1. Embedded System Design Process

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 : Develop a project of embedded system design 1. Design Process 2. Design Issues 3. Technology selection 4. Project plan 1 1. Embedded System Design Process Several models can be applied for embedded system design The waterfall model: in which there is a process for developing a system in steps, where results of one step flow into the next step. The spiral model: in which there is a process for developing a system in steps, and throughout the various steps, feedback is obtained and incorporated back into the process. Consecutive refinement model Most followed and simple model for building an Embedded System is Waterfall model 2 1

2 1. Embedded System Design Process CAD tools Requirement definition System specification System partitioning Customers System architects SW development Application SW Compilers Operating SW developer Interface design SW driver HW interface User interface Integration and testing HW design HW architecture HW synthesis Physical design HW designer Reused components No Meet requirement? Yes Delivery and maintenance System Specification Documents for System Specification 1. Product Specification Describe how the product will be. 2. Engineering Specification 3. Hardware Specification 4. Software Specification 5. Test Specification Describe what board, subsystem, and firmware will be used. Describe how the board will be implemented and how it works. Describe how the software will be implemented. Describe how the system will be tested. 4 2

3 1.1. System Specification 1. Product Specification: What the system is to do What the user interface is What the real world I/O consists of What the external interface to other system is (if any) What are the constraints? (speed, stability, low power, cost ) Example: Oven temperature control system Functions: control the heater and the fan of an oven I/O: temperature sensor, heater port, fan port User interface: LCD display, keypad External interface: UART System Specification 2. Engineering Specification: What kind of hardware will be used What are the requirements for hardware and software Example: Oven temperature control system 8051 microcontroller, LM35 sensor, LCD 16x2-B, ADC0809, RS232 IC Requirements PID control algorithm real-time processing Display current temperature value able to set operating temperature value Transfer data to computer through UART 6 3

4 1.1. System Specification 3. Hardware Specification: The requirements from engineering documents How the hardware implements the functionality The software interfaces to the hardware Example: Oven temperature control system PIC Microcontroller 12MHz, sensor LM35, LCD 16x2-B, Keypad 16, ADC0809, FET IRF260 for heater/fan control Microcontroller reads temperature value from LM35 through ADC, display this value to LCD, and then control heater and fan based on PID control algorithm System Specification 4. Software Specification: The requirements from engineering specification Interface to other software How the software implements the requirements Example: Oven temperature control system Temperature control algorithm Software functions: void LCD_display(String str) intpid_control(int temp, intdata[]) 8 4

5 5. Test Specification: 1.1. System Specification The device, equipment, environment for testing Prototype Testing process Example: Oven temperature control system Voltage meter, temperature meter Prototype: bread board Testing process: calibrate temperature sensor check LCD, keypad check output port (heater, fan) verify PID control algorithm 9 Group discussion 1.1. System Specification Write a specification document for your own class project 10 5

6 1.2. System partitioning System partitioning: divide the system into three parts: Hardware (HW): microcontrollers, memories, peripherals, Software (SW): OS, program, application software Interface: SW driver, HW interface, user interface Alternative way: divide the system into HW and SW which functions should be performed in hardware, and which in software? the more functions in software, the lower will be the product cost System partitioning System partitioning examples: Oven temperature control system No. Functions Hardware Software 1 Measure temperature - Sensor LM35 - AD converter -ADC reading function -Calculate temperature value from the sensor input value 2 Display temperature value - LCD LCD control function - Display function 3 Heating - Heater -Heater control function 4 Change the heating level - Button - Button reading function -Heating level setup function 5 Change heating time - Button - Timer function 12 6

7 Group discussion 1.2. System partitioning Apply system partitioning for your own class project Embedded System Design Issues Design issues are problems that make it difficult to design an embedded system 1. Constraint issues 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) Chapter

8 2. Embedded System Design Issues 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 Chapter Embedded System Design Issues 2. 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? Chapter

9 2. Embedded System Design Issues 2. Functional issues Examples for battery charger No. Issues Note 1 Battery can be over-heat, it need to be detected by a sensor Correct 2 Display a charging current and battery status Wrong 3 The system musthave a fuse for protection of over current 4 Support 3 charging modes? 5 Applyefficient algorithm for fast charging and increase battery life cycle Functional issues are problems which can affect to life, health, economy, environment, society, politics, ethics.?? Chapter Embedded System Design Issues 3. Real-time issues Determine whether the system is hard/soft/non real-time Determine the time constraint (delay) Example Door entry alarm Non/soft real-time system: delay < 1-2s Video recorder Soft real-time system: delay < 1ms Car airbag system? Weather temperature monitoring? Chapter

