Introduction to Embedded Systems Part of HWSW Codesign

Introduction to Embedded Systems Part of HW/SW Codesign of Embedded Systems Course (CE 40 -226) Codesign of Embedded Systems 1

Today programme n Introduction to Embedded Systems n What are embedded systems? n Challenges in embedded computing system design. n Design methodologies. Copyright Note: Main idea from Prof. Wolf’s overheads for his book: “Computers as Components”, MKP 2000. Plus some modifications and additions. Winter-Spring 2001 Codesign of Embedded Systems 2

What are embedded Systems n Definition: Embedded System n n Includes a programmable computer But, is not a general-purpose computer CPU output analog input analog Logic embedded computer Winter-Spring 2001 mem Codesign of Embedded Systems 3

Embedded Systems n Advantages n n Optimizations according to application characteristics don’t need all the general-purpose bells and whistles Winter-Spring 2001 Codesign of Embedded Systems 4

Embedded System: Examples Embedded System Winter-Spring 2001 Codesign of Embedded Systems 5

u. P early history n Late 1940’s: MIT Whirlwind computer n n n Designed for RT operations. Originally designed to control an aircraft simulator. u. P history n n First u. P: Intel 4004, early 1970’s. HP-35 calculator: comprising several chips, 1972. Winter-Spring 2001 Codesign of Embedded Systems 6

u. P early history (cont. ) n Usage in automobiles ECU n n n Starting in 1970’s. Control fuel/air mixture, engine timing, etc. Multiple modes of operation: warm-up, cruise, hill climbing, etc. Provides lower emissions, better fuel efficiency. Native example: Cadillac Iran! Winter-Spring 2001 Codesign of Embedded Systems 7

u. P varieties n u. Controller: includes n n n Digital signal processor (DSP): n n I/O devices On-board memory. Optimized for digital signal processing. Typical embedded word sizes: 8 -bit, 16 bit, 32 -bit. Winter-Spring 2001 Codesign of Embedded Systems 8

Application examples n n Simple control: front panel of microwave oven, etc Canon EOS 3 has three microprocessors. n n n 32 -bit RISC CPU runs autofocus and eye control systems Analog TV: channel selection, etc. Digital TV: programmable CPUs + hardwired logic Winter-Spring 2001 Codesign of Embedded Systems 9

Automotive embedded systems n Today’s high-end automobile may have 100 microprocessors: n n 4 -bit u. Controller checks seat belt; u. Controllers run dashboard devices; 16/32 -bit u. P controls engine. Native examples n n Peugeot Persia Xantia Winter-Spring 2001 Codesign of Embedded Systems 10

BMW 850 i brake and stability control system n Anti-lock brake system (ABS): n n Automatic stability control (ASC+T): n n pumps brakes to reduce skidding. controls engine to improve stability. ABS and ASC+T communicate. n ABS was introduced first---needed to interface to existing ABS module. Winter-Spring 2001 Codesign of Embedded Systems 11

BMW 850 i (cont. ) sensor brake ABS hydraulic pump brake sensor Winter-Spring 2001 Codesign of Embedded Systems 12

Characteristics of embedded systems n Functional requirements n n n Non-functional requirements n n n Sophisticated functionality. RT operation. Low manufacturing cost. Low power. Designed to tight deadlines by small teams. Winter-Spring 2001 Codesign of Embedded Systems 13

Functional Requirements n Sophisticated functionality. Often: n have to run sophisticated or multiple algorithms. n n n Cell phone, laser printer. provide sophisticated user interfaces. RT operation n Must finish operations by deadlines. n n n Hard RT: missing deadline causes failure. Soft RT: missing deadline results in degraded performance. Many systems are multi-rate: must handle operations at widely varying rates. Winter-Spring 2001 Codesign of Embedded Systems 14

Non-functional requirements n Many embedded systems are mass-market items that must have low manufacturing costs. n n Limited memory, microprocessor power, etc. Power consumption is critical in batterypowered devices. n Excessive power consumption increases system cost even in wall-powered devices. Winter-Spring 2001 Codesign of Embedded Systems 15

Design teams n n Often designed by a small team of designers. Often must meet tight deadlines. n n 6 month market window is common. Can’t miss back-to-school window for calculator. Winter-Spring 2001 Codesign of Embedded Systems 16

Why use u. P? n Alternatives: n n n field-programmable gate arrays (FPGAs), custom logic, etc. u. Ps are often very efficient: can use same logic to perform many different functions. u. Ps simplify the design of families of products. Winter-Spring 2001 Codesign of Embedded Systems 17

The performance paradox n n u. P uses much more logic to implement a function than does custom logic. But u. P is often at least as fast: n n n heavily pipelined; large design teams; aggressive VLSI technology. Winter-Spring 2001 Codesign of Embedded Systems 18

Power n n n Custom logic is a clear winner for low power devices. Modern u. P offer features to help control power consumption. Software design techniques can help reduce power consumption. n Transmeta’s Crusoe™ Processor Winter-Spring 2001 Codesign of Embedded Systems 19

Introduction to Embedded Systems Challenges in Embedded System Design Codesign of Embedded Systems 20

