1、Unit 5 Embedded Systems 教学目标 教学内容教学目标教学目标 掌握嵌入式技术的基本概念 了解嵌入式技术的的发展简史 掌握嵌入式系统的体系结构 了解嵌入式技术的应用情况 掌握嵌入式软件的体系结构教学内容教学内容 Text 1 Introduction of Embedded Systems Text 2 Embedded software architecturesText 1 Introduction of Embedded Systems Main Contents Words and Expressions ExercisesAn embedded system is
2、 a special-purpose computer system designed to perform one or a few dedicated functions,often with real-time computing constraints.It is usually embedded as part of a complete device including hardware and mechanical parts.In contrast,a general-purpose computer,such as a personal computer,can do man
3、y different tasks depending on programming.Embedded systems control many of the common devices in use today.In general,“embedded system”is not an exactly defined term,as many systems have some element of programmability.For example,Handheld computers share some elements with embedded systems such as
4、 the operating systems and microprocessors which power them but are not truly embedded systems,because they allow different applications to be loaded and peripherals to be connected.Embedded systems span all aspects of modern life and there are many examples of their use.Text 1 Introduction of Embed
5、ded SystemsText 1 Introduction of Embedded SystemsTelecommunications systems employ numerous embedded systems from telephone switches for the network to mobile phones at the end-user.Computer networking uses dedicated routers and network bridges to route data.Consumer electronics include personal di
6、gital assistants(PDAs),mp3 players,mobile phones,videogame consoles,digital cameras,DVD players,GPS receivers,and printers.Many household appliances,such as microwave ovens,washing machines and dishwashers,are including embedded systems to provide flexibility,efficiency and features.Advanced HVAC sy
7、stems use networked thermostats to more accurately and efficiently control temperature that can change by time of day and season.Home automation uses wired-and wireless-networking that can be used to control lights,climate,security,audio/visual,surveillance,etc.,all of which use embedded devices for
8、 sensing and controlling.Text 1 Introduction of Embedded SystemsTransportation systems from flight to automobiles increasingly use embedded systems.New airplanes contain advanced avionics such as inertial guidance systems and GPS receivers that also have considerable safety requirements.Various elec
9、tric motors brushless DC motors,induction motors and DC motors are using electric/electronic motor controllers.Automobiles,electric vehicles,and hybrid vehicles are increasingly using embedded systems to maximize efficiency and reduce pollution.Other automotive safety systems such as anti-lock braki
10、ng system(ABS),Electronic Stability Control(ESC/ESP),traction control(TCS)and automatic four-wheel drive.Medical equipment is continuing to advance with more embedded systems for vital signs monitoring,electronic stethoscopes for amplifying sounds,and various medical imaging(PET,SPECT,CT,MRI)for non
11、-invasive internal inspections.Text 1 Introduction of Embedded Systems In addition to commonly described embedded systems based on small computers,a new class of miniature wireless devices called motes are quickly gaining popularity as the field of wireless sensor networking rises.Wireless sensor ne
12、tworking,WSN,makes use of miniaturization made possible by advanced IC design to couple full wireless subsystems to sophisticated sensor,enabling people and companies to measure a myriad of things in the physical world and act on this information through IT monitoring and control systems.These motes
13、 are completely self contained,and will typically run off a battery source for many years before the batteries need to be changed or charged.Words and Expressionsreliability ri,laibilitin.可靠性portable p:tbl adj.轻便的，手提式的stationary stei()nri adj.不动的，稳定的，静止的microcontroller n.微型控制器，微控制器，单片机peripheral pri
14、frl n.（电脑的）外部设备；adj.不重要的，外围的chassis si n.底座，（车身）底盘，enclosure inklu n.附件，围墙，围绕，【计】围封部分programmability n.可编程性：减少应用方案的开发时间，降低系统运行和维护成本，提高系统使用效率；handheld adj.手持式，掌上型microprocessor maikrprses(r)n.微处理器flash memory n.闪存telecommunication telikmju:nikeinn.电传视讯,远距离通信,电磁通信Words and Expressions router ru:t(r),r
15、a-n.路由程序,路由器PDA 个人数字助理，掌上电脑，是Personal Digital Assistant的缩写GPS 即全球定位系统，Global Positioning SystemHVAC（Heat Ventilation Air Conditionar）暖通空调；Heating Ventilating and Air Conditioning制热、通风与空调控制thermostat:mstt n.恒温器，节温器surveillance s:veilns n.监视,监督avionics,eiviniks n.航空电子学(航空用电子设备,控制系统)，电子设备inertial guida
16、nce systems惯性制导系统considerable knsidrbladj.相当的,可观的,重要的hybrid vehicle混合驱动汽车，合成车anti-lock braking system(ABS)防抱死制动系统Words and Expressions electronic stethoscope电子听诊器 amplify mpli,fai v.扩大，详述，使.增幅，放大，加强non-invasive adj.非侵入，非损伤inspection inspekn n.检查,视察miniature minjt n.缩图,小画像；adj.小规模的,纤小的motemut n.微尘(尘埃
17、,瑕疵)，导火线wireless sensor无线传感器miniaturization,minitraizein n.小型化，微型化sophisticated sfistikeitid adj.高级的,先进的,复杂的myriad mirid adj.无数的 n.极大数量ExercisesI.True or false?If correct,write T in parentheses;Otherwise,write F.（）1.An embedded system is a special-purpose computer system designed to perform only one
18、 dedicated functions,often with real-time computing constraints.（）2.A general-purpose computer,such as a personal computer,can do many different tasks depending on programming.（）3.Since the embedded system is dedicated to specific tasks,design engineers can optimize it,increasing the size and cost o
19、f the product,or reducing the reliability and performance.（）4.In general,“embedded system”is an exactly defined term,as many systems have some element of programmability.（）5.Handheld computers share some elements with embedded systems such as the operating systems and microprocessors which power the
20、m but are not truly embedded systems,because they allow similar applications to be loaded and peripherals to be connected.（）6.Transportation systems from flight to automobiles increasingly use embedded systems.New airplanes contain advanced avionics such as inertial guidance systems and PDAs that al
21、so have considerable safety requirements.（）7.Home automation only uses wired-networking that can be used to control lights,climate,security,audio/visual,surveillance,etc.,all of which use embedded devices for sensing and controlling.ExercisesII.Fill in the blanks with proper words.An embedded system
