2. What is an embedded system
An embedded system is an electronic/electro-
mechanical system designed to perform a
specific function and is a combination of both
hardware and firmware (software).
3. EMBEDDED SYSTEM
To perform a specific function
Combination of both h/w and s/w
May or may not contain an O.S
The firmware of the embedded system is pre-
programmed and it is non alterable by the end user
4. CLASSIFICATION OF ES
1. Based on generation
2. Complexity & performance requirements
3. Based on deterministic behavior
4. Based on triggering
5. 1. CLASSIFICATION BASED ON
GENERATION
First generation : 8 bit µp like 8085- simple h/w –
f/w in assembly code
Second generation : 16 bit µp and 8/16 bit µc –
instruction set much more complex
Third generation : 32 bit µp and 16 bit µc – DSP
and ASIC came to picture – pipelining evolved
Fourth generation : advent of SOC multi core
processors- making use of high performance RTES
What is next?
6. 2. CLASSIFICATION BASED ON
COMPLEXITY AND PERFORMANCE
Small scale embedded system:
Simple
Not time critical
Low performance
Low cost
May or may not contain o.s
medium scale embedded system:
Slight complex in h/w and s/w
Medium performance
Low cost
Usually contain an o.s
Large scale embedded system :
Highly complex h/w and s/w
Demanding high performance
May contain multi-core processors and co processors
Usually contain RTOS for task scheduling and prioritization management
7. MAJOR APPLICATION AREAS
Consumer electronics
House hold appliances
Security systems
Automotive industry
Telecom
Computer networking systems
Healthcare
Measurement and instrumentation
Banking & retail
Card readers
8. PURPOSE OF EMBEDDED SYSTEMS
Each embedded system is designed to serve the
purpose of any one or a combination of the
following tasks:
Data collection/storage/representation
Data communication
Data processing
Monitoring
Control
Application specific user interface
9. ELEMENTS OF AN EMBEDDED
SYSTEM
MEMORY
System
core
I/O PORTS
(SENSORS)
O/P PORTS
(ACTUATOR
S)
Other
supporting
IC s and
subsystems
communication
interface
10. CORE OF THE EMBEDDED
SYSTEM
The core of the embedded system falls in to any
one of the following categories
1. general purpose and domain specific
processors ( µp, µC, DSP )
2. ASIC(Application specific IC)
3. programmable logic devices (PLD)
4. commercial off-the-shelf components
(COTS)
11. GPP vs. ASIP
General purpose processor :
Designed for general computational tasks
E.g.. Processor in the laptop
High volume production
Unit cost for a chip is low
ASIP instruction set and architecture optimized
to specific application
ASIP arises when the GPP are unable to meet the
application needs
12. µP Vs µC
µP
Representing a CPU performing
ALU operations according to a pre
defined set of instructions
It is a dependent unit requires
other chips like timers , memory
chips etc
Doesn't contain built in I/O port
Limited power saving options
Mostly general purpose in design
and operation
µC
Highly integrated chip that contains
CPU, RAM, on chip ROM , timer etc
It is a self contained unit
Most of the processors contain multiple
built in I/O ports
Includes lot of power saving features
Mostly application oriented or domain -
specific
13. RISC VS CISC
RISC
Lesser no. of instruction
Instruction pipeline
Orthogonal instruction set(operates on
any register and any addressing mode)
Operations are performed on registers
only except load and store
Large no. of registers are available
Programmer needs to write more code
to execute a task
Fixed length instruction
Less silicon usage
With Harvard Architecture
CISC
Greater no. of instructions
Generally no instruction pipelining
Non-orthogonal instruction set
Operations are performed on registers or
memory
Limited no. of registers are available
Programmer can achieve the same with a
single instruction
Variable length instructions
More silicon usage since additional decoder
logic is used for complex instruction
Can be Harvard or Von Neumann
14. Harvard Vs Von Neumann Architecture
Harvard Architecture
Separate buses for instruction and data
Easier to pipeline
Comparatively high cost
No memory alignment problem
Since data memory and program memory
are stored physically in different locations
no chances for corruption of program
memory
Von- Neumann Architecture
Single shared bus for instruction and data
Low performance compared to Harvard
Cheaper
Allows self modifying codes( modifies while
execution)
Since data memory and program memory
are stored physically in same chip chances
for corruption of program memory
15. Big endian Vs Little endian
Specifies the order in which the data is stored in
the memory in multi byte system
If word length is 2 byte then data can be stored
in 2 ways
Higher order of data byte at higher memory and
lower order just below that
Lower order of data byte at higher memory and
higher order just below that
16. Byte 0
Byte 1
Byte 2
Byte 3
Base address + 0
Base address +1
Base address+2
Base address+3
Little endian – lower order
byte of data at lowest
address
Base address + 0
Base address +1
Base address+2
Base address+3
Byte 3
Byte 2
Byte 1
Byte 0
Big endian
Big endian – higher order
byte of data at lowest
address
17. Load and store operation
