Embedded system development

Definition

Theembeddedsystemisapplication-centric,basedoncomputertechnology,andsoftwareandhardwarecanbetailored,suitableforapplicationAdedicatedcomputersystemwithstrictrequirements.Itisgenerallycomposedoffourparts:embeddedmicroprocessor,peripheralhardwaredevice,embeddedoperatingsystemanduser'sapplicationprogram.Itisusedtocontrol,monitorormanageotherdevices.

EmbeddedThesystemgenerallyreferstoanon-PCsystem,whichincludestwoparts:hardwareandsoftware.Thehardwareincludesprocessors/microprocessors,memoryandperipheraldevices,I/Oports,graphicscontrollers,etc.Thesoftwarepartincludesoperatingsystemsoftware(OS)(requiresreal-timeandmulti-taskoperation)andapplicationprogramming.Sometimesdesignerscombinethesetwokindsofsoftware.Theapplicationprogramcontrolstheoperationandbehaviorofthesystem;andtheoperatingsystemcontrolstheinteractionbetweenapplicationprogrammingandhardware.

Basicknowledge

1.Softwareknowledge:

1.Embeddedmicroprocessorstructureandapplication:

OrtraditionalInthecourseof"MicrocomputerPrinciplesandInterfaces",embeddedisatechnologythatcombinessoftwareandhardware.ThosewhoengageinembeddedsystemsshouldhaveafullunderstandingoftheworkingprinciplesandinterfacetechnologyoftheARMprocessor,includingtheassemblyinstructionsystem.Withoutunderstandingtheprincipleoftheprocessor,thereisnowaytowriteadriver.Somekeypartsofembeddeddevelopment,suchasBootloader,etc.,mainlyrelyonassemblytowriteprograms.

2.Embeddedoperatingsystemcourses:

Thosewhoareengagedinembeddedsystemsmusthaveatleastoneembeddedoperatingsystem(ofcoursethemorethebetter),themostimportantRTOSatpresentMainlyinclude:

(1),thetraditionalclassicRTOS:ThemostimportantistheVxworksoperatingsystem,anditsTornadodevelopmentplatform.Vxworksappearedearly,withstrongreal-timeperformance,minimalkernel,andhighreliability.Especiallyinsystemswithhighreal-timerequirementssuchascommunicationequipment,ithasarelativelywiderangeofapplications.

(2)EmbeddedLinuxoperatingsystem:ThereasonwhyembeddedLinuxiswidelyusedisofcoursethatitisfree,opensource,supportingsoftware,manysupporters,andlowcost.

(3),WindowsCEembeddedoperatingsystem:WindowsCEisMicrosoft'soperatingsystem,anditalsohasalargemarketshare,especiallyinPDAs,mobilephonesandotheroccasionsthatrequirehighinterfacerequirementsorrequirerapiddevelopment.

3.Otherrelatedsoftwarecoursesforembeddeddevelopment:

(1).Digitalimagecompressiontechnology:oneofthemostpopularapplicationfieldsofembedded,itisnecessarytomasterMPEGencodinganddecodingalgorithmsAndtechnologiessuchasDVD,MP3,PDA,HDTV,set-topbox,etc.allinvolveMPEGhigh-speeddecoding.

(2).Communicationprotocolandprogrammingtechnology:MostembeddeddeviceshavetobeconnectedtothelocalareanetworkortheInternet,soyoushouldfirstmastertheTCP/IPprotocolanditsprogramming;inaddition,masterthewirelesscommunicationprotocolandprogrammingItisalsoveryimportant.

(3)Networkandinformationsecuritytechnology:suchasencryptiontechnology,digitalcertificateCA,etc.

Second,hardwareknowledge:

Hardwarecoursessuchasanalogcircuit,digitalcircuit,computercompositionprinciple,microprocessorstructure,single-chipmicrocomputer,etc.arerequiredtobemasteredwhenengagedinembeddeddevelopment.

