communication interfaces-Embedded real time systems

IV.COMMUNICATION
INTERFACE
Prepared by
Raghunath M
UNIT IV: COMMUNICATION INTERFACE : Need for communication interfaces, RS232 / UART,
RS422 / RS485, USB, Infrared, IEEE 1394 Fire wire, Ethernet, IEEE 802.11, Blue tooth.

Communication interface are the devices through
with the E.S can interact with various subsystems and
the external world.
For embedded product communication interface can
be viewed in two different perspectives :
 Device/board level communication interface
(On board communication Interface)
 Product level communication interface
(External communication interface)

Onboard communication Interface
 The communication channel which interconnects
the various components within an embedded
product is referred as device/on broad level
communication interface.
EX: I2C
SPI
UART
I-Wire

1.INTER INTEGRATED CIRCUIT BUS[I2C bus] - contents
I2C bus
Introduction
BUS Lines
I2C Protocols
I2C related terms
Repeated Start Condition
Clock Stretching
Acknowledge (ACK) and Not Acknowledge (NACK)
10-bit Addresses
Advantages of I2C
Disadvantages of I2C
Applications of I2C

1.INTER INTEGRATED CIRCUIT BUS[I2C bus]
 It is a synchronous bi-directional half duplex two –
wire serial bus which provides communication link
between integrated circuits.
 It was designed by Philips Semiconductors in 1980s.
 It was developed to provide an easy way of
connection between a microprocessor /
microcontroller system and low speed peripheral
chips/Ic

It comprises of two bus lines
Serial Clock-SCL and Serial Data-SDA.
• SCL line is responsible for generating synchronization clock pulses.
• SDA is responsible for transmitting the serial data across devices.
• I2C bus is a shared bus system to which many number of I2C devices
can be connected.
• Devices connected to the I2C bus can act as either “Master” device or
“Slave” device.
• The Master device is responsible for controlling the communication by
initiating or terminating data transfer, sending data and generating
necessary synchronization clock pulses.
• The Slave devices wait for the commands from the Master and
respond upon receiving the commands.

Messages are broken up into two types of frame:
• an address frame, where the master indicates the slave to which the
message is being sent, and
• data frames, which are 8-bit data messages passed from master to
slave or vice versa.

I2C Protocols:
Start Condition:
To initiate the address frame, the master device leaves SCL high and pulls SDA low. This puts all slave
devices on notice that a transmission is about to start.
Address Frame:
The address frame is always first in any new communication sequence. For a 7-bit address, the address is
clocked out most significant bit (MSB) first, followed by a R/W bit indicating whether this is a read (1) or
write (0) operation.
The 9th bit of the frame is the NACK/ACK bit. This is the case for all frames (data or address). Once the
first 8 bits of the frame are sent, the receiving device is given control over SDA. If the receiving device
does not pull the SDA line low before the 9th clock pulse, it can be inferred that the receiving device
either did not receive the data or did not know how to parse the message.

Data Frames: After the address frame has been sent, data can begin being transmitted. The
master will simply continue generating clock pulses at a regular interval, and the data will be
placed on SDA by either the master or the slave, depending on whether the R/W bit indicated a
read or write operation.
Stop condition: Once all the data frames have been sent, the master will generate a stop
condition. Stop conditions are defined by a 0->1 (low to high) transition on SCL, with SCL
remaining high.

I2C related terms:
Repeated Start Condition
During an I2C communication, sometimes a master wants to send a specific command to a
slave device and read back response right away. In this situation there is a possibility that
another master (in case of multi-master bus) takes the control of the bus. To avoid these
conditions I2C protocol defines repeated start condition.
In normal cases I2C master will send start condition, address + R/W bit, send or receive any
number of bytes and mark the end by a stop condition. During repeated start condition,
master will send START CONDITION instead of stop condition and will keep the control over
the bus. Master can send any number of start condition using this method. Irrespective of
the number of start conditions, transfer must be end by exactly one stop condition.

