Embedded systems

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““EMBEDDED SYSTEM”EMBEDDED SYSTEM”

NAME = MINAL KHOPADET.E (I.T)

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EMBEEDED SYSTEMSEMBEEDED SYSTEMS

CONTENTSCONTENTS IntroductionIntroduction DefinitionDefinition What is an embedded What is an embedded

computer?computer? Uses of embedded Uses of embedded

systemsystem Examples of embedded Examples of embedded

systemsystem CharacteristicsCharacteristics CPU platformsCPU platforms ToolsTools ResourcesResources

Reliability & Real time Reliability & Real time issuesissues

High vs. Low volumeHigh vs. Low volume Embedded software Embedded software

architecturesarchitectures Fixed point arithmeticFixed point arithmetic Exotic custom OSExotic custom OS Additional software Additional software

componentscomponents Downfalls of embedded Downfalls of embedded

computerscomputers Popularity of embedded Popularity of embedded

systemsystem

Introduction of embedded Introduction of embedded systemsystem

An embedded system is a special-purpose An embedded system is a special-purpose computer system designed to perform one computer system designed to perform one or a few dedicated functions.or a few dedicated functions.

It is usually embedded as part of a It is usually embedded as part of a complete device including hardware and complete device including hardware and mechanical parts.mechanical parts.

““embedded system” is not an exactly embedded system” is not an exactly defined term , as many systems have defined term , as many systems have some element of programmability.some element of programmability.

Definition of embedded systemDefinition of embedded system

An embedded system can be defined as a An embedded system can be defined as a control system or computer system control system or computer system designed to perform a specific task.designed to perform a specific task.

An embedded system can also be defined An embedded system can also be defined as a single purpose computer.as a single purpose computer.

Most embedded systems are time critical Most embedded systems are time critical applications meaning that the embedded applications meaning that the embedded system is working in an environment system is working in an environment where timing is very important.where timing is very important.

What is an embedded computer?What is an embedded computer?

An embedded computer is frequently a computer An embedded computer is frequently a computer that is implemented for a particular purpose.that is implemented for a particular purpose.

In general, an embedded systemIn general, an embedded system Is a system built to perform its duty, completely or Is a system built to perform its duty, completely or

partially independent of human intervention.partially independent of human intervention. Is specially designed to perform a few tasks in the Is specially designed to perform a few tasks in the

most efficient way.most efficient way. Interacts with physical elements in our environment, Interacts with physical elements in our environment,

viz. controlling and driving a motor, sensing viz. controlling and driving a motor, sensing temperature, etc.temperature, etc.

Uses of embedded systemUses of embedded system From an implementation point of view, there is a major From an implementation point of view, there is a major

difference between a computer and an embedded difference between a computer and an embedded system.system.

Embedded systems are often required to provide Embedded systems are often required to provide Real-Real-Time responseTime response..

A Real-Time system is defined as a system whose A Real-Time system is defined as a system whose correctness depends on the timeliness of its response.correctness depends on the timeliness of its response.

In technical terminology, In technical terminology, Real-Time system Real-Time system can be can be classified as:classified as: Hard Real -Time systemsHard Real -Time systems Soft Real-Time systemsSoft Real-Time systems Hybrid Real-Time systemsHybrid Real-Time systems

Examples of embedded systemExamples of embedded system

Telecommunication systems employ embedded Telecommunication systems employ embedded system from telephone switches for the network system from telephone switches for the network to mobile phones at the end user.to mobile phones at the end user.

Consumer electronics include personal digital Consumer electronics include personal digital assistants (PDAs), mp3 players, digital cameras, assistants (PDAs), mp3 players, digital cameras, DVD players, video game consoles, GPS DVD players, video game consoles, GPS receivers & printers.receivers & printers.