Embeddeditselfisdevelopedfromsingle-chipmicrocomputers.Nowadays,manysingle-chipmicrocomputersalreadyhaveOS.Inthefieldofembeddeddevelopment,drivertalentsareveryscarce.Towriteadriver,youmustmastertheinternalworkingprinciplesoftheoperatingsystem,includingrelatedhardwareknowledge,whichistheso-calledsoftwareandhardwaretake-all,sotalentsinthisareaarehardtofind.

Features

Comparedwithgeneral-purposecomputersystems,embeddedcomputersystemshavethefollowingfeatures:

1.EmbeddedsystemsareusuallyembeddedforspecificapplicationsThebiggestdifferencebetweenCPUsandgeneral-purposeCPUsisthatembeddedCPUsmostlyworkinsystemsdesignedforspecificusergroups.Theyusuallyhavethecharacteristicsoflowpowerconsumption,smallsize,andhighintegration.Tasksareintegratedinsidethechip,whichisconducivetothetrendofminiaturizationofembeddedsystemdesign,greatlyenhancedmobility,andincreasinglytightercouplingwiththenetwork.

2.Embeddedsystemistheproductofcombiningadvancedcomputertechnology,semiconductortechnologyandelectronictechnologywithspecificapplicationsinvariousindustries.Thisdeterminesthatitmustbeatechnology-intensive,capital-intensive,highlydispersed,andconstantlyinnovativeknowledgeintegrationsystem.

3.Boththehardwareandsoftwareoftheembeddedsystemmustbedesignedefficiently,tailoredtosuit,andredundant,andstrivetoachievehigherperformanceonthesamesiliconchiparea,sothatitcanbeusedinspecificapplications.Thechoiceofprocessorismorecompetitive.

4.Embeddedsystemsandspecificapplicationsareorganicallycombined,anditsupgradingisalsocarriedoutsimultaneouslywithspecificproducts.Therefore,onceembeddedsystemproductsenterthemarket,theyhavealongerlifecycle.

5.Inordertoimprovetheexecutionspeedandsystemreliability,thesoftwareintheembeddedsystemisgenerallysolidifiedinthememorychiporthesingle-chipmicrocomputeritself,ratherthanstoredinacarriersuchasadisk.

6.Theembeddedsystemitselfdoesnothavetheabilityofbootstrappingdevelopment.Evenafterthedesigniscompleted,theuserusuallycannotmodifytheprogramfunctionsinit,andasetofdevelopmenttoolsandenvironmentcanbeusedfordevelopment.

Elements

Embeddedprocessor

Thefunctionalsoftwareoftheembeddedsystemisintegratedinthehardwaresystem,andtheapplicationsoftwareofthesystemisintegratedwiththehardware.Inthehardwareequipmentoftheembeddedsystem,theembeddedprocessoristhecorecomponentofthewholesystem,anditsperformancedirectlydeterminestherunningeffectofthewholesystem.InthePCmachinesalesmarket,withthebreakthroughofuniversalcPutechnologyandthedoublingofoperatingfrequency,theoldlow-endcPuhaslongdisappeared.Embeddedsystemdevelopmentisorientedtospecificapplications.Theapplicationmarketindifferentfieldsrequiresprocessorswithdifferentstylesandperformanceindicatorstodevelop.Therefore,intheembeddedprocessormarket,low-end4-bit,8-bitand16-bitprocessorsstillexist.,Therearealsomanyproductsforhigh-performance32-bitprocessors.WiththedevelopmentofVLSIandmicroelectronicstechnology,microcontrollerproductscontainingembeddedprocessorsandsomeperipheralcircuitshavealsoenteredthemarket,andsystemonchip(SoC)productshavealsobeguntoemerge.Thelaunchoftheseproductsnotonlyenrichesembeddedprocessorproducts,butalsomakesiteasierforengineersandtechnicianstodevelopembeddedsystemsandexpandtheapplicationareasofembeddedproducts.