Load – content of memory location loaded to a register
Stored- stores the content of data from the specified
register to specified memory
E.g.. Add contents of memory locations x,y and store the
result in location z
load R1,x
load R2,y
add R3,R1,R2
store R3,z
18. Instruction pipelining
conventional instruction execution –fetch-
decode-execute
Instruction pipelining refers to the overlapped
execution of instructions
Processing speed can be increased
19. ASIC
A micro chip designed to perform a unique
application
It integrates several functions to a single chip
and there by reduces the cost
Consumes a very small area and there by helps
in the design of smaller systems
Can be pre-fabricated or custom fabricated
Profitable only for large volume productions
20. Programmable logic devices
Logic devices can be classified into two (fixed and
programmable)
Circuits in fixed logic device are permanent- (for one function
or set of functions) –they can not be changed
PLD offer customers a wide range of logic capacity, features,
speed etc.
final design is completed much faster than that of fixed logic
device
During design phase customers can change the circuitry as
often as they want
PLDs are based on re-writable memory
Once design is final customers can go into many PLDs as they
need
21. CPLD AND FPGA
Two major types of PLDs are field programmable gate
arrays and complex programmable logic devices
FPGA – highest logic density, most features, highest
performance
Offers built in h/w processors, clk management systems,
device to device signaling
Used in wide range of applications telecom, DSP etc
CPLD - Small amount of logic density
Offer very predictable timing characteristics and so ideal for
critical control applications
Usually requires low amount of power
Very inexpensive
Ideal for cost-sensitive, battery operated
Ideal of portable applications such as mobile phones
22. Advantages of PLD
Offer customers much more flexibility during
design cycle
Do not require long lead time for production
part
Allows customers to orders just number of parts
they need, when they need them
Can be reprogrammed. To add new feature
simply upload a new programming file to the
PLD via internet
23. Commercial off-the-shelf components-
COTS
Provides easy integration and interoperability with existing
system components.
May be developed around a general purpose/domain
specific processor/application specific processor
E.g.- remote controlled toy car control units like RF
circuitry part, ADC , UV detectors etc.
Readily available in the market
Cheap
Developer can cut down development time
since no operational and manufacturing standards end
user should stick to a particular vendor for a particular
COTs
Manufacturer of the COTS component may withdraw the
product at any time
24. Memory
On-chip and off-chip memory
Program storage memory-nonvolatile
FLASH ROM
EEPROMPROM MROM EPROM
NVRAM
25. MASKED ROM
One time programmable
Pre programmed by the manufacturer
Make use of hardwired technology for storing
data
Least expensive
MROM is permanent in bit storage, it is
not possible to alter the bit information
26. PROM (OTP)
Not pre- programmed by the manufacturer
End user is responsible for programming
Programmed by PROM programmer which
selectively burns the fuses
Fuses which are burned represents 0 and not
burned represents 1
Can not be reprogrammed
Not useful for development
27. EPROM
Gives flexibility to reprogram the same chip
Stores information by changing the floating gate
of an FET
Quartz crystal window is used to erase
information
It needs to be taken out and put in UV eraser
for 20 to 30 min which is time consuming
Tedious & time consuming
28. EEPROM
Information can be altered by using electrical
signals
Can be reprogrammed in circuit
Can be erased in few milliseconds
Capacity is limited compared with standard
ROM
29. FLASH
Latest and most popular
Combines re programmability of EEPROM and
high capacity of standard ROM
Stores information in array of MOSFET
Erasing can be done at sector /page level
30. RAM
•It is data memory
•Read from it & write to it
•RAM is volatile – power turned off,
content destroyed
•Direct access memory
31. RAM
SRAM, DRAM AND NVRAM
SRAM- stores data in the form of voltage
Made up of flip flop
Fast .Typical access time is 10ns
Low capacity
High cost
Minimum of 6 transistors are used to build a
memory cell
Does not require refreshing
32. DRAM
Made up of MOSFET and a capacitor
Requires refreshing
High capacity
Less expensive
Slow . Typical access time is 60ns
NVRAM
Its RAM with battery backup
Contains SRAM and a minute battery
Life span is around 10 years
33. Memory shadowing
Execution of ROM is very slow compared to RAM
RAM access is three times as fast as ROM
This is to solve the execution speed problem in
processor based system
ROM BIOS is read and the system is configured
according to it during system boot up( its time
consuming)
During boot up copy the BIOS to the shadowed RAM
and write protect the RAM then disable the BIOS
reading
34. SENSORS AND ACTUATORS
Sensors : that converts energy from one form to
another for any measurement or control
purpose
E.g. Smart running shoe
Actuators:
Which converts signals to corresponding physical
action.
