Embedded System Notes for BE and ME Student

1. Unit I
Embedded System
Dr. P. H. Zope
Assistant Professor
SSBT s COET Bambhori Jalgaon
North Maharashtra University India
phzope@gmail.com
09860631040

2. UNIT I
Embedded system Introduction:
Introduction to Embedded System, History, Design challenges, optimizing design metrics,
time to market, applications of embedded systems and recent trends in embedded systems,
embedded design concepts and definitions, memory management, hardware and software
design and testing, communication protocols like SPI, SCI, I2C, CAN etc
Lectures 10, Marks 20
UNIT II
System Architecture:
Introduction to ARM core architecture, ARM extension family, instruction set, thumb
Instruction set, Pipeline, memory management, Bus architecture,
study of on-chip peripherals like I / O ports, timers, counters, interrupts, on-chip ADC, DAC,
RTC modules, WDT, PLL, PWM, USB etc. Lectures 10, Marks 20
UNIT III
Interfacing and Programming:
Basic embedded C programs for on-chip peripherals studied in system architecture. Need of
interfacing, interfacing techniques, interfacing of different displays including Graphic LCD
(320X240), interfacing of input devices including touch screen etc, interfacing of output
devices like thermal printer etc., embedded communication using CAN and Ethernet, RF
modules, GSM modem for AT command study etc. Lectures 10, Marks 20
Syllabus Embedded System

3. UNIT IV
Real Time Operating System Concept:
Architecture of kernel, task scheduler, ISR, Semaphores, mailbox, message queues, pipes,
events, timers, memory management, RTOS services in contrast with traditional OS.
Introduction to Ucos II RTOS, study of kernel structure of Ucos II, synchronization in Ucos II,
Inter-task communication in Ucos II, memory management in Ucos II, porting of RTOS.
Lectures 10, Marks 20
UNIT V
Embedded Linux:
Introduction to the Linux kernel, Configuring and booting the kernel, the root file system,
Root file directories, /bin, /lib etc., Linux file systems, Types of file system: Disk, RAM, Flash,
Network. Some debug techniques- Syslog and strace, GDB, TCP / IP Networking- Network
configuration, Device control from user space- Accessing hardware directly, Multi
processing on Linux and Inter Process Communication- Linux process model and IPCs,
Multithreading using pThreads - Threads verses Processes and pThreads, Linux and Real-
Time Standard kernel problems and patches. Lectures 10, Marks 20
Syllabus Embedded System

5. 5
UNIT I
Embedded system Introduction:
An embedded system is a computer system (a combination of hardware and
software) with a dedicated function within a larger mechanical or electrical
system, often with real-time computing constraints.
Embedded systems (ES) = information processing systems embedded into a larger
product
It is embedded as part of a complete device often including hardware and
mechanical parts.
Embedded systems control many devices in common use today.
• An example of an embedded system is a microprocessor that controls an automobile
engine.
• An embedded system is designed to run on its own without human intervention, and
may be required to respond to events in real time.
What is an Embedded System?

6. Applications
Areas

7. Application Areas• TV
• ste eo
• e ote o t ol
• pho e / o ile pho e
• ef ige ato
• i o a e
• ashi g a hi e
• ele t i tooth ush
• o e / i e o ead ooke
• at h
• ala lo k
• ele t o i usi al i st u e ts
• ele t o i to s (stuffed animals,handheld toys, pinballs, etc.)
• edi al ho e e uip e t (e.g. blood pressure, thermometer)
• …
• [PDAs?? Mo e like sta da d o pute s ste ]
Consumer Products

8. Application Areas
• Medical Systems
– pace maker, patient monitoring systems, injection systems, intensive
a e u its, …
• Office Equipment
– p i te , opie , fa , …
• Tools
– ulti ete , os illos ope, li e teste , GPS, …
• Banking
– ATMs, state e t p i te s, …
• Transportation
– (Planes/Trains/[Automobiles] and Boats)
• ada , t affi lights, sig alli g s ste s, …