Duetothediversityofembeddedsystemapplicationrequirements,thenumberofembeddedprocessorprovidersbasedontheRIscstructureonthemarketisalsoincreasing.Statisticsshowthatthetopthreecompaniesinmarketsalesattheendof1999wereARM,Motor01a,andMIPs.Amongthem,ARM'schipsalesreached150million,withamarketshareofover50%.Inthefaceofsuchanembeddedprocessormarket,howshoulddevelopersanddesignerschoose?Therearetwoprerequisiteshere.Oneistoin-depthstudyofspecificembeddedsystemapplicationrequirements,andobtaintheperformanceindicatorsoftheapplicationsystemaftersufficientapplicationrequirementsanalysis.Application-orientedisacharacteristicofembeddedsystems,andspecificapplicationrequirementsdeterminetheperformanceselectionofembeddedprocessors.Inspecialfieldssuchasindustrialcontrol,systemrequirementsanalystsnotonlyneedtointerviewstaffandsuperiorsinperson,butalsoneedtogototheworksitetoobtainfirst-handinformationandcollectsufficientinformation.Afterapplicationrequirementsanalysis,itisnecessarytodefinethebasicfunctionsandperformanceindicatorsoftheproduct,suchastheamountofdataprocessedbythesystemandprocessingreal-timerequirements,theworkingenvironmentduringnormalsystemoperation,unexpectedeventsthatmaybeencounteredduringsystemoperation,andthesystemThesizeandpowerconsumptionindicators.Thesecondprerequisiteis.Analyzeandstudytheperformanceindicatorsofvariousembeddedprocessorsprovidedbymajormanufacturersinthemarket,suchaspowerconsumption,volume,cost,reliability,speed,processingcapacity,electromagneticcompatibility,etc.cTheseparametersarealsocompetitionamongvarioussemiconductorchipmanufacturersHotspot.

Developershaveobtainedthefunctionalandnon-functionalindicatorsoftheproductthroughapplicationrequirementsanalysis,andafterstudyingtheperformanceparametersofembeddedprocessorsonthemarket,theycanmakebetterchoicesforembeddedprocessors.Thebasicprincipleoftheembeddedprocessorselectionistomeetthespecificfunctionalandnon-functionalindexrequirements,themarketapplicationrespondswell,andtheembeddedprocessorwiththeleasthardwareconfiguration.Forexample,thesimpledesignofsmartinstrumentationconsiderstheuseof4-bitor8-bitlow-endsingle-chip8051;theDsP(digitalsignalprocessing)chipofTI’sTMx320xseriesiscloselyrelatedtodigitalsignalprocessing;iftheproductfocusesoncommunicationfunctions,considerMotorola68Kseriesofembeddedprocessors;iftheproductfunctionsaremorecomplete,youcanchoosethehigh-performanceembeddedprocessorARMchipseriesofARM,arisingstarinthefieldofembeddedprocessors.Inadditiontotheabove-mentionedproductperformancerequirements,whenchoosinganembeddedprocessor,youalsoneedtoconsiderthedeveloper’sfamiliaritywiththisseriesofprocessors.cBecausetheembeddedprocessorsdevelopedbydifferentcompaniesarequitedifferent,theymovefromonetypeofprocessortoanother.Thedifficultyofclass-likeprocessorsismuchgreaterthanthetransferbetweendifferentprocessorsofthesameseries,andtherisksaremuchgreater.

Real-timeoperatingsystem

Withembeddedprocessorasthecenter,developersonlyprovidebaremetaloperatingplatformwhentheybuildthehardwarecircuit,sothatthelimitedhardwareresourcesoftheentiresystemshouldbefullyutilized,Alsoneed(embedded)real-timeoperatingsystemRTOs(RealTimeoperatingsystem)softwaresupport.RTosandgeneralcommercialmultitaskingos(suchasunix,windows,andLInux,etc.)havethesame...anddifferentaspects.Themainpurposeofcommercialmultitaskingosistofacilitateuserstomanagecomputerresourcesandpursuethemaximumutilizationofsystemresources;andRTOsThefocusisonreal-time,deterministic,andreliability,andofcoursealsoincludesthemanagementoflimitedresources.Generally,thecoreofRTOsisverysmall,rangingfromafewKBtomorethanadozenKB.PopularRTOsbasicallysupportpriority-basedPreemptiveschedulingstrategyandtimeslicerotation,withamicro-kernelstructure,standardcomponentsareavailableforselection.Supportvirtualstoragetechnologyandstorageprotectionmechanism.DuetothedifferentfunctionalrequirementsofspecificembeddedapplicationsanddifferentperformanceindicatorsfordifferentRTOs,RTOsTherearethreeoptions:

• First,accordingtotheapplicationneedsandthecompany’stechnicalstrength,considerindependentdevelopmentandresearch.);

• ThesecondistofullyconsidersystemrequirementsandpopularRTosperformanceindicatorsandcost-effectiveselectionofcommercialRTOs,suchaswIncE,Vxworks,etc.;

• ThethirdistoconsiderembeddedLinux(RTLinux).RTLjnuxisanopensourcefreesoftwarewithmanyInternettechnologyforums,whichcanbetailoredtosupportdifferentapplicationcategories.

Currentlytherearemorethan200kindsofcommercialRTosintheworld,andthediversityofapplicationfieldsmakesthemarketrespondwelltonearlyadozen,suchasVxworks,POS,Nucleus,QNx,wincEandChineseAcademyofSciencesHopen,etc.developedbytheSoftwareResearchCenter.TheseRTOswithdifferentnameshavesubtleandelusivedifferencesinthecoresoftware.Thekeypointistoconsidertheirperformanceevaluationindicators,includingschedulingalgorithms,RTOsthemselvesmemoryoverhead,RTOsmemorymanagementmode,andmaximuminterruption.Prohibitiontimeandmaximumtaskswitchingtime.Ofcourse,italsoincludesrelatedfactorssuchasthepurchasecostofRTOsandthetechnicalsupportprovided.Forapplicationswithhighreal-timerequirements,themaximuminterruptionprohibitiontimeandmaximumtaskswitchingtimeofRTOsneedtobeconsidered.Thesmallerthetwoparameters,thebetter.Toreducethevalues​​ofthesetwoparameters,inadditiontochoosingahigheroperatingfrequencyembeddedprocessor,itisalsocloselyrelatedtothetaskschedulingandinterrupthandlingmechanismofRTOs.WhenchoosingRTOs,itisusuallyItisnecessarytoconsiderwhichprocessorhardwareplatformsandAPIsaresupportedintermsofsystemfunctions,whetheritsupportscoreusermode,whetheritsupportsmemorymanagementunitMmu,portability,debuggingsupport,standardsupport,etc.Ifyoudevelopnetworkapplications,youalsoneedtoconsiderWhethertheRTOssupportTCP/IPnetworkcomponentsandI/Oservices.Ifdevelopinggamesandentertainmentmarkets,itisnecessarytofocusontheabilityoftheRTostosupportmultimedia.ThediversityofmarketapplicationrequirementsmakesRTOsitselfshouldsupportusercustomizationcapabilities,andselectstandardcomponentsonthebasisofmicrokernelsaccordingtoapplicationneeds.

Emulatoranddebugger

Debuggingisanimportantpartoftheembeddedsystemdevelopmentprocess.Thereisabigdifferencebetweenembeddedsystemdevelopmentanddebuggingandgeneralpcsystemdevelopmentanddebugging.InthedevelopmentofageneralPCcomputersystem,thedebuggerandthedebuggedprogramaretwoprocessesrunningonthesamehardwareandsoftwareplatform.Inanembeddedsystem,thedebuggerisanapplicationprogramrunningonadesktopoperatingsystem.Thedebuggerisrunningonanoperatingsystembasedonaspecifichardwareplatform,andthetwoprogramsneedtocommunicateinrealtime.Whendebugginganembeddedsystem,theintegrateddevelopmentanddebuggingtool(debugger)runningonthehostcomputerisconnectedtothetargetcomputerthroughtheemulator.Ethernetinterface.TheemulatorisconnectedtothetargetcomputerthroughtheJTAGport.

