EMBEDDED SYSTEMS - Nanocdac

                                  

INTRODUCTION:

To define an Embedded system we have lot of definitions such as:

             An Embedded system is one that has computer hardware with software

embedded in it as one of its important components.

             An Embedded system is a special-purpose system in which the computer is

completely encapsulated by the device it controls.

             An Embedded system can also be defined as a computer system designed for

specific control functions within a larger system, often with real-time computing

constraints.

           An Embedded device includes both hardware and mechanical parts.

           An Embedded system contains processing cores that are either micro

controllers or digital signal processors (DSP).

           An important point to be noted while discussing about Embedded systems is

that a processor is an important unit in the Embedded system hardware. It is the

heart of the Embedded system.

          The main characteristic of an Embedded system is that it is being dedicated to

handle a particular task. Since the embedded system is dedicated to specific tasks,

design engineers can optimize it to reduce the size and cost of the product and

increase the reliability and performance.

           In general an Embedded system has lot of applications.

 Let us now discuss about the applications of Embedded systems in detail.

APPLICATIONS OF EMBEDDED SYSTEMS:

             Embedded systems have wide range of applications in different fields. The

applications of Embedded system range from portable devices like digital watches

and MP3 players, to large stationary installations like traffic lights, factory controllers,

and largely complex systems like hybrid vehicles, MRI and avionics. Complexity varies

from low, with a single micro controller chip, to very high with multiple units,

peripherals and networks mounted inside a large enclosure. Embedded systems are

widespread in consumer, industrial, commercial and military applications.

        Let us now discuss the category wise applications of Embedded systems.

Applications of Embedded systems in consumer electronics are as follows

Consumer electronics has also benefited a lot from Embedded systems. Consumer

electronics include:

  

·      Personal Digital Assistants(PDAs)

·      Mp3 players

·      Household appliances

·      Mobile phones

·      Videogame consoles

·      Digital cameras

·      DVD players

·      GPS receivers

·      Printers

             Even the household appliances that include microwave ovens, washing

machines and dishwashers, are including washing machines to provide

flexibility, efficiency and features.

Applications of Embedded systems in Telecommunications are as follows:

 The industry which uses mostly the Embedded system technology is nothing but   

 Telecommunication industry. The telecom industry utilizes numerous Embedded

systems from telephone switches for the network to mobile phones at the end-user.

Computer networking uses dedicated routers and network bridges to route data.

Embedded engineers help in ensuring high speed networking. This is the most critical

part of Embedded systems applications. The ethernet switches and network

interfaces are designed to provide the necessary bandwidth. This will allow in rapidly

incorporating ethernet connections into advanced Embedded applications.

      Embedded systems were used for large, safety critical and business critical

applications that include

·      Rocket and satellite control

·      Energy production control

·      Telephone switches

·      Air traffic control

Apart from the above applications embedded systems are also used in several other industries like

·      Transportation industry

·      Fire safety

·      Safety and security

·      Medical Applications and

·      Life critical systems as these systems can be isolated from hacking and thus be more reliable.

  Medical systems use Embedded systems for vital signs monitoring, electronic

stethoscopes for amplifying sounds and various medical imaging (PET, CT, MRI)

for non-invasive internal inspections. Embedded systems within medical

equipment is often powered by industrial computers.

CHARACTERISTICS OF EMBEDDED SYSTEMS:

·      Sophisticated functionality

·      Real-time operation

·      Low manufacturing cost

·      Application dependent processor

·      Restricted memory

·      Low power

EMBEDDED SYSTEM CONSTRAINTS:

 An Embedded system is software designed to keep in view three constraints:

1) Available system memory

2) Available Processor speed

2) The need to limit the power dissipation.

      When running the system continuously in cycles of wait for event, run, stop and

wake- up.

WHAT MAKES EMBEDDED SYSTEM DIFFERENT?

·      Real-time operation

·      Size

·      Cost

·      Time

·      Safety

·      Reliability

·      Energy

·      Security.

CLASSIFICATIONS OF EMBEDDED SYSTEMS:

Embedded systems are classified into three types:

1) Small scale Embedded systems

2) Medium scale Embedded systems

3) Sophisticated Embedded systems

Small scale Embedded systems contains single 8 bit or 16 bit microcontroller. It

has little hardware and software complexity. These small scale Embedded

systems may even be battery operated. Usually “C” is used to develop these

Embedded systems. The need to limit power dissipation when system is running

continuously. The Programming tools required for this kind of Embedded system

are:

 Editor, Assembler and Cross Assembler.

