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Paper persentation: Embedded system






Embedded system

ABSTRACT:-
An embedded system can be defined as the computing device that has computer hardware, either with software embedded in it as one of its most important component. It may be an independent system or a part of a larger system. The emergence of embedded systems is a recent development. As a scientific discipline it resembles the state of microelectronics (and VLSI design, in particular) around 1980. Today’s challenge is similar to back then, except that the stakes are probably higher. Embedded systems will appear in virtually all devices, and intelligent devices have the tendency to oust their "stupid" counterparts from the market place, just like CD players have ousted gramophone players. Thanks to developments in microelectronics, the computing power of the desktop computers is now becoming available on the palmtops. Embedded systems are heterogeneous. Since they are mixtures of hardware and software, trade-off is important design decisions: do we realize a function in hardware or in software? But embedded systems are more heterogeneous than just combining computer science & digital electronics.
This paper presents an overview of existing modes of Embedded Systems, architecture & their application. A look has also been given to future deployment of Embedded Systems.


1. INTRODUCTION:-
An embedded system can be defined as the computing device that has computer hardware with software embedded in it as one of its most important component. It may be either an independent system or a part of a larger system. As its software usually embeds in ROM ,it does not need secondary memories as in a computer. Nearly 99% of the processors manufactured end up in embedded systems. Embedded systems find applications in every industrial segment. Embedded systems can be categorized as stand-alone systems, real-time systems, networked information appliances & mobile devices. Just in the 10 years, such changes have occurred more rapidly that they see more revolutionaries than evolutionary. As these systems have brought about radical changes in Electronics and Computer, they have also begun to impact other human activities.

INTRODUCTION TO EMBEDDED SYSTEM:-
An embedded system is some combination of computer hardware & software, either fixed in capability or programmable, that is specifically designed for a particular kind of application device. Hardware & software that forms a component of some larger system & is expected to function without human intervention. Typically an embedded system consists of a single-board microcomputer with software in ROM, which starts running a dedicated application as soon as power is turned on & does not stop until power is turned off. An embedded system is any device controlled by instructions stored on a chip. These devices are usually controlled by a microprocessor that executes the instructions stored on a Read Only Memory (ROM) chip. Here an example of a chip “PIC” is shown

An embedded system is pre-programmed to perform a dedicated or narrow range of functions as part of a larger system, usually with minimal end-user or operator intervention. The term 'embedded' implies that these chips are an integral part of the system. Broadly speaking, these programmable devices or systems are generally used to perform, control or monitor processes, machinery, environments, equipment and communications tasks.
Embedded systems have several things to do at once–respond to several
Events at once; cope with unusual conditions without human intervention, while being subjected to a deadline. In fact a general computer system is made up of numerous embedded systems. If an embedded system is designed well, the existence of the processor & the software could be completely unnoticed by a user of the device.


2. CATEGORIES OF EMBEDDED SYSTEM:-

2.1 Stand-alone Embedded Systems:-
As the name implies, stand-alone systems work in stand-alone mode. They take inputs, process them & produce the desired output. The input can be electrical signal from transducers or commands from a human being such as pressing of a button. The output can be electrical signals to drive another system, an LED or LCD display for displaying of information to the users. Embedded Systems used in process control,automobiles,consumer electronic items etc. fall into this category in a process control system, the inputs are from sensors that convert a physical entity such as temperature or pressure into its equivalent electrical signal. These electrical signals are processed by the system and the appropriate electrical signals are produced.

2.2. Real-time Systems:-
Embedded Systems in which some specific work has to be done in specific time period are called real-time systems. For example- Consider a system that has to open a valve within 30 milliseconds when the humidity crosses a particular threshold. If the valve is not opened within 30 milliseconds, a catastrophe may occur. Such systems with strict deadline are called hard real-time systems. On the other hand, if we consider a DVD player and we give some command from a remote control, & there is a delay of a milliseconds in executing the command, but this delay won’t lead to a serious implication. Such systems are called as soft real-time systems.