Clock Stretching:
• We have seen that master device determines the clock speed in I2C communication. This avoid the need of
synchronizing master and slave exactly to a predefined baud rate. But there can be some situations when I2C slave
device is not able to cooperate with clock signals given by master. Clock stretching is the mechanism used to slow
down master device for slave device to complete it’s operation. I2C slave device is allowed to hold down the clock
signal when it needs master to slow down on the 9th clock of every data transfer before the ACK stage.
Acknowledge (ACK) and Not Acknowledge (NACK)
• Each byte of data in I2C communication includes an additional bit known as ACK bit. This bit provides a provision
for the receiver to send a signal to transmitter that the byte was successfully received and ready to accept another
byte.
10-bit Addresses
• Generally I2C bus uses 7-bit addressing, which means that devices are limited to 127 devices and address clashes
can happen. 10-bit address scheme is introduced to solve this problem. 10-bit address devices can be mixed with
7-bit devices and it increases the address range about 10 times.

Advantages of I2C:
• Needs only 2 lines (SCL & SDA) + Ground as reference
• Supports up to 1008 slave devices
• Supports multi-master system
Disadvantages of I2C:
• Needs more complex hardware
• Data rate less than SPI
I2c Applications:
• EEPROMs
• Real Time Clock ICs
• Temperature Sensors
• Accelerometers
• Gyro meters
• LCDs

2.SERIAL PERIPHERAL INTERFACE(SPI BUS) - Contents
 SPI BUS
 Introduction
 The SPI bus Lines
 SPI Configuration
 Typical SPI Bus
 Daisy-Chained SPI Bus
 SPI Data Transmission
 SPI Modes –Clock Polarity & Phase
 Advantages of SPI
 Disadvantages of SPI
 Applications of SPI
 Differences Between I2C and SPI

2.SERIAL PERIPHERAL INTERFACE(SPI BUS)
• The Serial Peripheral Interface bus (SPI) is a synchronous serial communication
interface specification used for short distance communication, primarily in
embedded systems.
• Interface was developed by Motorola in the late 1980s and has become a de-
facto standard.
• SPI devices communicate in full duplex mode using a master-slave architecture
with a single master.
• Sometimes SPI is called a four-wire serial bus

The SPI bus specifies four logic signals:
SCLK: Serial Clock (output from master)
MOSI: Master Output Slave Input, or Master Out Slave In (data output from
master).
MISO: Master Input Slave Output, or Master In Slave Out (data output from
slave).
SS: Slave Select (often active low, output from master)

SCK (Serial Clock)
• The SPI used clock signal to synchronize the transfer of data across the SPI
interface.
• The SCK is always driven by the master and received by the slave, The clock is
programmable to be active high or active low.
•The SCK is only active during a data transfer. Any other time, it is either in its
inactive state, or tri stated.
MISO (Master in Slave out)
• The MISO signal is a unidirectional signal used to transfer serial data from the
the master to slave.
• When a device is a slave, serial data is output on this signal.
• When a device is a master, serial data is input on this signal.
• When a slave device is not selected, the slave drives the signal high
impedance

MOSI (Master out Slave in)
The MOSI signal is a unidirectional signal used to transfer serial data from the slave to the
master.
•When a device is a Master, serial data is output on this signal.
• When a device is a Slave, serial data is input on this signal.
SSEL(Slave Select)
• The SPI slave select signal is an active low signal that indicates which slave is currently
selected to participate in a data transfer.
• Each slave has its own unique slave select signal input.
• The SSEL must be low before data transactions begin and normally stays low for the
duration of the transaction.
• If the SSEL signal goes high any time during a data transfer, the transfer is considered to
be aborted.
• In this event, the slave returns to idle, and any data that was received is thrown away.
There are no other indications of this exception

SPI Configuration
• Typical SPI bus: Master and independent Slaves
• Daisy-Chained SPI bus: Master and cooperative slaves
Typical SPI Bus
• With multiple slave devices, an independent SSEL
signal is required from the master for each slave
device (3).
• In the independent slave configuration, there is
an independent slave select line for each slave.
This is the way SPI is normally used.
• Since the MISO pins of the slaves are connected
together, they are required to be tri-state pins.

