Embedded Systems: Introduction

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Embedded Systems Introduction

• Prof. Santanu Chaudhury
• Prof. Wajeb Gharibi

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Syllabus

• Overview of Embedded Systems Embedded System
  Architecture Processor Examples - ARM, PIC,
  etc. features of digital signal processor SOC,
  memory sub-system, bus structure (PC-104, I2C
  etc.), interfacing protocols (USB, IrDA etc),
  peripheral interfacing testing debugging,
  power management Embedded System Software
  Program Optimization, Concurrent Programming,
  Real-time Scheduling and I/O management
  Networked Embedded Systems special networking
  protocols (CAN, Bluetooth) Applications.

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Books

• Computers as components Principles of Embedded
  Computing System Design, Wayne Wolf, Morgan
  Kaufman Publication, 2000
• ARM System Developers Guide Designing and
  Optimizing System Software, Andrew N. Sloss,
  Dominic Symes, Chris Wright, , Morgan Kaufman
  Publication, 2004.
• Design with PIC Microcontrollers, John B.
  Peatman, Pearson Education Asia, 2002
• The Design of Small-Scale embedded systems, Tim
  Wilmshurst, Palgrave2003
• Embedded System Design, Marwedel, Peter, Kluwer
  Publishers, 2004.
•  

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Definition

• Embedded system any device that includes a
  computer but is not itself a general-purpose
  computer.
• Hardware and Software - part of some larger
  systems and expected to function without human
  intervention
• Respond, monitor, control external environment
  using sensors and actuators

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Embedding a computer
Simplest model
output
analog
input
CPU
analog
mem
Embedded computer
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Examples

• Personal digital assistant (PDA).
• Printer.
• Cell phone.
• Automobile engine, brakes, dash, etc.
• Television.
• Household appliances.
• Surveillance Systems.

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Product Palm Vx handheld. Microprocessor
32-bit Motorola Dragonball EZ.
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Product Motorola i1000plus iDEN Multi-Service
Digital Phone.Microprocessor Motorola 32-bit
MCORE.
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Application examples

• Simple control front panel of microwave oven,
  etc.
• Camera Canon EOS 3 has three microprocessors.
• 32-bit RISC CPU runs auto-focus
• Analog TV channel selection, etc.
• Digital TV Decompression, Descrambling, etc.

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Automotive embedded systems

• Todays high-end automobile may have 100
  microprocessors
• 4-bit microcontroller checks seat belt
• microcontrollers run dashboard devices
• 16/32-bit microprocessor controls engine.

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ExampleAutomobile
sensor
sensor
brake
brake
hydraulic pump
Automated Braking System
brake
brake
sensor
sensor
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Characteristics of embedded systems

• Sophisticated functionality.
• Real-time operation (always?).
• Low manufacturing cost.
• Application dependent Processor (?)
• Restricted Memory
• Low power.
• Power consumption is critical in battery-powered
  devices.
• Excessive power consumption increases system cost
  even in wall-powered devices.

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Manufacturing Cost

• Manufacturing cost has different components.
• Non-recurring Engineering cost for design and
  development
• cost of production and marketing each unit
• Best technology choice will depend on the number
  of units we plan to produce

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Real-time operation

• Must finish operations by deadlines.
• Hard real time missing deadline causes failure.
• Soft real time missing deadline results in
  degraded performance.
• Many systems are multi-rate must handle
  operations at widely varying rates.

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Application dependent requirements

• Fault-tolerance
• Continue operation despite hardware or software
  faults
• Safe
• Systems to avoid physical or economic damage to
  person or property

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More Features

• Dedicated systems
• Predefined functionality accordingly hardware
  and software designed
• Programmability rarely used during lifetime of
  the system
• Real-time, fault-tolerant, safe

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More Examples
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Product Programmable Digital Thermostat. Micropr
ocessor 4-bit
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Product Vending machine.
Web-enabled Cash-less Vending machine
Microprocessor 8-bit Motorola 68HC11.
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Product Automatic toothbrush. Microprocessor
8-bit Zilog Z8.
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Product NASA's Mars Sojourner Rover.Microproces
sor 8-bit Intel 80C85.
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Product GPS Receiver.Microprocessor 16-bit.
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Product MP3 Player. Microprocessor 32-bit
RISC.
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Product DVD player. Microprocessor 32-bit
RISC.
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Product Sony Aibo ERS-110 Robotic Dog.
Microprocessor 64-bit MIPS RISC.
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Types of Embedded System

• Similar to General Computing
• PDA, Video games, Set-top boxes, automatic teller
  machine
• Control Systems
• Feed-back control of real time systems
• Vehicle engines, flight control, nuclear reactors
• Signal Processing
• Radar, Sonar, DVD players
• Communication and Networking
• Cellular phones, Internet appliances

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Nature of System Functions

• Control laws
• Sequencing Logic
• Signal Processing
• Application Specific Interfacing
• Fault Response

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Architecture
More Complete Model
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Implementing Embedded System

• Hardware
• Processing Element
• Peripherals
• Input Output Devices
• Interfacing Sensors Actuators
• Interfacing Protocols
• Memory
• Bus
• Software
• System Software
• Application

Hardware Software Partitioning of tasks
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Hardware Evolution

• Systems-on-Chip
• Application Specific Processors
• DSP
• General Purpose Microprocessors
  Micro-controllers

Faster Clock Rate Higher Degree of Integration
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Software

• Programs must be logically and temporally correct
• Must deal with inherent physical concurrency
• Reactive systems
• Reliability and fault-tolerance are critical
  issues
• Application Specific and single purpose

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Multi-Tasking and Concurrency

• Embedded systems need to deal with several inputs
  and outputs and multiple events occurring
  independently.
• Separating tasks simplifies programming, but
  requires somehow switching back and forth among
  different tasks (multi-tasking).
• Concurrency is the appearance of simultaneous
  execution of multiple tasks.

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Example Concurrency in Temperature Controller
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Challenges in embedded system design

• How much hardware do we need?
• What is word size of the CPU? Size of Memory?
• How do we meet our deadlines?
• Faster hardware or cleverer software?
• How do we minimize power?
• Turn off unnecessary logic? Reduce memory
  accesses?

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Embedded System Design
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Design goals

• Performance.
• Overall speed, deadlines.
• Functionality and user interface.
• Manufacturing cost.
• Power consumption.
• Other requirements (physical size, etc.)

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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.

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Design Development Process
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Top-down vs. bottom-up

• Top-down design
• start from most abstract description
• work to most detailed.
• Bottom-up design
• work from small components to big system.
• Real design uses both techniques.

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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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Concluding Remarks

• 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.