2.3 Network Information Appliances:-
Embedded systems that are provided with network interfaces & accessed by networks such as Local Area Network or the Internet are called networked information appliances. Such embedded systems are connected to a network, typically a network running TCP/IP (Transmission Control Protocol/Internet protocol) protocol suite, such as the Internet or the Company’s Intranet. These systems have emerged in recent years.
Here are some examples of such systems:-
A networked process control system consists of a number of embedded systems connected as a LAN. Each embedded system can send real-time data to a central location from where entire process control system can be monitored. The monitoring can be done using a web browser such as the Internet Explorer.
The door-lock of your home can be a small-embedded system with TCP/IP and HTTP server software running on it. When your children stand in front of the door-lock after they return from school, the web camera in the door-lock will send an alert to your desktop over the Internet and then you can open the door-lock just by clicking the mouse.



3.OVERVIEW OF EMBEDDED SYSTEM ARCHITECTURE:-
Every embedded system consists of custom – built hardware built around a Central Processing Unit (CPU). This hardware also contains memory chips onto which software is loaded. The software residing on the memory chip is called the firmware. The embedded system architecture can be represented as a layered architecture as shown in fig-4. The operating system runs above the hardware and the application software run above the operating system. It is not compulsory to have an operating system in every embedded system. For small appliances such as remote control units, air conditioner, toys etc., there is no need for an operating system. For applications involving complex processing, it is advisable to have an operating system. In such a case, you need to integrate the application software with the operating system & then transfer entire software into a memory chip. Once the software is transferred to the memory chip, the software will continue to run for a long time & you don’t need to reload the new software.



3.1 Building Block of hardware of an Embedded System:-

Central Processing Unit (CPU):-
The CPU is a unit that centrally fetches
& processes a set of general-purpose instructions. The CPU instruction set includes instructions for data transfer operations, ALU operations, stack operations, input &output operations & program control, sequencing & supervising operations. The general-purpose instruction set is always specific to a specific CPU. One example of an older generation Microprocessor is Intel 8085.It is an 8-bit processor. Another is Intel 8086 or 8088, which is a 16-bit processor.

The CPU can be of the following:-
Microcontroller, microprocessor or Digital Signal Processor (DSP).
A micro-controller is a low-cost processor. Its main attraction is that on the chip itself, there will be many other components such as memory, ADC
etc. on the other hand, microprocessors are more powerful, but you need to use many external computers with them. DSP is mainly used for applications in which signal processing is involved.

Processor in the System:-
An embedded system processor chip or Core can be one of the following.

1. General Purpose Processor (GPP):-
a) Microprocessor
b) Microcontroller
c) Embedded processor
d) Digital signals processor (DSP)
e) Media Processor

2. Application Specific System Processor
(ASSP) As Additional Processor

3. Multiprocessor system using General
Purpose processors (GPPS) & Application Specific Instruction Processors (ASIPs)

4. GPP core(s) or ASIP core (s) integrated into either an Application Specific Integrated Circuit
Circuit (ASIC) or a Very Large Scale
Integrated Circuit (VLSI) circuit or an FPGA core integrated with processor unit(s) in a VLSI (ASIC) chip.

Block diagram of Component of the Embedded System Hardware:-



Processor:-
A processor is the heart of the embedded system. For an embedded system designer, knowledge of microprocessors & Microcontrollers is a prerequisite. A processor has two essential units:

1. Program flow Control Unit (CU)
2. Execution Unit (EU)

The CU includes a fetch unit for fetching instruction from the memory. The EU has circuits that implement the instructions pertaining to data transfer operation & data conversion from one form to another. The EU includes the Arithmetic and Logical Unit (ALU)
& also the circuits that execute instructions for a program control tasks, say, halt, interrupt, or jump to another set of instructions. It can also execute instructions for a call or branch to another program & for a call to a function. Processors runs the cycle of fetch & execute the instruction defined in the processor instruction set are executing in the sequence that they are fetched from the memory. A processor
is mostly in the form of an IC chip; alternatively it could be in core form in an ASIC or at a Soc. Core means a part of the functional circuit on the VLSI chip.