10 2. Embedded System Design Issues 4. Concurrent issues 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 Chapter Embedded System Design Issues 5. Reactive issues Continuous / discontinuous interaction Power on demand Turn ON when using Ex:MP3 player, Tivisystem 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 Chapter

11 2. Embedded System Design Issues Group discussion Discuss about design issues of your own class project Chapter Technology Selection Technology A manner of accomplishing a task, especially using technical processes, methods, or knowledge Three key technologies for embedded systems Processor technologies: general-purpose, applicationspecific, single-purpose IC technologies: Full-custom, semi-custom, PLD Design technologies: Compilation/synthesis, libraries/ip, test/verification 22 11

12 Processor selection 3. Technology Selection number of IO pins required interface required memory requirements number of interrupts required real-time considerations development environment processing speed required General-purpose processor Application-specific processor Single-purpose processor 23 Processor technology Processor not equal to general-purpose processor Controller Datapath Controller Datapath Controller Datapath Control logic and State register IR PC Register file General ALU Control logic and State register IR PC Registers Custom ALU Control logic State register index total + Data memory Data memory Program memory Assembly code for: Data memory Program memory Assembly code for: total = 0 for i =1 to General-purpose ( software ) 24 total = 0 for i =1 to Application-specific Single-purpose ( hardware ) 12

13 IC technology The manner in which a digital (gate-level) implementation is mapped onto an IC IC: Integrated circuit, or chip IC technologies differ in their customization to a design IC s consist of numerous layers (perhaps 10 or more) IC technologies differ with respect to who builds each layer and when IC package IC source gate oxide channeldrain Silicon substrate 25 Compilation/synthesis: Design technology C Compilers: CCS C, mikroc, KeilC, Code Composer Studio, Libraries/IP Stellarisware, Tivaware, STM32 Library, OS: Embedded Linux, RTOS Test/verification Development kits Simulation tools: Proteus, Orcad, PSIM 26 13

14 4. Project plan Build a team Build a plan 27 Build a team Important points about teams Teams bring together complementaryskills and experiences Teams establish communication to support realtime problem solving Teams develop decisions by consensusrather than by authority 28 14

15 TEAM CONTRACT Team Contract Team name: BK1 Date: 26 Aug Team member Roles Signature Nguyễn Văn A Trần Văn B Nguyễn Thị C Tasks Leader, system engineer Hardware design Software design Team rules 1. Participate in all team meetings 2. Listen carefully to all comments at meetings 3. Complete all assigned tasks before deadlines 4. Focus on results rather than excuses after. Responsible member 1. Develop system architecture Nguyễn Văn A 2. Design hardware Trần Văn B 3. Develop software Nguyễn Thị C 4. Integrate and test All Team meeting 9AM, Wednesday, weekly 29 Build a plan Project planning activities Identify the task Develop teams Develop schedule Estimate time Plan tasks Refine plan Approve plan Cancel plan Proceed plan 30 15

16 Project plan example (1) Project planning Team name Product name Main features Estimated Time Estimated Cost Team members Schedule BK_DEE Home security system -Fire alarm -Door alarm -Send warning to home owner 3 months (8 hours / a day) Start: 20 Aug End: 20 Nov Components : 300,000 VNĐ Tools : 100,000 VNĐ Materials : 100,000 VNĐ Total : 500,000 VNĐ Student 1: leader Student 2: hardware design Student 3: software design 31 Project plan example (2) Project planning Schedule Month 1 Month2 Month 3 1. Design system architecture 2. Design hardware part 2.1. Design central control board 2.2. Design interface 2.3. Implement hardware board 3. Develop software part 3.1. Develop control algorithm 3.2. Develop driver, user interface 3.3. Implement software program 4. Integrate and test 4.1. Simulate operations 4.2. Verify system 32 16

17 Class assignment Design a embedded system for washing machine No. Specification 1 Product specification 2 Engineering specification 3 Hardware specification 4 Software specification 5 Test specification Describe -Washing process: soak, wash, rinse, spin -Mode: manual, fuzzy -Constraints -Inputs: -Outputs: -Use interface: -Microcontroller: -Sensors: -Actuators: -Functions: -Control algorithm: -Platform: -Test process: 33 Group discussion 1. Consider the project car s door mechanism Write system specification for this project 34 17

18 Group discussion 2. Consider the project car door mechanism Write team contract and plan for the project 35 18