22、 is a _ computer system designed to perform one or a few dedicated functions,often with real-time computing constraints.2.Physically,embedded systems range from _devices such as digital watches and MP4 players,to large stationary installations like traffic lights,factory controllers,or the systems c
23、ontrolling nuclear power plants.3.New airplanes contain advanced _ such as inertial guidance systems and GPS receivers that also have considerable safety requirements.4.Automobiles,electric vehicles,and hybrid vehicles are increasingly using embedded systems to _ efficiency and reduce pollution.Text
24、 2 Embedded software architectures Main Contents Words and Expressions ExercisesThere are several different types of software architecture in common use.Simple control loopIn this design,the software simply has a loop.The loop calls subroutines,each of which manages a part of the hardware or softwar
25、e.Interrupt controlled systemSome embedded systems are predominantly interrupt controlled.This means that tasks performed by the system are triggered by different kinds of events.An interrupt could be generated for example by a timer in a predefined frequency,or by a serial port controller receiving
26、 a byte.Text 2 Embedded software architecturesText 2 Embedded software architecturesThese kinds of systems are used if event handlers need low latency and the event handlers are short and simple.Usually these kinds of systems run a simple task in a main loop also,but this task is not very sensitive
27、to unexpected delays.Sometimes the interrupt handler will add longer tasks to a queue structure.Later,after the interrupt handler has finished,these tasks are executed by the main loop.This method brings the system close to a multitasking kernel with discrete processes.Cooperative multitaskingA nonp
28、reemptive multitasking system is very similar to the simple control loop scheme,except that the loop is hidden in an API.The programmer defines a series of tasks,and each task gets its own environment to“run”in.When a task is idle,it calls an idle routine,usually called“pause”,“wait”,“yield”,“nop”(s
29、tands for no operation),etc.Text 2 Embedded software architecturesThe advantages and disadvantages are very similar to the control loop,except that adding new software is easier,by simply writing a new task,or adding to the queue-interpreter.Preemptive multitasking or multi-threadingIn this type of
30、system,a low-level piece of code switches between tasks or threads based on a timer(connected to an interrupt).This is the level at which the system is generally considered to have an“operating system”kernel.Depending on how much functionality is required,it introduces more or less of the complexiti
31、es of managing multiple tasks running conceptually in parallel.As any code can potentially damage the data of another task(except in larger systems using an MMU)programs must be carefully designed and tested,and access to shared data must be controlled by some synchronization strategy,such as messag
32、e queues,semaphores or a non-blocking synchronization scheme.Text 2 Embedded software architectures Because of these complexities,it is common for organizations to buy a real-time operating system,allowing the application programmers to concentrate on device functionality rather than operating syste
33、m services,at least for large systems;smaller systems often cannot afford the overhead associated with a generic real time system,due to limitations regarding memory size,performance,and/or battery life.A microkernel is a logical step up from a real-time OS.The usual arrangement is that the operatin
34、g system kernel allocates memory and switches the CPU to different threads of execution.User mode processes implement major functions such as file systems,network interfaces,etc.In general,microkernels succeed when the task switching and intertask communication is fast,and fail when they are slow.Ex
35、okernels communicate efficiently by normal subroutine calls.The hardware,and all the software in the system are available to,and extensible by application programmers.Microkernels and exokernelsMonolithic kernelsIn this case,a relatively large kernel with sophisticated capabilities is adapted to sui
36、t an embedded environment.This gives programmers an environment similar to a desktop operating system like Linux or Microsoft Windows,and is therefore very productive for development;on the downside,it requires considerably more hardware resources,is often more expensive,and because of the complexit
37、y of these kernels can be less predictable and reliable.Common examples of embedded monolithic kernels are Embedded Linux and Windows CE.Despite the increased cost in hardware,this type of embedded system is increasing in popularity,especially on the more powerful embedded devices such as Wireless R
38、outers and GPS Navigation Systems.Here are some of the reasons:Ports to common embedded chip sets are available.Monolithic kernelsThey permit re-use of publicly available code for Device Drivers,Web Servers,Firewalls,and other code.Development systems can start out with broad feature-sets,and then t
39、he distribution can be configured to exclude unneeded functionality,and save the expense of the memory that it would consume.Many engineers believe that running application code in user mode is more reliable,easier to debug and that therefore the development process is easier and the code more porta
40、ble.Many embedded systems lack the tight real time requirements of a control system.A system such as Embedded Linux has fast enough response for many applications.Features requiring faster response than can be guaranteed can often be placed in hardware.Many RTOS systems have a per-unit cost.When use
41、d on a product that is or will become a commodity,that cost is significant.Exotic custom operating systemsA small fraction of embedded systems require safe,timely,reliable or efficient behavior unobtainable with the one of the above architectures.In this case an organization builds a system to suit.