Daisy-Chained SPI Bus
• Some products with SPI bus are
designed to be capable of being
connected in a daisy chain
configuration, the first slave output
being connected to the second slave
input, etc.
• The SPI port of each slave is designed
to send out during the second group
of clock pulses an exact copy of what it
received during the first group of clock
pulses.
• Such a feature only requires a single
SSEL line from the master, rather than
a separate SSEL line for each slave

SPI Data Transmission
• A typical hardware setup using two shift registers to form an inter-
chip circular buffer
• To begin a communication, the master first configures the Clock,
using a frequency less than or equal to the maximum frequency the
slave device supports.
• The master then pulls the slave select SSEL low for the desired chip.
• During each SPI clock cycle, a full duplex data transmission occurs
• The master sends a bit on the MOSI line; the slave reads it from that
same line.

• The slave sends a bit on the MISO line; the master reads it from that
same line
• Transmissions normally involve two shift registers of some given word
size, such as eight bits, one in the master and one in the slave; they
are connected in a ring.
• After that register has been shifted out, the master and slave have
exchanged values.
• Then each device takes that value and does something with it, such as
writing it to memory
• If there are more data to exchange, the shift registers are loaded with
new data and the process repeats.

SPI Modes –Clock Polarity & Phase
We already seen that clock for data transfer is generated by the SPI master. So the master should set
the clock frequency for SPI transfer. In addition to this clock polarity and clock phase are there, which
has to match with SPI slaves for proper data transfer
Clock Polarity :
CPOL or CKP Clock polarity is the idle / active state of the clock. If idle state is 0, active
state will be 1 and vice versa. •
Clock Phase :CPHA, Inverted Clock Phase (Clock Edge) :
NCPHA or CKE Clock phase or clock edge defines when to transfer data. Data can be
transferred during LOW (0) to HIGH (1) or HIGH to LOW transitions.

Bits that are sampled on the rising edge of the clock cycle are shifted out on the falling edge of the clock
cycle, and vice versa.

Each transaction begins when the slave-select line is driven to logic low (slave select is typically an active-low
signal). The exact relationship between the slave-select, data, and clock lines depends on how the clock polarity
(CPOL) and clock phase (CPHA) are configured.
With non-inverted clock polarity (i.e., the clock is at logic low when slave select transitions to logic low):
•Mode 0: Clock phase is configured such that data is sampled on the rising edge of the clock pulse and shifted out
on the falling edge of the clock pulse. This corresponds to the first blue clock trace in the above diagram. Note
that data must be available before the first rising edge of the clock.
•Mode 1: Clock phase is configured such that data is sampled on the falling edge of the clock pulse and shifted
out on the rising edge of the clock pulse. This corresponds to the second blue clock trace in the above diagram.
With inverted clock polarity (i.e., the clock is at logic high when slave select transitions to logic low):
•Mode 2: Clock phase is configured such that data is sampled on the falling edge of the clock pulse and shifted
out on the rising edge of the clock pulse. This corresponds to the first orange clock trace in the above
diagram. Note that data must be available before the first falling edge of the clock.
•Mode 3: Clock phase is configured such that data is sampled on the rising edge of the clock pulse and shifted out
on the falling edge of the clock pulse. This corresponds to the second orange clock trace in the above diagram.

Advantages of SPI:
• Simple hardware
• Full duplex communication
• Simple software implementation
• High Speed
• No speed limit (practically it will be limited by the clock
frequency, rise time, fall time etc.)
• Not Limited to 8 bit data
• Signals are unidirectional through all lines, makes easy
isolation
• No need of unique address in slaves like in RS485 or I2C.
• No need of precision oscillators in slave devices as it uses
master’s clock
• No complex transceivers are required

