualsocandisplaytheFunctionspalettebyrightclickinganopenareaontheblockdiagram.TackdowntheFunctionspalettebyclickingthepushpinonthetopleftcornerofthepalette.

ToolsPalette

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AutomaticSelectionTool

YoucanviewtheToolsPaletteonboththefrontpanelandblockdiagram.Toviewthepalette,selectViewToolsPalette.YoualsocandisplaytheToolspalettebyholdingshift+rightclickinganopenareaonthefrontpanelorblockdiagram.Ifyouenabletheautomaticselectiontoolandyoumovethecursoroverobjectsonthefrontpanelorblockdiagram,LabVIEWautomaticallyselectsthecorrespondingtoolfromtheToolspalette.ToggleautomaticselectiontoolbyclickingtheAutomaticSelectionToolbuttonintheToolspalette.

UsetheOperatingTooltochangethevaluesofacontrolorselectthetextwithinacontrol.UsethePositioningTooltoselect,move,orresizeobjects.ThePositioningToolchangesshapewhenitmovesoveracornerofaresizableobject.UsetheLabelingTooltoedittextandcreatefreelabels.TheLabelingToolchangestoacursorwhenyoucreatefreelabels.UsetheWiringTooltowireobjectstogetherontheblockdiagram.

Section2PracticeQuestions

1. Whichofthefollowingisthebestmethodtoupdateanindicatoronthefrontpanel?

a.UseaValuepropertynodeb.Wiredirectlytotheindicatorterminalc.Usealocalvariabled.Useafunctionalglobalvariable

Section2Answers1.B

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Section3:SoftwareConstructsinLabVIEW1. Frontpanelwindowandblockdiagramobjects

a. Controls,indicators,IOcontrolsandrefnumsi. Controlfrontpanelobjectforsimulatinginput,displaysvaluesthatwillbepassedTOfunctionsonblockdiagram

1. Knobs,pushbuttons,etc.2. Usuallyhasawhitebackground

ii. Indicatorfrontpanelobjectforoutput,displaysvaluespassedFROMfunctionsonblockdiagram

1. Graphs,LEDs,etc.2. Usuallyhasagraybackground

iii. I/OControlsiv. Refnums

b. Terminals,constants,nodesi. Terminalsrepresentationoffrontpanel(FP)objects(controlsandindicators)ontheblockdiagram(BD);entryandexitpointsfordataexchangebetweenFPandBD

1. RememberpositionofterminaldoesntmatterlabelanddatatypedefineswhatFPobjecttheterminalisconnectedto

ii. ConstantsonlyonBDiii. Nodes

1. Functiona. Paleyellowbackgroundb. FundamentaloperatingelementsofLV

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c. Doubleclickingselectsitem2. subVI

a. VIwithinaVIb. AnyVIhaspotentialtobeasubVIc. DoubleclickonsubVItoopenFPd. ExpressVIs=specialtype

i. Configurationwindow3. Structure

a. Examples:whileloop,forloop,casestructure,sequencestructurec. Palettes,updatemodes,andlegendsofchartsandgraphs

i. Palettes1. Graphpalette

a. Cursormodefocustocursorsocursormovesb. zoommodehorzorvertonlyzoom,boxzoom,zoomin/out(shift+click

forzoomout)c. dragmodeclickanddragplotviewaroundscaleautoupdates

ii. Updatemodes1. Chartaddspointeachiterationmaintainshistory

a. Stripchartentireplotredrawneachiterationinorderforplottoappeartoscrolltotheleft

b. Scopechartpointsplotteduntilendofxscalereached,thenplotclears,andplotbeginsatfarleftagain

c. Sweepchartredlinethatindicatesthefrontedgeofnewdatabeingplottedoverolddata.

2. Graphredrawspoint(s)eachiterationa. Useachartinsidealooptoseefullsetofdata(dynamicallyupdates)b. Useagraphoutsidealooptoseefullsetofdata

iii. Legends1. Plotlegend

a. Showscolorofeachplotandplotname2. Scalelegend

a. Showsxandyscaletitles,canlockscales,showfulldatarange,andedittheformatofthenumbers

3. Cursorlegenda. Onlyavailableforgraphsb. Listscursorsandcoordinatesc. Cancreatecursorsfromhere

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d. MechanicalactionofBooleanobjects[reallyhelpfulexampleVI:MechanicalActionofBooleans.viintheExampleFindersearchmechanical]

i. Switch1. Whenpressedvaluechangeondownclickofleftmousebutton2. Whenreleasedvaluechangeonreleaseofleftmousebutton3. Untilreleasedvaluechanceondownclickandreleaseofleftmousebutton

ii. LatchhastobereadbyLVandreturnstoitsoriginalstate1. Whenpressedvaluechangeondownclickofleftmousebutton2. Whenreleasedvaluechangeonreleaseofleftmousebutton3. Untilreleasedvaluechanceondownclickandreleaseofleftmousebutton

e. Propertynodesi. Accesspropertiesofanobject(item)ii. Allowyoutomodifyobjectsappearanceorbehavior(forexample)programmaticallyiii. Operatetoptobottomiv. Bydefault,iferroroccurshalfwaydown,remainingpropertymodificationswillnotexecuteanderrorwillbeoutput

2. Datatypesanddatastructures[formoredetails(morethancoveredonCLAD)>http://zone.ni.com/reference/enXX/help/371361B01/lvexcodeconcepts/manager_data_types/]

a. Numerici. representnumbersii. chooserepresentation=numberofbitsusedtostorethenumber(morebits,moreprecisionpossible);ieI32,U8,DBL

iii. Orange(DBL),Blue(Integer),Gray(FXP)b. String

i. SequenceofASCIIcharactersii. Tables,textentry,labelsareexamplesofstringobjectsiii. Changedisplayformat:Normal,\Codes,Password,Hexiv. Pink

c. Booleani. True/Falseii. Greeniii. Mechanicalaction(seeabove)

d. EnumeratedControl/Constant/Indicator(Enum)i. Pairsofstringandnumericindefinedlistii. Usefulbecauseeasiertomanipulatenumbersthanstringssometimes(statemachines)

e. pathdatatypei. platform(OS)independent;thefilemanager(lowlevelLV)determineshowthedatatype