Medium Scale Embedded systems contains single or few 16 or 32 bit micro

controllers or DSP or RISC (Reduced Instruction Set Computer).It has both

hardware and software complexity. The Programming tools required for this kind

of Embedded system are:

RTOS, Source code engineering tool, Simulator, Debugger and Integrated

Development Environment (IDE).

 Sophisticated embedded systems have enormous hardware and software

complexity. These kinds of Embedded systems need scalable processor or

configurable processor and PLA. These embedded systems are constrained by

the processing speed available in their hardware units. The Programming tools

required for this kind of Embedded system are:

For these Embedded systems programming tools may not be available at a

reasonable cost or may not be available at all. A compiler or retarget able

compiler must have to be developed for this kind of Embedded systems.

COMPONENTS OF EMBEDDED SYSTEM:

·      It has Hardware

Processor, Timers, Interrupt controller, I/O devices, Memories, Ports etc.

·      It has main application software which may perform concurrently the series

of tasks or multiple tasks.

   

·      It has Real time operating system(RTOS)

RTOS defines the way the system works which supervise the application

 software .It sets the rules during the execution of the application program.

A small scale Embedded system may not need an RTOS.

A diagram for Embedded system hardware is shown below.

                         EMBEDDED SYSTEM HARDWARE

SPECIALITIES OF EMBEDDED SYSTEMS:

 While designing the embedded systems, developers have to keep the below

specialties in mind: -
 Performance:-
Many embedded systems have time constraints. For instance, in a process control

system, a constraint can be: “if the temperature exceeds 40 degrees, open a valve

within 10 milliseconds.” The system meets such deadlines.

 If the deadlines are missed, it may result in a catastrophe. You can imagine the

damage that can be done if such deadlines are not met in a safety system of a nuclear

 plant.

 Power Consumption:-
Most of the embedded systems operate through a battery. To reduce the battery

drain & avoid frequent recharging of the battery, the power consumption of an

embedded system has to be very low.

 Cost:-
For an embedded system used in safety applications of a nuclear plant or in a

spacecraft, cost may not be a very important factor. However, for an embedded

system used in consumer electronics or office automation, the cost is of utmost

importance. Suppose you have designed a toy in which the electronics will cost

US$20. By a careful analysis design, if you can telecom operator will change the

algorithm for the calculation of the bill amount. This is very cumbersome, considering

that a memory chip will have to replace in thousands of PCO.

Size: - 
Size is certainly a factor for many embedded systems. We do not like a mobile phone

that has to be carried on our backs. The size and the weight

(ie.compactness) are the important parameters in embedded systems used in

aircraft, missiles etc. because in such cases, every inch & every grain matters.

Software Up gradation capability:-
Embedded systems are meant for a very specific task. So, once the software is

transferred to the embedded system, the same software will run throughout its life.

However, in some cases, it may be necessary its upgrade the software. Consider the

example of a Public Call Office (PCO).

At the PCO, an embedded system is used which displays the amount to be paid by a

telephone user. The amount is calculated by a firmware, based on the calling number

& the duration of the call from time to time, the broadband & wireless network, &

consumer electronic products.

 RECENT TRENDS IN EMBEDDED SYSTEMS:-

In old good days, developing embedded systems was confined to very specialists.

Most of the embedded systems are written only in assembly language & hence

writing, debugging & maintaining the code were very difficult & time consuming.

With the availability of powerful processors & advanced development tools,

embedded software development is no longer ‘rocket science’.

Processor Power:-
The growing importance of embedded systems can be gauged by the availability of

processors about 150 varieties of processors are available from around 50

semiconductor vendors. Powerful 8-bit, 16- bit, 32-bit and 64-bit micro controllers, &

microprocessors are available to cater to the different market segments the clock

speed & memory addressing capability of these processors are also increasing. Very

powerful digital signal processors are also available for real time analyses of audio

and video signals. As a result, the power of desktop computers is now available on

 palm tops.
Mobile Devices:-
Mobile devices such as mobile phones, Personal Digital Assistants, smart phones etc.

are a special category of an embedded system. Though the PDA does many general-

purpose tasks, they need to be designed just like the conventional embedded

systems. The limitations of the mobile devices-memory constraints, small size, display

etc. are same as those found in the embedded systems. Hence mobile devices are

considered as embedded systems.

