分布式测控系统基于单片机的自动程序生成1原文.docx
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分布式测控系统基于单片机的自动程序生成1原文.docx
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分布式测控系统基于单片机的自动程序生成1原文
Distributedmeasurementandcontrolsystembasedonmicrocontrollerswithautomatic
programgeneration
MiodragBolic1,VujoDrndarevicandBrankoSamardzic2
ElectronicsDepartment,InstituteofNuclearScienceVINCA,P.O.Box522,11001Belgrade,Yugoslavia
Received29June2000;
revised30January2001;
accepted9February2001
Availableonline1May2001.
Abstract
Thepaperdescribesanopenarchitecture
microcontroller
baseddistributedmeasurementandcontrolsystemwith
automatic
generationofapplicationprogram.Interpretationoffunctionsandgenerationofprogramforcontrolofthenewlyaddeddistributedunitordistributedunitofanewtypeconnectedtothesystemperformsautomatically,withoutuserassistance.TheelementsofthesystemareinterconnectedbymeansofaserialcommonbusaccordingtothereducedOSIprotocol.Theproposedconceptwastestedinasystemdevelopedbyusing8-bitAtmel
microcontrollers
of89Sand89Cseries.Apartfromthecentralunit,intelligentdistributedunitsweredevelopedforthecontrolofasteppermotor,programmablelinearmovement,controlofhalogenlamps,acquisitionandgenerationofanalogue,digitalandtimingpulsesandarealtimeclock(RTC).
AuthorKeywords:
Distributedsystem;Measurement;Control;
Microcontroller
;Autoconfiguration;Programgeneration
ArticleOutline
1.Introduction
2.Descriptionofthesystem
3.Communicationprotocol
4.Configurationofthesystem
5.Anexampleofsettingparameters
6.Discussion
References
Vitae
1.Introduction
Amodernindustrialdataacquisitionandcontrolsystemconsistsofanumberofintelligentunitslocatednexttothecontrolprocessorfacility.Intelligentdistributedunitsareinterconnectedandconnectedtothecentralunitbyacommonbus.Suchaconceptionofdistributionanddecentralisationofthefunctionsofthesystemisfoundedonapplicationofembedded
microcontrollers
andlowpowerintegratedelectronicsforsignalconditioninganddataconversionandastandardisedfieldbusforcommunication[1and2].
Theintelligentdistributedunitcollectsinputdata,producesoutputs,carriesoutcomplexdigitalsignalprocessing,storesdataand,alongwiththeresults,transmitsstatusanddiagnosticdata,Viaacommonprocessororanadditionalcommunicationprocessorconnectionisestablishedwithotherunitsorthecentralunit.Themostcommonlyusedphysicallinkistheeconomicserialcommonbus.Byapplicationoftheimportantprincipleofeconomicuseofcommonresourcesconsistingofacommonbusandacentralprocessor,itispossibletoreachahigh-qualitysolutionforacomplexsystemfordataacquisitionandautomation,preservingspeedandefficiencyofoperation.
Thecentralunitofamoderndistributedsystemismostfrequentlyapersonalcomputer(PC).Thankstothewell-knowncharacteristicsofhardwareandwide-spreadandcheapsoftwarewithintegratedmeasurementandcontrolfunctions,PCisagoodchoiceinmostcases[3and4].Thereareapplications,however,whichdonotrequirethepowerandresourcesofaPC,butsmalldimensions,lowcostsandoperationindifficultclimaticandmechanicalconditions.Typicalexamplesarethesupervisionandcontrolsystemsinvehiclesandindustrialmachinery.Suchadataacquisitionandcontroldistributedsystem,whoseelementsaredesignedbyuseofcommon8-bit
microcontrollers,
hasbeendescribedinthispaper.Althoughbasedonmodesthardwarerecourses,thesystemisconceivedtobeabletodetectdistributedunitsconnectedtothebus,tointerpretfunctionsofdistributedunitsandtoautomaticallygenerateapplicationprogram.Duetotheseuniquefunctions,addingofnewdistributedunitordistributedunitofanewtypedoesnotrequireanychangeofsoftware.Integrationofthenewlyaddedunitsintosystemisbeingperformedautomatically.
2.Descriptionofthesystem
Thedistributeddataacquisitionandcontrolsystemhasamodularstructureandconsistsofacentralunitanddistributedunits(Fig.1).Thecentralunitconfiguresthesystem,controlstheworkofthesystemanddisplaysmeasuring,statusordiagnosticdatafortheselecteddistributedunit.Thedistributedunitcanhavebothmeasuringandcontrollingfunctions.Theoperationofthedistributedunitisautonomousandtakesplaceonthebasisofparametersenteredthroughthecentralunit.Aspecifictypeofdistributedunitistherealtimeclock(RTC)whichprovidesthesystemwiththedataonexacttimeanddate.
Full-sizeimage(16K)
Fig.1.Blockdiagramofdistributedsystem.
ViewWithinArticle
Thecentralunitconsistedofa8-bitAtmelAT89C55
microcontroller.Thismicrocontroller
has20 kBinternalflashmemory,whichisquitesufficientforstoringthesystemprogram.External4 kBRAMisusedfortemporarystorage.I2CprotocolisusedforcommunicationbetweentheexternalRAMandthe
microcontroller.