A General Purpose Processor is used because of the following:-

1) Processing by the known instructions
Available at redefined general-purpose instruction set result in fast system development.
2) Once the board & input/output interfaces are designed for a GPP, these
Can be used for a new system by just changing the embedded software in the
Board ROM.
3) Ready availability of a compiler
Facilitates embedded software development in high level language.
4) Ready availability of a well tested &
Debugged processor specific APIs & the
Codes previously designed for other
Applications results in fast development
of new system.

Microprocessor:-
A microprocessor is a single VLSI chip
that has a CPU &may also have some other units (for eg: floating-point processing arithmetic unit, pipelining &super-scaling units) that are additionally present & that result in faster processing of instructions.

Memory:-
The memory is categorized as Random Access Memory (RAM) and Read Only Memory (ROM). The contents of RAM will be erased if power is switched off. So, the firmware is stored in the ROM. When the power is switched on, the CPU reads the ROM, the program is transferred to RAM and program is executed.

Input devices:-
Unlike the desktops, the I/P devices to an embedded system have very limited capability. There will be keyboard or a mouse, & hence interacting with the embedded system is no easy task. Many embedded systems will have a small keypad-you press one key to give a specific command. A keypad may be used to I/P only the digits. Many embedded system uses in process control do not have any I/P device for user interaction; they take I/Ps from sensors or transducers & produce electrical signals.

Output devices:-
The output devices of the embedded systems also have very limited capability. Some embedded systems will have a few Light Emitting Diodes to indicate the health status of the system modules. A small Liquid Crystal Display
(LCD)may also be used to display some important parameters.

Communication interfaces:-
The embedded systems may need to interact with other embedded systems or they may have to transmit data to a desktop.

Application-specific circuitry:-
Sensors, transducers, special processing & control circuitry may be required for an embedded system, depending on its application. The circuitry interacts with the processor to carry out the necessary work.


4. SPECIALITIES OF EMBEDDED SYSTEMS:-
While designing the embedded systems, developers have to keep the below specialties in mind: -

4.1 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.

4.2 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.

4.3 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.

4.4 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.

4.5 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.


5. 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’.
5.1 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.

5.2 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.

5.3 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.

5.4 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.


5.5 Programming Languages:-
Fig. 6
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.

5.6 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

5.7 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.


6. APPLICATION AREAS:-
In today’s world the electronic devices have been dominated. The children need embedded systems to play smart video games & to operate automatic chocolate
Vending machines! Young people need embedded systems to borrow smart cards from parents to see movies! Housewives need embedded system for smart Internet – compliant home appliances, such as, microwave, television, music system, & so on.
Nearly 99%of the processors manufactured end up in embedded systems. The embedded system market is one of the highest growth areas as these systems are used in very market segment- consumer electronics, office automation, biomedical engineering, wireless communication,& data communication, military and so on.

6.1 Consumer appliances:-
At home we use a number of embedded systems that include digital camera, digital diary, DVD player, electronic toy, microwave oven, remote controls for TV & air conditioner etc. Today’s high-tech car has about 20 embedded systems for transmission control, spark control, navigation etc. Even wristwatches are now becoming embedded systems.

6.2 Industrial automation:- Today a lot of industries use embedded systems for process control. These include pharmaceutical, cement, sugar, oil exploration, nuclear energy, electricity generation & transmission. The embedded systems for industrial use are designed to carry out the specific task such as monitoring the temperature, pressure, humidity, voltage, current etc. & then take appropriate action based on monitored levels to control other devices.

6.3 Medical electronics:- Almost every medical equipment in the hospital is an embedded system. This equipment’s include diagnostic aids such as ECG, EEG, blood pressure measuring devices & X-ray scanners etc.

6.4 Computer Networking:- Computer networking products such as bridges, routers, Integrated Services Digital Networks (ISDN), Asynchronous Transfer Mode & relay switches are the embedded systems that implement the necessary data communication protocols.

