Overview of embedded system

Prepared By: D. Y. Vankawala

System Definition
 A way of working, organizing or performing one or
many tasks according to a fixed set of rules, program or
plan.
 Also an arrangement in which all units assemble and
work together according to a program or plan.

Examples of Systems
 Time display system – A watch
 Automatic cloth washing system – A washing
machine

Embedded system definitions
 An embedded system is a system that has software
embedded into computer-hardware, which makes a system
dedicated for an application (s) or specific part of an
application or product or part of a larger system
 An embedded system is one that has a dedicated purpose
software embedded in a computer hardware.
 It is a dedicated computer based system for an
application(s) or product. It may be an independent system
or a part of large system. Its software usually embeds into a
ROM (Read Only Memory) or flash.
 It is any device that includes a programmable computer but
is not itself intended to be a general purpose computer.

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 Embedded Systems are the electronic systems that
contain a microprocessor or a microcontroller, but we
do not think of them as computers– the computer is
hidden or embedded in the system.

Characteristics of embedded
system
1. Dedicated functions
2. Dedicated complex algorithm
3. Dedicated (GUIs) and other user interfaces for the
application
4. Real time operations— Defines the ways in which the
system works, reacts to the events and interrupts,
schedules the system functioning in real time and
executes by following a plan to control the latencies and
to meet the deadlines. [Latency — Waiting interval
between the instance at which a need to run the codes
arises for task (or interrupt service routine) following an
event and instance of start executing the codes]

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5. Multi-rate operations — Different operations may
take place at distinct rates. For example, the audio,
video, network data or stream and events have the
different rates and time constraints to finish
associated processes.

Automatic Chocolate Vending
Machine
(ACVM)

ACVM
 Coin insertion slot
 Keypad on the top of the machine.
 LCD display unit on the top of the machine. It displays
menus, text entered into the ACVM and pictograms,
welcome, thank and other messages.
 Graphic interactions with the machine.
 Displays time and date.
 Delivery slot so that child can collect the chocolate and
coins, if refunded.
 Internet connection port so that owner can know status of
the ACVM sales from remote.

ACVM Hardware units
 Microcontroller or ASIP (Application Specific Instruction Set
Processor) .
 RAM for storing temporary variables and stack
 ROM for application codes and RTOS codes for scheduling the
tasks.
 Flash memory for storing user preferences, contact data, user
address, user date of birth, user identification code, answers of
FAQs.
 Timer and Interrupt controller
 A TCP/IP port (Internet broadband connection) to the ACVM
for remote control and for getting ACVM status reports by
owner.
 ACVM specific hardware
 Power supply

ACVM Software components
 Keypad input read
 Display
 Read coins
 Deliver chocolate
 TCP/IP stack processing
 TCP/IP stack communication

Room Temperature
Controller(Digital Thermostat)

Hardware Specification Digital inputs and outputs: These are simple external pins whose logic state
can be controlled by the processor to either be a logic 1 or a logic 0. They can
also be used as input pins so that the processor can receive binary inputs from
the external world. They can be used individually or grouped together to create
parallel ports.
 Serial interfaces: These are interfaces that send or receive data using one or
two pins in a serial mode. They are less complex to connect but are more
complicated to program because the data may also be augmented with
additional information as required by the data transfer protocol.
 Analog to digital converters: While processors operate on the digital data,
the surrounding world is analog in nature. Therefore, interfaces between the
system and the external world requires analog to digital conversions and vice
versa.
 Displays: Displays are used by the processor to display the status information,
error messages, and output results. They could be simple LEDs, seven segment
displays, or character LCD panels.
 Keypads: Keypads are used by the end user to provide inputs to the embedded
system. The inputs could be anything such as entering the password, changing
functional settings, switching between menu items, etc.
 Thermostat Circuit: It is temperature sensor circuit which senses the
temperature of surrounding and gives the voltage which is equivalent of
surrounding temperature.

Functioning
 The surrounding temperature is sensed by the thermostat (a
temperature sensor) and is converted to a proportional analog
voltage. The processor cannot manipulate this signal directly, so
it is converted to an equivalent digital number through a process
called analog-to-digital conversion (ADC). The processor then
compares this temperature reading with the high and low
temperatures settings defined by the user, and turns the
heater/AC on or off if required. The user uses Keypad to enter
the temperature settings, which are saved into the memory. The
processor displays the temperature settings and the current
temperature on the LCD screen. The software to perform the
entire function of monitoring and controlling the temperature is
stored in the memory. The processor reads instructions from the
memory and executes them.