Disadvantages of SPI:
• More pins/wires are required. Minimum 3 wires (in single slave) are required.
• Can be used only from short distances •
• No error detection protocol is defined
• Usually supports only one master
• Not have ack mechanism to confirm receipt of data and does not have flow
control.
• SPI Master, not have knowledge of whether slave exist or Not.
• Not particular addressing scheme.
Applications of SPI:
• SD Cards
• LCD Displays
• RTC (real time clocks)
• Ethernet Controllers

Differences Between I2C and SPI

3.universal asynchronous receiver-transmitter (UART) - contents
 UART Introduction
 UART communication
 UART serial communication
 Rule/conditions of UART serial communication
 UART Throughput
 Advantages of UART
 Disadvantages of UART
 Applications of UART
 USART (Universal Synchronous/Asynchronous Receiver/Transmitter)
 Practical differences between synchronous mode and asynchronous mode

3.universal asynchronous receiver-transmitter (UART)
• UART stands for Universal Asynchronous Receiver/Transmitter.
• It’s not a communication protocol like SPI and I2C,but a
physical circuit in microcontroller, or a stand-alone IC.
• It is a computer hardware device for asynchronous serial
communication in which data format and transmission speeds
are configurable.
• A UART’s main purpose is to transmit and receive serial data.
• One of the best things about UART is that it only uses two
wires to transmit data between devices

• In UART communication, two UARTs communicate directly with each other.
• The transmitting UART converts parallel data from a controlling device like a CPU into serial
form, transmits it in serial to the receiving UART, which then converts the serial data back into
parallel data for the receiving device.
• The UART that is going to transmit data receives the data from a data bus. The data bus is
used to send data to the UART by another device like a CPU, memory, or microcontroller. Data
is transferred from the data bus to the transmitting UART in parallel form. After the
transmitting UART gets the parallel data from the data bus, it adds a start bit, a parity bit,
and a stop bit, creating the data packet
• Next, the data packet is output serially, bit by bit at the Tx pin. The receiving UART reads the
data packet bit by bit at its Rx pin. The receiving UART then converts the data back into
parallel form and removes the start bit, parity bit, and stop bits. Finally, the receiving UART
transfers the data packet in parallel to the data bus on the receiving end
UART communication

The data in UART serial communication is organized in to blocks called Packets or
Frames.
UART serial communication

START BIT
• The UART data transmission line is normally held at a high voltage level when it’s
not transmitting data.
• To start the transfer of data, the transmitting UART pulls the transmission line from
high to low voltage level.
• When the receiving UART detects the high to low voltage transition, it begins
reading the bits in the data frame at the frequency of the baud rate.
DATA FRAME
• The data frame contains the actual data being transferred. It can be 5 bits up to 8
bits long if a parity bit is used.
• If no parity bit is used, the data frame can be 9 bits long. In most cases, the data is
sent with the least significant bit first

PARITY
• Parity describes the evenness or oddness of a number.
• The parity bit is a way for the receiving UART to tell if any data has changed during
transmission(Bits can be changed by electromagnetic radiation, mismatched baud rates, or
long distance data transfers).
• After the receiving UART reads the data frame, it counts the number of bits with a value of
1 and checks if the total is an even or odd number.
• If the parity bit is a 0 (even parity), the all bits in the data frame should total to an even
number. If the parity bit is a 1 (odd parity), the all bits in the data frame should total to an
odd number.
• When the parity bit matches the data, the UART knows that the transmission was free of
errors. But if the parity bit is a 0, and the total is odd; or the parity bit is a 1, and the total is
even, the UART knows that bits in the data frame have changed.
STOP BITS
• To signal the end of the data packet, the sending UART drives the data transmission line
from a low voltage to a high voltage for at least two bit durations.