9. Application Areas
• Automobiles
– engine management, trip computer, cruise control,
immobilizer, car alarm,
– ai ag, ABS, ESP, …
• Building Systems
– elevator, heater, air conditioning, lighting, key card
e t ies, lo ks, ala s ste s, …
• Agriculture
– feedi g s ste s, ilki g s ste s, …
• Space
– satellite s ste s, …

10. Examples of embedded systems
• PDA
• Microwave
• Programmable washing Machine
• Digital answering machine
• GPS
• Intelligent credit card
• Cruise control
• Car engine timing

11. Examples of embedded systems
• Industrial controller
• Guided missiles
• Digital TV
• Flight controller
• Measuring instruments
• Medical instruments
• Gaming devices
• and on and on ……
Mars, December 3, 1999
Crashed due to uninitialized variable

12. Embedded system Configuration
Hardware
Operating
System
Programs
Hardware
Including Operating
System Components
User Program
Typical Embedded system
Configuration
Typical Computer system
Configuration

14. A Typical Embedded System
Algorithms for
Digital Control
Data Logging
Data Retrieval
and Display
Operator
Interface
Interface
Engineering
System
Remote
Monitoring System
Real-Time
Clock
Database
Ope ato s
Console
Display
Devices
Real-Time Computer

16. Embedded Hardware
• CPU
– Intel x86
– PowerPC(Mac) G3,G4,G5
– SPARC, Alpha
– ARM
– MIPS
– ……
• DATA Wide
– 8 Bit controllers(still!)
– 16 Bit controllers(mainly)
– 32 Bit controllers(start popular)
– 64 Bit controllers(high performance)

17. Characteristics of Embedded Systems

18. Characteristics of Embedded Systems

20. CHARACTERISTICS OF EMBEDDED SYSTEMS
• Single Functioned
• Tightl Co st ai t
• ‘eal Ti e a d ‘ea ti e
• Co ple Algo ith s
• Use I te fa e
• Multi ‘ate

21. An Embedded System can execute a specific function repeatedly
i.e., dedicated function
Single Functioned
As an example, Air conditioner will be cooling the room. Cooling is
its dedicated functionality and it cannot be used for any other
purposes. AC a t be used for making calls.
Likewise mobile phone is an Embedded System that can be used to
make and receive calls and it a t be used for controlling room
temperature.

22. Consider the list of embedded systems that are being used every day.
1. Pager.
2. Microwave oven.
3. Mobile phone.
4. ATMs.
5. Car braking systems.
6. Automobile cruise controllers.
7. Pace makers.
8. Modem.
9. Network cards and many more.

23. Tightly Constraint
Whatever system is being designed, they have constraints. Embedded
Systems are also tightly constraint in many aspects. Few aspects are
being analyzed here.
1. Manufacturing Cost
2. Performance
3. Size
4. Power
The above four parameters decide the success of Embedded System.

24. Real Time and Reactive
What is real time? —A nice question to start with!
Take an instance of travel in BMW car. (Great feel it would be).
(The braking system is an embedded system). And unfortunately a
lorry is coming opposite to the car... The driver is applying brake
there!. What would be the action required? It should immediately
stop the car right. This is a real time and reactive behaviour. The brake
may be applied at any point in time. And the vehicle should be
stopped immediately at the instance of applying brake. It is never
known when brake has to be applied, so the system should be ready
to accept the input at any time and should be ready to process it.

25. Few examples can be spotted for Real time and Reactive behavior
of an Embedded System:
(a) Pace Maker’s action.
(b) Flights Landing Gear Control.
(c) ECG Machines output.
A d so o … Ma e a ples ould e ited he e!

26. Complex Algorithms
The processor inside the embedded system should perform
operations that are complex in nature.
An example is digital camera. It is used to take color photographs,
motion pictures, black and white pictures, etc. It needs to pull in lots
of complex algorithms for performing all the above mentioned
operations.
So as a point to conclude, every embedded system will have lots of
complex algorithms running inside it.