Embeddedsystemdevelopmentanddebuggingmethodsincluderapidprototypingsimulationmethodandreal-timeonlinedebuggingmethod.Therapidprototypingsimulationmethodisusedtosimulateandanalyzetheoperationoftheapplicationprogramdirectlyonthehostcomputerwhenthehardwaredevicehasnotbeencompleted.Inthisprocess,thesystemdoesnotdirectlydealwiththehardware.AspecificsoftwaremoduleinthedevelopmentanddebuggingsoftwaresimulatestheexecutionprocessofthehardwarecPusystem,andatthesametime,thesimulationexceptionisfedbacktothedeveloperforerrorlocationandmodification.Thereal-timeonlinedebuggingmethoddebugstheapplicationprogramonthespecifictargetmachineplatform.Theexecutionofthesysteminthedebuggingstateisexactlythesameastheactualoperatingmode.Thismethodismoreconducivefordeveloperstolocateandmodifysystemhardwareandsoftwarefaultsinrealtime,andimproveproductdevelopmentspeed.Theselecteddebuggerisanintegrateddevelopmentenvironmentrunningonthehost.Generally,itneedstointegrateediting,assembly,compilation,linkinganddebuggingenvironments.Itsupportslow-levelassemblylanguage,candc++languages,basedonafriendlygraphicaluserinterface(GuI),andsupportsUsersobserveormodifytheregisterandmemoryconfigurationoftheembeddedprocessor,thetypesandvalues​​ofdatavariables,theuseofstacksandregisters,supportforprogrambreakpointsettings,single-step,breakpoint,full-speedoperationandotherfeatures.Thediversityofapplicationrequirementshasledtomanyprovidersofemulatorsanddebuggersinthemarket.Tornadofromwindriverisagooddevelopmentanddebuggingtool.Accordingtopracticalexperience,generallychoosetheemulatorsanddebuggersoflarger,reputablecompanies.Althoughthepricesarerelativelyhigh,thesecompanieshavestrongtechnicalstrength,goodafter-salesservice,andthedevelopmentofdebuggersandemulatorsarecloselyintegrated.Ifyouencountertechnicalobstaclesinthedevelopmentanddebuggingprocess,youcanobtaintechnicalsupportintimebyphoneoremail.IfyouchooseARMseriesembeddedprocessors,youcanbuyMulti-IcEemulators.AndattachARM250integrateddevelopmentdebuggingenvironmentandsoon.

Thetechnicallevelandstructureratioofthedevelopmentteam

Inadditiontotheembeddedprocessors,RTOs,emulators,debuggersandotherequipmentselectedintheembeddedsystemdevelopment,developmentneedstobeconsideredThetechnicallevelandstructureratiooftheteam.Theexperienceddevelopmentteamhasadeepunderstanding:inthedevelopmentofcivilianproducts,theproductcanenterthemarketwithintheexpectedtimetogainbenefits,andtheproportionofnewtechnologiesintheentiretechnologyrangecanonlyreach20%.Ifthislimitisexceeded,theestimatedtimelimitLargedeviationsmayoccur.Analyzedfromtheperspectiveofhigh-levelplanners:Fornewtechnologieswithin20%,thecompanycanconcentrateitseffortsandinvestenoughmanpower,materialandfinancialresourcestoconductbreakthroughresearch,andundernormalcircumstances,satisfactoryresultscanbeachieved.Ifthenewtechnologyexceedstherangeof20%,Iamafraidthatthereismorethanenoughenergy.Theoperationofthecompanyisguidedbythemarket,anditisthemarketthatgivesthemlife.

