2. Embedded Computing Design & Co-design of Embedded Systems Maziar Goudarzi

3. 2005 Design & Co-design of Embedded Systems 2 Today Program Introduction to Embedded Systems –What are embedded systems? –Challenges in embedded computing system design. –Design methodology. Copyright Note: Main idea from Prof. Wolf’s overheads for his book: “Computers as Components”, MKP 2001. Plus some modifications and additions. Copyright Note: Main idea from Prof. Wolf’s overheads for his book: “Computers as Components”, MKP 2001. Plus some modifications and additions.

4. © 2000 Morgan Kaufman Overheads for Computers as Components3 Introduction zWhat are embedded systems? zChallenges in embedded computing system design. zDesign methodologies.

5. © 2000 Morgan Kaufman Overheads for Computers as Components4 Definition zDefinition: Embedded System yIncludes a programmable computer yBut, is not a general-purpose computer CPU mem input output analog embedded computer Logic

6. © 2000 Morgan Kaufman Overheads for Computers as Components5 Embedded Systems zAdvantages yOptimizations according to application characteristics ydon’t need all the general-purpose bells and whistles

7. © 2000 Morgan Kaufman Overheads for Computers as Components6 Examples Embedded System

8. © 2000 Morgan Kaufman Overheads for Computers as Components7 Early history zLate 1940’s: MIT Whirlwind computer was designed for real-time operations. yOriginally designed to control an aircraft simulator. zFirst microprocessor was Intel 4004 in early 1970’s. zHP-35 calculator used several chips to implement a microprocessor in 1972.

9. © 2000 Morgan Kaufman Overheads for Computers as Components8 Early history, cont’d. zUsage in automobiles ECU yStarting in 1970’s. yControl fuel/air mixture, engine timing, etc. yMultiple modes of operation: warm-up, cruise, hill climbing, etc. yProvides lower emissions, better fuel efficiency. yNative example: Cadillac Iran!

10. © 2000 Morgan Kaufman Overheads for Computers as Components9 Microprocessor varieties zMicrocontroller: includes I/O devices, on- board memory. zDigital signal processor (DSP): microprocessor optimized for digital signal processing. zTypical embedded word sizes: 8-bit, 16- bit, 32-bit.

11. © 2000 Morgan Kaufman Overheads for Computers as Components10 Application examples zSimple control: front panel of microwave oven, etc. zCanon EOS 3 has three microprocessors. y32-bit RISC CPU runs autofocus and eye control systems. zAnalog TV: channel selection, etc. zDigital TV: programmable CPUs + hardwired logic.

12. © 2000 Morgan Kaufman Overheads for Computers as Components11 Automotive embedded systems zToday’s high-end automobile may have 100 microprocessors: y4-bit uController checks seat belt; yuControllers run dashboard devices; y16/32-bit uP controls engine. zNative examples ySamand LX yPeugeot Persia ELX yXantia,...

13. © 2000 Morgan Kaufman Overheads for Computers as Components12 BMW 850i brake and stability control system zAnti-lock brake system (ABS): y pumps brakes to reduce skidding. zAutomatic stability control (ASC+T): y controls engine to improve stability. zABS and ASC+T communicate. yABS was introduced first---needed to interface to existing ABS module.

14. © 2000 Morgan Kaufman Overheads for Computers as Components13 BMW 850i, cont’d. brake sensor brake sensor brake sensor brake sensor ABS hydraulic pump

15. © 2000 Morgan Kaufman Overheads for Computers as Components14 Characteristics of embedded systems zSophisticated functionality. zReal-time operation. zLow manufacturing cost. zLow power. zDesigned to tight deadlines by small teams.

16. © 2000 Morgan Kaufman Overheads for Computers as Components15 Functional complexity zSophisticated functionality. Often: yhave to run sophisticated or multiple algorithms. xCell phone, laser printer. yprovide sophisticated user interfaces. zRT operation yMust finish operations by deadlines. xHard RT: missing deadline causes failure. xSoft RT: missing deadline results in degraded performance. yMany systems are multi-rate: must handle operations at widely varying rates.

17. © 2000 Morgan Kaufman Overheads for Computers as Components16 Non-functional requirements zMany embedded systems are mass- market items that must have low manufacturing costs. yLimited memory, microprocessor power, etc. zPower consumption is critical in battery- powered devices. yExcessive power consumption increases system cost even in wall-powered devices.

18. © 2000 Morgan Kaufman Overheads for Computers as Components17 Design teams zOften designed by a small team of designers. zOften must meet tight deadlines. y6 month market window is common. yCan’t miss back-to-school window for calculator.

19. © 2000 Morgan Kaufman Overheads for Computers as Components18 Why use microprocessors? zAlternatives: yfield-programmable gate arrays (FPGAs), custom logic, etc. zMicroprocessors are often very efficient: can use same logic to perform many different functions. zMicroprocessors simplify the design of families of products.

20. © 2000 Morgan Kaufman Overheads for Computers as Components19 The performance paradox zMicroprocessors use much more logic to implement a function than does custom logic. zBut microprocessors are often at least as fast: yheavily pipelined; ylarge design teams; yaggressive VLSI technology.

21. © 2000 Morgan Kaufman Overheads for Computers as Components20 Power zCustom logic is a clear winner for low power devices. zModern microprocessors offer features to help control power consumption. zSoftware design techniques can help reduce power consumption. yTransmeta’s Crusoe™ Processor (one of the optional reading-assignments)

22. Embedded Computing Challenges in Embedded System Design

23. © 2000 Morgan Kaufman Overheads for Computers as Components22 Challenges in embedded system design zHow much hardware do we need? yHow big is the CPU? Memory? zHow do we meet our deadlines? yFaster hardware or cleverer software? zHow do we minimize power? yTurn off unnecessary logic? Reduce memory accesses?

