Networking for Embedded Systems

1
Introduction to Embedded Systems
2
Introduction

• What are embedded systems?
• What makes them different?
• Real time operation
• Many sets of constraints on designs
• Challenges in embedded computing system design.
• Design methodologies.

3
Definition

• Embedded system any device that includes a
  programmable computer but is not itself a
  general-purpose computer.
• Computer purchased as part of some other piece of
  equipment
• Typically dedicated software (may be user-
  customizable)
• Often replaces previously electromechanical
  components
• Often no real keyboard
• Often limited display or no general- purpose
  display device dont need all the
  general-purpose bells and whistles.

4
What is an embedded system
5
Examples
Office systems and mobile equipment Building systems Manufacturing and Process Control
Answering machines Copiers Faxes Laptops and notebooks Mobile Telephones PDAs, Personal organisers Still and video cameras Telephone systems Time recording systems Printer Microwave Air conditioning Backup lighting and generators Building management systems CTV systems Fire Control systems Heating and ventilating systems Lifts, elevators, escalators Lighting systems Security systems Security cameras Sprinkler systems Automated factories Bottling plants Energy control systems Manufacturing plants Nuclear power stations Oil refineries and related storage facilities Power grid systems Power stations Robots Switching systems Water and sewage systems
6
Examples
Transport Communications Other equipment
Aeroplanes Trains Buses Marine craft Jetties Automobiles Air Traffic Control Signalling Systems Radar Systems Traffic Lights Ticketing machines Speed cameras, Radar speed detectors Telephone systems Cable systems Telephone switches Satellites Global Positioning System Automated teller systems Credit card systems Medical Imaging equipment Domestic Central Heating control VCRs
7
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.

8
BMW 850i brake and stability control system

• Anti-lock brake system (ABS) pumps brakes to
  reduce skidding.
• Automatic stability control (ASCT) controls
  engine to improve stability.
• ABS and ASCT communicate.
• ABS was introduced first---needed to interface to
  existing ABS module.

9
BMW 850i, contd.
sensor
sensor
brake
brake
hydraulic pump
ABS
brake
brake
sensor
sensor
10
Embedded systems rule the market place

• 80 Million PCs vs. 3Billion Embedded CPUs
  Annually
• Embedded market growing PC market mostly
  saturated

11
Why are embedded systems different from desktop
computers ?
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Four General Embedded Systems Types
General Computing Applications similar to
desktop computing, but in an embedded package
Video games, set- top boxes, wearable computers,
automatic tellers Control Systems Closed- loop
feedback control of real- time system Vehicle
engines, chemical processes, nuclear power,
flight control Signal Processing Computations
involving large data streams Radar, Sonar,
video compression Communication Networking
Switching and information transmission
Telephone system, Internet
13
Characteristics of an embedded system

• Real-Time Operation
• Reactive computations must occur in response
  to external events
• Correctness is partially a function of time
• Small Size, Low Weight
• Hand- held electronics and Transportation
  applications -- weight costs money
• Low Power
• Battery power for 8 hours (laptops often last
  only 2 hours)
• Harsh environment
• Heat, vibration, shock, power fluctuations, RF
  interference, lightning, corrosion
• Safety- critical operation
• Must function correctly and Must not function
  in correctly
• Extreme cost sensitivity
• . 05 adds up over 1,000, 000 units

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Embedding a computer
output
analog
input
CPU
analog
mem
embedded computer
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Why use microprocessors?

• Microprocessors simplify the design of families
  of products.
• Microprocessors are often very efficient can use
  same logic to perform many different functions,
  but Microprocessors use much more logic to
  implement a function than does custom logic.
• Alternatives field-programmable gate arrays
  (FPGAs), ASICs, custom logic, etc.
• What about MicroControllers or DSPs.
• Custom logic is a clear winner for low power
  devices.

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An Embedded Control System Designers View
17
A Customer View
18
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.

19
Challenges in embedded system design

• How much hardware do we need?
• How big is the CPU? 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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Challenges, etc.

• 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?
• How do we work on the system?
• Observability, controllability?
• What is our development platform?

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Embedded System Designer Skill Set
Appreciation for multi- disciplinary nature of
design Both hardware software skills
Understanding of engineering beyond digital
logic Ability to take a project from
specification through production Communication
teamwork skills Work with other disciplines,
manufacturing, marketing Work with customers to
understand the real problem being solved Make a
good presentation even better -- write trade
rag articles And, by the way, technical skills
too Low level Microcontrollers, FPGA/ ASIC,
assembly language, A/ D, D/ A High level
Object- oriented Design, C/ C, Real Time
Operating Systems Meta level Creative
solutions to highly constrained problems Likely
in the future Unified Modeling Language,
embedded networks Uncertain future Java,
Windows CE
22
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.

23
Design goals

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

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Levels of abstraction
requirements
specification
architecture
component design
system integration
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Our requirements form
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Example GPS moving map requirements

• Moving map obtains position from GPS, paints map
  from local database.

I-78
Scotch Road
lat 40 13 lon 32 19
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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.

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GPS moving map needs, contd.

• 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 form
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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.

31
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.

32
Architecture design

• What major components go satisfying the
  specification?
• Hardware components
• CPUs, peripherals, etc.
• Software components
• major programs and their operations.
• Must take into account functional and
  non-functional specifications.

33
GPS moving map block diagram
display
GPS receiver
search engine
renderer
database
user interface
34
GPS moving map hardware architecture
CPU
display
frame buffer
GPS receiver
memory
panel I/O
35
GPS moving map software architecture
database search
renderer
pixels
position
timer
user interface
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Designing hardware and software components

• Must spend time architecting the system before
  you start coding.
• Some components are ready-made, some can be
  modified from existing designs, others must be
  designed from scratch.

37
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.

38
Summary

• 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.
• References
• Overheads for Computers as Components,
  W.Wolf.Morgan Kaufman.
• Embedded Systems in the Real World, Phillip
  Koopman. Carnegie Mellon University.