27. User Interface
Multi Rate
Embedded Systems need to control and drive certain operations at
one rate and certain other operations at different rate. Example can
be Digital Camera. It is used to take pictures which are still. Also it is
capable of shooting video. So it has to be capable of driving the first
operation from a speed different than the second one.
Designing system with easier and comfortable interface is most
important. Also it should have options required for the operation of
the device.
Example is ATM machine; it has got comfortable interfaces and
options.

28. 28
Characteristics of Embedded Systems
• Application-specific functionality – specialized for one or one
class of applications
• Deadline constrained operation – system may have to perform
its function(s) within specific time periods to achieve successful
results
• Resource challenged – systems typically are configured with a
modest set of resources to meet the performance objectives
• Power efficient – many systems are battery-powered and must
conserve power to maximize the usable life of the system.
• Form factor – many systems are light weight and low volume to
be used as components in host systems
• Manufacturable – usually small and inexpensive to manufacture
based on the size and low complexity of the hardware.

29. CHALLENGES IN DESIGNING AN EMBEDDED SYSTEM

30. Meeting Deadlines
How can the deadline be met that is meant for the product? Meeting
deadline accurately will need high speed hardware. Increasing
hardware components with quality would increase the cost of the
product. This is the first challenge in front of designers.
Hardware Selection
Embedded Systems never had a luxury of having much hardware. Taking
memory into consideration first, Embedded Systems will have very little
inbuilt memory.
Adding more memory of smaller size will increase cost factor. So keep
memory only as much as needed. It can have an expansion slot for the
system, if user is willing to expand memory, who bothers, let user expand.
Coming to processor selection, if a very high speed processor is selected, it
would end up in draining the battery at the earliest. But it a t be
compromised with speed also. So select a processor that perfectly fits in
with requirement. Too high speed processor would cost more and can drain
battery also.

31. Is it upgradable and maintainable?
Will it work?
Assume that a mobile phone has been designed and it is released in the market.
But after reaching people the product was found with problems in one or two aspects. The
developer would know that problem and it can be fixed. But how will it reach the phone that
had already reached public?
So it must be supporting with upgradation of versions of software for it. Keep this in mind
that the product should be upgradable with the same hardware! Secondly, when writing
software for embedded systems, it should be kept in mind on maintainability. The code
should not be just written in such a way that only developer who developed it can
understand. It should be understandable for other engineers also. Other engineers should
also be able to understand and fix bugs in the code if any, if need be.
Nice Question. Is t it? Yeah. Please ensure if the system that has been designed is really
working fine. How can it be ensured? Through rigorous testing it is possible; it needs to be
proceeded with testing in many ways. First can be unit testing, next stage is Sanity Testing
and the third stage can be Regression testing.
Also even if the product has entered, it has to be constantly monitored. If any customer
complaint rises, that bug has to be looked into and has also to be fixed. And more
importantly, the bug that is fixed should not introduce any new bugs. Let s now get to know
about the categorization of the embedded systems!

32. 32
Design Constraints

33. 33
Design Challenges
• Does it really work?
– Is the specification correct?
– Does the implementation meet the spec?
– How do we test for real-time characteristics?
– How do we test on real data?
• How do we work on the system?
– Observability, controllability?
– What is our development platform?
• More importantly – optimising design
metrics!!

34. CATEGORIZATION OF EMBEDDED SYSTEMS
Embedded Systems can be categorized based on the complexity in
building, cost factors, purpose of the system, tools and other related
environment availability, etc.

36. Features of an embedded system
Embedded systems do a very specific task, they cannot be
programmed to do different things.
• Embedded systems have very limited resources, particularly the memory.
Generally, they do not have secondary storage devices such as the CDROM
or the floppy disk.
• Embedded systems have to work against some deadlines. A specific job
has to be completed within a specific time. In some embedded systems,
called real-time systems, the deadlines are stringent. Missing a dead line
may cause a catastrophe – loss of life or damage to property.