24. © 2000 Morgan Kaufman Overheads for Computers as Components23 Challenges, etc. zDoes it really work? yIs the specification correct? yDoes the implementation meet the spec? yHow do we test for real-time characteristics? yHow do we test on real data? zHow do we work on the system? yObservability, controllability? yWhat is our development platform?

25. Embedded Computing Design Methodology

26. © 2000 Morgan Kaufman Overheads for Computers as Components25 Design methodologies zA procedure for designing a system. zUnderstanding your methodology helps you ensure you didn’t skip anything. zCompilers, software engineering tools, computer-aided design (CAD) tools, etc., can be used to: yhelp automate methodology steps; ykeep track of the methodology itself.

27. © 2000 Morgan Kaufman Overheads for Computers as Components26 Design goals zFunctionality and user interface. zPerformance. yOverall speed, deadlines. zManufacturing cost. zPower consumption. zOther requirements (physical size, etc.)

28. © 2000 Morgan Kaufman Overheads for Computers as Components27 Levels of abstraction requirements specification architecture component design system integration

29. © 2000 Morgan Kaufman Overheads for Computers as Components28 Top-down vs. bottom-up zTop-down design: ystart from most abstract description; ywork to most detailed. zBottom-up design: ywork from small components to big system. zReal design uses both techniques.

30. © 2000 Morgan Kaufman Overheads for Computers as Components29 Stepwise refinement zAt each level of abstraction, we must: yanalyze the design to determine characteristics of the current state of the design; yrefine the design to add detail.

31. © 2000 Morgan Kaufman Overheads for Computers as Components30 Requirements zPlain language description of what the user wants and expects to get. zMay be developed in several ways: ytalking directly to customers; ytalking to marketing representatives; yproviding prototypes to users for comment.

32. © 2000 Morgan Kaufman Overheads for Computers as Components31 Functional vs. non- functional requirements zFunctional requirements: youtput as a function of input. zNon-functional requirements: ytime required to compute output; ysize, weight, etc.; ypower consumption; yreliability; yetc.

33. © 2000 Morgan Kaufman Overheads for Computers as Components32 Our requirements form

34. © 2000 Morgan Kaufman Overheads for Computers as Components33 Example: GPS moving map requirements zMoving map obtains position from GPS, paints map from local database. lat: 40 13 lon: 32 19 I-78 Scotch Road

35. © 2000 Morgan Kaufman Overheads for Computers as Components34 GPS moving map needs zFunctionality: For automotive use. Show major roads and landmarks. zUser interface: At least 400 x 600 pixel screen. Three buttons max. Pop-up menu. zPerformance: Map should scroll smoothly. No more than 1 sec power-up. Lock onto GPS within 15 seconds. zCost: $500 street price = approx. $100 cost of goods sold.

36. © 2000 Morgan Kaufman Overheads for Computers as Components35 GPS moving map needs, cont’d. zPhysical size/weight: Should fit in dashboard. zPower consumption: Current draw comparable to CD player (OR: Should run for 8 hours on four AA batteries).

37. © 2000 Morgan Kaufman Overheads for Computers as Components36 GPS moving map requirements form

38. © 2000 Morgan Kaufman Overheads for Computers as Components37 Specification zA more precise description of the system: yshould not imply a particular architecture; yprovides input to the architecture design process. zMay include functional and non-functional elements. zMay be executable or may be in mathematical form for proofs.

39. © 2000 Morgan Kaufman Overheads for Computers as Components38 GPS specification zShould include: yWhat is received from GPS; ymap data; yuser interface; yoperations required to satisfy user requests; ybackground operations needed to keep the system running.

40. © 2000 Morgan Kaufman Overheads for Computers as Components39 Architecture design zWhat major components go satisfying the specification? zHardware components: yCPUs, peripherals, etc. zSoftware components: ymajor programs and their operations. zMust take into account functional and non-functional specifications.

41. © 2000 Morgan Kaufman Overheads for Computers as Components40 GPS moving map block diagram GPS receiver search engine renderer user interface database display

42. © 2000 Morgan Kaufman Overheads for Computers as Components41 GPS moving map hardware architecture GPS receiver CPU panel I/O display frame buffer memory

43. © 2000 Morgan Kaufman Overheads for Computers as Components42 GPS moving map software architecture position database search renderer timer user interface pixels

44. © 2000 Morgan Kaufman Overheads for Computers as Components43 Designing hardware and software components zMust spend time architecting the system before you start coding. zArchitecture components ySome are ready-made, ySome can be modified from existing designs yOthers must be designed from scratch.

45. © 2000 Morgan Kaufman Overheads for Computers as Components44 System integration zPut together the components. yMany bugs appear only at this stage. zHave a plan for integrating components to uncover bugs quickly, test as much functionality as early as possible.

46. © 2000 Morgan Kaufman Overheads for Computers as Components45 What we learned today zEmbedded computers are all around us. yMany systems have complex embedded hardware and software. zEmbedded systems pose many design challenges: design time, deadlines, power, etc. zDesign methodologies help us manage the design process.

47. 2005 Design & Co-design of Embedded Systems 46 Other Notes Course web-page is now established http://ce.sharif.edu/courses/84-85/1/ce226/index.php