1、CS4101 嵌入式系統(tǒng)概論Design and Development,Recap,More and more physical things will be augmented or embedded with computing Things become “smarter” Computing becomes ubiquitous An embedded system is a system that is embedded with programmable computers for specific applications of that system Why embedded

2、 systems? Faster, more flexible development at lower cost More complex functionalities,Suppose You Have a Product Idea,To develop a device that can record, for each day, the number of stairs that the user has climbed up or down From this number, we can then calculate the amount of CO2 saved and calo

3、ries burned Let us call this device stair counter How to start from here?,Typical Design Flow,requirements,specification,architecture,component development,system integration,Top-down design,Bottom-up design,Real design often iterative,Requirements,Plain language description of what the user wants a

4、nd expects to get e.g. to develop a device that can record, for each day, the number of stairs that the user has climbed up or down Describe how the end product is usedby the user May be developed in several ways: talking directly to customers talking to marketing representatives providing prototype

5、s to users for comment,Requirements,Often need to know target customers and business model Stair counter as an add-on of cell phone Stair counter as a consumer product Stair counter as a gift ,Requirements,Functional requirements:Internals as a black box and describe only the outputs as a function o

6、f input; Show number of stairs climbed up or down Show amount of CO2 saved Do not count in other cases Non-functional requirements: Performance, reliability, etc. Size, weight, etc. Power consumption Cost ,Describe “WHAT”, not “HOW”,Requirements Form,Specification,More precise, usually quantitative

7、description of the system: Should not imply a particular architecture List assumptions e.g., update screen 0.25 sec after eachstep, error rate 95%, cost $300 May include functional and non-functional elements May be executable or may be in mathematical form for proofs e.g. UML (Unified Modeling Lang

8、uage),Architecture Design,What major components satisfy the specification? HOW Need to know what are available Hardware components: CPUs, peripherals, etc. e.g. MSP430 CPU, 3-axis accelerometer Software components: Major programs and their operations e.g. no OS, accelerometer driver, LCD driver Must

9、 take into account functional and non-functional specifications,Design Considerations,Environment which the embedded system is in External and internal stimulus sources that interact with the embedded system I/O Actions and events caused by stimulus Elements of the embedded system that could be affe

10、cted by the stimulus Desired system responses to the stimulus, which reflects one or more system requirements algorithm/workflow How the system responses can be measures,Component Development,Actual implementation of individualhardware and software components Must spend time architecting the system

11、before you start coding Some components are ready-made, some can be modified from existing designs, others are to be designed from scratch e.g. MSP430 CPU, 3-axis accelerometer Good surveys help,System Integration,Put together the components Many bugs appear only at this stage Require good interface

12、 definition fromthe start Have a plan for integrating components to uncover bugs quickly, test as much functionality as early as possible test and verification,System Development,Now that you have better idea of the requirements, specifications, and architecture of the stair counter How to proceed t

13、o develop the components and integrate the system? But, Real hardware? Programming environment?,Development Environment,Host: a computer running programming tools for development Target: the HW on which code will run After program is written, compiled, assembled and linked, it is transferred to the

14、target,Host system,Target system,X86,MSP430,What If Real HW Not Available?,Development board: Before real hardware is built, software can be developed and tested using development boards Development boards usually have the same CPU as the end product and provide many IO peripherals for the developed

15、 software to useas if it were running on thereal end product Tools for program development Integrated Development Environment (IDE): cross compiler, linker, loader, OS and related libraries and packages,Cross Compiler,Runs on host but generates code for target Target usually have different architect

16、ure from host. Hence compiler on host has to produce binary instructions that will be understood by target,Development Process,Process for creating instructions that are built on host but meant for the target Tools are compatible with each other a toolchain Binutils: as, ld Glibc：C runtime Lib GCC：C

17、/C+ compiler,Linker/Locators,For computers: Linker: creates an image file to be run on host Loader: loads image file into memory during run-time For embedded systems: Locater: creates a file, containing binary image or other format, that will be copied onto target, which run on its own (not through loader) It needs exact addresses beforehand Certain parts of program need in ROM and some in RAM Normally done by dividing program in segments Locator needs to be told where in memory to place segments,Summary,Development of a system usually in