Embedded System Design

Transcription

1 ĐẠI HỌC QUỐC GIA TP.HỒ CHÍ MINH TRƯỜNG ĐẠI HỌC BÁCH KHOA KHOA ĐIỆN-ĐIỆN TỬ BỘ MÔN KỸ THUẬT ĐIỆN TỬ Embedded System Design : Embedded System Overview 1. What is an embedded system? 2. Embedded system models 3. Embedded system features 4. Real-time embedded system 1 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 2 1

2 1. What is an embedded system? 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 3 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 4 2

3 Embedded System Examples A car door mechanism Window stall sensor, door sensor Window motor, lock actuator Window control buttons 5 Embedded System Examples The Derbot Vehicle Two microswitch bump detectors an untrasound detector Two light sensors a servo actuator Derbot is powered from six AA Alkaline cells 6 3

4 Embedded System Examples The Derbot Vehicle operates as an embedded system reading in values from its diverse sensors and computing outputs to its actuators Embedded System Models Application software: Application software layer System software layer Hardware layer application programs, GUI, control programs System software Operating system, system drivers, system library Hardware Processors, memory, peripherals, input/output devices, PCB 8 4

5 3. Embedded System Features Components of Embedded Systems Clock Peripherals Display Power ROM Embedded software Embedded Processor Buttons RAM Sensors A/D I/O Actuators Embedded processor is a heart of the embedded system: micro processor: 8086, ARM7, ARM9 micro controller: 8051, ARM Cortex M, PIC16F, 68HC11, 9 3. Embedded System Features 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 10 5

6 3. Embedded System Features 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, Embedded System Features 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 12 6

7 An embedded system example A digital camera CCD Digital camera chip A2D CCD preprocessor Pixel coprocessor D2A lens JPEG codec Microcontroller Multiplier/Accum DMA controller Display ctrl Memory controller ISA bus interface UART LCD ctrl 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 Embedded System Features 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 14 7

8 Embedded System Requirements 5 basic requirements for an embedded system Real time/ reactive operation Cost / resource Small size/ low weight Safe and reliable Low power, cooling 15 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 16 8

9 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 Real time Embedded Systems 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 18 9

10 4. Real time Embedded Systems 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) Real time Embedded Systems 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 20 10

11 Quiz 1. What is an embedded system? 2. What are embedded system features? 3. What are issues of embedded system design? 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 issue of embedded system design? Give example. 8. What is the most importance part of an embedded system? 9. What are differences between hard and soft real time systems? 21 11