Thecompanyvalues​​themarket,andthelaborpaidbythemarketcanonlyoperatenormally.Companiesgenerallytrytoavoidrisksduringthedevelopmentprocess,andalwaysuseriskanalysisasanimportantreferencefactorthroughoutthedevelopmentprocess.Companiesgenerallychooseaconservativedevelopmentmodel,basedonthecurrenttechnicalstrengthofthedevelopersandthetechnicalreservesthathavebeenreached,intheprocessoftechnicaldemonstrationofmanyalternatives,fullyanalyzethecostandbenefit,thesizeoftherisk,theinputresources,andthetechnicallevelofthedevelopers.Takeallfactorsintoconsideration,weightheprosandcons,andtrytochoosereliableandlow-riskdesignschemes.Inprojectdevelopment,whenassigningdevelopers,itisnecessarynotonlytoensurethesuccessofthetaskscompletedwithinagiventimeperiod,butalsototrainsuccessors.Thedevelopmentofanyprojectwillformamodularstructureafteranalyzingtherequirementsandgoingthroughtheoutlinedesignanddetaileddesign,anditsworkdifficultyalsohasacertainlevelofdifficulty.Inthisway,whenthecompanyselectsprojectpersonnel,itneedsreasonablepersonnelstructurearrangements.Nowthegenerallyrecognizedratiooftalentstructureis1(doctorateorequivalent)3(masterorequivalent):7(bachelor,collegeorequivalent).Inprojectdevelopment,inadditiontothetechnicallevelandstructureratioofthedevelopers,thedemocratizationandscientificmanagementdecision-makingwithintheteamisalsoaveryimportantlink.

Coretechnology

Processortechnology

Processortechnologyisrelatedtothecomputingenginestructurethatrealizessystemfunctions.Manynon-programmabledigitalsystemscanalsoberegardedasprocessingThedifferencebetweentheseprocessorsliesintheirdegreeofspecializationforspecificfunctions,whichresultsintheirdesignindicatorsbeingdifferentfromotherprocessors.

(1)General-purposeprocessors

Thistypeofprocessorcanbeusedfordifferenttypesofapplications.Animportantfeatureisthestoredprogram,becausethedesignerdoesnotknowwhattheprocessorwillrun.Itisakindofoperation,soitisimpossibletobuildaprogramwithdigitalcircuits.Anotherfeatureistheuniversaldatapath.Inordertohandlevariouscalculations,thedatapathisuniversal.Thedatapathgenerallyhasalargenumberofregistersandoneormoregeneralarithmeticlogicunits.Thedesigneronlyneedstoprogramthememoryoftheprocessortoperformtherequiredfunctions,thatis,designrelatedsoftware.Theuseofgeneral-purposeprocessorsinembeddedsystemshassomeadvantagesindesignindicators.ThetimetomarketinadvanceandthecostofNREarelow,becausethedesigneronlyneedstowritetheprogram,withoutanydigitaldesign,andtheflexibilityishigh,andthechangeofthefunctioncanbedonebymodifyingtheprogram.Comparedwithaself-designedprocessor,theunitcostislowerwhenthenumberissmall.

Ofcourse,thismethodalsohassomedefectsindesignindicators.Whenthequantityislarge,theunitcostisrelativelyhigh,becausewhenthequantityislarge,thecostoftheself-designedNREcanbeamortized,whichcanreducetheunitcost.Atthesametime,forsomeapplications,performancemaybepoor.Duetotheinclusionofunnecessaryprocessorhardware,thesizeandpowerconsumptionofthesystemmaybecomelarger.

(2)Single-purposeprocessor

Single-purposeprocessorisadigitalcircuitdesignedtoexecuteaspecificprogram.Italsoreferstocoprocessors,accelerators,peripherals,etc.Forexample,theJPEGcodecexecutesasingleprogramtocompressordecompressvideoinformation.Embeddedsystemdesignerscancreatesingle-purposeprocessorsbydesigningspecificdigitalcircuits.Designerscanalsousepre-designedcommercialsingle-purposeprocessors.

Usingsingle-purposeprocessorsinembeddedsystemshassomeadvantagesanddisadvantagesintermsofindicators.Theseadvantagesanddisadvantagesarebasicallytheoppositeofgeneral-purposeprocessors.Theperformancemaybebetter,thevolumeandpowermaybesmaller,theunitcostmaybelowerwhenthequantityislarge,andthedesigntimeandNREcostmaybehigher,andtheflexibilityispoor,andthequantityissmall.Theunitcostishigh,andtheperformanceisnotasgoodasgeneral-purposeprocessorsforsomeapplications.