Acts as o/p device
35. i/o subsystems
Facilitates the interaction to the embedded system with the
external world
LED:
o/p device
Pn junction diode
Anode to +ve terminal and cathode to –ve terminal
A resistor in series to limit the current
7 segment LED display
o/p device to display alphanumeric characters
8 LEDs
a- g segments
Two configurations- common anode and common cathode
Used for low cost application
36. Optocoupler
To isolate two parts or a circuit (for suppressing
interference in data communication, high voltage
separation etc)
Combines a LED and a photo-transistor in a single
package
Can be used in i/p and o/p circuits
Stepper motor
Electro- mechanical device which generates discrete
displacement in response to dc electrical signals
Dc motor gives continuous rotation
Consumer electronic products, robotics control,
paper feed mechanism of a printer
37. Two phase stepper motor is classified into two.
Uni polar and bi polar
Unipolar: contains two winding per phase
Direction of rotation is controlled by changing
direction of current
Current in one direction flows through one coil
and in opposite direction through the other coil
38. Bipolar:
Contains single winding per phase for reversing
the motor rotation the current flow through the
winding is reversed.
The stepping of stepper motor can be
implemented by changing sequence of activation
of the stator windings
39. Different stepping modes
Full step: both phases are energized simultaneously
Wave step: only one phase energized at a time
Step Coil a Coil b Coil c Coil d
1 H H L L
2 L H H L
3 L L H H
4 H L L H
step Coil a Coil b Coil c Coil d
1 H L L L
2 L H L L
3 L L H L
4 L L L H
40. HALF STEP: Combination of wave and full
step
Highest torque and stabilitystep Coil a Coil b Coil c Coil d
1 H L L L
2 H H L L
3 L H L L
4 L H H L
5 L L H L
6 L L H H
7 L L L H
8 H L L H
41. RELAY
Electro-mechanical device
Contains a relay coil made up of insulated wire on a
metal core and a metal armature with one or more
contacts
When voltage is applied to relay coil , current flows
and generates magnetic field which attracts
armature core and moves the contact point
Widely used configurations are single pole single
throw normally open, single pole single throw
normally closed, single pole double throw
42. Piezo buzzer: is a piezoelectric device for generating
audio indications in embedded application
Contains piezo electric diaphragm which produces sound
in response to the voltage
Self driving and external driving (predefined tone and
different tone)
Push button switch:It is an input device.
Push to make and push to break (normally closed and
normally opened)
In the pushed state it breaks/makes circuit connection
Used for generating a momentary pulse
Used as reset and start in embedded application
Depending on the way in which push button interfaced
to the controller it can generate either a HIGH or LOW
pulse
43. Key board: input device of user interfacing
Can use push button switches , but it is a wastage of
port pins
So matrix key board which reduces the number of
interface connections
For detecting a key press uses scanning technique.