6.5 Wireless technologies:- Advances in mobile communications are paving way for many interesting applications using embedded systems. The mobile phone is one of the marvels of the last decade of the 20th century. It is very powerful embedded system that provides voice communication while we are on the move.

6.6 Instrumentation:- Testing & measurement are the fundamental requirements in all scientific and engineering activities. The measuring equipment we use in laboratories to measure parameters such as weight, temperature, voltage, current etc. are all embedded systems. Test equipment such as oscilloscope, logic analyzer, protocol analyzer, radio communication test set etc, are embedded systems built around powerful processors

6.7 Security:- Security of persons and information has always been a major issue. We need to project our homes and offices, & also the information we transmit & store. Developing embedded systems for security applications is one of the most lucrative businesses nowadays.

6.8 Finance:- Financial dealing through cash & cheques are now slowly paving way for transactions using smart cards and ATM (Automatic Teller Machine, also expanded as Any Time Money) machine. Smart card, of the size of a credit card, has a small micro-controller and memory; & it interacts with the smart card reader / ATM machine & acts as an electronic wallet.


7. SPECIFIC APPLICATIONS:-
7.1 AUTOMATIC TELLER MACHINE (ATM):-
ATM is an electronic device that allows a bank's customers to make cash withdrawals and check their account balances without the need for a human teller. Many ATMs also allow people to deposit cash or cheques, transfer money between their bank accounts or even buy postage stamps. The world's first ATM was developed by De la Rue & installed in Enfield Town in North London on June 27, 1967 by Barclays Bank. The idea of a personal identification number (PIN) stored on a physical card being compared with the PIN entered when retrieving the money was developed by the British engineer James Good fellow in 1965.In modern ATMs, customers identify themselves by using a plastic card with a magnetic stripe, which encodes the customer's account number, & by entering a four-digit pass code (PIN). If the PIN is entered incorrectly for several times in row then the ATM retains the card for a security purpose to avoid the use of card by an unauthorized user. There are ATMs that are accessible to blind and visually impaired peoples. This is one of the great inventions. These are types of ATMs whose keypads are equipped with Braille system.

7.2 EMBEDDED SYSTEM IN A SHOE:-
The microprocessor embedded in this Adidas running shoe calculates the pressure between the runner's foot & the ground five million times per second & continuously changes the cushioning to match an adjustable comfort level. The computer controls a motor that lengthens & shortens a cable attached to a plastic cushioning element.

7.3 BRAILLE INTERFACE TO MICROCONTROLLER:-
In today’s world mobile phone has become the most simplest and effective way of communication .What to do if we want to send a message to our friend. Simple, we write a sms and send it to our friend. That’s very cool and handy for us. But, what if one of our friends is blind. Being blind does not mean he should be deprived of the simplest facility available on mobile phone. There should be some way that blind people can also read messages, isn’t it? So basically our aim is to enable blind person to read sms.



Next question how is it possible?
This is possible through Braille. Braille is a matrix of engraved dots. There is a coding for each English character. Blind person can read the text just by touching it. This comes through training. And Braille’s are used in almost all blind school nowadays. Blind person are using it extensively to communicate with mobiles, typewriters and even computers.
The message can be transferred to the Braille structure. This is done by interfacing a microcontroller to the mobile through a cable. This uses serial communication. The mobile communicates microcontroller through AT commands .The microcontroller outputs signal to the relay drive circuit. The message is also displayed on the LCD connected to the microcontroller. There are six relays which drive the mechanical structure, consisting of six thick wires. There is encoding for each English alphabet and character. The wires corresponding to the particular alphabet or character is raised up and the blind person can feel it through their fingers.


10. 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.


11. REFERENCES:-

Embedded Systems Architecture, Designing and Programming – By Rajkamal.
Embedded Systems Programming and Designing – By Michael Barr.
Designing Of Embedded Hardware – By John Keysoukisi.
Embedded System Design – By Frank Vahid.
www.embedded.com www.nptel.iitm.ac.in