Baud Rate
• The speed at which the data is transmitted is mentioned using Baud Rate.
• Both the transmitting UART and Receiving UART must agree on the Baud Rate for a successful data
transmission.
• Baud Rate is measured in bits per second(bps)
• Some of the standard baud rates are 4800 bps, 9600 bps, 19200 bps, 115200 bps etc.
Out of these 9600 bps baud rate is the most commonly used one
Rule/conditions of UART serial communication
UART transmitter and receiver must agree on some rules of serial communication for error free
transfer of data.
The rules include: • Synchronization Bits (Start and Stop bits) • Parity Bit • Data Bits and • Baud Rate

UART Throughput
• 9600 baud means 9600 Hz – 9600 bits per second (bps)
• Throughput refers to how much data can be transferred from one location to another in a given amount
of time

Advantages of UART:
• Requires only two wires for full duplex data transmission (apart from the power lines).
• No need for clock or any other timing signal.
• Parity bit ensures basic error checking is integrated in to the data packet frame.
Disadvantages of UART:
• Size of the data in the frame is limited.
• Speed for data transfer is less compared to parallel communication.
• Transmitter and receiver must agree to the rules of transmission and appropriate baud rate
must be selected
• Doesn’t support multiple slave or multiple master systems
Applications of UART:
UART is normally used in microcontrollers for exact requirements, and these are also available in
various communication devices like wireless communication, GPS units, Bluetooth module, and
many other applications.

USART (Universal Synchronous/Asynchronous Receiver/Transmitter)
• A USART (Universal Synchronous/Asynchronous Receiver/Transmitter) is a
microchip that facilitates communication through a computer's serial port
using the RS- 232C protocol.
• Like a UART (Universal Asynchronous Receiver/Transmitter), a USART
provides the computer with the interface necessary for communication with
modems and other serial devices. However, unlike a UART, a USART offers
the option of synchronous mode.
• In program-to-program communication, the synchronous mode requires that
each end of an exchange respond in turn without initiating a new
communication. Asynchronous operation means that a process operates
independently of other processes

Practical differences between synchronous mode (which is possible only with a USART) and asynchronous
mode (which is possible with either a UART or a USART) can be outlined as follows.
• Synchronous mode requires both data and a clock. Asynchronous mode requires only
data.
• In synchronous mode, the data is transmitted at a fixed rate. In asynchronous mode, the
data does not have to be transmitted at a fixed rate.
• Synchronous data is normally transmitted in the form of blocks, while asynchronous data
is normally transmitted one byte at a time.
• Synchronous mode allows for a higher DTR (data transfer rate) than asynchronous mode
does, if all other factors are held constant.

1-WIRE INTERFACE - contents
1-wire interface- Introduction
Advantages of 1-wire interface
Disadvantages of 1-wire interface
Applications of 1-wire interface.

4.1-WIRE INTERFACE
• 1-Wire is a device communications bus system designed by Dallas Semiconductor
Corp.
• 1-Wire is similar in concept to I²C, but with lower data rates and longer range. It is
typically used to communicate with small inexpensive devices such as digital
thermometers and weather instruments.
• One distinctive feature of the bus is the possibility of using only two wires: data and
ground

• There is always one master in overall charge, which may be a PC or a microcontroller. The master
initiates activity on the bus, simplifying the avoidance of collisions on the bus. Protocols are built into
the software to detect collisions. After a collision, the master retries the required communication.
• Many devices can share the same bus. The most significant byte is a standard (for the 1-wire bus) 8-bit
CRC
• The master starts a transmission with a reset pulse, which pulls the wire to 0 volts for at least 480 µs.
This resets every slave device on the bus. After that, any slave device, if present, shows that it exists
with a "presence" pulse: it holds the bus low for at least 60 µs after the master releases the bus.
• To send a "1", the bus master sends a very brief (1– 15 µs) low pulse. To send a "0", the master sends a
60 µs low pulse, When receiving data, the master start sends a 1–15-µs 0-volt pulse to slave each bit. If
the transmitting does unit wants to send a "1", it to the nothing, and the bus goes transmitting pulled-
up voltage. If the a "0", it pulls slave wants to send the data line to ground for 60 µs.