To prevent de-bounce issue a technique should be
applied
s/w technique and h/w technique
s/w easy to implement and the key is read after de-
bounce delay
PPI: To extend i/o capabilities of processors
8255 is popular
Supports 24 i/o pins which ca be grouped in to 8 bit
parallel ports (port A, port B, port C)
44. Communication interface
For communicating with various subsystems of the
embedded system and with external world
On boards communication interfaces
for interconnecting the various ICs and other peripherals
within embedded system
I2C bus (inter integrated circuit bus)
Synchronous bidirectional half duplex two wire serial interface
bus
Comprise of two bus lines, serial clock and serial data (SCL
and SDA)
Many number of I2C devices can be connected
Devices connected to I2C can act as master or slave device
I2C bus three different data rates (100kbps,400kbps,3.4mbps)
45. Serial peripheral interface SPI bus:
Synchronous, bidirectional, full duplex four wire serial
interface bus
It’s a single master multi-slave system
Requires four signal lines for communication (master out slave
in, master in slave out, serial clock, slave select)
Master device is responsible for generating the clock signal
Master selects the required slave device
SPI works on the principle of shift register. Master and slave
devices contain a special shift register for the data to transmit
or receive.
Size of SR is device dependent. Normally it is a multiple of 8
Compared to I2C ,SPI is most suitable for transfer of data in
streams
Limitation is , it doesn’t support an acknowledgement
mechanism
46. UART (universal asynchronous Receiver Transmitter)
Asynchronous form of data transmission
Serial data transmission doesn’t require a clock signal to
synchronize the end of transmission
It relies upon the pre defined agreement between the
devices
For proper communication the transmit line of the
sending device should be connected to the receiving
device
It also provides h/w handshaking signal support for
controlling the serial data flow
Nowadays most the microprocessors are available with
integrate UART functionality
47. 1-wire interface
asynchronous half duplex communication protocol
It makes use of only a single signal line called DQ for
communication and follows master-slave communication
model
It allows power to be sent along the signal wire as
well.(I2C uses internal capacitor to power the device)
Supports a single master and one or more slave devices
Every 1-wire device contains a globally unique 64 bit id
stored within it for addressing
Communication over the 1-wire bus is divided into
timeslots of 60micro sec
48. Parallel interface:
Used for communicating with peripheral device
which are memory mapped to the host of the
system
Device which supports parallel bus can directly
connect to this bus
Controlled by the control signal interface between
the device and the host(rd/wr,select)
Always initiated by host processor, if device wants
to initiate then it should use interrupts
Direction of data is controlled by rd/wr
Decoder circuit activates the chip select line to
activate the device
49. External communication interface
Channels/buses use by the embedded system to communicate with the
external world
RS 232/ RS 422/RS485:
full duplex, wired, asynchronous serial communication interface
Developed by EIA( electronics industries association ) during 1960
Logic 0 is represented with voltage between +3 and + 25,
logic 1 using voltage between -3 and -25
Logic 0 is known as space and logic 1 as mark
Supports baud rates up to 20 kbps
still popular in industrial applications
Supports two different types of connectors- DB-9 and DB-25
Supports only point to point communication
Not suitable for multi- drop communication
More susceptible to noise and reduced operating distance
50. Universal serial bus:Wired high speed serial bus for data communication
Follows star topology with a USB host at the centre and one or more
USB peripheral devices connected to it.
Transmits data in packet format
Improves the noise immunity
Has the ability to supply power to the connecting devices
Mini and micro USB connectors are available for small form factor
devices like portable media player
Supports four different types of data transfers
1 control: s/w to query, configure and issue commands to the USB
device
2 Bulk: for sending block of data to a device,
3 Isochronous data: for real time data communication (data transmitted as
streams in real time. Does not support error checking and
retransmission. Audio devices and medical equipment)
