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CS4101 嵌入式系統概論Design and Developmentdocin/sundae_mengRecaptMore and more physical things will be augmented or embedded with computingtThings become“smarter”tComputing becomes ubiquitoustAn embedded system is a system that is embedded with programmable computers for specific applications of that systemtWhy embedded systems?tFaster,more flexible development at lower costtMore complex functionalitiesdocin/sundae_mengSuppose You Have a Product IdeatTo develop a device that can record,for each day,the number of stairs that the user has climbed up or downtFrom this number,we can then calculate the amount of CO2 saved and calories burnedtLet us call this device stair countertHow to start from here?docin/sundae_mengTypical Design FlowrequirementsspecificationarchitecturecomponentdevelopmentsystemintegrationTop-downdesignBottom-updesignReal design often iterativedocin/sundae_mengRequirementstPlain language description of what the user wants and expects to gette.g.to develop a device that can record,for each day,the number of stairs that the user has climbed up or downtDescribe how the end product is usedby the usertMay be developed in several ways:ttalking directly to customersttalking to marketing representativestproviding prototypes to users for commentrequirementsspecificationarchitecturecomponentdevelopmentsystemintegrationdocin/sundae_mengRequirementstOften need to know target customers and business modeltStair counter as an add-on of cell phonetStair counter as a consumer producttStair counter as a gifttdocin/sundae_mengRequirementstFunctional requirements:Internals as a black box and describe only the outputs as a function of input;tShow number of stairs climbed up or downtShow amount of CO2 savedtDo not count in other casestNon-functional requirements:tPerformance,reliability,etc.tSize,weight,etc.tPower consumptiontCosttDescribe“WHAT”,not“HOW”docin/sundae_mengRequirements Formname Stair counter purpose Count and show stairs climbed and CO2 saved inputs Power-on/off button outputs Back-lit LCD 200 X 300 performance Update on every step manufacturing cost$150 power 100 mW physical size/weight No more than 2”X 3”,4 oz.docin/sundae_mengSpecificationtMore precise,usually quantitative description of the system:tShould not imply a particular architecturetList assumptionste.g.,update screen 0.25 sec after eachstep,error rate 95%,cost$300tMay include functional and non-functional elementstMay be executable or may be in mathematical form for proofste.g.UML(Unified Modeling Language)requirementsspecificationarchitecturecomponentdevelopmentsystemintegrationdocin/sundae_mengArchitecture DesigntWhat major components satisfy the specification?HOWtNeed to know what are availabletHardware components:tCPUs,peripherals,etc.te.g.MSP430 CPU,3-axis accelerometertSoftware components:tMajor programs and their operationste.g.no OS,accelerometer driver,LCD drivertMust take into account functional and non-functional specificationsrequirementsspecificationarchitecturecomponentdevelopmentsystemintegrationdocin/sundae_mengDesign ConsiderationstEnvironment which the embedded system is intExternal and internal stimulus sources that interact with the embedded system I/OtActions and events caused by stimulustElements of the embedded system that could be affected by the stimulustDesired system responses to the stimulus,which reflects one or more system requirements algorithm/workflowtHow the system responses can be measuresdocin/sundae_mengComponent DevelopmenttActual implementation of individualhardware and software componentstMust spend time architecting the system before you start codingtSome components are ready-made,some can be modified from existing designs,others are to be designed from scratchte.g.MSP430 CPU,3-axis accelerometertGood surveys helprequirementsspecificationarchitecturecomponentdevelopmentsystemintegrationdocin/sundae_mengSystem IntegrationtPut together the componentstMany bugs appear only at this stagetRequire good interface definition fromthe starttHave a plan for integrating components to uncover bugs quickly,test as much functionality as early as possible test and verificationrequirementsspecificationarchitecturecomponentdevelopmentsystemintegrationdocin/sundae_mengSystem DevelopmenttNow that you have better idea of the requirements,specifications,and architecture of the stair countertHow to proceed to develop the components and integrate the system?tBut,tReal hardware?Programming environment?requirementsspecificationarchitecturecomponentdevelopmentsystemintegrationdocin/sundae_mengDevelopment EnvironmenttHost:a computer running programming tools for developmenttTarget:the HW on which code will runtAfter program is written,compiled,assembled and linked,it is transferred to the targetHost systemTarget systemX86MSP430docin/sundae_mengWhat If Real HW Not Available?tDevelopment board:tBefore real hardware is built,software can be developed and tested using development boardstDevelopment boards usually have the same CPU as the end product and provide many IO peripherals for the developed software to useas if it were running on thereal end producttTools for program developmenttIntegrated Development Environment(IDE):cross compiler,linker,loader,tOS and related libraries and packagesdocin/sundae_mengCross CompilertRuns on host but generates code for targettTarget usually have different architecture from host.Hence compiler on host has to produce binary instructions that will be understood by targetdocin/sundae_mengDevelopment ProcesstProcess for creating instructions that are built on host but meant for the targettTools are compatible with each other a toolchaintBinutils:as,ldtGlibc：C runtime LibtGCC：C/C+compilerdocin/sundae_mengLinker/LocatorstFor computers:tLinker:creates an image file to be run on hosttLoader:loads image file into memory during run-timetFor embedded systems:tLocater:creates a file,containing binary image or other format,that will be copied onto target,which run on its own(not through loader)tIt needs exact addresses beforehandtCertain parts of program need in ROM and some in RAMtNormally done by dividing program in segments tLocator needs to be told where in memory to place segmentsdocin/sundae_mengSummarytDevelopment of a system usually involves:tRequirement,specification,architecture design,component development,system integration,test and validationtDevelopment environment of an embedded system often includestDevelopment host with toolchain:cross compiler,linker/loader,library,emulatortDevelopment boarddocin/sundae_meng
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