Introduction to Embedded Systems Introduction to Embedded (Real Time) Systems Lecture 1.
Introduction to Embedded Systems
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Transcript of Introduction to Embedded Systems
Introduction to Embedded SystemsPart of HW/SW Codesign of Embedded Systems Course (CE 40-226)Codesign of Embedded Systems 1
Today programme
Introduction to Embedded Systems What are embedded systems? Challenges in embedded computing system design. Design methodologies.Copyright Note:
Main idea from Prof. Wolfs overheads for his book:Computers as Components, MKP 2000. Plus some modifications and additions.
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What are embedded Systems
Definition: Embedded System
Includes a programmable computer But, is not a general-purpose computerCPU Logicmem embedded computer output input
analoganalog
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Embedded Systems
Advantages
Optimizations according to application characteristics
dont need all the general-purpose bells and whistles
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Embedded System: ExamplesEmbedded System
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uP early history
Late 1940s: MIT Whirlwind computer
Designed for RT operations. Originally designed to control an aircraft simulator. First uP: Intel 4004, early 1970s. HP-35 calculator: comprising several chips, 1972.Codesign of Embedded Systems 6
uP history
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uP early history (cont.)
Usage in automobiles ECU
Starting in 1970s. 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!Codesign of Embedded Systems 7
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uP varieties
uController: includes
I/O devices On-board memory. Optimized for digital signal processing.
Digital signal processor (DSP):
Typical embedded word sizes: 8-bit, 16bit, 32-bit.Codesign of Embedded Systems 8
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Application examples
Simple control: front panel of microwave oven, etc Canon EOS 3 has three microprocessors.
32-bit RISC CPU runs autofocus and eye control systems
Analog TV: channel selection, etc. Digital TV: programmable CPUs + hardwired logicCodesign of Embedded Systems 9
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Automotive embedded systems
Todays high-end automobile may have 100 microprocessors:
4-bit uController checks seat belt; uControllers run dashboard devices; 16/32-bit uP controls engine.
Native examples
Peugeot Persia XantiaCodesign of Embedded Systems 10
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BMW 850i brake and stability control system
Anti-lock brake system (ABS):
pumps brakes to reduce skidding.
Automatic stability control (ASC+T):
controls engine to improve stability.ABS was introduced first---needed to interface to existing ABS module.Codesign of Embedded Systems 11
ABS and ASC+T communicate.
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BMW 850i (cont.)sensorbrake ABS hydraulic pump
sensorbrake
brakesensorWinter-Spring 2001
brakesensorCodesign of Embedded Systems 12
Characteristics of embedded systems
Functional requirements
Sophisticated functionality. RT operation. Low manufacturing cost. Low power.
Non-functional requirements
Designed to tight deadlines by small teams.Codesign of Embedded Systems 13
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Functional Requirements
Sophisticated functionality. Often:
have to run sophisticated or multiple algorithms.
Cell phone, laser printer.
provide sophisticated user interfaces. Must finish operations by deadlines.
RT operation
Hard RT: missing deadline causes failure. Soft RT: missing deadline results in degraded performance.
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Many systems are multi-rate: must handle operations at widely varying rates.Codesign of Embedded Systems 14
Non-functional requirements
Many embedded systems are mass-market items that must have low manufacturing costs.
Limited memory, microprocessor power, etc.
Power consumption is critical in batterypowered devices.
Excessive power consumption increases system cost even in wall-powered devices.
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Design teams
Often designed by a small team of designers. Often must meet tight deadlines.
6 month market window is common. Cant miss back-to-school window for calculator.
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Why use uP?
Alternatives:
field-programmable gate arrays (FPGAs), custom logic, etc.
uPs are often very efficient: can use same logic to perform many different functions. uPs simplify the design of families of products.Codesign of Embedded Systems 17
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The performance paradox
uP uses much more logic to implement a function than does custom logic. But uP is often at least as fast:
heavily pipelined; large design teams; aggressive VLSI technology.