4 Interrupt transfer: for transferring small amount of data.
51. IEEE 1394( Firewire):
wired, isochronous high speed serial communication bus
Supports peer to peer connection and point to multipoint
communication
Allowing 63 devices to be connected on the bus in a tree
topology
Can support a cable length of up to 15ft
Supports data rate of 400 to 3200 Mbits/sec
Supports 3 types of connectors (4pin, 6pin, 9pin)
Used of devices like digital camera, camcorder for data
transfer and storage
Unlike USB doesn’t require a host for communicating
between devices (directly connect a scanner with a printer)
Data rate is far higher than USB
h/w implementation costlier than USB
52. Infrared( IrDA):
serial, half duplex, line of sight based wireless technology for
data( remote control of TV)
Supports point to point and point to multipoint
communication
Communication range 10cm to 1m
IR supports data rates ranging from 9600 bits/s to 16 Mbps
Infrared light emitting diode is the IR source and photodiode
acts as receiver
Has two parts , physical link part and a protocol part
Popular for file exchange and data transfer in low cost devices
Even now most of the mobile phones supports IrDA
53. Blue tooth(BT):
low cost, low power, short range wireless technology for data
and voice
Supports a data rate of up to 1Mbps
Range approximately 30ft
Like IrDA it has two parts
Each BT device has a 48 bit unique identification number
Supports point to point and point to multipoint
communication
A device can act as master or slave
Popular in mobile phones
54. Wi-Fi:
wireless fidelity is popular for wireless
communication for networked communication
Supports IP protocol
Each device is addressed by IP address
An intermediate agent called wi-fi router
Supports data rate 1Mbps- 150 Mbps
Offers range of 100- 300ft
55. ZigBee:
low power, low cost, wireless n/w protocol
Supports distance upto 100m
Supports Data rate of 250Kbps
3 device category ( coordinator, router, end device)
Coordinator- acts as the root of the n/w. responsible of
initiating the n/w and can store information about the
n/w
Router-for passing information from one device to other
End device-for data communication
Eg: smoke detector, heating control , lighting control
56. General packet radio service(GPRS):
for transferring data over a mobile communication n/w
like GSM
Data is sent as packets
At receiving end reconstructed by combining packets
The radio channel is shared between several users instead
of dedicating to a cell phone user
Mainly for mobile enabled embedded devices
57. Embedded firmware
Refers to the control algorithm and or the configuration
settings that an embedded system developer dumps into the
memory of the embedded system
Various methods-
Write program in high level languages like embedded C
Write the program in assembly language using the instructions
supported by your application’s target processor
These should be converted to machine code before loading to
the memory which is called ‘ HEX file creation’
For a beginner it is better to use HLL.(writing code is easy,
highly portable, not developer dependent )
Assembly language is tedious , time consuming and highly
dependent on developer
58. Other system components
Circuits/IC s necessary for the proper functioning
of the embedded system
Reset circuit: to ensure that the device is not
operating at a voltage level when the device is not
guaranteed to operate when power ON
Reset signal starts the execution from the reset
vector from the address 0x0000
Either active H or active L
Some micro processors/controllers contains built in
reset circuitry
59. Brown-out protection circuit :
protection circuit prevents the processor/controller
from unexpected program execution behavior when
the supply voltage falls below a specified voltage
May lead to data corruption
Essential for battery powered devices
This holds the processor in reset state until it rises
above the threshold voltage
60. Oscillator unit: is responsible for generating
the clock for the processor
Certain processors integrate built in oscillator
and simply require an external quartz crystal for
producing the clock
Speed of the processor depends on clock
frequency
Power consumption increases with increase in
clock frequency
Accuracy of the program execution depends on
accuracy of clock signal
61. Real time clock: for keeping track of time
Holds information like current time, date, month, year
and day of the week etc.
Should function even in the absence of power. So
contains a battery back up
Available in the form of IC s
Essential for synchronizing the operations of the OS
kernel
Can interrupt the OS by asserting the interrupt line
OS kernel identifies the interrupt ( IRQ no)
The kernel can perform necessary operations like system
date time updation , managing s/w timers etc
62. Watchdog timer:
To monitor the firmware execution and reset the system
processor when the program execution hangs up.
( alt+ctl+del)
It’s a h/w timer
It inc/dec a counter with each clock pulse and generates a
reset signal when reaches 0
Most processors implement as built in or using an external
IC
When watchdog timeout occurs an interrupt is generated
instead of resetting in modern systems and interrupt
handler handles the situation in an appropriate fashion
63. PCB and passive components
Backbone is PCB
After finalizing the components and the
connection a schematic design is created and
PCB is fabricated
Apart from subsystems You can have resistor,
capacitor, diodes etc on your board
64. Characteristics of an embedded
system
Unlike general purpose computing system, embedded system posses
certain specific characteristics and these are unique.
