Let me welcome you to this course that will be conducted jointly by myself and Dr. Kamalika

Datta.

In this course we shall be talking about various aspects of Embedded System Design, in particular

we shall be emphasizing on some hands-on design examples.

As the vehicle of demonstration we shall be primarily working with two different embedded

system platforms; one is based on an ARM based board and the other one will be a standard

Arduino Uno based board.

Now before we proceed with the actual experimentation, it is always good to have some theoretical

background and some motivation behind why we need an embedded system, what are the main

characteristics of an embedded system and what are the design alternatives.

So, in this context the first lecture of this course, is titled Introduction to Embedded

Systems.

Here we shall be primarily talking about embedded systems, what it is basically and some typical

applications, and inside an embedded systems what kind of typical subsystems we normally

get to see.

These are a few things that we shall be discussing as part of this course.

The first thing I want to emphasize is that, we have been very lucky that we have been

born and brought up in an age of computing.

Since our birth many of you have seen computer systems around you, but of course, the scenario

was not the same maybe 4 or 5 decades back.

There has been a fantastic proliferation of electronics, computing systems, low power

devices, and there are various kinds of advancements that have taken place over the years.

The first thing I want to emphasize is that computer systems are everywhere today.

If you look around you; well I am not talking about in a technical environment, not in your

laboratory, not in your college well even in your residence when you wake up from your

sleep.

If you look around you, you will find several instances of some computational devices that

will be sitting somewhere.

This is the kind of environment where we have all grown up.

Traditionally speaking, we have become familiar with computers that are either desktops, laptops,

servers etc. that are more conventional in some sense.

Desktop computers are typically machines where you have learnt your computing on.

Today laptops have become very much affordable, most of us own our personal laptops.

So, laptops are replacing the role that desktops used to have earlier.

Talking about mobile phones this is a very underestimated computing device.

Whatever is inside a mobile phone today, if you think of the computational capability

of the computers that existed 30 to 35 years back, believe me the processes that are inside

a mobile phone are of the tune of 1 million times more powerful as compared to what you

used to see in the large computer systems in those days.

But mobile phones we use for some specific applications, for its use as a phone, sending

messages.

And of course, for recreational purposes we can watch video, we can browse internet, and

there are so many new applications that you can run on mobile phones today.

But what I want to say is that, there is another kind of computing system that is often hidden

from us.

Hidden means we cannot see those computing systems.

Like we know desktop can compute, a laptop can compute, a mobile phone can also compute

in some sense.

But if you look at a refrigerator, if we look at our air conditioning machine, do they look

like a computing machine?

No.

But inside those machines there is some computing brain hidden, that is what I am referring

to as this hidden thing.

These are far more common in our daily life and pervasive, as they are everywhere, and

the point I want to make is that, they are hidden in the environment for which they were

created.

Now, such systems are traditionally referred to as embedded systems.

We mean these are computing systems, but they are embedded inside the environment.

By the term environment we mean the surroundings or actually the scenario for which the system

was designed.

Let me take the example of an air conditioning machine again.

An AC machine is supposed to be housed inside a room normally.

Now this computing system that is sitting inside an AC machine, for that computing system

the AC machine is the environment.

It does not interact with anybody outside that AC machine.

It is responsible for controlling the AC machine, it is responsible for responding to whatever

you are pressing on your remote control, you are given giving some commands to the ac machine

and so on.

These are the kind of commands that those computing machines inside are responsible

to respond to.

Talking about embedded systems again, what are these embedded systems?

I already gave an example.

So, now it must be somewhat clear to you.

Embedded systems are computers they are embedded within other systems.

Now on the right side I have given some pictures.

You see these examples, here you see a washing machine, this is a refrigerator, this is a

laser printer, this is a digital camera, this is an automobile and here you can see a missile

that is flying through the sky.

These are all examples of embedded systems, they are fairly powerful computing systems

or devices inside them of course, the power of these computing systems depend on the specific

application.

For some applications you do not need too much computation power, but for a system like

missile lot of computations need to take place in real time.

As the missile flows in its trajectory, there is continuous feedback from the environment

and there are some corrective actions that need to be taken such that the missile can

follow the correct path and hit the target in a precise way.

So, it depends on the environment.

Now this “other systems” can refer to anything, it is very hard to define in a very

specific way.

But broadly speaking you can say that these other systems are any computing system, which

are not our conventional computers like desktop, laptop, servers etc.