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isdefinedf. Arrayandclusterdatatypes

i. Arrays1. Composedofelements(data)anddimension(size)2. Allelementsmustbeofsamedatatypedefinedwhencreated(placing

numericalcontrolinanarrayshellcontrolcreatesanumericarraycontrol)g. Waveform

i. Threepartstoit1. t0:timezero2. delta_t:timeincrement3. Y:value,intensity,voltage,etc.

h. Timestampdatatypei. timezoneindependentnumberofsecondsthathaveelapsedsince12:00a.m.,Friday,January1,1904,UniversalTime.Ifyearandmonthareoutofrange,theresultsareunpredictable.Ifyearisbefore1904,timestampisnegative.

i. Variantdatatypei. Allowsyoutohandledatainageneralway

3. Workingwithobjectsanddatatypesonfrontpanelwindowsa. Ranges,formats,representation,andscaling

i. Appropriateuse1. Example:ifyouaremeasuringtheangleofahalfrotationtherangeshouldbe0

180b. Customizingcontrols

i. Customcontrol1. Singleinstanceofuniquecontrolorindicator

ii. Typedefinitions1. Linkedtofilesochangestofilewillbeseenineachinstanceoftypedeffed

control/indicator2. Appearanceisnotlinkedtofiledatatype(I32,U8,listofenum,string)

iii. Stricttypedefinitions1. Linkedtofilesochangestofilewillbeseenineachinstanceoftypedeffed

control/indicator2. AppearanceISlinkedsoEVERYTHINGexceptlabel,description,anddefault

valuechanges4. Programcontrolstructuresanddatastorage

a. Loopingstructures(forloopsandwhileloops)i. ForLoop

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1. ExecutessetnumberoftimesdefinedbyNterminalorindexedtunnel2. Possibleexecutezerotimes3. Tunnelsautomaticallyoutputanarrayofdata

ii. WhileLoop1. Stopsexecutingbasedonthevalueattheconditionalterminal2. Mustrunatleastonce(dowhileloop)3. Tunnelsautomaticallyoutputlastvalue

iii. Indexingonloopboundaries1. Input:oneelementinthearraywillbepassedinwitheachloopiteration2. Output:anelementisaddedtothearraywitheachloopiteration,theentirearray

willbepassedoutiv. Shiftregisters

1. Pairofterminalsonleftandrightsideofloopforcedtobealigned2. Valuereadfromoutputofshiftregister(leftside)willbethesamevalueasthe

valuepassedtotheshiftregisterinput(rightside).3. 1stiterationofloop:

a. ifinitialized(valuepassedintoshiftregisterfromoutsidetheloop),theinitializingvaluewillbethevaluereadfromtheshiftregister.

b. Ifuninitialized,thevalueintheshiftregisterfromthelasttimetheloopwasexecutedwillbethevaluereadfromtheshiftregister(thisisutilizedinfunctionalglobals)ifneverrunbefore,usesdefaultvalue(usually0)

b. Caseandsequencestructuresi. Flatandstackedsequencestructures

1. Canbeusedtoforceexecutionorder,butusuallyanotherway(errorwire)2. Shouldbeavoidedbecausecannotbestoppedinthemiddle.3. Stackedmeansthatyouonlyseeoneframeatatimescrollthroughtosee

othersii. Caseselectorvaluesanddatatypes

1. Caseselectoracceptsvaluestodeterminewhichcasetoexecute2. Ifvaluecaseselectorreadsdoesnotmatchanyofthecases,defaultcasewill

execute.3. Enumsusefulbecausedonthavetoworryabouttyposwithstrings,andplain

numericsarehardertokeeptrackof.4. Errorwirecanbewiredtocaseselectortoprogrammaticallychoosetoexecute

certaincodewhenthereisorisnotanerrorcasestructureturnsredandgreentoindicateerrorcaseandnoerrorcase.

iii. Datapassingtunnelsandsequencelocals1. Tunnelspassvaluesinoroutofstructures

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a. Colorwillmatchdatatypei. Solidallcaseswired,noindexing,normalii. Open(notseenonloops;output/rightsideonly)oneormorecasesisntprovidingavaluetooutput

iii. Smallwhitesquareinsideusedefaultifunwirediv. Whitewithbracketsofdatatypecolor(seenonlyonloops)autoindexingenabled

2. Sequencelocalonlyforstackedsequencestructuresa. Similartoshiftregisterinthatitpassesdatafromoneinstance(loop,

sequenceframe)toanotherb. Arrowtoindicateifinputorouput

c. Eventstructuresi. Notifyandfilterevents(userinterface)

1. Notifya. Leftsideofeventstructureb. eventhappened,getvaluesfromeventc. GreenarrowinEditEventwindow

2. Filtera. eventisabouttohappen,abletochangewhathappensb. rightsideofeventstructurec. redarrowinEditEventwindowandendswith?

ii. Value(signaling)propertiesofcontrols1. Thesepropertiescanbecaughtbyaneventstructure

iii. Dynamiceventsanduserevents1. Dynamicevents

a. usewhenonlywanteventtoberegisteredduringpartoftheapplicationsexecution

b. enableyoutohandleeventsinasubVIc. rightclickoneventstructuretoselectShowDynamicEventTerminals

2. UserEventsa. Programmaticallycreateaneventthatyoudefine(insteadoftheones

alreadyavailablethroughtheeventstructure)b. UseGenerateUserEventtohaveeventoccurandbesenttoevent

structuretobehandledd. Formulanode

i. Allowsyoutousetexttoexecuteafunctionandmathematicalformulas(cos,sin,log,etc)e. Conditionaldisableanddiagramdisablestructures