Application and domain specific: embedded systems are developed to
do the intended functions only
They can not be used for any purpose
You can not replace an embedded control unit developed for a
particular domain say telecom with another control unit designed to
sey another domain like consumer electronics
Reactive and real time: emb.sys. are in constant interaction to the real
world
Any changes happening in the real world (event)are captured by the
sensors or i/p devices
The event may be periodic or unpredicted one(should not miss)
So emb.sys. are generally reactive
Timing behavior or the system should be deterministic
Should not miss deadlines
65. Operates in harsh environment: the environment in which the
emb.sys. deployed may be a dusty one or high temperature zone
System placed in such areas should be capable to with stand all
operating conditions
Distributed: emb.sys. may be a part of larger system
Automatic vending m/c contains card reader, vending unit etc.
They are independent but work together to achieve a common
goal
Small size and weight: size, weight, shape etc will be one of the
deciding factors to choose a product
Most applications demands small sized and low weight products
Power concerns: designed in such a way as to minimize the heat
dissipation
May require cooling fan which occupies additional space
Even it’s a critical constraint battery operated systems, more the
power consumption the less the battery life
66. Quality attributes of ES
QA are the non-functional requirements that
need to be documented properly in any system
design.
If the quality attributes are more concrete and
measurable it will give a positive impact on the
end product
Operational QA
Non-operational QA
67. Operational quality attributes
Attributes related to e.s when it is in the operational mode or online mode
Response: quickness of the system
How fast the system is tracking the changes in input variables
In flight control application any response delay in the system will create
potential damages to the safety of the flight
Response time for a toy is not time critical
Throughput: efficiency of the system
Rate of production or operation of a defined process
Rates can be expressed in terms of units of products , batched produced,
or any other meaningful measurements.
Generally measured in terms of benchmark (reference point)
Reliability: how much % you can rely upon the proper functioning of sys.
Mean time between failure MTBF (frq of failure in hr/wk/mon) & mean
time to repair MTTR ( how long the system is allowed to be out of order
following a failure ) are the terms used in defining the system reliability
68. Maintainability: deals with the support and maintenance
to the end user in the case of technical issues and
failures or on the basis of a routine checkup
As reliability increases maintainability reduced
Two types (preventive or corrective maintenance)
User should replace the cartridge after n number of
printouts (scheduled / periodic /preventive)
If paper feeding part of the printer fails required
immediate repairs (maintenance to unexpected
failure/ corrective)
69. Security : confidentiality( from unauthorized
disclosure), integrity ( from unauthorized
modification) , availability ( from
unauthorized users)
Safety: deals with the possible damages that
can happen to the operators or public
Eg. Due to breakdown or emission of
radioactive
70. Non operational quality attributes
Attributes that needs to addressed for the product not on the
basis of operational aspects
Testability: & debug ability: how easily one can test her design
and by which mean she can test it.
h/w testing( peripherals and total h/w function) and firmware
testing
Debugging the product as such for figuring out the probable
sources that create unexpected behavior in the system
h/w level debugging ( issues created by h/w problems) and
firmware debugging ( errors that appear as a result of flaws in
the firmware)
Evolvability: related to biology.
Ease with which the embedded product can be modified to take
advantage of new f/w or h/w technologies
71. Portability : measure of system independence
If the product is capable of functioning as such
in various environments
processors/controllers/os
Product can be ported to a new platform
Should be flexible and portable
Assembly language portability is poor
72. Time to prototype and market
Time to market: time elapsed between the
conceptualization of a product and time at which
the product is ready for selling
It’s a critical factor because embedded technology is
one where rapid technology change is happening
Time to prototype: its an informal kind of rapid
product development in which the important
features of the product under consideration are
developed
If prototype is developed faster, the actual
development time can be brought down
significantly.
73. Per unit cost and revenue : cost will be closely monitored
by both end users
Proper market study should be carried out before
deciding per unit cost
During design and development only investment no
returns
Once the product is ready to sell and its introduced to
the market – product introduction stage
In growth phase product grabs high market share
During maturity phase the growth and sales will be
steady and revenue reaches at its peak
Product retirement/decline phase starts with the drop in
sales volume, market share and revenue
At some point of decline stage the manufacturer
announces discontinuing of the product
Unit cost is very high during the introductory stage