(3)Dedicatedprocessor

Thededicatedinstructionsetprocessor(ASIP)isaprogrammableprocessoroptimizedforaspecifictypeofapplication.Suchspecificapplicationshavethesamecharacteristics,suchasembeddedcontrol,digitalsignalprocessing,andsoon.TheuseofASIPinembeddedsystemscanguaranteegoodperformance,powerandsize,andprovidegreaterflexibility,butthistypeofprocessorstillrequiresexpensiveNREcoststobuildtheprocessoritselfandcompiler,single-chipmicrocomputeranddigitalsignalProcessorsaretwotypesofwidelyusedASIPs.Digitalsignalprocessorsaremicroprocessorsthatperformcommonoperationsondigitalsignals,andmicrocontrollersaremicroprocessorsoptimizedforembeddedcontrolapplications.UsuallycontrolapplicationsCommonperipherals,suchasserialcommunicationperipherals,timers,counters,pulsewidthmodulators,anddigital/analogconverters,areintegratedonthemicroprocessorchip,whichmakestheproductsmallerandlowercost.

ICtechnology

(1)Fullcustomization/VLSI

InthefullcustomizationICtechnology,itisnecessarytooptimizeeachsystemaccordingtothedigitalimplementationofaspecificembeddedsystem.Atthelevel,designersstartfromthelayoutsize,position,andconnectionofthetransistortoachievetheoptimalperformanceofhighchipareautilization,highspeed,andlowpowerconsumption.Usingmaskstoproduceactualchipsinmanufacturingplants,fullycustomizedICdesignsareoftencalledlarge-scaleintegratedcircuitdesigns,whichhavehighNREcostsandlongmanufacturingtimes,andaresuitableforlargenumbersorapplicationswithstrictperformancerequirements.

(2)Semi-customASIC

Semi-customASICisaconstraineddesignmethod,includinggatearraydesignmethodandstandardcelldesignmethod.Itisthesemi-finishedhardwareofsomeuniversalunitcomponentsandcomponentgroupsthataremadeonthechip.Thedesigneronlyneedstoconsiderthelogicalfunctionofthecircuitandthereasonableconnectionbetweenthefunctionalmodules.Thisdesignmethodisflexible,convenient,cost-effective,shortensthedesigncycle,andimprovestheyield.

(3)ProgrammableASIC

Alllayersintheprogrammabledevicealreadyexist.Afterthedesigniscompleted,thedesignedchipcanbefiredinthelaboratorywithoutICmanufacturersparticipate,andthedevelopmentcycleissignificantlyshortened.ProgrammableASIChaslowerNREcost,higherunitcost,higherpowerconsumption,andslowerspeed.

Design/VerificationTechnology

Thedesigntechnologyofembeddedsystemmainlyincludeshardwaredesigntechnologyandsoftwaredesigntechnology.Amongthem,thetechnologyinthefieldofhardwaredesignmainlyincludestwoaspects:chip-leveldesigntechnologyandcircuitboard-leveldesigntechnology.

Thecoreofchip-leveldesigntechnologyiscompilation/synthesis,library/IP,test/verification.Compilation/synthesistechnologyenablesdesignerstodescribetherequiredfunctionsinanabstractmanner,andautomaticallyanalyzeandinsertimplementationdetails.Thelibrary/IPtechnologyusesapre-designedlow-levelabstractionimplementationforthehigh-level.Test/verificationtechnologyensuresthecorrectfunctionofeachlevelandreducesthecostofrepeateddesignbetweenlevels.