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i. ProgrammaticallyenableanddisablecodeusefulifwantingtomakefileI/Ofunctioncorrectlyinbothdevelopmentandexecutableenvironments

ii. Usefulintroubleshootingcodetonarrowdownproblemspotf. Timedstructuresloopandsequence

i. Moreusefulinarealtimeoperatingsystem(deterministic)ii. EachlooporframewilloperateinthetimeyouspecifywillindicateifdoesntusingFinishedLate?DataNodeelement

iii. Cansetpriorityofloop,processortheloopshouldusetoexecute,etcg. Variableswireisalwayspreferred,raceconditionspossible

i. Local1. WithinasingleVI

ii. Global1. VItoVI2. LookslikeafrontpanelonlyVIthatstoresthevalues

iii. FunctionalGlobal1. VItoVI2. FPandBDuninitializedshiftregisterusedtostoredata3. Protectsdatafromtwoinstancestryingaccessatsametimeandcausingrace

conditioniv. Shared

1. VItoVIacrossanetwork2. DeployedtonetworkforusebymultipleVIsonthenetwork

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Section4:ProgrammingVisandfunctions1. Numeric,Boolean,string,path,andvariant

a) (seeabove)2. Conversion,comparison,andmanipulation

a) Functionsspecificallyforconverting:num>string,string>num,path>string,string>path,etcb) Functionsspecificallyformanipulatingcertaindatatypes:buildpath,strippath,concatenatestring,

bool>numarray,etc3. Arraysandclusters

a) Bothhaveshellsb) Arrays

1. mustbesamedatatype2. dimensionanddata3. indexelementfromarray

c) Clusters1. Groupingofmanydatatypes(includingarraysandotherclusters)2. Unbundleandbundleclusterelements

4. Timinga) Waittimers

1. Wait1. Willwaituntilthespecifiedtimehaselapsed2. Wheninaloop,runsinparalleltoothercodeinsideloop(assumingnodependencieson

othercodeinloop)ifcodetakeslongerthanthewaittime,nextloopiterationwillbeginimmediately,otherwisethewaitwillcompleteandthennextloopiterationwillbegin

2. Waituntilnextmillisecondmultiple

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1. Willwaituntilamultipleofthetimespecifiedisreached2. Wheninaloopandassumingnodependencyonothercodeinloop,itwillruninparallelif20

msiswiredtoit,imaginemarksalongatimelineevery20ms.Ifthecoderuns45ms,thenextloopiterationcannotbeginuntilthenextmark,whichwouldbeat60ms.

b) tickcount(ms)1. startsatzero(cannotconvertintorealdate/time)2. maxvalue=(2^32)1;thereforecanrolloverbacktozeroifallowedtocountpastitsmax>bad

informationc) date/timefunctionsd) Timingfunctionsrelatedtotimedstructures

5. fileI/Oformatsa) ASCII

1. Textfile2. Goodtousewhenwanttoopenwithanotherprogram(notepad,textedit,word,etc)

b) Binary1. Takesleastamountofmemory2. Efficient3. Cannotbeeasilyreadbyuseroropenedbyanotherprogram4. Mustknowhowtodecodethefile

c) Datalog1. Typeofbinaryfile2. Usedtowriteclustereddatatofile

d) Storage(.tdm)1. Internalstructurepubliclydocumented(createdbyNI)2. TypeofbinaryfilewithanindexfileforfasterI/Operformance3. Abletoapplypropertiestofileatdifferentlevels:file,group,channel

e) Waveformf) XML(ExtensibleMarkupLanguagestandardized)

1. SetoffunctionsspecificallyforXML2. Platformindependent

g) Configuration1. inifile2. Setoffunctionsspecificallyforconfigfiles3. Platformindependent

6. WaveformandwaveformfileI/Oa) StorageVIsusedtowritewaveformdatatobinarymeasurementfiles(.tdm)

7. Dynamicanduserevents

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a) (seeabove)

Section5:DataCommunicationandSynchronizationVIsandFunctions

LocalVariables

Localvariablesallowdatatobepassedbetweenparallelloops.Youcanreadorwriteasinglecontrolorindicatorfrommorethanonelocationintheprogram.Localvariablesbreakthedataflowparadigmandshouldbeusedsparingly.Sometimesyoumayneedtoaccessafrontpanelobjectfrommorethanoneplaceontheblockdiagramortopassdatabetweenstructuresthatyoucannotconnectbyawire.Toaccomplishthesetasks,youwouldusealocalvariable.

LocalvariablesarelocatedontheFunctionspaletteunderProgrammingStructures.Youusealocalvariablebyfirstselectingtheobjectyouwanttoaccess.YoucaneitherclickonthelocalvariablewiththeOperatingtoolandselecttheobjectyouwanttoaccess,orrightclickonthelocalvariableandchoosetheobjectfromtheSelectItemmenu.Next,youmustdecidetoeitherreadorwritetotheobject.RightclickonthelocalvariableandchooseChangetoReadorChangetoWrite.

GlobalVariables

UseglobalvariablestoaccessandpassdataamongseveralVIsDiffersfromlocalvariablesbecauselocalvariablesareusedtoaccessandpassdatabetweenparallelloops(withinoneVI).Whenyoucreateaglobalvariable,LabVIEWautomaticallycreatesaspecialglobalVI,whichhasafrontpanelbutnoblockdiagram.

SharedVariable

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Representsasharedvariableontheblockdiagram.UsesharedvariablestosharedataamongVIsorbetweenlocationsontheblockdiagramthatyoucannotconnectwithwires.

DataSocket

UsetheDataSocketVIandfunctionstopassdatabetweenVIsprogrammatically.DataSocketbeusedwithbasicallyanyprotocolthatutilizestheTransmissionControlProtocol(TCP)insomeform.

TouseDataSocketsitisnecessarytosetuptheDataSocketsServer,aprogramthatrunsononeofthemachinesinthenetworkandactsasanintermediary,sothatmultipleclientscanread/writedata.ThedatatransferusestheDatasocketTransferProtocol(DSTP).Protocols

UsetheProtocolsVIsandfunctionstoexchangedatabetweenapplicationsbyusingprotocolssuchasTCP/IP,UDP,serial,IrDA,Bluetooth,andSMTP.

Notifiers

UsetheNotifierOperationsfunctionstosuspendtheexecutionofablockdiagramuntilyoureceivedatafromanothersectionoftheblockdiagramorfromanotherVIrunninginthesameapplicationinstance.

Queues

UsetheQueueOperationsfunctionstocreateaqueueforcommunicatingdatabetweensectionsofablockdiagramorfromanotherVI.