SerialRS-485interfaceisachievedbyAnalogDevicesADM485tranceiver.Thiscircuitenablescontrolofsendingandreceptionofdata.Torestoreproperoperationofthesystemincaseofinadvertentcorruption,watch-dogtimerLTC1232hasbeenadded.
Forthefollow-upofthesystem’soperationandenteringofworkingparametersofthedistributedunit,asimpleterminalisusedwhichconsistsofanalphanumericalLCDdisplaywithcapacityoftwo16-characterlinesandfourfunctionkeysmarkedwith↑,↓,√and×.Theprogramofthe
microcontroller
consistsofthreeparts:
thepartwhichreferstothecommunicationprotocol,thepartoftheprogramwhichoperatesastheinterpreterofthecommunicationstring,andthepartwhichcontrolstheuserinterface,i.e.theterminal.Fig.2presentstheblockdiagramofthecentralunit.
Full-sizeimage(11K)
Fig.2.Centralunit.
ViewWithinArticle
Thedistributedunitisanintelligentaddressablemodule,whichoperatesautonomouslyinthesystem.Itindependentlycontrolstheacquisitionandthegenerationofthesignal,carriesoutcomplexcalculationsandcommunicateswiththecentralunit.Thecentralunitpresentsthestatusandchangesofoperatingparametersofthedistributedunit.Eachdistributedunitcontainsan8-bitAtmelAT89C4051
microcontroller.
Theconfigurationstringandoperatingparametersofthedistributedunitarestoredin8 kBAT24C65EEPROM.The
microcontroller
ofthedistributedunithasthreemainfunctions:
itcontrolsthehardware,processessignalsanddataandcommunicateswiththecentralunit.Inordertoperformthefunctionsassignedtoit,eachdistributedunithasspecificcircuitsusedasaninterfacebetweenthe
microcontroller
andthephysicalphenomenonthatismeasuredortheprocessthatiscontrolled.
Anumberofdistributedunitsweredevelopedwithdifferentfunctions:
connectingofsensorsandmeasuringofphysicalquantities,controlofstepperanddcmotor,programmablelinearmovement,controlofoperationofhalogenlamps,generationofanalogous,digitalandtimesignalsandRTC.Fig.3presentsanexampleofadistributedunitusedtocontrolatwo-phasebipolarsteppermotor.L293Dfourpush–pulldriversareusedtocontrolthesteppermotor.ThechangeofrotationspeedisachievedbyPWMcontrol,andthechangeofdirectionbythechangeoftimesequenceofcontrolsignals.
Full-sizeimage(12K)
Fig.3.Distributedunitusedtocontrolsteppermotor.
ViewWithinArticle
Thesystemoperatesintwosteps.Thefirststepconsistsofallocationofaddressesandthesecondreferstoconfigurationofthesystem.Afterturningon,thecentralunitdetectstheconnecteddistributedunits.Adistributedunit,whichisoutoforder,whichhasnoaddressortheaddressofwhichisinvalid,shallbeignored.Thedetecteddistributedunitsareattributedcorrespondingmenususedforsettingunitparameters.
After
automatic
detectionandconfigurationoftheprogramsofdistributedunits,theyworkautonomouslywiththemostrecentlysetparameters.Settingofoperatingparameters,readingofresultsandstatusanddiagnosticinformationisachievedviathecentralunitterminal.Byusingthekeysoftheterminal,auserselectstheunithe/shewishestoaddress,movesthroughthemenuswhichrefertoindividualunitfunctions,changesfunctionparametersorreadsresultsorstatus.Movementthroughmenusisachievedinthesameway,whichcontributestosimpleandeasysettingofparameters.Immediatelyafterbeingset,aparameterisforwardedtothedistributedunitwhereitisstoredinEEPROM.
3.Communicationprotocol
InterconnectionofelementsofthesystemiscarriedoutaccordingtothereducedOSImodel[5].Thismodelisconvenientfordefiningprotocolsforindustrialcommunication.AccordingtothereducedOSImodel,thecommunicationprotocolisdefinedinthreelayers:
thephysicallayer,thetransportlayerandtheapplicationlayer.
ThephysicallayerisachievedthroughastandardRS-485serialinterface.Atwistedpairisusedforthetransferofdata.Themaximumof127modulescanbeconnectedinthenetworkwithmulti-droptopology.Themaximumcablelengthdependsontransferrate.Attransferrateof9.6 kB/s,itis1200 m,andattransferrateof10 MB/s,themaximumcablelengthis100 m.
Thetransportlayerdefinesaccesstechniquestothenetwork,addressingofdataanddetectionoferrorsinthetransfer.Theaccesstothenetworkiscentralised,withthecentralunitasthemasterinthebus.Distributedunitsareslaveunits.Themaster,byapplyingtimemultiplextechniques,allocatesaccesstimetodistributedslaveunits.
Datacontainninebits,themostsignificantbitbeingthecontrolone,andtheeightlesssignificantonesaretheinformationbits.Thelogi
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