Operating Systems:- 
Unlike the desktop on which the options for an operating system are limited, a very

of operating systems are available which can be ported on to the embedded system.

The advantage of embedding an operating system is that the software development

will be very fast & marinating the code is very easy. The software can be developed in

a high level language such as “C”. So time to market the system gets reduced. If real

 time performance is require a real time operating system can be used. In addition

too many commercial embedded operating system open source software

campaigned let to development of many open source operating system. The

attraction of open source software is that it is free & also the complete source code is

available to customize the software as per your application needs.
Communication Interfaces and Networking Capability:- 

With the availability of low-cost chips, embedded systems can be provided

networking capability through communication interfaces such as Ethernet, 802.11b

wireless LAN & infrared. Network enabling of an embedded system has many

advantages: it can be accessed over a network for remote control or monitoring.

Programming Languages:-
Development of embedded system was done mostly in assembly languages.

However, due to the availability of cross-compilers, most of the development is now

done in high-level languages such as C. the object-oriented languages like C++ & Java

are now catching up.
Development Tools:- 

Availability of a number of tools for development, debugging & testing as well as for

modeling the embedded systems is now paving way for the fast development of

robust & reliable systems. Development tools such as BREW (Binary Routine

Environment for wireless), Wireless Application Protocol (WAP) development tools

facilitate easy development of applications for mobile devices.

Programmable Hardware:-

PLDs& FPGA pave the way for reducing the components on an embedded system,

 leading to small, low-cost systems. After developing the prototype of an embedded

system, for mass production, FPGA can be developed having all the functionality of

the processors, peripherals & application-specific circuitry.

CONCLUSION:

An embedded system is closely integrated with the main system It may not interact

directly with the environment.Thus embedded systems contain programmed

instruction running via processor  Chips. They perform control, protection &

monitoring tasks. In broad terms Embedded systems are programmable devices or

systems which are generally used to control or monitor things like processes

machinery, environmental equipment & communications. The range of

embedded system is vast & includes all industrial & commercial sectors. Embedded

systems are rapidly becoming a catalyst for change in the computing, data

communication, telecommunications, industrial control & entertainment sector. The

objective of this study is to enlighten readers about the application of embedded

systems; the embedded systems technology; & the impact of the technology on

various markets.

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WIRELESS SENSOR NETWORKS

A wireless sensor network is a collection of nodes organized into a corporate

network. Each node consists of processing capability (one or more

microcontrollers, CPUs or DSP chips), may contain multiple types of memory

(program, data and flash memories), have a RF transreceiver (usually with a

single Omni directional antenna), have a power source (e.g., batteries and solar

cells), and accommodate various sensors and actuators. The nodes

communicate wirelessly and even self organize after being deployed in an ad

hoc fashion. Systems of 1000s or even 10000s nodes are anticipated. Such

systems can revolutionize our live and work.

Currently wireless networks are beginning to be deployed at an accelerated

pace. It is not un reasonable to expect that in 10-15 years that the world will be

covered with wireless sensor networks with access to them via the Internet.

This can be considered as the Internet becoming physical network. This new

 technology is exciting with unlimited potential for numerous application areas

including environmental, medical, military, transportation, entertainment, crisis

management  homeland defense, and smart spaces.

In computer science and telecommunications, wireless sensor networks are an active

research area with numerous workshops and conferences arranged each year. The

topology of the wireless sensor networks can vary from a simple star network to an

advanced multi-hop wireless mesh network.

CHARACTERISTICS:

The main characteristics of a WSN include:

·        Power consumption constrains for nodes using batteries or energy harvesting

·        Ability to cope with node failures

·        Mobility of nodes

·        Communication failures

·        Heterogeneity of nodes

·        Scalability to large scale of deployment

·        Ability to withstand harsh environmental conditions

·        Ease of use

HARDWARE AND SOFTWARE:

 One of the major challenge in a Wireless Sensor Network is to produce low cost and

tiny sensor nodes. Now a days, many companies are producing WSN and the

commercial situation can be compared to home computing in 1970s. Most of the

nodes are still in the research and development stage particularly their software.

 

 To determine the lifetime of Wireless Sensor Networks, energy is the scarcest

resource for the Wireless Sensor nodes. The key component for the software of a

Wireless Sensor Network is ad-hoc communications.