Semaphores

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UsetheSemaphoreVIstolimitthenumberoftasksthatcansimultaneouslyoperateonashared(protected)resource.Aprotectedresourceorcriticalsectionofcodemightincludewritingtoglobalvariablesorcommunicatingwithexternalinstruments.

Section5PracticeQuestions

1. Whichofthefollowingcannotbeusedtotransferdata?

a.Semaphoresb.Queuesc.Notifiersd. Localvariables

2. Whichofthefollowingillustratesanadvantageofaglobalvariableoveralocalvariable?

a.AglobalvariablecanpassdatabetweentwoindependentVIsrunningsimultaneouslyb.Onlytheglobalvariablecanpassarraydata,localvariablescannotc.Globalvariablesfollowthedataflowmodel,andthereforecannotcauseraceconditionsd.Globalvariablesdonotrequireownedlabelstooperate

Section5Answers1. A2. A

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Section6:VIServerandFunctions

InLabVIEWprogramming,aVIServercanbeusetoprogrammaticallycontrolfrontpanelobjects,VIs,andLabVIEW,andtodynamicallyload,edit,andrunVIsonacomputerorremotelyacrossanetwork.YoucancontrolbrowseraccesstotheVIsandconfigurewhichVIsremoteapplicationscancontrol.

ConfiguringtheVIServerPageSelectToolsOptionstodisplaytheOptionsdialogboxandselectVIServerfromtheCategorylisttodisplaythispage.IfatargetinaLabVIEWprojectsupportstheVIServer,youalsocanrightclickthetarget,suchasMyComputer,selectPropertiesfromtheshortcutmenu,andselectVIServerfromtheCategorylisttodisplaythispage.ToconfigureVIServeroptionsforthe mainapplicationinstance,displaythispagefromthe Optionsdialogbox.ToconfigureVIServeroptionsforatarget,displaythispagefromthePropertiesdialogboxforthetarget.ToconfigureVIServersettingsforaprojectapplicationinstance,rightclickthetargetintheProjectExplorerwindow.TheVIServerpageincludesthefollowingcomponents: ProtocolsUsethissectiontoconfiguretheVIServer.ThedefaultVIServersettingsareActiveXenabledandTCP/IPdisabled.o TCP/IPEnablesVIserversupportforTCP/IP.Ifyouallowremoteapplicationstoconnectusing

TCP/IP, youalsoshould specify which machineaddressescanaccess theVI Server in theMachineAccesssectionofthispage.Thischeckboxdoesnotcontainacheckmarkbydefault.

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PortSets the TCP/IP port at which the VI server listens for requests. FromToolsOptions thisportnumberis3363,bydefault,whichisaregisteredportnumberreservedforusebyLabVIEW.Fortargets,thedefaultis0causingtheoperatingsystemtodynamically select aport. If youwant to runmultiple application instances on themachine,eachwithitsownVIServerrunning,youmusthaveauniqueVIServerportnumber.Youalsocanusethe Server:PortpropertytosettheLabVIEWVIServerportprogrammatically.

ServicenameSetstheservicenamefortheVIServerTCPInstance.Toretrieveanapplicationreferencewithouttheportnumber,useServicenameinconjunctionwiththeOpenApplicationReference functionbywiringa Servicename tothepolymorphicportnumber or Service name input.

IfyoudisplaythispagefromtheOptionsdialogbox,thisservicenameisMainApplicationInstance/VIServerbydefault.IfyoudisplaythispagefromthePropertiesdialogboxforatarget, the service name is target name/VI Server by default. You can use theServer:ServiceNamepropertytosettheservicenameprogrammatically.

UsedefaultSets Servicename toitsdefaultvalue.Thischeckboxcontainsacheckmarkbydefault.Toedit Servicename,removethecheckmarkfromthecheckbox.

o ActiveX(Windows) Enables VI server support for ActiveX Automation. This checkbox isavailable only from the ToolsOptions navigation. This checkbox contains a checkmark bydefault.

VIScriptingUsethissectiontoenableVIScripting.o ShowVIScriptingfunctions,propertiesandmethodsEnablesVIScriptingfunctionsonthe VI

ScriptingpaletteandadditionalVIServerpropertiesandmethods.Allfunctions,properties,andmethodsyouenablethroughVIScriptingdisplayasblue.

DisplayadditionalVIScriptinginformationinContextHelpwindowDisplays connectorpaneterminalnumbersintheContextHelpwindow.PlaceacheckmarkintheShowVIScriptingfunctions,propertiesandmethodscheckboxtoenablethisoption.

AccessibleServerResourcesUsethissectiontoindicatethetasksthatremote applications canaccomplish.

o VIcallsAllowsremoteapplications to call VIs exported through theVI Server. If youallowremoteapplicationsaccesstoVIs,specifywhichVIscanbeexported.Thischeckboxcontainsacheckmarkbydefault.

o VIpropertiesandmethodsAllowsremoteapplicationstoreadandsetthepropertiesofVIsandtocallmethodsforVIsthroughtheVIServer.If youallowremoteapplicationsaccesstoVIs,specifywhichVIscanbeexported.Thischeckboxcontainsacheckmarkbydefault.

o ApplicationpropertiesandmethodsAllowsremoteapplicationstoreadandsetthepropertiesoftheapplicationinstanceandtocallmethodsfortheapplicationinstancethroughtheVIServer.Thischeckboxcontainsacheckmarkbydefault.

o ControlpropertiesandmethodsAllowsremoteapplicationstoreadandsetthepropertiesof

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controls and to call methods for controls through the VI Server. This checkbox contains acheckmarkbydefault.

MachineAccessUsethissectiontocontrolmachineaccesstoVIsthrough theVIServer.o MachineaccesslistListsmachinesthatdoanddonothaveaccesstotheVIServer.Youalso

can use the Server:TCP/IP Access List property to list programmatically the TCP/IPaddresses of machines that may access the VI server.Note: If you change the Machine access list, machines that are currentlyconnectedtotheVIserverwill notbedisconnectedevenif theyarenolongerallowedaccesstotheserver.

o Machinename/addressEnterthenameorIPaddressofthemachineyouwanttoaddtotheMachineaccesslist.

o AllowaccessAllowsaccesstothemachine(s)selectedinMachineaccesslist.o DenyaccessDeniesaccesstothemachine(s)selectedinMachineaccesslist.o AddAddsanewentrytothe Machineaccesslist.Thenewentryappearsbelowtheselected

entryintheMachineaccesslist.o RemoveRemovestheselectedentryfromtheMachineaccesslist.