Washing Machine
(Various inputs and outputs in
Washing Machine)

Inputs
 User push button: These are various buttons used for
the interaction with user.
 Water Temperature: The temperature sensor senses
the current temperature of the water and give this
temperature as an input to the controller.
 Drum Speed: Current speed of drum is sensed and this
input is also given to the controller.
 Water Level Sensor: this input gives current
temperature of the water.
 Door close switch: it is used to sense whether the door
is closed or not.Prepared By: D. Y. Vankawala

Outputs
 Drum Motor: It is connected with the washing machine
drum and it is used for rotating drum.
 Water Heater: This signal is the output from controller and
input for water heater which is used to switch on or off the
heater.
 Water Pump: This signal is used to control the water pump
of the washing machine.
 Water Valves: This signal is used to open or close the water
valve of washing machine.
 User Display: It indicate the current ongoing activity and
other signals related to washing machine.
 Door Release: It is the signal for releasing the door for
washing machine.

Data flow diagram for washing
Machine

Principle of washing machine

Block Diagram

Working

Development cycle for washing
Machine

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 Problem Definition: In this stage of development
first we have to define a definition for washing
machine which is used to identify various requirement
of problems and also we can understand the whole
problem related to washing machine.
 Economic appraisal and decision to go ahead:
Once the problem definition is completed then the
next step is whether the definition is economically
appraise of not. If it is appraise, then they took
decision to go ahead for same definition.

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 System Analysis: Next step for development cycle is to analyze
whole the system and indentify requirement of various hardware
and software.
 Software and Hardware Development: Once identification of
various software and hardware is done, next step to develop
software and then develop hardware according to that software.
 Error Correction(Debugging): Once software and hardware is
developed, then next step is to test both. If there is error during
testing then it is solved by testing hardware and software.
 Final Documentation: Once all the error is solved then next
step is to create the final product and prepare the final
documentation.

Operating System (OS)

Overview
 An operating System (OS) is an intermediary between
users and computer hardware. It provides users an
environment in which a user can execute programs
conveniently and efficiently.
 In technical terms, it is software which manages
hardware. An operating System controls the allocation
of resources and services such as memory, processors,
devices and information.

Definition
 An operating system is a program that acts as an
interface between the user and the computer hardware
and controls the execution of all kinds of programs.

 Following are some of important functions of an operating
System.
 Memory Management
Memory management refers to management of Primary
Memory or Main Memory. Main memory is a large array of words or
bytes where each word or byte has its own address. Main memory
provides a fast storage that can be access directly by the CPU. So for a
program to be executed, it must in the main memory.
 Processor Management
In multiprogramming environment, OS decides which process
gets the processor when and how much time. This function is called
process scheduling.
 Device Management
Operating System does the following activities for device management.
1. Keeps tracks of all devices. Program responsible for this task is known
as the I/O controller.
2. Decides which process gets the device when and for how much time.
3. Allocates the device in the efficient way.
4. De-allocates devices.

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 File Management
A file system is normally organized into directories for easy navigation and usage. These
directories may contain files and other directions. Operating System does the following
activities for file management.
1. Keeps track of information, location, uses, status etc. The collective facilities are often
known as file system.
2. Decides who gets the resources.
3. Allocates the resources.
4. De-allocates the resources.
 Security
By means of password and similar other techniques, preventing unauthorized access to
programs and data.
 Control over system performance
Recording delays between request for a service and response from the system.
 Job accounting
Keeping track of time and resources used by various jobs and users
 Error detecting aids
Production of dumps, traces, error messages and other debugging and error detecting
aids.
 Coordination between other software and users
Coordination and assignment of compilers, interpreters, assemblers and other software
to the various users of the computer systems

Types of OS

1. Batch operating system
 The users of batch operating system do not interact
with the computer directly. Each user prepares his job
on an off-line device like punch cards and submits it to
the computer operator. To speed up processing, jobs
with similar needs are batched together and run as a
group. Thus, the programmers left their programs with
the operator. The operator then sorts programs into
batches with similar requirements.

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 The problems with Batch Systems are following.
1. Lack of interaction between the user and job.
2. CPU is often idle, because the speeds of the
mechanical I/O devices are slower than CPU.
3. Difficult to provide the desired priority.