Any computing system that is not one of these, they are sitting somewhere and working with

the environment, they can be classified as embedded systems.

Some typical examples are given here.

And again just as I said depending on the application, processor can be very simple

and inexpensive.

Because there are many devices, let me take an example again.

Suppose you have gone to the market to buy a microwave oven, they are available for prices

ranging for Rs. 3000 and more.

They are pretty cheap in comparison.

There are embedded processors inside micro ovens also.

Now if I say that I need a very powerful Pentium processor to be sitting inside a microwave

oven, the price of that Pentium processor itself will be 5000 rupees including all accessories

and peripherals, then this will be economically not viable.

They have to be very cheap depending on the applications.

Today a very large number of embedded systems are being used all over the world in various

applications, billions of them versus millions of conventional computing units.

So, the number of such embedded computing devices far outnumber the number of conventional

computing devices today.

There are some common features that are present in most embedded systems, let us look at some

of them.

First thing is that they are special purpose or single functional.

Like an air conditioning machine, there is a processor inside, the sole purpose of that

processor is to ensure that the ac machine is working properly, and nothing else.

So, it is not trying to help you in calculation in doing some maths, and so on.

So, it is very special purpose in that sense.

It typically it executes a single program related to the application for which it was

built, and it can take inputs from the environment.

You think of an ac machine; the inputs from the environment means, well the user can send

some commands via the remote control.

The ac machine itself can have some sensors inside it, can sense what is the current room

temperature, what is the current humidity level.

Accordingly it can activate the various subsystems inside in a very optimum way.

You think of a refrigerator there normally there are some control panels.

You can set the temperatures and other factors there.

It depends again on the application, through the environment you can send some commands

to the processor, and the processor will respond accordingly.

Some examples I have given, like microwave oven, washing machine, ac machine.

And for most of these embedded systems there are very

tight constraints on cost, energy and also form factor.

The processor has to be low cost otherwise the system will not be economically viable.

The processor must not consume too much energy from the power source or from the battery

wherever it is working.

Because the processor is hidden from you and it is expected that the user should not worry

too much about energy.

Form factor; you think of an ac machine nowadays that are very sleek, now you cannot afford

to have a computer inside which is very bulky and big because that will make your system

also bulky and big.

So, depending again on the system, your computing system must be made very compact and should

fit inside without any appreciable increase in area.

So, low cost, low power, small size, relatively fast these are some of the characteristics,

and another important thing is that it should have real time response.

You think of ac machine, suddenly due to some reason the temperature of the room has gone

up.

It must turn on the compressor at high power to bring down the temperature.

So, it must respond to these external inputs in real time, it cannot say that well I shall

respond to this after 10 minutes.

Real time means, whenever an input comes, within some specified time the system should

respond to that input.

Most embedded systems respond in real time.

They take inputs from the system environment and should carry out the computations; the

tolerable delay varies from application to application.

So, these are some of the common features.

Now, there are some design constraints as well; some of these are pretty obvious.

The processor should be a low cost thing.

You should not make it too expensive because that will also make your system inside which

it is embedded, it will make that also quite expensive.

You cannot afford to use a very sophisticated processor inside such a machine; like inside

a microwave you cannot afford to put a sophisticated processor like the Pentium, because the cost

of the Pentium itself is pretty high.

Low energy consumption is another property which is pretty common.

Well even for machines which operate from electric power, like a refrigerator if you

put it on and go away, it is expected that it will consume very low power.

And secondly, there are many gadgets which also operate on battery.

For them obviously, energy consumption is a big issue.

And because these processors are very simple, the amount of memory they have is also pretty

small.

So, whatever program you write, whatever computation you do they must fit inside that limited memory

space.

I mentioned many applications demand real time response; within a specified time, the

system should respond to the inputs.

Now, how can we define an embedded system based on whatever we talked about so, far?

Well embedded system can be loosely defined as a microcontroller based system.

This is true for most of the embedded systems.

The processor that is inside has to be low cost it has to be low power, it has to be

small in size.

There is some kind of processor called microcontroller that we shall be talking about throughout

this course, they satisfy all these criteria.

Most of the embedded systems have microcontrollers inside them, they are like a complete computer

in a single chip.

Whatever you need, processor, memory, IO everything is inside a single chip and therefore, it

is very low cost.

So, it should be a microcontroller based system and not general purpose.

It should control a function or a range of limited set of functions.