ExportedVIsUsethissectiontoadd,edit,andremoveVIsfromtheExportedVIslist.o ExportedVIslistListstheVIsthatcanbeexported.YoualsocanusetheServer:VIAccessList

propertytolistprogrammaticallytheVIsontheVIServerthatareaccessiblebyremoteclients.o ExportedVIEnteraVItolistinExportedVIs.YoucanusewildcardsintheVInameordirectory

pathyouenter.o AllowaccessAllowsaccesstotheVI(s)selectedin ExportedVIs.Thisoptionisselectedby

default.o DenyaccessDeniesaccesstotheVI(s)selectedinExportedVIs.o AddAddsanewentrytoExportedVIs.o RemoveRemovestheselectedentryfromExportedVIs.

UserAccessUsethissectiontocontroluseraccesstoVIsthroughtheVIServer.YoualsocanusetheDomainAccountManagertomanagedomainusersandgroups.o Userandgroupaccess listLists users and groups that can and cannot access the VI

Server. If you do not include users or groups in this list, all users and groups associatedwith machines that have access permission can access the VI Server.Note: If the User and group access list is changed, users that are currentlyconnected to the server will not be disconnected even if they are no longerallowedaccesstotheVIServer.

o AllowaccessAllowsaccesstotheusersandgroupsselectedinUserandgroupaccesslist.o DenyaccessDeniesaccesstotheusersandgroupsselectedinUserandgroupaccesslist.o AddDisplaysthe AddUsersandGroupsdialogbox,inwhichyoucanselectadomain,user,

andgroup.o RemoveRemovestheselectedentryfromtheUserandgroupaccesslist.

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VIServerApplication

CompletethefollowingstepstocreateaVIServerapplication:1. ConfiguretheVIServer toallowtheTCP/IPprotocol.2. Use the OpenApplication Reference function to open a reference to a local or remote

application instance. Note:Ifyouhavemultipleapplicationinstancesopensimultaneously,suchasifyouareworkingwitha LabVIEWproject ortargetsofaLabVIEWproject,multipleVIServerscan be listening on different ports. Open an application reference to a specificapplicationinstancebystatingthemachinenameandtheportorservicename.3. UsetheOpenVIReferencefunctiontoopenareferencetoaVIonthelocalorremotecomputerthatalreadyexists in memory for theapplication instance, or to dynamically loadaVI fromdisk.However,beawarethatiftheinputtovipathisafilepath,thisfunctionwaitsuntiltheuserinterfaceisidletoloadtheVIfromdisk.4. UsethePropertyNodetogetorsetpropertiesortheInvokeNodeto invoke

methods.5. YoualsocanuseaCallByReferenceNodetocalladynamicallyloaded VI .6. UsetheCloseReferencefunctiontocloseanyopenreferences.

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Section7:ErrorshandlingVIsandFunctions

HaveyoueverwonderwhatisthelowestlineinmostoftheVIs?ThatlineisanspeciallinecalledErrorIn/Out.ThislineisanspecialclusterTypecalledErrorcluster,whichconsistsof:

1. Boolean:Indicatingifthereisanerror.2. 32bitInteger:Indicatingthecodeoftheerror.3. String:Indicatingthesourceoftheerror,i.e.thecauseoftheerror.

Thisclusterhasthesamepropertiesofanyotherclusters,howeverithasotherspecialfeatures.Thefirstofthemisthatthislineisusuallyusedtoguaranteesequence.FollowingtheLabVIEWrulethatestablishesthatanysubVIorfunctionneedstohaveallitsinputsinordertorun,iftheoutputerrorlineisconnectedtotheinputofanothersubVI,thesecondsubVIwontrununtilthepreviousends.

Anothercharacteristicoftheerrorclusteristhat,whenconnectedtoacasestructure,itwillcreatetwocases:ErrorandNoError,whichcanbeusedtoskipstepsthatcantbeexecutedunlesseverythingelsehasnoerrors.AlsoisusedtoguaranteesequencewhentherearefunctionsorVIsthatdoesnthaveerrorline.

Therearetwodifferentwaysofhandlingerrors,automaticandmanually. Automatic:WhenLabVIEWisconfiguredtohandletheVIsautomatically(File>VI

Properties>Execution>EnableAutomaticErrorHandling),whenitencountersaunwiredErrorline,itwillhalttheexecutionandhighlightwheretheerroroccurred.

Manual:TohandleerrosmanuallytherearecertainVIsmeanttodoitwhicharepresentattheProgramming>Dialog&UserInterface:

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o SimpleErrorhandlerandGeneralErrorHandler:Displayswhenanerroroccurred,showingthecauseoftheerrorandoptionallyanerrordialogbox,thedifferencebetweenthesimpleandthegeneralisthatthegeneralalsoacceptscustomerrorcodes.

o Merging,creating,clearingandsearchingerrorVIs:alsotheusermayneedtoclearerrorsiftheprogramsolvestheproblembyitself,also,whenbuildingSubVIsitisimportanttoaddthepreviouserrorstotheerrorsthatcanbeaddedfromthesubVI,andafterseveralsubVIsaddingerror,isusefultosearchforthefirsterror,sincetheerrorhandlerVIsshowstheerrorwithmostpriority.

o UserinterfaceDialogBoxes:ThisVIsareusedtoinformtheuserwheneveranerroroccurredandalsotoallowtheusertodecidetheactiontoimplementiftheprogramrequiresit.

WhencreatingVIs,wemightproduceerrorsthatLabVIEWdoesntinterpretthemaserrors.Forexample,whenwehaveadivisionby0:

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LabVIEWwillgiveinfiniteasresult,however,forsomeapplicationthatmeansthatanerroroccurred.Forthosecases,itispossibletocreateyourownerrorcodesandimplementtheminlabVIEW.Todoso,itisnecessarytocreatea*error.txtfile.FortunatelyLabVIEWhasaninterfacemeanttohelpcreatingthisfile:Tools>Advanced>EditErrorCodes.Itwillaskyouifyouwanttocreateanewfileoreditone,eitherwayyoucanaddorediterrors.