2. Time-sharing operating systems
 Time sharing is a technique which enables many people, located at
various terminals, to use a particular computer system at the same
time. Time-sharing or multitasking is a logical extension of
multiprogramming. Processor's time which is shared among multiple
users simultaneously is termed as time-sharing. The main difference
between Multiprogrammed Batch Systems and Time-Sharing Systems
is that in case of multiprogrammed batch systems, objective is to
maximize processor use, whereas in Time-Sharing Systems objective is
to minimize response time.
 Multiple jobs are executed by the CPU by switching between them, but
the switches occur so frequently. Thus, the user can receive an
immediate response. For example, in a transaction processing,
processor execute each user program in a short burst or quantum of
computation. That is if n users are present, each user can get time
quantum. When the user submits the command, the response time is
in few seconds at most.
 Operating system uses CPU scheduling and multiprogramming to
provide each user with a small portion of a time. Computer systems
that were designed primarily as batch systems have been modified to
time-sharing systems.

 Advantages of Timesharing operating systems are
following
1. Provide advantage of quick response.
2. Avoids duplication of software.
3. Reduces CPU idle time.
 Disadvantages of Timesharing operating systems are
following.
1. Problem of reliability.
2. Question of security and integrity of user programs
and data.
3. Problem of data communication.

Distributed operating System
 Distributed systems use multiple central processors to
serve multiple real time application and multiple users.
Data processing jobs are distributed among the processors
accordingly to which one can perform each job most
efficiently.
 The processors communicate with one another through
various communication lines (such as high-speed buses or
telephone lines). These are referred as loosely coupled
systems or distributed systems. Processors in a distributed
system may vary in size and function. These processors are
referred as sites, nodes, and computers and so on.

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 The advantages of distributed systems are following.
1. With resource sharing facility user at one site may be
able to use the resources available at another.
2. Speedup the exchange of data with one another via
electronic mail.
3. If one site fails in a distributed system, the remaining
sites can potentially continue operating.
4. Better service to the customers.
5. Reduction of the load on the host computer.
6. Reduction of delays in data processing.

Network operating System
 Network Operating System runs on a server and and
provides server the capability to manage data, users,
groups, security, applications, and other networking
functions. The primary purpose of the network
operating system is to allow shared file and printer
access among multiple computers in a network,
typically a local area network (LAN), a private network
or to other networks. Examples of network operating
systems are Microsoft Windows Server 2003, Microsoft
Windows Server 2008, UNIX, Linux, Mac OS X, Novell
NetWare, and BSD.

 The advantages of network operating systems are
following.
1. Centralized servers are highly stable.
2. Security is server managed.
3. Upgrades to new technologies and hardware can be easily
integrated into the system.
4. Remote access to servers is possible from different
locations and types of systems.
 The disadvantages of network operating systems are
following.
1. High cost of buying and running a server.
2. Dependency on a central location for most operations.
3. Regular maintenance and updates are required.

Real Time operating System
 Real time system is defines as a data processing system in which
the time interval required to process and respond to inputs is so
small that it controls the environment. Real time processing is
always on line whereas on line system need not be real time. The
time taken by the system to respond to an input and display of
required updated information is termed as response time. So in
this method response time is very less as compared to the online
processing.
 Real-time systems are used when there are rigid time
requirements on the operation of a processor or the flow of data
and real-time systems can be used as a control device in a
dedicated application. Real-time operating system has well-
defined, fixed time constraints otherwise system will fail. For
example Scientific experiments, medical imaging systems,
industrial control systems, weapon systems, robots, and home-
appliance controllers, Air traffic control system etc.

 There are two types of real-time operating systems.
 Hard real-time systems
Hard real-time systems guarantee that critical
tasks complete on time. In hard real-time systems
secondary storage is limited or missing with data
stored in ROM. In these systems virtual memory is
almost never found.
 Soft real-time systems
Soft real time systems are less restrictive. Critical
real-time task gets priority over other tasks and retains
the priority until it completes. Soft real-time systems
have limited utility than hard real-time systems. For
example, Multimedia, virtual reality, Advanced
Scientific Projects like undersea exploration etc.

Types of mobile OS

Introduction
 Design and capabilities of a Mobile OS (Operating System)
is very different than a general purpose OS running on
desktop machines:
 mobile devices have constraints and restrictions on their
physical characteristic such as screen size, memory,
processing power and etc.
 Scarce availability of battery power
 Limited amount of computing and communication
capabilities
 Thus, they need different types of operating systems
depending on the capabilities they support. e.g. a PDA OS
is different from a Smartphone OS.
 Operating System is a piece of software responsible for
management of operations, control, coordinate the use of
the hardware among the various application programs, and
sharing the resources of a device.