Many household appliances, such as microwave Many household appliances, such as microwave ovens, washing machines and dishwashers are ovens, washing machines and dishwashers are including embedded systemsincluding embedded systems

Examples of embedded systemExamples of embedded system

Transportation system from flight to Transportation system from flight to automobiles increasingly use embedded automobiles increasingly use embedded systemssystems

Medical equipments uses embedded Medical equipments uses embedded system for vital signs monitoring, system for vital signs monitoring, electronic stethoscopes for amplifying electronic stethoscopes for amplifying sounds and various medical imaging sounds and various medical imaging (PET, SPECT, CT, MRI) for non-invasive (PET, SPECT, CT, MRI) for non-invasive internal inspections internal inspections

Why study Embedded system?Why study Embedded system?

Embedded systems are playing important Embedded systems are playing important roles in every day life, even though they roles in every day life, even though they might not necessarily be visible.might not necessarily be visible.

Recent poll data shows that embedded Recent poll data shows that embedded computer systems currently outnumber computer systems currently outnumber humans in USA.humans in USA.

Embedded system is rapidly growing Embedded system is rapidly growing industry where growth opportunities are industry where growth opportunities are numerous. numerous.

CharacteristicsCharacteristics

Embedded systems are designed to do some Embedded systems are designed to do some specific task, rather than be a general-purpose specific task, rather than be a general-purpose computer for multiple tasks.computer for multiple tasks.

Many embedded systems are small, Many embedded systems are small, computerized parts within a large device that computerized parts within a large device that serves a more general purpose.serves a more general purpose.

The program instructions written for embedded The program instructions written for embedded systems are referred to as firmware, and are systems are referred to as firmware, and are stored in read-only or flash memory chips. stored in read-only or flash memory chips.

CPU platforms Ready made CPU platforms Ready made computer boards computer boards

Embedded Embedded

processors processors

are broken into two are broken into two categoriescategories• Ordinary Ordinary

microprocessor (mP)microprocessor (mP)• Microcontroller (mC)Microcontroller (mC)

Which have many moreWhich have many more

peripherals on chip,peripherals on chip,

reducing cost and size. reducing cost and size.

PC/104 are PC/104+ PC/104 are PC/104+ are ready mode are ready mode computer boards computer boards intended for small, intended for small, low-volume low-volume embedded & embedded & buggerized systemsbuggerized systems

TOOLSTOOLS

As for other software, embedded system As for other software, embedded system designers use compilers, assemblers, and designers use compilers, assemblers, and debuggers to develop embedded system debuggers to develop embedded system software.software.

They may also use some more specific They may also use some more specific tools astools asDebugger or emulatorsDebugger or emulatorsUtilities to add a checksum or CRC to a Utilities to add a checksum or CRC to a

program. program.

Custom compilers and linkers.Custom compilers and linkers.An embedded system may have it’s own An embedded system may have it’s own

special language or design tool, or add special language or design tool, or add enhancements to an existing language such enhancements to an existing language such as Forth or Basic.as Forth or Basic.

Another alternative is to add a Real-time Another alternative is to add a Real-time operating system or Embedded operating operating system or Embedded operating system, which may have DSP capability like system, which may have DSP capability like DSP nano RTOS. DSP nano RTOS.

ResourcesResources

To save costs, embedded systems have the To save costs, embedded systems have the cheapest processors. This means programs cheapest processors. This means programs need to be written as efficient as possible.need to be written as efficient as possible.

For same reason, embedded systems usually For same reason, embedded systems usually have the least memory. This means their have the least memory. This means their algorithms must be memory efficient & can’t algorithms must be memory efficient & can’t afford to leak memory.afford to leak memory.

Most embedded processors do not have Most embedded processors do not have hardware FPUs (Floating-Point Processing Unit)hardware FPUs (Floating-Point Processing Unit)

Reliability & Real-Time issuesReliability & Real-Time issues

Specific reliability issues may include :Specific reliability issues may include :Embedded systems frequently control Embedded systems frequently control

hardware, and must be able to respond to hardware, and must be able to respond to them in real time. Failure to do so could cause them in real time. Failure to do so could cause inaccuracy in measurements or even damage inaccuracy in measurements or even damage hardware.hardware.