Alltheerrorsaresavedat>Shared>Errors.

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Section8:VIDesignPatterns

AgeneralVIdesignpatternconsistsof3mainparts:

1.Startup:Initializehardwareorgettingsignalsordatafromafile.2.Mainapplication:Analyzetheinputsignalordatacontinuouslyuntilitis

terminatedbyaconditionalterminalorauseraction.3.Shutdown:Displaysoutputdataorlogintofile.

DesignPatternSelectionFlowChart

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StateMachineDesignPatternThestatemachinedesignpatternisusedforalgorithmsthatcanbeexplicitly representedwithastate

diagram.

AstatemachineinLabVIEWconsistoffollowingblockdiagramcomponents:1.WhileLoop:Executecurrentstatecontinuously.2.ShiftRegister:Usedtostoreandtransitnextstatetocurrentstate.3.CaseStructure:Containsprogramcodeforeachstate.4.StateFunctionalityCode:Programcodeforeachstateincasestructure.5.TransitionCode:Determinenextstate.

StateMachineDesignPattern

QueuedMessageHandler:Itisusedtoimplementcodeforauserinterface.Messagesisqueuedandhandledonebyoneintheorderofthequeue.Eachsubdiagraminthequeuedmessagehandlerrepresentsahandlingroutine.Itissimilartoastatemachinedesignbutwiththeshiftregisterholdingontothequeuedmessage.

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ParallelLoop&Master/SlaveDesignPattern

ParallelLoopDesignPattern

Aboveblockdiagramillustratestheparallelloopdesignpattern.Theerror clusterwiresareusedtoexecutebothwhileloopsinparallel.However,thisdesignpatternisnotefficientastheremightbearaceconditionwhenimplementingdataaccessingmechanismwheretheremaybemultipleloopsaccessingthedataatthesameinstanceoftime.

Asolutiontothiswouldbeusingthemaster/slavedesignpatternasdepictedin blockdiagrambelow.

Master/SlaveDesignPattern

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Themaster/slavedesignpatternisusedforexecutingtwoormoreprocesses simultaneouslyandpassdataamongprocesses.Thisdesignpatternmayconsist multiple parallel loops, each running at different rates.Therewillbealoopacts asthemasterwhichcontrolsalltheotherloopsknownastheslaveloops.The

raceconditionisavoidedbyusinganotifiestopassdatafromthemastertothe slave. Benefitsofusingnotifiesinmaster/slavedesignpatternisthatallslave loopsaresynchronizedtothemasterloop.Slaveloopexecutesonlywhen the masterloopsendsanotification.

Producer/Consumer(Data)DesignPattern

Producer/Consumer(Data)DesignPatternThisdesignpatternenhancesthedatasharingamongmultipleloopsrunningatdifferentrates.Theparallel loops are separated into 2 categories: the loop producing data (producer) and the loopconsumingdata(consumer).Mainbenefits:Processmultiplesetsofdatainorder.Queuesdataintheconsumerloop.Basically, thedata is continuously queuedby theproducer into theconsumer loopqueueand isprocessedbytheconsumerloopatitsownpace.

UserInterfaceEventHandlerDesignPattern

Theeventbaseddesignpatternbenefitsintermsofefficiencyastheyonlyrespondwhenaneventoccurs.

Itconsistsoffollowingblockdiagramcomponents:

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1.EventStructure:Containsprogramcodeforeachdetecteduserinterfaceevent.2.WhileLoop:Monitoruserinterfaceeventcontinuously.3.TimeoutTerminal:Controlswhenthetimeouteventexecutes.4.EventDataNode.

UserInterfaceEventHandlerDesignPattern

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Producer/Consumer(Event)DesignPattern

Producer/Consumer(Event) DesignPattern

Thisdesignpatternissimilartotheproducer/consumer(data)designpattern, however, the consumerloopexecutesasaneventoccurrenceisdetectedinthe producerloop.

Mainbenefits:Efficientlyrespondsasynchronouslytotheuserinterface.Queuescantransferanydatatype.

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FunctionalGlobalVariable

UninitializedshiftregistersinfororwhileloopscanbeusedtoholddataaslongastheVInevergoesoutofmemory.Theshiftregisterholdsthelaststateoftheshiftregister.Thus,aloopwithanuninitializedshiftregisterisafunctionalglobalvariable.

MainBenefits:

Controlaccesstodatainashiftregister.

Eliminatethepossibilityofaracecondition.

FunctionalGlobalVariable

AboveisaVIexampleofafunctionalglobalvariable,whentheenumeratedinputisSet,theinputvalueisshiftedandstoredintotheshiftregister.Ontheotherhand,whentheenumeratedinputisGet,itwillretrievedthestoredvaluefromtheshiftregisteranddisplayitattheoutput.

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DesignPatternsTableofComparison

DesignPattern Use Pros ConsGeneral Standardcontrolflow Distinct initialize,run

andstopphasesUnabletoreturntoapreviousstate

StateMachine State sequencesystemcontrol

Controlssequences Doesnotstorefuturesequences toexecute

Queued MessageHandler

Enhanced statemachine with storingof future sequencestoexecute(message)

Stores futuresequences toexecute

Does not usememoryefficiently

ParallelLoop Multiple taskprocessinginaVI

Efficient use ofcomputingresources

Bad synchronizationand have racecondition

Master/Slave Parallel loops withsynchronization

Passes messagesand handles loopsynchronization

Does not lend itselfwelltopassingdata

Producer/Consumer(Data)

Data producing andprocessinginparallel

Storesdata for laterprocessing

Does not provideloopsynchronization

User Interface EventHandler

Responds to userinterfaceevent

Handles userinterfacemessages

Does not allow forintensive processingapplications

Producer/Consumer(Event)

Producer/Consumer(Data) whichresponds to userinterfaceevent

Separates the userinterface fromprocessorintensivecode

Does not integratenonuser interfaceeventswell

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Section9:SubVIDesign

ModularityisthepropertyofscalingaVIinsubmoduleswhichhavespecialfeaturesandcanberecycledinotherVIs.ThesemodulesarecalledsubVIs,and,sinceaSubVIisaVImodifiedintoasmallblockvisualization,doubleclickingitwillopenafrontpanelandablockdiagram.