The algorithms and protocols need to address the following issues:

Ø Life time Maximization

Ø Robustness and fault tolerance

Ø Self-configuration

 The lifetime of a Wireless Sensor Network is based upon the limited energy resource.

In order to conserve power the node should shut off the radio power supply when

not in use.

APPLICATIONS:

Ø Area monitoring

Ø Environmental/Earth monitoring

Ø Air Quality monitoring includes Interior monitoring and Exterior monitoring

Ø Air pollution monitoring

Ø Forest fire detection

Ø Landslide detection

Ø Water quality monitoring

Ø Agriculture

Ø Industrial monitoring which includes machine health monitoring

 Simulation of Wireless Sensor Networks:

  At present, agent-based modeling and simulation is the only paradigm which allows

  the simulation of complex behavior in the environments of wireless sensors

 (such as flocking). Agent-based simulation of wireless sensor and ad-hoc networks

is a relatively new paradigm. Agent-based modeling was originally based on social

simulation.

Network simulators like OPNET, NetSim and NS2 can be used to simulate a wireless

sensor network.

Standards:

The prominent standards of Wireless Sensor networks include:

Ø Wireless HART

Ø IEEE 1451

Ø Zigbee/802.15.4

Ø Zigbee IP

Ø 6LowPAN

 The IEEE focuses on the physical and MAC layers and the Internet Engineering task

force works on the layer 3. Standards are not used much i.e. used very less in the case

of Wireless Sensor Networks.

MAC:

A medium access control (MAC) protocol coordinates actions over a shared channel.

The most commonly used solutions are contention-based. One general contention-

based strategy is for a node which has a message to transmit to test the channel to

see if it is busy, if not busy then it transmits, else if busy it waits and tries again later.

After colliding, nodes wait random amounts of time trying to avoid re-colliding. If two

or more nodes transmit at the same time there is a collision and all the nodes

colliding try again later. Many wireless MAC protocols also have a doze mode where

nodes not involved with sending or receiving a packet in a given timeframe go into

sleep mode to save energy. Many variations exist on this basic scheme.

 MAC protocol for wireless sensor networks must consume little power, avoid

collisions, be implemented with a small code size and memory requirements, be

efficient for a single application, and be tolerant to changing radio frequency and

networking conditions.

             One example of a good MAC protocol for wireless sensor networks is B-MAC.

  B-MAC is highly configurable and can be implemented with a small code and

 memory size. It has an interface that allows choosing various functionality and only

 that functionality as needed by a particular application.

 B-MAC contains four main parts :

Ø Clear Channel Assessment (CCA)

Ø Packet backoff

Ø Link layer acks

Ø Low power listening.

 For CCA, B-MAC uses a weighted moving average of samples when the channel is idle

in order to assess the background noise and better be able to detect valid packets

and collisions.

The packet backoff time is configurable and is chosen from a linear range as opposed

to an exponential backoff scheme typically used in other distributed systems. This

reduces delay and works because of the typical communication patterns found in a

wireless sensor network. B-MAC also supports a packet by packet link layer

acknowledgement. In this way only important packets need pay the extra cost.

A low power listening scheme is employed where a node cycles between awake and

sleep cycles. While awake it listens for a long enough preamble to assess if it needs to

stay awake or can return to sleep mode. This scheme saves significant amounts of

energy.

TYPES OF WIRELESS SENSOR NETWORKS:

1.Unstructured Wireless Sensor Network	2.Structured Wireless Network
·      Dense collection of nodes	·      Few and scarcely distributed nodes
·      Ad-hoc deployment	·      Pre planned deployment
·      Difficulty in network maintenance	·      Lower network maintenance

Diagramatically a Wireless sensor Network can be represented as

                   

FUTURE SCOPE:

The Wireless sensor networks helps the present technology to Blend and

interconnect individual smart devices, Enable access to information about the real

world and also interact and influence the real world. Also this Wireless Sensor

Network receives live information from the road authority about the state of the

Roads including traffic jams, road accident and weather. The capability and

 accessibility of the networks can also be increased to a large extent with the help of

this Wireless Sensor Networks.

REFERENCES:

Jennifer Yick, Biswanath Mukherjee, Dipak Ghosal, Wireless Sensor networks Survey,

Elsevier, 2008.