42、In some cases,the system may be partitioned into a“mechanism controller”using special techniques,and a“display controller”with a conventional operating system.A communication system passes data between the two.Additional software componentsIn addition to the core operating system,many embedded syste
43、ms have additional upper-layer software components.These components consist of networking protocol stacks like CAN,TCP/IP,FTP,HTTP,and HTTPS,and also included storage capabilities like FAT and Flash memory management systems.If the embedded devices has audio and video capabilities,then the appropria
44、te drivers and codes will be present in the system.In the case of the monolithic kernels,many of these software layers are included.In the RTOS category,the availability of the additional software components depends upon the commercial offering.Words and Expressionspredominantly,pridminnt adj.占优势的，支
45、配其他的，优越的，突出的，最显著的，主要的subroutine,sbru:ti:n n.子程序，【计算机】=subprogram21世纪大英汉词典triggered trid adj.有触发器的，触发器启动的，有扳机的frequency fri:kwnsi n.频繁，频率handler hndl n.处理程序21世纪大英汉词典latency leitnsi n.潜伏，潜在，等待时间queue kju:n.【计算机】等候行列，排队nonpreemptive adj.非抢占式scheme ski:m n.方案,计划,阴谋；v.计画,设计,体系，结构,图谋idle aidl adj.【机械学】空转的
46、；慢转的；怠速的；【电子学】空载的；无功的routine ru:ti:n n.【计算机】程序；例行程序Interpreter n.【计算机】翻译器，译印机，解释程序，翻译程序functionality,fknliti n.函数性(泛函性,官能度),功能（尤指软件、硬件的功能）21世纪大英汉词典 Words and Expressionsconceptually knseptjuli adv.概念地21世纪大英汉词典parallel prlel adj.【电子学、计算机】并联的；n.【电子学、计算机】并联的potentially ptenli adv.潜在地，假定地.MMU abbr.Memor
47、y Manager Unit内存管理单元synchronization,sikrnaizein n.同步化21世纪大英汉词典semaphore semf:n.信号灯,旗语non-blocking adj.非阻塞microkernel微核Shell n.命令解译程序（连接并解译用户命令，调用并执行存储器中的程序）allocate lukeit vi.&vt.【计算机】分配，指定，保留extensible ikstensbl adj.可展开的，可伸展的，可延续的；可扩大的，可扩展的；可延伸的Words and Expressionsdownside daun,said n.消极面,负面 navig
48、ation,nvigein n.航行,航海guarantee,grnti:v.&n.保证,担保；vt.保证RTOS abbr.Real Time Operating Systems实时操作系统exotic,iztik adj.1.外来的，非本地的；2.【核物理学】异的；极不稳定的 unobtainable nbteinbl adj.无法得到的,难获得的partition p:tin n.分割,隔离物,隔墙;v.区分,隔开,分割mechanism meknizm n.机械,机构,结构,机制，原理upper-layer adj.上层的category ktigri n.种类,类别availabil
49、ity,veilbilti n.有效性；可用性，可得性，利用(或获得)的可能性ExercisesI.True or false?If correct,write T in parentheses;Otherwise,write F.（）1.The loop calls subroutines,each of which manages all of the hardware or software.（）2.This gives programmers an environment different to a desktop operating system like Linux or Mic
50、rosoft Windows,and is therefore very productive for development.（）3.An interrupt could be generated for example by a timer in a predefined frequency,or by a serial port controller receiving a byte.（）4.After the interrupt handler has finished,these tasks are executed by any loop.（）5.A nonpreemptive m