EverySubVIneedsanIconandaConnectorpanetobecalledSubVI:a. Icon:GraphicalrepresentationofaVI.Customizable(doubleclick)b. ConnectorPane:MapoftheterminalsofaVI.Inputstotheleft,Outputstotheright(accessing

viarightclick>ShowConnector)

TheiconmustbemodifiedinordertorepresentwhatdoestheSubVIdoes,forthisreasontheIconEditorhasabuiltinpaintwindowtomodifytheimage:

TheconnectorPanerepresentstheInputsandOutputsofaSubVI.Therearemanytypesofconnectorssuitedforanyapplication.Itisimportanttonotethat,forconvention,InputsgoesleftandOutputsgoesRight.TolinktheterminalwiththeI/O:

FirstClicktheterminalintheconectorPane TheclickontheInputorOutput,theterminalwillchangecolorasaconfirmation FinallychooseiftheconnectorisRequired,RecommendedorOptionalbyRightClickingthe

terminal>ThisConnectionis>

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WhendesigningSubVIs,itisimportanttoconsiderthepreviouserrorsastheerrorsthattheSubVIisadding,oneofthemostcommonerrorhandlingmethodsinSubVIisthenextone:

ApolymorphicVIisanspecialVIthatacceptsseveralDataTypes,anexamplecouldbethemultiplyfunction,sinceitcanacceptanydataType.InordertocreateapolymorphicVIisnecessarytocreatealltheVIsthataregoingtobepartofthepolymorphicVIwiththesameconnectorpaneconfiguration.Afterthatgoto:File>New>PolymorphicVI.Anewwindowwillprompt,whereyouwillhavetoaddalltheVIs.TheiconofthisVIwillalsoneedtobecreatedbyclickingintotheEditIcon.ThisVIwillautomaticallydecidewhichinstanceoftheVIsaddedtouse.

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Section10:DebuggingVIs

WhenyourunaVIitmayhappenthatitdoesntevenrunoritdoessomethingyouwerentexpecting.

IftheVIdoesntrun,thefirststepistochecktheBrokenarrowatthetopoftheBlockDiagramortheFrontPanel:

Thenextwindowwillprompt:

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ThemostcommoncausesforaVItobebrokenare:3. Theblockdiagramcontainsabrokenwire.4. ArequiredterminalofaSubVIisnotwired5. ASubVIisbroken.

SooncetheVIisnotbroken,thenextstepistorunit,ifitworksthedebuggingprocessisover!However,itmighthappenthattheVIgivesanunexpectedresultorithaltsatthemiddleoftheexecutionduetoerrors.Thedebuggingprocessisthenextone:

1. Checktheerrorsiftheyexist.2. UsethecontextHelpinSubVItocheckthedefaultvaluesandbesurethatthedefaultvaluecorresponds

towhatyouwant.3. Eliminateallthewarnings4. CheckDataTypes,sometimeswhenusingdifferentdatatypes,informationcanbelostduetoDataType

casting.

Ifthatdoesntwork,thenextstepistodebugtheexecutionoftheVIusingthenexttoolsaloneorcombined: HighlightExecution:AnanimationoftheblockDiagramexecutionwithvaluesattheoutputs.This

methodshowsthemovementofData.

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SingleStepping:ExecutesonlyonestepoftheVI.UsedwiththeHighlightedExecutionprovidesanincredibledebuggingtool.

ProbingTools:Showsthevalueoverawire.InHighlightingexecutionorSingleStepping.ClickontheWire

Breakpoints:PausetheexecutionwheneverthereisnewDataAtaWire.

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SuspendwhenExecuted:ThisworksasaBreakpoingforSubVIs.OncetheSubVIisexecuteditwillpausethewholeVI.AndwillopenthefrontpaneloftheSubVI.

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Section11:VIDesignandDocumentation

1. Userinterfaceandblockdiagramlayouta. UI

i. Onemonitororless1. Tabstoorganizeandcondenseiftoomanycontrols/indicatorstolimittoone

monitorii. Groupcontrolsandindicatorslogically

1. Relateditemsshouldbegroupedtogether2. Usedecorationstoclarifyoremphasizegroupings

iii. Fontandcolor1. Usebrightcolorssparinglyandonlyforthingsthatneedtostandout(i.e.stop

button)2. Fontshouldbeuniform3. Boldtextforgroupingtitlesorheading4. Textsizeshouldbelogical

a. largertextforheadingsorimportantinformation,b. textshouldbesizedtothecontrolfillbuttons,butnotoverwhelmthe

frontpanelb. blockdiagram

i. minimizewirecrossingsandbendsii. dataflowshouldgolefttorightiii. terminalsshouldbealigned:inputsontheleft,outputsontheright

2. Modularandhierarchicaldesigna. UsesubVIswhencodeisrepeatedb. ComplexcodethatachievesasinglefunctioncanbeplacedinasubVI

3. subVIiconsandconnectorpanelayouta. connectorpanelayout(onlyaccessiblefromfrontpanel)

i. Left=inputs,Right=outputsii. Bottomterminalsonsidesareusuallyreservedforerrorwiresiii. Topterminalsonsideareusuallyreservedforreferencewires

b. Iconsi. PictureshoulddescribewhattheVIdoesii. Shouldhavebordernofloatingwireconnectionsconfusesprogrammeriii. RelatedsubVIsshouldhavearelatedicons(example:DAQmxhasbarattopthatsaysDAQmx)

4. VIproperties

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a. Documentationi. Showsupincontexthelp

b. Passwordprotecti. Ifdistributingcodetoothers,youcanputapasswordontheblockdiagramsotheycantreuseorrecreateit

c. Windowappearancei. Basicallyallowsyoutoselectthewindowtypethemaindifferencebetweenthemisthenumberofmenubarsvisible.

d. Windowsizeusefulifwillberunonamonitorwithdifferentresolutionfromdevelopmentmachine

e. RunTimepositionwhenitrunsdoyoualwayswantittoappearinaspecificlocationonthemonitor?

