Lecture 02 Introduction to Embedded Systems

Jin-Tai Yan

Department of Computer Science & Information Engineering

2016/09/26

What is an Embedded System ?

• An embedded system is a computer system embedded in a device with a dedicated function

• Wikipedia -- Embedded System is a special-purpose computer system designed to perform one or a few dedicated functions

it does not provide programmability to users

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� it does not provide programmability to users

Preview of Embedded Systems

• Embedded systems cover a wide range of electronics gadgets

� iPhone, Android phone, MP3 player.

� Refrigerator, Washer, TV..

� Embedded systems are virtually everywhere in your life

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Characteristics in Embedded Systems

• Since embedded system is dedicated to specific tasks, design engineers try to optimize hardware/software components of the systems� Reduce power and cost

� Increase reliability and performance

• Even though embedded systems cover a wide range of special-purpose systems, there are common special-purpose systems, there are common characteristics� Low cost - Cheap to be competitive

• Memory is very small compared to a general-purpose computer system

• Lightweight processors are used in embedded systems

� Low power - In case of portable devices• Low-power processors are used in embedded systems

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Characteristics in Embedded Systems(Cont)

� High performance - Meet the computing requirements of applications

• Users want to watch video on portable devices

• Gaming gadgets like playstation should provide high performance

� Real-time property - Job should be done within a time limit

• Aerospace applications, Car control systems, Medical gadgets are critical in terms of time constraint – Otherwise, it could lead to critical in terms of time constraint – Otherwise, it could lead to catastrophe such as loss of life

• It is challenging to satisfy the characteristics

� You may not be able to achieve high performance while maintaining low power consumption and making use of cheap components

� you got to do your best in a given circumstance to be competitive in the market

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Development in Embedded Systems

• Watches

• Refrigerators

• Picture Frames

• Desks

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Evolution of Watches

Evolution of Refrigerators

Evolution of Picture Frames

Evolution of Desks

Applications in Embedded Systems

• Phone and Tablets

• Robotics

• Automotives

• Military

• Networking Devices

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• Networking Devices

• Medical Devices

• Implantable Medical Devices

• Other Gadgets

Phones and Tablets

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• Communication

� Wifi

� GSM/3G/LTE

� Bluetooth/NFC

• Graphics and Video Processing

• OS

• Android / Windows / iOS

Robotics

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Automotives

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Example: Mercedes S-Class

Automotive Electronics Platform

Electronics Devices in Automotives

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Powertrain Device in Automotive

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Cars Are Getting Smarter

• Electronics represents 40% of total cost of a car

• 90% of new car features require software

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Military

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Networking Devices

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Medical Devices

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Implantable Medical Devices

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Other Gadgets

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Why is it different from Desktop Development ?

• Embedded Systems normally come with constraints in hardware resources

� Processing

� Memory

� Storage

� Power

� Display

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� Display

� Input/Output devices

• Embedded system applications often comes with real time system constraints

� Latency

� Throughput

• System has a strong association between the HW and SW

Cross-Platform Development

• Development Environment is different from target environment

• Need for cross platform development and debugging tools

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Embedded Systems Classification

• Two main families of embedded system platforms:

� Microcontroller Family

� Microprocessor Family

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Embedded Systems: Microcontrollers

• Examples: PIC (MicroChip), AVR (Atmel), …

• Used for example in Arduino Boards

• Originally 8/16 bit but recently there are 32 bit chips

• Simple instruction set

• No or simple OS Support

• Limited performance (clock speed up to 10s MHz)

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• Limited performance (clock speed up to 10s MHz)

• Programming in assembly, or C

• Useful in small systems with lower Cost

• Typical usage:

� Interfacing to sensors

� Control of motors in simple robotics systems

� Simple home automation

Embedded Systems: Microprocessors

• Examples: ARM, Intel ATOM, MIPS

• Used for example in Raspberry Pi, BeagleBone Black, …

• 32 bit (and sometimes 64 bits)

• Support Linux and other RTOSs

• Higher performance (clock speed in 100s MHz to few GHz)

• Programming in C/C++ (sometimes with little assembly), Java, Python

• Strong library support (act as a small computer)

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• Strong library support (act as a small computer)

• Useful in more complicated systems but with higher cost

• Typical Usage:

� Sophisticated control systems

� Audio Processing

� Image Processing

� Video Processing

� Communication Systems

� Advanced guidance and navigation systems

HW/SW Stack in Embedded Systems

• Identical to the general-computer systems

Application Software

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OS / Device Drivers

Hardware

Components in Embedded Systems(1)

• Hardware � It is mainly composed of processor (1 or more), memory,

I/O devices including network devices, timers, sensors etc.

