Embedded system and Development

Rajani Bhandari

Senior Project Manager

HCL Technologies

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Topics

Introduction to Embedded systemsHow embedded is different from PCDesign constraints in embedded softwareExamples of Embedded applicationsSoftware development cycle in embedded

applicationsArchitecture of embedded applications.Development Guidelines

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Introduction to Embedded systems

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Introduction of Embedded system

An embedded system is a combination of computer hardware and software accomplished with additional mechanical or other parts designed to perform a

Embedded software is used in real life like cell phone, pager, digital camera, portable video games, Calculators, oven, washing machine etc.

: :Embedded systems often must cost just a few dollars, must be sized to fit on a single chip, must perform fast enough to process data in real-time, and must consume minimum power to extend battery life. High user expectations in terms of performance

Specific Function

In every electronic device

Limited Resources

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Connect via peripherals

Embedded Systems talk with the outside world via peripherals, such as:

Serial Communication Interfaces (SCI): RS-232, RS-422, RS-485 etc.

Universal Serial Bus (USB) Multi Media Cards (SD Cards, Compact Flash etc.) Networks: Ethernet, Lon Works, etc. Analog to Digital/Digital to Analog (ADC/DAC)

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Examples In Your Daily Life

…wake up …

…have breakfast …

…set home safety system …

…get into your car …

…on your way to your office…

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Examples In Your Daily Life(cont’)

…in Your office…

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Examples In Your Daily Life(cont’)

…Back Home …

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A “short list” of embedded systems

And the list goes on and on

Anti-lock brakes

Auto-focus cameras

Automatic teller machines

Automatic toll systems

Automatic transmission

Avionic systems

Battery chargers

Camcorders

Cell phones

Cell-phone base stations

Cordless phones

Cruise control

Curbside check-in systems

Digital cameras

Disk drives

Electronic card readers

Electronic instruments

Electronic toys/games

Factory control

Fax machines

Fingerprint identifiers

Home security systems

Life-support systems

Medical testing systems

Modems

MPEG decoders

Network cards

Network switches/routers

On-board navigation

Pagers

Photocopiers

Point-of-sale systems

Portable video games

Printers

Satellite phones

Scanners

Smart ovens/dishwashers

Speech recognizers

Stereo systems

Teleconferencing systems

Televisions

Temperature controllers

Theft tracking systems

TV set-top boxes

VCR’s, DVD players

Video game consoles

Video phones

Washers and dryers

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Embedded Vs PC

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Difference - Embedded and PC

An embedded system have defined process and function whereas PC is generic

Computer system can be manufactured with general requirement and the manufacturer does not know what the customer will do, while embedded system is Application Specific .

Numerous embedded system make up the computer Tightly constrained: Embedded system design is tightly constraint.

Important factors to be considered are as cost, size, performance, and power.

Reactive and real-time: Continually reacts to changes in the system’s environment. Must compute certain results in real-time without delay

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Difference - Embedded and PC App- Coding

Embedded

Closer to the Hardware Use native data types

Fewer System ResourcesNo Operating SystemMore efficient algorithms

Higher frequency = higher power

PC Application

Abstracted Hardware

Plenty of ResourcesHas an Operating System

Embedded vs PC App - Testing

EmbeddedDebugging is very difficultEmulators or simulators are

required at the time of development

Usually a simple interfaceOften involves extra hardware

PC ApplicationUsually simple to get a basic

debug outputCan be very sophisticated

testing

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Design challenges

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Design Challenges

Cost Unit Cost- Cost of manufacturing each unitNON recurring Engg Cost: Monetary cost of designing the system

The physical space required by the system and measured in bytes for software and gates for hardware.

