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 features 3. Embedded system design issues 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 Features 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, micro controller: 8051, ARM Cortex M, PIC16F, 68HC11, 8 4

5 2. 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 9 2. 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, 10 5

6 2. 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 11 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 -- only to a small extent 12 6

7 2. 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 13 Design issues are problems that make it difficult to design an embedded system 1. Constraints cost may matter more than speed long life cycle Reliability/safety Low power Size / weight Examples: Portable heart beat monitor Long life cycle (10 years) Reliability (accuracy 99%) Low power (5 using days) Light weight (<1kg) 14 7

8 1. Constraints Examples for smart home system No. Constraints Note 1 Low price (< dong) Correct 2 Ability to detect smoke and fire Wrong 3 Low power (100mW when idle, 3W when active) Correct 4 Response time for control < 1ms? 5 Support remote control by smartphones? 6 Easy to install? Constraints are limitations or restrictions of some parameters of the system Functional issues safety critical applications damage to life, health, economy affect to environment, society, politics Example: Message LED for a shop Display message for customers Malfunctions result in small damage Message LED for a stock market Display stock data Malfunctions could damage to economy Battery charger? 16 8

9 2. Functional issues Examples for battery charger No. Constraints Note 1 Battery can be over heat, it need to detect by a sensor Correct 2 Display a charging current and battery status Wrong 3 The system must have a fuse for protection of over? current 4 Support 3 charging modes? 5 Apply efficient algorithm for fast charging and increase battery life cycle? Functional issues are problems which can affect to life, health, economy, environment, society, politics, ethics Real time systems Not only right output but at the right time Processing time is the most important one Output not in right time could make damage Example Door entry alarm Non real time system: delay < 1 2s Video recorder Critical real time system: delay < 1ms Car airbag system? Weather temperature monitoring? 18 9

10 4. Concurrent systems System and environment run concurrently multi functions interface with other systems May need a scheduler to manage concurrent tasks Examples: Weather temperature monitoring Multi functions: Read temperature values from the sensor Write data to memory Display data on LCD Reactive systems Continuous / discontinuous interaction Power on demand Turn ON when using Ex: MP3 player, Tivi system Always ON, once started run forever Continuous interaction with their environment Termination is a bad behavior => watchdog timer Ex: Camera surveillance system, data acquisition system Response to external periodic/non periodic events Events are periodic: the system needs a scheduler to capture the events Events are non periodic: the system needs to estimate miss event cases 20 10

11 Group discussion Discuss about design issues of your own class project 21 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 22 11

12 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 23 Class assignment 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? 24 12