Challenges in embedded system design n How much hardware do we need? n n How do we meet our performance deadlines? n n How big is the CPU? Memory? Faster hardware or cleverer software? How do we minimize power? n Turn off unnecessary logic? Reduce memory accesses? Winter-Spring 2001 Codesign of Embedded Systems 21

Challenges, etc. (cont. ) n Does it really work? n n n Is the specification correct? Does the implementation meet the spec? How do we test for real-time characteristics? How do we test on real data? How do we work on the system? n n Observability, controllability? What is our development platform? Winter-Spring 2001 Codesign of Embedded Systems 22

Introduction to Embedded Systems Design Methodology Codesign of Embedded Systems 23

Design methodologies n n n A procedure for designing a system. Understanding your methodology helps you ensure you didn’t skip anything. Compilers, software engineering tools, computer-aided design (CAD) tools, etc. , can be used to: n n help automate methodology steps; keep track of the methodology itself. Winter-Spring 2001 Codesign of Embedded Systems 24

Design goals n Functional requirements n Performance. n n n Overall speed, deadlines. Functionality and user interface. Non-functional requirements n n n Manufacturing cost. Power consumption. Other requirements (physical size, etc. ) Winter-Spring 2001 Codesign of Embedded Systems 25

Levels of abstraction requirements specification architecture component design system integration Winter-Spring 2001 Codesign of Embedded Systems 26

Top-down vs. bottom-up n Top-down design: n n n Bottom-up design: n n start from most abstract description; work to most detailed. work from small components to big system. Real design uses both techniques. Winter-Spring 2001 Codesign of Embedded Systems 27

Stepwise refinement n At each level of abstraction, we must: n n analyze the design to determine characteristics of the current state of the design; refine the design to add detail. Winter-Spring 2001 Codesign of Embedded Systems 28

Requirements n n Plain language description of what the user wants and expects to get. May be developed in several ways: n n n talking directly to customers; talking to marketing representatives; providing prototypes to users for comment. Winter-Spring 2001 Codesign of Embedded Systems 29

Functional vs. non-functional requirements n Functional requirements: n n output as a function of input. Non-functional requirements: n n n time required to compute output; size, weight, etc. ; power consumption; reliability; etc. Winter-Spring 2001 Codesign of Embedded Systems 30

Our requirements form Winter-Spring 2001 Codesign of Embedded Systems 31

Example: GPS moving map requirements Moving map obtains position from GPS, paints map from local database. I-78 Scotch Road n lat: 40 13 lon: 32 19 Winter-Spring 2001 Codesign of Embedded Systems 32

GPS moving map needs n n Functionality: For automotive use. Show major roads and landmarks. User interface: At least 400 x 600 pixel screen. Three buttons max. Pop-up menu. Performance: Map should scroll smoothly. No more than 1 sec power-up. Lock onto GPS within 15 seconds. Cost: $500 street price = approx. $100 cost of goods sold. Winter-Spring 2001 Codesign of Embedded Systems 33

GPS moving map needs, (cont. ) n n Physical size/weight: Should fit in hand. Power consumption: Should run for 8 hours on four AA batteries. Winter-Spring 2001 Codesign of Embedded Systems 34

GPS moving map requirements form Winter-Spring 2001 Codesign of Embedded Systems 35

Specification n A more precise description of the system: n n should not imply a particular architecture; provides input to the architecture design process. May include functional and non-functional elements. May be executable or may be in mathematical form for proofs. Winter-Spring 2001 Codesign of Embedded Systems 36

GPS specification n Should include: n n n What is received from GPS; map data; user interface; operations required to satisfy user requests; background operations needed to keep the system running. Winter-Spring 2001 Codesign of Embedded Systems 37

Architecture design n n What major components go satisfying the specification? Hardware components: n n Software components: n n CPUs, peripherals, etc. major programs and their operations. Must take into account functional and non-functional specifications. Winter-Spring 2001 Codesign of Embedded Systems 38

GPS moving map block diagram GPS receiver search engine database Winter-Spring 2001 renderer display user interface Codesign of Embedded Systems 39

GPS moving map hardware architecture display frame buffer CPU GPS receiver memory Winter-Spring 2001 panel I/O Codesign of Embedded Systems 40

GPS moving map software architecture position Winter-Spring 2001 database search renderer user interface timer Codesign of Embedded Systems pixels 41

Designing hardware and software components n n Must spend time architecting the system before you start coding. Architecture components n n n Some are ready-made, Some can be modified from existing designs Others must be designed from scratch. Winter-Spring 2001 Codesign of Embedded Systems 42

System integration n Put together the components. n n Many bugs appear only at this stage. Have a plan for integrating components to uncover bugs quickly, test as much functionality as early as possible. Winter-Spring 2001 Codesign of Embedded Systems 43

What we learned today n Embedded computers are all around us. n n n Many systems have complex embedded hardware and software. Embedded systems pose many design challenges: design time, deadlines, power, etc. Design methodologies help us manage the design process. Winter-Spring 2001 Codesign of Embedded Systems 44

Homework n A simplified ISDN transceiver n n n part 1: un-encoded transmitter refer to the homework definition page Due date: n Esfand 6 th Winter-Spring 2001 Codesign of Embedded Systems 45