37. • Embedded systems are constrained for power, As many embedded
systems operate through a battery, the power consumption has to be very
low.
• Embedded systems need to be highly reliable. Once in a while, pressing
ALT-CTRL-DEL is OK on your desktop, but you cannot afford to reset your
embedded system.
• Some embedded systems have to operate in extreme environmental
conditions such as very high temperatures and humidity.

38. • Embedded systems that address the consumer market (for example
electronic toys) are very cost-effective. Even a reduction of Rs.10 is lot of
cost saving, because thousands or millions systems may be sold.
• Unlike desktop computers in which the hardware platform is dominated
by Intel and the operating system is dominated by Microsoft, there is a
wide variety of processors and operating systems for the embedded
systems. So, choosing the right platform is the most complex task .

39. Classification of Embedded Systems
Based on functionality and performance requirements,
embedded systems are classified as :
• Stand-alone Embedded Systems
• Real-time Embedded Systems
• Networked Information Appliances
• Mobile Devices

40. Stand-alone Embedded Systems
As the name implies, stand-alone systems work in stand-
alone mode. They take inputs, process them and
Produce the desired output.
The input can be electrical signals from transducers or
commands from a human being such as the pressing of a
button.
The output can be electrical signals to drive another
System,an LED display 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.

41. Real-time Systems
Embedded systems in which some specific work has to be
done in a 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 deadlines are called hard real-
time systems.

42. In some embedded systems, deadlines are imposed, but
not adhering to them once in a while may not lead to a
catastrophe.
For example, consider a DVD player. Suppose, you give a
command to the DVD player from a remote control, and
there is a delay of a few milliseconds in executing that
command.
But, this dela o t lead to a se ious i pli atio . Su h
systems are called soft real-time systems .

43. Hard Real-Time Embedded System

44. Networked Information Appliances
Embedded systems that are provided with network
interfaces and 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 a o pa s Intranet.
These systems have emerged in recent years. These
systems run the protocol TCP/IP stack and get connected
through PPP or Ethernet to an network and communicate
with other nodes in the network.

45. Here are some examples of such systems
• A networked process control system consists of a
number of embedded systems connected as a local area
network.
• Each embedded system can send real-time data to a
central location from where the entire process control
system can be monitored.
• The monitoring can be done using a web browser such
as the Internet Explorer.
• A web camera can be connected to the Internet. The
web camera can send pictures in real-time to any
computer connected to the Internet.
• In such a case, the web camera has to run the HTTP
server software in addition to the TCP/IP protocol stack.

46.  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
through a click of the mouse.

47. This slide shows a weather monitoring system connected
to the Internet. TCP/IP protocol suite and HTTP web
server software will be running on this system. Any
computer connected to the Internet can access this
system to obtain real-time weather information.

48. The networked information appliances need to run the
complete TCP/IP protocol stack including the application
layer protocols. If the appliance has to provide
information over the Internet, HTTP web server software
also needs to run on the system.

49. Mobile Devices
Mobile devices such as mobile phones, Personal Digital
Assistants (PDAs), smart phones etc. are a special
category of embedded systems. Though the PDAs do
many general purpose tasks, they need to be designed
just like the o e tio al e edded s ste s.

50. The limitations of the mobile devices – memory
constraints, small size, lack of good user interfaces such as
full fledged keyboard and display etc. are same as those
found in the embedded systems discussed above. Hence,
mobile devices are considered as embedded systems.
However, the PDAs are now capable of supporting general
purpose application software such as word processors,
games, etc.