5. DocumentingVIsa. Controls/indicators

i. Descriptionandtipstripii. Labelsiii. Captions

1. UsecaptionsinsteadoflabelstolocalizeaVIwithoutbreakingtheVI.Unlikealabel,acaptiondoesnotaffectthenameoftheobject(whichyoumaybeusingtoaccessthatitemprogrammaticallythroughVIServer),andyoucanuseacaptionasamoredescriptiveobjectlabel.Thecaptionappearsonlyinthefrontpanelwindow.

b. FPandBDi. Freelabelstextboxesnotassociated/tiedtoanobjectii. SelfdocumentingcodeusingclustersandtheUnbundlebyNamesothatthelabelsarevisibleintheunbundle

iii. Wirelabelsforlongwires(nowavailableinLV2010,otherwiseusefreelabelstolabelwires)

c. VIi. DocumentationunderVIProperties

1. ThiswillshowupintheContextHelpWindow2. RightclickonVIIcon>>VIProperties>>Documentation

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Section12:Memory,Performance,andDeterminism

1. Toolsforidentifyingmemoryandperformanceissuesc. Profilememoryandperformance

i. Tools>>Profile>>ProfilePerformanceandMemoryii. toolforanalyzinghowyourapplicationusesexecutiontimeandmemory.iii. identifythespecificVIsorpartsofVIstooptimize

1. Forexample,ifyounoticethataparticularsubVItakesalongtimetoexecute,youcanfocusyourattentiononimprovingtheperformanceofthatVI.

iv. providesaroughestimateoftheaverageexecutiontimeoftheVIsusedinanapplication.

1. limitedtomillisecondresolution.2. Duetothenondeterministicexecution,executiontimeshouldbeaveragedover

severaliterationsforaccuratemeasurements.VITimedisplaysthetotalamountoftimespendexecutingeachVI.

d. Showbufferallocationsi. Tools>>Profile>>ShowBufferAllocations

1. Showswherebuffersarecreatedontheblockdiagram2. DoesNOTshowbuffersize,whichisdependentondatatype3. Fewerbufferallocations(usingwiresinsteadoflocalvariables,whichcreatesa

copy)meansfasterperformancee. VImetricsVIAnalyzer

i. interactivelyandprogrammaticallytestVIstoidentifyareasforimprovement.ii. maincategories: BlockDiagramChecksblockdiagramperformanceandstyleissues,suchaswiring,loopandstructureusage,coerciondots,andunnecessaryelementsontheblockdiagram. ComplexityMetricsChecksforVIcomplexity,suchasnesting,codereuse,andmodularity.

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DocumentationChecksfordocumentationfordevelopersanduserswithinaVI,suchasVIandcontroldescriptionsandblockdiagramcomments.ChecksthespellingonVIs,frontpanels,andblockdiagrams. FrontPanelChecksfrontpaneldesignanduserinterfaceissues,suchascontrolusage,fontselection,andlabels. GeneralChecksperformanceandstyleissuesthatdonotfitintotheothercategories,suchasfileproperties,iconsandconnectorpanes,andVIproperties. VIMetricsChecksblockdiagramandfrontpanelmetrics,suchasthenumberofconnectorpaneinputsandoutputs,controlsandindicators,andnodes.

2. Programmingpracticesa. Enforcingdataflow

i. Helpfultouseanerrorwiretoenforcedataflowb. UIupdatesandresponsetouserinterfacecontrols

i. NoneedtoupdateUIfasterthan510persecond,becausehumanscantdetectachangefasterthanthatandmonitorshavealimitedupdateratetoo

ii. WaystoupdateUI1. Best:wiredirectlytoterminal2. Better:localvariablemayrequirecopytobemade>slowdown3. Good:propertynodesmayrequirecopyandtoloadfrontpanelintomemoryif

notalreadyiii. UseEventstructureoverpollingfrontpanelsleepingfunctions(likeeventstructure)aremoreefficient

c. Datatypeselection,coercion,andbufferallocationi. Fornumbersthatcanonlybeintegers,useI32,U32,I16,U16,I8,Uii. BitdepththenumberinU8oru16isbasedonhowmanybitsyouneedtorepresentthenumber

1. Forexample,aU8numbercancountfrom0to255,ifyouweretoaddanothertoaU8whenitisat255itwouldwraparoundto0.

iii. Avoidcoercioncausestwomemorylocationsforeachversionofthevalueandislessefficientonlowlevel

iv. Tocreatefilesthattaketheleastamountofmemory,usethesmallestnumericrepresentationpossibleforyourprecisionneeds.

v.Optimizecodetoallocatefewernumberofbuffersd. Array,string,andloopoperations

i. BuildingarraysdynamicwillusesignificantlymorememorybecauseLVhastoreallocateanentirenewmemoryspacewhenanelementisaddeditisbettertoinitializeanarraytothemaximumsizeandusereplacearraysubset

1. Appendingtoanarrayisbetterthanprependingtoanarraybecauseofbufferallocationrequirements

2. AutoindexingisalsobetterbecauseLVcanpredictthebuffersizeaheadoftime(hastoknowfornumberofloopiterationsanyway)

e. Localandglobalvariables,propertynodes,andreferences

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i. DonotuseavariablewhereawirecanbeusedgoesagainstLVsdataflowparadigm1. Usingapropertynodetoupdateafrontpanelvaluecausesthefrontpanelofthe

targetVItoloadintomemory=slowsdowncodeiffrontpanelisnotalreadyinmemory

ii. CancallsubVIsbyreferenceinsteadofjustputtingthemontheblockdiagram1. Onblockdiagram:subVIloadedintomemorywhenmainVIisloaded(everseen

thescreenwhereLVislookingforthesubVIs?itpromptsyoutochooseitifitcantfindit)

2. Byreference:subVIloadedwhencalled

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Section 1: LabVIEW Programming ConceptsSection 2: LabVIEW EnvironmentSection 3: Software Constructs in LabVIEWSection 4: Programming Vis and functionsSection 5: Data Communication and Synchronization VIs and FunctionsSection 6: VI Server and FunctionsSection 7: Errors handling VIs and FunctionsSection 8: VI Design PatternsSection 9: SubVI DesignSection 10: Debugging VIsSection 11: VI Design and DocumentationSection 12: Memory, Performance, and Determinism