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Power
Custom logic is a clear winner for low power devices. Modern uP offer features to help control power consumption. Software design techniques can help reduce power consumption.
Transmetas Crusoe ProcessorCodesign of Embedded Systems 19
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Introduction to Embedded SystemsChallenges in Embedded System Design
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Challenges in embedded system design
How much hardware do we need?
How big is the CPU? Memory? Faster hardware or cleverer software? Turn off unnecessary logic? Reduce memory accesses?
How do we meet our performance deadlines?
How do we minimize power?
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Challenges, etc. (cont.)
Does it really work?
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? Observability, controllability? What is our development platform?
How do we work on the system?
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Introduction to Embedded SystemsDesign Methodology
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Design methodologies
A procedure for designing a system. Understanding your methodology helps you ensure you didnt skip anything. Compilers, software engineering tools, computer-aided design (CAD) tools, etc., can be used to:
help automate methodology steps; keep track of the methodology itself.Codesign of Embedded Systems 24
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Design goals
Functional requirements
Performance.
Overall speed, deadlines.
Functionality and user interface. Manufacturing cost. Power consumption. Other requirements (physical size, etc.)Codesign of Embedded Systems 25
Non-functional requirements
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Levels of abstractionrequirementsspecification architecture component design system integrationWinter-Spring 2001 Codesign of Embedded Systems 26
Top-down vs. bottom-up
Top-down design:
start from most abstract description; work to most detailed. work from small components to big system.
Bottom-up design:
Real design uses both techniques.Codesign of Embedded Systems 27
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Stepwise refinement
At each level of abstraction, we must:
analyze the design to determine characteristics of the current state of the design; refine the design to add detail.
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Requirements
Plain language description of what the user wants and expects to get. May be developed in several ways:
talking directly to customers; talking to marketing representatives; providing prototypes to users for comment.
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Functional vs. non-functional requirements
Functional requirements:
output as a function of input.
Non-functional requirements:
time required to compute output; size, weight, etc.; power consumption; reliability; etc.Codesign of Embedded Systems 30
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Our requirements formname purpose inputs outputs functions performance manufacturing cost power physical size/weight
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Example: GPS moving map requirements
lat: 40 13 lon: 32 19Winter-Spring 2001 Codesign of Embedded Systems 32
Scotch Road
Moving map obtains position from GPS, paints map from local database.
I-78
GPS moving map needs
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.Codesign of Embedded Systems 33
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GPS moving map needs, (cont.)
Physical size/weight: Should fit in hand. Power consumption: Should run for 8 hours on four AA batteries.
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GPS moving map requirements formname purpose inputs outputs functions performance manufacturing cost power physical size/weight GPS moving map consumer-grade moving map for driving power button, two control buttons back-lit LCD 400 X 600 5-receiver GPS; three resolutions; displays current lat/lon updates screen within 0.25 sec of movement $100 cost-of-goodssold 100 mW no more than 2: X 6:, 12 oz.
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Specification
A more precise description of the system:
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.
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GPS specification
Should include:
What is received from GPS; map data; user interface; operations required to satisfy user requests; background operations needed to keep the system running.Codesign of Embedded Systems 37
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Architecture design
What major components go satisfying the specification? Hardware components:
CPUs, peripherals, etc.major programs and their operations.
Software components:
Must take into account functional and non-functional specifications.Codesign of Embedded Systems 38
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GPS moving map block diagramGPS receiver search engine renderer display
database
user interface
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GPS moving map hardware architecturedisplay frame buffer CPU GPS receiver memory
panel I/O
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GPS moving map software architecturepositiondatabase search renderer
pixels
user interface
timer
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Designing hardware and software components
Must spend time architecting the system before you start coding. Architecture components
Some are ready-made, Some can be modified from existing designs Others must be designed from scratch.
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System integration
Put together the components.
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.
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What we learned today
Embedded computers are all around us.
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.Codesign of Embedded Systems 44
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Homework
A simplified ISDN transceiver
part 1: un-encoded transmitter refer to the homework definition page Esfand 6th
Due date:
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