Mobile OS Structure
 A mobile OS is a software platform on top of which
other programs called application programs, can run
on mobile devices such as PDA, cellular phones,
smartphone and etc.
Low-Level Hardware, Manufacturer Device Drivers
Device Operating System Base, Kernel
OS Libraries
Applications

Different Types of Mobile OS
1. IOS (iPhone)
2. Android (Google)
3. Symbian (Nokia)
4. Blackberry OS (Blackberry)
5. Windows Phone OS (Microsoft)

1. IOS (iPhone)
iOS (previously iPhone OS) is a mobile operating system developed and
distributed by Apple Inc. Originally released in 2007 for the iPhone and iPod
Touch, it has been extended to support other Apple devices such as the iPad
and Apple TV. Unlike Microsoft's Windows CE (Windows Phone) and Google's
Android, Apple does not license iOS for installation on non-Apple hardware.
As of 2012 Apple's App Store contained more than 700,000 iOS applications,
which have collectively been downloaded more than 30 billion times .
 The user interface of iOS is based on the concept of direct manipulation, using
multi-touch gestures.
 Interface control elements consist of sliders, switches, and buttons. The
response to user input is immediate and provides a fluid interface. Interaction
with the OS includes gestures such as swipe, tap, pinch, and reverse pinch, all
of which have specific definitions within the context of the iOS operating
system and its multi-touch interface.
 Internal accelerometers are used by some applications to respond to shaking
the device (one common result is the undo command) or rotating it in three
dimensions (one common result is switching from portrait to landscape
mode).

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iOS is derived from OS X, with which it shares
the Darwin foundation, and is therefore a Unix
operating system. iOS is Apple's mobile version of
the OS X operating system used on Apple
computers. In iOS, there are four abstraction
layers: the Core OS layer, the Core Services layer,
the Media layer, and the Cocoa Touch layer. The
current version of the operating system (iOS 5.1.1)
dedicates 1-1.5 GB of the device's flash memory for
the system partition, using roughly 800 MB of that
partition (varying by model) for iOS itself.

IOS feature
 Mac OS X has a preemptive multitasking environment.
 Preempting is the act of taking the control of
operating system from one task and giving it to
another task.
 It supports real-time behavior.
 In Mac OS X, each application has access to its own 4
GB address space.
 Not any application can directly modify the memory of the
kernel. It has a strong mechanism for memory protection.

2. Android(Google)
 Android is a Linux-based operating system designed primarily for touchscreen
mobile devices such as smartphones and tablet computers, developed by
Google in conjunction with the Open Handset Alliance. Initially developed by
Android Inc, whom Google financially backed and later purchased in 2005,
Android was unveiled in 2007 along with the founding of the Open Handset
Alliance, a consortium of 86 hardware, software, and telecommunication
companies devoted to advancing open standards for mobile devices. Google
releases the Android code as open-source, under the Apache License. The
Android Open Source Project (AOSP), lead by Google, is tasked with the
maintenance and further development of Android. Additionally, Android has a
large community of developers writing applications ("apps") that extend the
functionality of devices. Developers write primarily in a customized version of
Java. and apps can be downloaded from online stores such as Google Play
(formerly Android Market), the app store run by Google, or third-party sites. In
June 2012, there were more than 600,000 apps available for Android, and the
estimated number of applications downloaded from Google Play was 20
billion. The first Android-powered phone was sold in October 2008, and by the
end of 2010 Android had become the world's leading smartphone platform. It
had a worldwide smartphone market share of 59% at the beginning of 2012 .

Android Feature
 Android is a powerful Operating System supporting a large
number of applications in Smart Phones. These
applications make life more comfortable and advanced for
the users. Hardwares that support Android are mainly
based on ARM architecture platform.
 Android comes with an Android market which is an online
software store. It was developed by Google. It allows
Android users to select, and download applications
developed by third party developers and use them. There
are around 2.0 lack+ games, application and widgets
available on the market for users.

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 Android applications are written in java programming
language. Android is available as open source for
developers to develop applications which can be
further used for selling in android market. There are
around 200000 applications developed for android
with over 3 billion+ downloads. Android relies on
Linux version 2.6 for core system services such as
security, memory management, process management,
network stack, and driver model. For software
development, Android provides Android
SDK (Software development kit).

3. Symbian(Nokia)
Symbian is a mobile operating system designed for smartphones
originally developed by Symbian Ltd. but currently maintained by
Accenture.[18] The Symbian platform is the successor to Symbian OS
and Nokia Series 60. The latest version, Symbian ver.3, was officially
released in Q4 2010 and first used in the Nokia N8 [19]. The first
Symbian phone the touchscreen Ericsson R380 Smartphone was
released in 2000 [20] and was the first device to be marketed as a
'smartphone' [21]. It combined a PDA with a mobile phone [22]. Later
in 2000, the Nokia 9210 communicator was released, also with
Symbian. The later 9500 was Nokia's first camera phone and first Wi-Fi
phone. The 9300 was smaller, and the E90 Communicator included
GPS. In 2007, Nokia launched the Nokia N95 which integrated various
multimedia features: GPS, a 5 megapixel camera with autofocus and
LED flash, 3G and Wi-Fi connectivity and TV-out. In the next few years
these features would become standard on high-end smartphones. The
Nokia 6110 Navigator was a Symbian based dedicated GPS phone
introduced in June 2007.