Developmentprocess

Thefirststep:Establishadevelopmentenvironment

TheoperatingsystemgenerallyusesRedhatLinux,choosecustominstallationorfullinstallation,anddownloadthecorrespondingGCCthroughthenetworkInstallthecross-compiler(forexample,arm-linux-gcc,arm-uclibc-gcc),orinstalltherelevantcross-compilerprovidedbytheproductmanufacturer;

Step2:Configurethedevelopmenthost

ConfigureMINICOM,thegeneralparametersare115200Baud/s,thedatabitis8bits,thestopbitis1,9,noparity,softwareandhardwareflowcontrolissettonone.ThesameistruefortheconfigurationofHyperTerminalunderWindows.TheMINICOMsoftwareisusedasamonitorandkeyboardinputtoolfordebuggingtheinformationoutputoftheembeddeddevelopmentboard.TheconfigurationofthenetworkismainlytoconfiguretheNFSnetworkfilesystem,andthefirewallneedstobeturnedofftosimplifytheprocessofsettinguptheembeddednetworkdebuggingenvironment.

Step3:EstablishthebootloaderBOOTLOADER

DownloadsomeopensourceBOOTLOADERfromtheInternet,suchasU.S.BOOT,BLOB,VIVI,LILO,ARM-BOOT,RED-BOOT,etc.,transplantandmodifyaccordingtothespecificchip.Somechipsdonothaveabuilt-inbootloader,forexample,Samsung’sARV17,ARM9serieschips,soyouneedtowritetheFLASHprogrammingprogramonthedevelopmentboard,youcandownloadthecorrespondingprogrammingprogramonline,andtherearealsoopensourcecodeJunderLinux.-FLASHprogram.Ifyoucan'tprogramyourowndevelopmentboard,youneedtomodifythesourcecodeaccordingtoyourspecificcircuit.Thisisthefirststeptomakethesystemwork.Iftheuserpurchasesthemanufacturer’semulator,itiseasiertoburnFLASH.Althoughtheycannotunderstandthecoretechnology,itcangreatlyincreasethedevelopmentspeedforthosewhoneedtodeveloptheirownapplicationsquickly.

Step4:DownloadthetransplantedLinuxoperatingsystem

SuchasMCLiunx,ARM-Linux,PPC-Linux,etc.,ifthereisaLinuxtransplantedspecificallyfortheCPUusedTheoperatingsystemisgreat.Afterdownloading,addspecifichardwaredrivers,andthendebugandmodify.ForCPUswithMMU,youcanusethemoduletodebugthedrivers,butforsystemslikeMCLiunx,youcanonlycompilethekernelfordebugging.

Step5:Establisharootfilesystem

DownloadandusetheBUSYBOXsoftwareforfunctionreductiontogenerateabasicrootfilesystem,andthenaddotherprogramsaccordingtoyourownapplicationneeds.Sincethedefaultstartupscriptgenerallydoesnotmeettheneedsoftheapplication,itisnecessarytomodifythestartupscriptintherootfilesystem.Itsstoragelocationislocatedinthe/etcdirectory,including:/etc/init.d/rc.S,/etc/profile,/etc/.profile,etc.,automaticallymounttheconfigurationfile/etc/fstabofthefilesystem,andthespecificconditionswillvaryfromsystemtosystem.Therootfilesystemisgenerallysetasread-onlyintheembeddedsystem,andtoolssuchasmkcramfsgenromfsneedtobeusedtogeneratetheburnedimagefile.

Step6:CreateFLASHdiskpartitionsforapplicationprograms

Generally,JFFS2orYAFFSfilesystemsareused.Thisneedstoprovidedriversforthesefilesystemsinthekernel.SomesystemsuseoneLinearFLASH(NORtype)512KB～32MB,somesystemsusenon-linearFLASH(NANDtype)8MB～512MB,andsometwoareusedatthesametime,theFLASHpartitionschemeneedstobeplannedaccordingtotheapplication.

Step7:Developtheapplicationprogram

Itcanbeplacedintherootfilesystem,YAFFS,JFFS2filesystem,andsomeapplicationsdonotusetherootfilesystem.Theapplicationandthekernelaredesignedtogether,whichissomewhatsimilartothewayofμC/OS-II.

Step8:Burnthekernel

Rootfilesystemandapplication,releasetheproduct.