51. 51
Design challenge – optimizing design metrics
• Common metrics
• NRE cost (Non-Recurring Engineering cost): The
one-time monetary cost of designing the system
• Unit cost: the monetary cost of manufacturing each copy of
the system, excluding NRE cost
• Size: the physical space required by the system
• Performance: the execution time or throughput of the
system
• Power: the amount of power consumed by the system
• Flexibility: the ability to change the functionality of the
system without incurring heavy NRE cost

52. 52
Design Metrics
• Common metrics (continued)
• Time-to-prototype: the time needed to build a working version
of the system
• Time-to-market: the time required to develop a system to the
point that it can be released and sold to customers
• Maintainability: the ability to modify the system after its initial
release
• Correctness, safety, many more

53. 53
Trade-off in Design Metrics
• Expertise with both
software and hardware
is needed to optimize
design metrics
– Not just a hardware or
software expert, as is
common
– A designer must be
comfortable with various
technologies in order to
choose the best for a
given application and
constraints
SizePerformance
Power
NRE cost

54. 54
Time-to-market: a demanding design metric
• Time required to develop
a product to the point it
can be sold to customers
• Market window
– Period during which the
product would have highest
sales
• Average time-to-market
constraint is about 8
months
• Delays can be costly
Revenues($)
Time (months)

55. 55
Losses due to delayed market entry
• Simplified revenue model
– Product life = 2W, peak at W
– Time of market entry defines
a triangle, representing
market penetration
– Triangle area equals revenue
• Loss
– The difference between the
on-time and delayed triangle
areasOn-time Delayed
entry entry
Peak revenue
Peak revenue from
delayed entry
Market rise Market fall
W 2W
Time
D
On-time
Delayed
Revenues($)

56. 56
Time to Market Design Metric
• Simplified revenue model
Product life = 2W, peak at W
Time of market entry defines a triangle,
representing market penetration
Triangle area equals revenue
• Loss
The difference between the on-time and delayed
triangle areas
• Avg. time to market today = 8 mth
• 1 day delay may amount to $Ms
On-time Delayed
entry entry
Peak revenue
Peak revenue from
delayed entry
Market
rise
Market
fall
W 2W
Time
D
On-time
Delayed
Revenues($)

57. 57
NRE and unit cost metrics
• But, must also consider time-to-market
$0
$40,000
$80,000
$120,000
$160,000
$200,000
0 800 1600 2400
A
B
C
$0
$40
$80
$120
$160
$200
0 800 1600 2400
Number of units (volume)
A
B
C
Number of units (volume)
totalcost(x1000)
perproductcost
• Compare technologies by costs -- best depends on quantity
Technology A: NRE=$2,000, unit=$100
Technology B: NRE=$30,000, unit=$30
Technology C: NRE=$100,000, unit=$2
Source: Embedded System Design:
Frank Vahid/ Tony Vargis (John Wiley &
Sons, Inc.2002)

58. Example
The design of a particular disk drive has an NRE cost of $100,000 and a unit cost of
$20. How much will we have to add to the cost of each product to cover our NRE
cost, assuming we sell: (a) 100 units, and (b) 10,000 units?

59. (a) added cost = NRE / # units produced
= $100,000 / 100
= $1,000
(b) added cost = NRE / # units produced
= $100,000 / 10,000
= $10
Example
The design of a particular disk drive has an NRE cost of $100,000 and a unit cost of
$20. How much will we have to add to the cost of each product to cover our NRE
cost, assuming we sell: (a) 100 units, and (b) 10,000 units?

60. Example
For a particular product, you determine the NRE cost and unit cost to be the
following for the three listed IC technologies: FPGA: ($10,000, $50); ASIC:
($50,000, $10); VLSI: ($200,000, $5). Determine precise volumes for which each
technology yields the lowest total cost.

61. Example
For a particular product, you determine the NRE cost and unit cost to be the
following for the three listed IC technologies: FPGA: ($10,000, $50); ASIC:
($50,000, $10); VLSI: ($200,000, $5). Determine precise volumes for which each
technology yields the lowest total cost.
Total cost = NRE cost + (unit cost * # units produced)
FPGA = 10,000 + 50x
ASIC = 50,000 + 10x
VLSI = 200,000 + 5x
10,000 + 50x = 50,000 + 10x
40x = 40,000
x = 1,000
50,000 + 10x = 200,000 + 5x
5x = 150,000
x = 30,000
Technology Amount
FPGA < 1,000 units
ASIC 1,000 - 30,000 units
VLSI > 30,000 units