Thiết kế hệ thống Nhúng chương 1

ĐẠI HỌC QUỐC GIA TP.HỒ CHÍ MINH TRƯỜNG ĐẠI HỌC BÁCH KHOA KHOA ĐIỆN-ĐIỆN TỬ BỘ MÔN KỸ THUẬT ĐIỆN TỬ 1 Embedded System Design Chapter 1: Embedded System Overview 1.. Bộ môn Kỹ Thuật Điện

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ĐẠI HỌC QUỐC GIA TP.HỒ CHÍ MINH TRƯỜNG ĐẠI HỌC BÁCH KHOA

KHOA ĐIỆN-ĐIỆN TỬ

BỘ MÔN KỸ THUẬT ĐIỆN TỬ

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Embedded System Design Chapter 1: Embedded System Overview

1 What is an embedded system?

2 Embedded system models

3 Embedded system features

4 Real-time embedded system

1 What’s an Embedded System?

• Embedded systems =

– information processing systems that

interact with physical processes and are

embedded into a larger product

• Two types of computing

– Desktop – produced millions/year

– Embedded –billions/year

• Non-Embedded Systems

– PCs, servers, and notebooks

• The future of computing!

– Automobiles, entertainment,

communication, aviation, handheld

devices, military, medical equipment …

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Bộ môn Kỹ Thuật Điện Tử - ĐHBK

• Embedded system is

– any device that includes a programmable computer but is not itself a

general-purpose computer - Wayne Wolf

– An embedded computer system includes a micro-computer with

mechanical, chemical and electrical devices attached to it, programmed

for a specific dedicated purpose, and packaged as a complete system

-Jonathan W Valvano

– An embedded system is one that has computer-hardware with software

embedded in it as one of its most important component - Raj Kamal

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Chapter 1

Embedded System Examples

• The refrigerator

– Maintain a moderately stable, low temperature within it.

– Sense its internal temperature and compare that with the temperature required

– Lowers the temperature by switching on a compressor

– The temperature measurement requires one or more sensors

– Controlling the compressor requires some form of electronic interface

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• A car door mechanism

– Window stall sensor, door sensor

– Window motor, lock actuator

– Window control buttons

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• The Derbot Vehicle

– Two microswitch bump

detectors

– an untrasound detector

– Two light sensors

– a servo actuator

• Derbot is powered from six

AA Alkaline cells

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• The Derbot Vehicle

– operates as an

embedded system

– reading in values from

its diverse sensors and

computing outputs to

its actuators.

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Chapter 1

2 Embedded System Models

• Application software:

– application programs, GUI, control programs…

• System software

– Operating system, system drivers, system library

• Hardware

– Processors, memory, peripherals, input/output devices, PCB

…

Application software layer System software layer Hardware layer

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3 Embedded System Features

• Embedded processor is a heart of the embedded system:

– micro-processor: 8086, ARM7, ARM9…

– micro-controller: 8051, ARM Cortex-M, PIC16F, 68HC11,

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Embedded Processor

Sensors

Display

RAM ROM

Embedded software

Actuators

Peripherals

Buttons

Power Clock

Chapter 1

Components of Embedded Systems

• Memory

– ROM: embedded program

– RAM: processing data

• Embedded program

– OS / non-OS supported

– realtime / non-realtime

– timer, interrupt, serial port…

• Clock:

– crystal

• Power:

– +5V / +3.3V / +2.5V

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• Peripherals:

– I/O port

– UART

– I2C

– ADC

– PWM

• User interface:

– Button / keypad / switch

– LCD / 7-segment LED / LED indicator

• Sensors:

– temperature, light, ultrasound, pressure, …

• Actuators:

– motor, solenoid, relay, …

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Chapter 1

Common Characteristics:

• Single-functioned

– Executes a single program, repeatedly

• Tightly-constrained

– Low cost, low power, small, fast, etc

• Reactive and real-time

– Continually reacts to changes in the system’s environment

– Must compute certain results in real-time without delay

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An embedded system example

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Microcontroller

CCD preprocessor Pixel coprocessor A2D

D2A

JPEG codec

DMA controller

Memory controller ISA bus interface UART LCD ctrl

Display ctrl Multiplier/Accum

Digital camera chip

lens

CCD

• Single-functioned always a digital camera

• Tightly-constrained Low cost, low power, small, fast

• Reactive and real-time: needs to respond to the pressing of buttons

by a user

A digital camera

Chapter 1

3 Common Characteristics:

• Single-functioned

– Executes a single program, repeatedly

• Tightly-constrained

– Low cost, low power, small, fast, etc

• Reactive and real-time

– Continually reacts to changes in the system’s environment

– Must compute certain results in real-time without delay

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Embedded System Requirements

• 5 basic requirements for an embedded system

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Real-time/

reactive operation

Small size/

low weight

Low power, cooling

Safe and reliable

Cost / resource

Chapter 1

Embedded System Quality

• 8 basic dimensions of quality

1 Performance: The primary operating characteristics of a product

2 Feature: Those characteristics that supplement a product’s basic

functions

3 Reliability:The probability of a product malfunctioning

4 Durability:A measure of the amount of use one gets from a

product before it breaks down

5 Serviceability:Ease and time to repair after breakdown

6 Conformance: the degree to meet standards

7 Aesthetics: How a product looks

8 Perceived quality: This dimension is associated with reputation

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Chapter 1

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4 Real-time Embedded Systems

• Definition:

– A real-time system is one that must process information

and produce a response within a specified time

– Any system in which the time at which output is produced

is significant

• Almost embedded systems are real-time

• Hard real-time system:

– missing a deadline is a total system failure

– Many of these systems are considered to be safety critical

– In general there is a cost function associated with the

system

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• Soft real-time

– the system's quality of service degrades after its deadline

– Deadline overruns are tolerable, but not desired

– Often connected to Quality-of-Service (QoS)

Examples

• Hard real-time system

– a car engine control system is a hard real-time system

because a delayed signal may cause engine failure or

damage

– heart pacemakers is hard real-time systems

• Soft real-time system

– Multimedia systems

– LED display control systems

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Quiz

2 What is the model of an embedded system?

3 What are embedded system features?

4 What are five basic requirements of an embedded system?

5 What are eight dimension of quality of an embedded

system?

6 What are common characteristics of an embedded system?

7 What is real-time embedded system? Give example

8 What is the most importance part of an embedded system?

9 What are differences between hard and soft real-time

systems?

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