The system cannot safely be shut down for The system cannot safely be shut down for repair, or it is too inaccessible to repair. repair, or it is too inaccessible to repair. Examples= space systems, undersea cables, Examples= space systems, undersea cables, navigation beacons, bore-hole systems. navigation beacons, bore-hole systems.

The system must be kept running for safety The system must be kept running for safety reasons. ”LIMP MODES” are less tolerable. reasons. ”LIMP MODES” are less tolerable. Often backups are selected by an operator. Often backups are selected by an operator. Examples= reactor control systems, train Examples= reactor control systems, train signals, aircraft navigationsignals, aircraft navigation

The system will lose large amount of money The system will lose large amount of money when shut down :when shut down :

Examples=Telephone switches, bridge & Examples=Telephone switches, bridge & elevator control, fund transfer & market elevator control, fund transfer & market making, automated sales and services.making, automated sales and services.

High vs Low volumeHigh vs Low volume

For high volume For high volume systems minimizing systems minimizing cost is usually the cost is usually the primary design primary design consideration.consideration.

Engineers typically Engineers typically select hardware that select hardware that is just “Good Enough” is just “Good Enough” to implement the to implement the necessary functions. necessary functions.

For low –volume or For low –volume or prototype embedded prototype embedded systems general systems general purpose computers purpose computers may be adapted by may be adapted by limiting the programs limiting the programs or by replacing the or by replacing the operating system with operating system with a real-time operating a real-time operating system. system.

Embedded software architecturesEmbedded software architectures

Simple Control Loop =Simple Control Loop = In this design, the software simply has a loop. In this design, the software simply has a loop.

The loop calls each of which manage a part of The loop calls each of which manage a part of the hardware or software.the hardware or software.

Interrupt Controlled System =Interrupt Controlled System =Some embedded systems are predominantly Some embedded systems are predominantly

interrupt controlled.interrupt controlled.This kinds of systems are used if event This kinds of systems are used if event

handler need low latency and the event handler need low latency and the event handlers are short and simple. handlers are short and simple.

This task is not very sensitive to unexpected This task is not very sensitive to unexpected delays.delays.

This method brings the system close to a This method brings the system close to a multitasking kernel with discrete processes.multitasking kernel with discrete processes.

Non-preemptive multitasking =Non-preemptive multitasking =• A non-preemptive multitasking system is very A non-preemptive multitasking system is very

similar to the simple control loop scheme similar to the simple control loop scheme except that the loop is hidden in an API.except that the loop is hidden in an API.

The advantages and disadvantages are similar The advantages and disadvantages are similar to the loop control loop, except that adding to the loop control loop, except that adding

new software is easier by writing a new task or new software is easier by writing a new task or adding to the queue-interpreter.adding to the queue-interpreter.

• Preemptive multitasking =Preemptive multitasking =• In this type, a low-level piece of code switches In this type, a low-level piece of code switches

between tasks or threads based on a timer between tasks or threads based on a timer connected to an interrupt.connected to an interrupt.

• In this level system is generally considered to In this level system is generally considered to have an “Operating System” kernel.have an “Operating System” kernel.

Microkernels and exokernels =Microkernels and exokernels =A microkernel is a logical step up from a real-A microkernel is a logical step up from a real-

time OS.time OS.Operating system kernel allocates memory Operating system kernel allocates memory

and switches the CPU to different threads of and switches the CPU to different threads of execution.execution.

Microkernel succeed when the task switching Microkernel succeed when the task switching and inter-task communication is fast, & fail and inter-task communication is fast, & fail when they are slow. when they are slow.

Monolithic kernels =Monolithic kernels = In this case a relatively large kernel with In this case a relatively large kernel with

sophisticated capabilities are adapted to suit sophisticated capabilities are adapted to suit an embedded environment.an embedded environment.

This gives, an environment similar to a This gives, an environment similar to a desktop operating system therefore very desktop operating system therefore very productive for development.productive for development.

It requires more hardwareIt requires more hardwareThese kernels can be less predictable and These kernels can be less predictable and

reliable.reliable.Examples of monolithic kernels are Examples of monolithic kernels are

Embedded Linux and Windows CE.Embedded Linux and Windows CE.