Execution cost

The amount of power consumed which determines life time of battery. Maximum Source of power : Antennas – Bluetooth, Wi-Fi, RF . Digital displays

Time-to market constraint. Hardware and software development goes in parallelMissing this window – significant loss

Size

Performance

Power

Time Line

Flexiblity Change functionality without heavy NRE cost. Code should be maintainable

Design Metrics

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SizePerformance

Power

NRE cost

Improving one often leads to a degradation in another

Examples of embedded system

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Car cruise controllers reacts to brake sensor and speed

It Compute acceleration and deceleration System

Failure

Delayed computation

Mobile evolution – impact on design matrices

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1980 analog cellular technologyDigital Mobile Communication 1990

Wide Band Mobile Communication 2000

Broadband Mobile Communication 2010

Factors Affected Cost Design Complexity Size Performance Power Consumption

Digital camera- An embedded system example

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Microcontroller

CCD preprocessor Pixel coprocessorA2D

D2A

JPEG codec

DMA controller

Memory controller ISA bus interface UART LCD ctrl

Display ctrl

Multiplier/Accum

Digital camera chip

lens

CCD

Time to Market- Design challenge

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Re

ven

ue

s ($

)

Time (months)

Market window:Period during which the product would have highest salesAverage time-to-market constraint is about 8 months. Delays can be costly.

Design Challenge

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After decision of mass production of embedded system and a small bug found at that time may be very expensive. Even a 1 day delay can cost equivalent ……… Any Guesses??

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Software Development Life cycle

Embedded system Life Cycle

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Development of Hardware and software goes in parallel which is a major challenge.

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Architecture of embedded application

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Architecture of embedded system

Application Software

Operating System

Hardware

Hardware architecture

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Development Guidelines

Guidelines for embedded application development

Power: Optimal Power usage Transferring data on Air

Reset Device Design for the restoration of configuration

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Memory Guidelines Data Type Life time of variable Memory allocation on heap or stack. Memory should be freed if

not required Stateless components Logging and Instrumentation

User Interface Simple UI Hour glass as visual indicator for blocking operation Resolution and LCD size Design for usability by supporting for touch, stylus driven, 5-way Do not update ui frequently

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Key rules for best coding

Maintainability Reliability Efficiency

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Maintenance problems

Unstructured code

Insufficient domain knowledge

Insufficient documentation

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Efficiency

Optimal Utilization of ResourcesDesign and architecture of softwareMemory management

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Coding standards

Readability of code Size of Function Variable naming Code Commenting Long methods Private, public or local variable naming rule Formatting and indentation

Complexity of code Multiple return statement Nested loop or conditions

Uninitialized variables

Duplicate code prone to errors

Avoid Hard Coding

Use of enum to indicate discrete values

Multilingual support

Reusable code or shared libraries

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Sample code

// This class provides the functionality // of adding numbers#include <iostream>using namespace std;

class Adder{ public: // constructor Adder(int i = 0) { total = i; } // interface to outside world // Adds a number and calculates

total void addNum(int number) { total += number; } // interface to outside world //get sum total result int getTotal() { return total; }; private: // hidden data from outside world int total;};

int main( ){ Adder a; a.addNum(10); a.addNum(20); a.addNum(30);

cout << "Total " << a.getTotal() <<endl; return 0;}

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Which one is better

bool MyApplication::ReportGenerator::GenerateReport() { bool returnValue = false; if (isAdmin() && isConditionOne() && isConditionTwo() && isConditionThree()) { returnValue = generateReport(); } return returnValue; }

bool MyApplication::ReportGenerator::GenerateReport()

{ if ( ! isAdmin () ) return false ;

if ( ! isConditionOne () ) return false ;

if ( ! isConditionTwo () ) return false ;

if ( ! isConditionThree() ) return false ;

return generateReport() ;

}

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Sample Code

function do_stuff() {// …

if (is_writable($folder)) { if ($fp = fopen($file_path,'w')) {

if ($stuff = get_some_stuff()) {

if (fwrite($fp,$stuff)) {

// ... } else {

return false;

}

} else {return false;

}} else { return false;}

} else {return false;

}}

function do_stuff() {

// ...

if (!is_writable($folder)) {return false;}

if (!$fp = fopen($file_path,'w')) {return false;}

if (!$stuff = get_some_stuff()) {return false;}

if (fwrite($fp,$stuff)) {// ...

} else {return false;}

}

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Quality software On-time to bring customer Delight

Good Coding and Design brings >>>

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Questions ??

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Thanks!!