And another point is that, this is not meant to be programmed by the user.

Like a laptop or a desktop you can write a program, well you can write a program to compute

the factorial of a number, to find the sum of n numbers etc.

But whenever you think of an embedded system inside a device like your ac machine.

You normally do not use it for your day to day computation, you cannot program it yourself.

It comes to you factory programmed, you cannot modify the program, it is a fixed program

system -- you are only using that program.

The user can give inputs for example, through the remote controls, but cannot change the

functionality.

You cannot change an ac machine to something else like a room heater for example.

The user normally cannot make any modifications to the software, but of course, nowadays systems

are becoming more sophisticated; you think of a set top box that you use with your TV

sets.

Set top box are also embedded systems, there are quite powerful processors inside them.

Now sometimes you may have noticed that while watching some programs or when you are switching

it on, it says downloading updates.

Well the software that is running inside the set top box also gets periodically updated

by the service provider.

That facility is provided inside that set top box.

Just like your standard operating systems like windows that frequently needs some updates

to be installed.

That means, you need some modifications to your existing software to make it better in

some sense.

So, normally you cannot program your washing machine or refrigerator or a car, but maybe

tomorrow with the next generation embedded systems coming, you may be able to program

them also.

Like when you drive a vehicle you may program it and customize it according to your need,

but as of today the systems come with very limited choice to the users; may be a few

things user can specify, but not all.

This is a schematic diagram of an embedded system.

The embedded computer is sitting in the middle, which has some hardware, the microcontroller

and some program which is running on its software.

It takes inputs through some sensors, and it can control something through some outputs,

and there are typically some user interfaces like some switches, some small keyboards,

like some touch sensors maybe a remote control, these are all user interfaces and it can also

have some links to other subsystems.

This is a general schematic of an embedded system.

Now, what embedded system is not?

Well it is not a microprocessor sitting inside a traditional computing system.

We call it a computer, we do not call it an embedded system.

Well it is a microprocessor used to control another piece of technology like ac machine,

like microwave, like refrigerator and so on, this is what an embedded system is.

It is embedded inside some other system.

Now as I had said for low cost microcontrollers, that they are single chip devices.

You see here I have shown a picture of a microcontroller that belongs to the PIC family.

This is a PIC microcontroller, this is a layout diagram where processor, memory, IO subsystems

everything is embedded inside the same chip.

Now talking about some applications of embedded systems, you can summarize some of them, but

they are limited by imagination, there is no limit to what you can imagine.

And the number of such applications will only increase day by day.

Today we are talking about IoTs, tomorrow IoT will be everywhere, maybe some of those

devices will be inside your body, you will be carrying those devices along with you.

In the consumer segment you can think of refrigerator, washing machine, AC machine, camera, this

already we have talked about.

Even in your office you use printers and fax machines, photocopying machines, scanners,

biometric scanner, cameras for surveillance, they are all examples of embedded systems.

You think of automobiles; today all automobiles are intelligent in some sense, there are some

computational devices that try to utilize the infrastructure inside those automobiles

in an efficient way.

So, airbags, anti-lock braking systems, engine control, door lock, GPS, everything here these

are controlled by embedded processors.

For communication the mobile phones is the biggest example; you think of the network

switches that we use for communication routers, switch, Wi-Fi hotspots, telephones there are

processors inside each of them today.

Then you can have automatic door locking systems we see it many places; automatic baggage screenings

in airports and railway stations, surveillance systems, intelligent toilets, where there

are some embedded systems inside toilets that can respond to users’ needs automatically

these are all examples of embedded systems.

Again talking about that diagram, this is what embedded system looks like.

We have to have an embedded computer with some hardware, you have to write some software

to do it, and of course there has to be a proper user interface to make it usable.

And user interface has to be simple enough, it should not be a full big large keyboard

where you can type anything and everything.

It will be very specific to a particular application.

This is just like a cartoon I am showing.

This rectangular box is a processor.

Inside the processor you can see so many things.

You can see a digital to analog converter, you can see analog to digital converter, counters,

timers, pulse width modulator, so many subsystems.

In addition to processor, memory, IO ports etc. a typical microcontroller today that

forms the heart of an embedded system can contain analog to digital interfaces, because

most of the inputs from the outside world are analog in nature, they are continuous

in nature, like temperature, humidity, pressure, etc.

With this we come to the end of this lecture.

We shall be continuing with our discussion in our next lecture.

Thank you.