Fixed-Point ArithmeticFixed-Point Arithmetic

Some embedded microprocessors may have an Some embedded microprocessors may have an external unit for performing floating point external unit for performing floating point arithmetic (FPU) but most low-end embedded arithmetic (FPU) but most low-end embedded system have no FPU.system have no FPU.

As a result, many embedded projects enforce a As a result, many embedded projects enforce a no floating point rule on their programmers.no floating point rule on their programmers.

A common technique used to avoid the need for A common technique used to avoid the need for floating point number is to change the floating point number is to change the magnitude of data stored in your variable so you magnitude of data stored in your variable so you can utilize fixed point mathematics.can utilize fixed point mathematics.

Exotic custom operating Exotic custom operating systemssystems

A small fraction of embedded systems A small fraction of embedded systems requires safe, timely, reliable or efficient requires safe, timely, reliable or efficient behavior unobtainable with the one of the behavior unobtainable with the one of the above architectures.above architectures.

In such cases this operating system builds In such cases this operating system builds a software to this kind of situation. a software to this kind of situation.

These components consist of networking These components consist of networking protocol stacks like CAN, TCP/IP, FTP, protocol stacks like CAN, TCP/IP, FTP, HTTP and HTTPS. HTTP and HTTPS.

It also consist of storage capabilities like It also consist of storage capabilities like FAT and Flash memory management FAT and Flash memory management systems.systems.

In the RTOS category, the availabilities of In the RTOS category, the availabilities of the additional software components the additional software components depends upon the commercial offering.depends upon the commercial offering.

Additional software componentsAdditional software components

Downfalls of embedded systemDownfalls of embedded system

An embedded system is frequently programmed An embedded system is frequently programmed once, and the software cannot be patched.once, and the software cannot be patched.

They are often installed in a system for which They are often installed in a system for which unreliability is not an option.unreliability is not an option.

Embedded system needs to be tested & Embedded system needs to be tested & analyzed extensively.analyzed extensively.

The memory capacity & processing power is The memory capacity & processing power is limited.limited.

Some embedded systems run a scaled down Some embedded systems run a scaled down version of operating system called an RTOS version of operating system called an RTOS (real-time operating system)(real-time operating system)

Advantages of embedded Advantages of embedded systemsystem

Ports to common embedded chip sets are Ports to common embedded chip sets are available.available.

They permit re-use of publicly available code for They permit re-use of publicly available code for Device Drivers, Web Services, Firewalls, and Device Drivers, Web Services, Firewalls, and other code.other code.

Distribution can be configured to unneeded Distribution can be configured to unneeded functionality & save the expense of the memory.functionality & save the expense of the memory.

Running application code in user mode is more Running application code in user mode is more reliable, easier to debug therefore the reliable, easier to debug therefore the development process is easier and the code development process is easier and the code

Advantages of embedded Advantages of embedded systemsystem

is more portable.is more portable.• Many embedded systems lack the tight Many embedded systems lack the tight

real-time requirements of a control system. real-time requirements of a control system. (e.g. Embedded Linux)(e.g. Embedded Linux)

• Features requiring faster response than Features requiring faster response than can be guaranteed can often be placed in can be guaranteed can often be placed in hardware.hardware.

• Many RTOS systems have a per-unit cost. Many RTOS systems have a per-unit cost.

ReferencesReferences

http://www.netrino.com/Embedded-http://www.netrino.com/Embedded-system/Glossarysystem/Glossary

http://www.embedded.com/underhehoodhttp://www.embedded.com/underhehoodhttp://www.usenix.org/publications/login/http://www.usenix.org/publications/login/

2007-12/pdfs/hesier.pdf2007-12/pdfs/hesier.pdfhttp://en.wikibooks.org/wiki/embedded http://en.wikibooks.org/wiki/embedded

systems/Embedded system Basicssystems/Embedded system Basics^Yashavant Kanetkar “Go Embedded”^Yashavant Kanetkar “Go Embedded”

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