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Example: Digital Camera

�Digital Camera Block Diagram

Example: Digital Camera

�Memory �Controllers

�Processor

�Interface

�Software�(Application Programs)

�Analog �Digital �Analog

�Coprocessors

�Converters

�Processor

�ASIC

Components in Embedded Systems(2)

• Operating Systems(OS)� Multitasking (multithreaded) OS is required, as

embedded applications become complicated • Networking, GUI, Audio, Video

• CPU is context-switched to process multiple jobs

� Operating system footprint should be small enough to fit into memory of an embedded systeminto memory of an embedded system

• Real-time operating systems (RTOS) such as VxWorks and uC/OS-II have been used because they are light-weighted in terms of memory requirement

• Heavy-weighted OSs such as iOS, Android, Windows Mobile, and embedded Linux (uClinux) are used, as embedded processors support computing power and advanced capabilities such as MMU (Memory Management Unit)

• Device drivers for I/O devices

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Real-Time Systems

• Real-Time Operating System (RTOS)� Multitasking operating system intended for real-time

applications

� RTOS facilitates the creation of real-time systems

� RTOS does not necessarily have a high throughput

� RTOS is valued more for how quickly and/or predictably it can respond to a particular event

• Hard real-time systems are required to complete a

Hard real-time systems

• Hard real-time systems are required to complete a critical task within a guaranteed amount of time

• Soft real-time systems are less restrictive

� Implementing real-time system requires a careful design of scheduler

• System must have the priority-based scheduling

• Real-time processes must have the highest priority

• Process dispatch latency must be small

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OSs in Embedded Systems

• RTOSs

� pSOS

� VxWorks

� VRTX (Versatile Real-Time Executive)

� uC/OS-II

• Palm OS & Symbian OS

� Palm OS: Embedded operating system initially developed by U.S. � Palm OS: Embedded operating system initially developed by U.S. Robotics-owned Palm Computing, Inc. for personal digital assistants (PDAs) in 1996

� Symbian OS: Proprietary operating system designed for mobile devices by Symbian Ltd. A descendant of Psion's EPOC and runs exclusively on ARM processors

• Android (http://www.android.com/)

� Open Handset Alliance Project

� Based on modified version of Linux 2.6 kernel

� Currently supporting ARM, MIPS, Power Architecture and x86

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uClinux

• A port of Linux to systems without a Memory Management Unit (MMU)

� http://www.uclinux.org/

• uClinux has been ported to many microcontrollers� ARM7TDMI (ARM)� ARM7TDMI (ARM)

� Dragonball, ColdFire, 68K Derivatives, QUICC (Motorola)

� Blackfin (ADI)

� i960 (Intel)

� Microblaze (Xilinx)

� V850E (NEC)

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Operating Systems in Embedded Systems

• uClinux (source: Wikipedia) - as of 2009

� The use of a Linux operating system in embedded computer systems

� According to survey conducted by Venture Development Corporation, Linux was used by 18% of embedded engineers

� Embedded versions of Linux are designed for devices with relatively limited resources, such as cell phones and set-top boxes

� Due to concerns such as cost and size, embedded devices usually have much less RAM and secondary storage than desktop computers, and are much less RAM and secondary storage than desktop computers, and are likely to use flash memory instead of a hard drive

� Since embedded devices are used for specific purposes rather than general purposes, developers optimize their embedded Linux distributions to target specific hardware configurations and usage situations

• These optimizations can include reducing the number of device drivers and software applications, and modifying the Linux kernel to be a real-time operating system

� Instead of a full suite of desktop software applications, embedded Linux systems often use a small set of free software utilities such as busybox, and replace the glibc C standard library with a more compact alternative such as dietlibc, uClibc, or Newlib.

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Components in Embedded Systems (3)

• Application Software

� Run on top of operating system

� Execute tasks that users wish to perform

• Web surfing, Audio, Video playback

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Design Flow in Embedded System

Planning & Architect

(modeling & simulation)

Hardware Design with CAD tools

ASIC/SoC design

ASIC/SoC chip

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simulation) with CAD tools

System prototype board

Hardware debugging & Software development Final product

� ASIC: Application-Specific Integrated Circuit

� SoC: System-on-Chip