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					  Embedded Systems

Controlling the real world with
          computers
                    Overview
•   Definition / Examples
•   Range
•   Development
•   Programming
•   Hardware Vs Software
    – Electronics
    – Engineering
• Analog and Digital
                  Definition
• An embedded computer is a computer that
  is part of some machine or equipment.
• Examples
  –   Microwave Oven
  –   XRay machine
  –   Anti-Lock brakes
  –   Guided Missile Controller
  –   Ship guidance system
Analog

     Computers that interact and control the
  real world, move between messy reality and
                tidy computers

                     Digital
           Examples House
•   TV
•   VCR
•   CD music player
•   DishWasher
•   Washing Machine
•   Radio Alarm
•   Toys
               Examples cars
•   AntiLock brakes
•   Ignition Control
•   Emission Control
•   Digital Dashboard
•   Intelligent HeadLights
    – automatically dip when they detect on-coming
      traffic
          Examples Medicine
•   X-Ray Controller
•   Blood diagnosis
•   Magnetic Resonance Imaging (MRI)
•   CAT scanners
•   Implanted Heart Monitors
•   DNA analysis
           Examples Systems
•   Air Traffic Control
•   Process Control (manage factory)
•   Car Traffic Control (see link)
•   Traffic Lights control
•   Telecommunications systems
                     and ...
•   Digital watches
•   Mobile Phones
•   ATMs DrinkLink
•   Robots
    – Mars Explorer
    – Landmine clearing
• GPS
                Huge Range
• Numbers
  – Counting all Personnel computers in existance:
    50 Million
  – Number of embedded systems in one year: 2
    billion
• Power
  – Microprocessor 4-bit, 8 bit, 16 bit, 32 bit
  – Memory 1K – 1 M – 1 G
                   History
• 1974 The Microprocessor invented
  – (CPU on a chip), Intel's 4004
  – Led gradually to the Pentium
• Equipment makers realised they could use
  this in their machines.
                Development
• Processing Power (word size, MIPS)
    – Engineers calculate required processing power
•   Memory (ROM and RAM)
•   Development Cost
•   Number of units
•   Expected Lifetime
•   Reliability
Criterion     Low             Middle          High
Processor     4 or 8 bit      16 bit          32 or 64 bit
Memory        < 16 KB         64 KB to 1 MB > 1 MB
Development   < $100,000      $100,000 to     > $1,000,000
Cost                          $1,000,000
Production    < $10           $10 to $1,000   > $1,000
Cost
Number of     < 100           100 – 10,000    > 10,000
units
Expected      days – months   Years           decades
Lifetime
Reliability   May             Must work       must be fail-
              occasionally    reliably        proof
              fail
      Programming Embedded
             Systems
• Need to have knowledge of
  hardware/electronics
• Need to operate in constrained environment
  – No or simple Operating System
  – Low memory, slow processor
• Infinite Loop
  – E.g. anti lock brakes
• Reliability
 Programming Small Embedded
          Systems
• No hard disk, where does the code go?
  – EPROM
• No monitor, how can you see it?
• Use a standard computer to develop, and
  put the program onto EPROM.
• No monitor, how can you debug it?
  – detective work. And advanced tools (e.g.
    Oscilloscope)
        HardWare/Electronics
• to control Electriconic equipment
  – e.g. Motors
• to read Electronic sensors
  – Temperature sensor
  – Light sensor
  – GPS system
            Analog / Digital
• Real World is analog (continuously
  varying)
• Computer World digital. Values only have
  descrete quantities
• Reading a temperature sensor, need an
  analog to digital convertor.
• Controlling an analog motor, need a digital
  to analog convertor.
              Analog / Digital

Temperature
Sensor
                  A/D    Microprocessor




                             D/A

          Motor

				
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