Symbian Feature
 Symbian OS is 32 bit.
 It is a multitasking operating system and very less dependence on peripherals.
 Kernel runs in the privileged mode and exports its service to user applications
via user libraries.
 Real-time: it has a real-time, multithreaded kernel.
 Data Caging : it allows applications to have their own private data partition.
This feature allows for applications to guarantee a secure data store. It can be
used for e-commerce applications, location aware applications and etc.
 Multimedia: it supports audio, video recording, playback and streaming, and
Image conversion.
 Platform Security : Symbian provides a security mechanism against malware.
It allows sensitive operations can be accessed by applications which have been
certified by a signing authority. In addition, it supports full encryption and
certificate management, secure protocols ( HTTPS, TLS and SSL) and WIM
framework.
 Internationalization support: it supports Unicode standard.
 Fully object-oriented and component- based
 Optimized memory management.

4. Windows phone OS
 Windows Mobile OS is a proprietary and not open source OS originally
created to be a mobile version of Windows with a user interface
compliant to the current Windows version. It is based on the Windows
CE v5.2 kernel, which most hardware specific components are offered
as open source. Windows CE is a minimalistic real-time multi-tasking
OS that can run in less than a megabyte of memory. Windows Mobile
was updated to version 6.5 in October 2009 and the analysis is based
on this update. With this update a new user interface inspired by
trends from smartphones user interfaces. The update also included
access to the new application store from Microsoft called Windows
Marketplace. The amount of applications available is limited and the
functionality is not creative and fancy like iPhone and Android. The
Microsoft application store is not the only one for the Windows Mobile.
Due to the many years on the market existing web sites contains a lot of
applications available to the device. Most of them lack the creative
layout and innovative steps known from the iPhone.

5. Blackberry OS
 BlackBerry is a line of phone devices developed and
designed by Research In Motion (RIM). The first
BlackBerry smartphone was released in 1999. The latest
BlackBerry 7 devices were announced in the Summer of
2011. BlackBerry devices are smartphones, which are
designed to function as personal digital assistants, portable
media players, internet browsers, gaming devices, cameras
and much more. They are primarily known for their ability
to send and receive push email and instant messages while
maintaining a high level of security through on-device
message encryption. BlackBerry devices support a large
variety of instant messaging features, with the most
popular being the proprietary BlackBerry Messenger
service.

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 The operating system is implemented supporting true
multi-tasking without noticeable performance lack
and due to the implementation of the OS; the
applications load fast and perform really well on slow
devices. The general layout and browsing through
menus feels classic but it works smoothly. Multi-touch
is supported in the newer versions of the OS.
Blackberry OS does not support any Flash versions and
the use of the internet seems to be intended for
surfing, e-mail and traditional client server calendar
synchronisation.

Comparison of IOS, Android and
windows OS

Characteristics of real time system
 Large and complex — vary from a few hundred lines
of assembler or C to 20 million lines of estimated code
for the Space Station Freedom.
 Concurrent control of separate system
components— devices operate in parallel in the real-
world; better to model this parallelism by concurrent
entities in the program
 Facilities to interact with special purpose
hardware — need to be able to program devices in a
reliable and abstract way.
 Mixture of Hardware/Software: some modules
implemented in hardware, even whole systems, SoC

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 Extreme reliability and safety — embedded systems typically control
the environment in which they operate; failure to control can result in
loss of life, damage to environment or economic loss.
 Guaranteed response times — we need to be able to predict with
confidence the worst case response times for systems; efficiency is
important but predictability is essential.
 Stability --- Under overload conditions, real-time systems need to
continue to meet the deadlines of the most critical tasks, though the
deadlines of non-critical tasks may not be met. This is in contrast to
the requirement of fairness for traditional systems even under overload
conditions.
 Time constraints --- Every real-time task is associated with some time
constraints. One form of time constraints that is very common is
deadlines associated with tasks. A task deadline specifies the time
before which the task must complete and produce the results. It is the
responsibility of the real-time operating system (RTOS) to ensure that
all tasks meet their respective time constraints

Overview of embedded system

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