advantages of 1-wire interface
• Multiple slaves are accessed using only 2-wires in this interface type
• Due to use of less wires, the interface is cheaper.
• It is easy to implement the interface.
• The interface supports longer distance (about 300 meters)
disadvantages of 1-wire interface
• It is implemented both in the hardware as well as software. The synchronization of data at the receiver has to be taken
care in software which is a complex task.
• Though the interface supports longer distance, it is limited due to noise and cable capacitance.
• It supports slower speed of communication.
• 1-wire slave devices are manufactured by Dallas semiconductor only
Applications of 1-wire interface.
• SDI-12, a single data wire communications scheme/data loggers
• Touch memory
• Medical-pulse oximetry device
• Sensor/cable id authentication

EXTERNAL COMMUNICATION INTERFACE
• External communication interface refers to the different communication channels used by
embedded system to communicate with the external world.
• The product level communication interface is responsible for data transfer between the
E.S and other devices or modules.
• The external communication interface can be either a wired media or a wireless media
and it can be a serial or a parallel interface
• Various external communication interfaces are
1.RS232 /RS 422 AND RS485
2.USB (UNIVERSAL SERIAL BUS)
3.INFRARED
4.Bluetooth
5.Wi-Fi
6.IEEE 1394 Fire wire
7. Ethernet

1.RS232 /RS 422 AND RS485 - contents
1.RS232
Introduction
DB9 Connector
Electrical Characteristics
How RS232 Works?
Advantages
Disadvantages
Applications
RS232-cables
2.RS 422
Introduction
Working
Differential transmission method
RS422-9 Pin connector (DB-9)
Advantages
Disadvantages
Applications
RS422-cables
3.RS-485
Introduction
Working
RS485 pin out DB9 connector
Electrical Characteristics
Advantages
Disadvantages
Comparison B/w rs232-422-485
Applications

1.RS232 /RS 422 AND RS485
RS-232
• RS-232 (Recommended Standard 232).
• It is basically a interface standards.
• It is commonly used in computer serial ports.
• The standard defines the electrical characteristics and timing of signals.
• RS-232 was first introduced in 1962.
• For many years, an RS-232-compatible port was a standard feature for
serial communication.
• The standard continued to be revised and updated by the Electronic
Industries Alliance and since 1988 by the Telecommunications Industry
Association (TIA).
• The C revision of the standard was issued in August 1969.
• The current version of the standard is TIA232-F ,issued in 1997.

• RS232 is a standard protocol used for serial communication, it is used for connecting
computer and its peripheral devices to allow serial data exchange between them.
• It is used in serial communication up to 50 feet with the rate of 1.492kbps. As EIA defines,
the RS232 is used for connecting Data Transmission Equipment (DTE) and Data
Communication Equipment (DCE)
• Universal Asynchronous Data Receiver &Transmitter (UART) used in connection with RS232 for
transferring data between printer/projector and computer.
• The microcontrollers are not able to handle such kind of voltage levels(5v), connectors are
connected between RS232 signals.
• These connectors are known as the DB9 Connector as a serial port and they are of two type’s Male
connector (DTE) & Female connector (DCE).

DCD, or Data Carrier Detect:
This is an input for DTE devices and an output for DCE devices. This signal is used to show that there is a valid
connection between the DTE and DCE devices
TxD, or Transmit Data:
This is an output for DTE devices and an input for DCE devices. This is the data channel from the DTE device to the
DCE device.
RxD, or Receive Data:
This is an input for DTE devices and an output for DCE devices. This is the data channel from the DCE device to the
DTE device.
RTS, or Request To Send:
This is an output for DTE devices and an input for DCE devices. This signal is typically used to gate flow from the
DCE device to the DTE device.
CTS, or Clear To Send:
This is an input for DTE devices and an output for DCE devices. This signal typically is used to gate flow from the
DTE device to the DCE device
DSR, or Data Set Ready:
This is an input for DTE devices and an output for DCE devices
SG, or Signal Ground: This is a signal return for all signal lines
DTR, or Data Terminal Ready: This is an output for DTE devices and an input for DCE devices.
RI, or Ring Indicator: This is an input for DTE devices and an output for DCE devices. This signals the DTE device
that there is an incoming call.

Electrical Characteristics
• Voltage Levels
The logic ‘1’ in RS232 is described as being in the voltage range of -15V to -3V and
logic ‘0’ is described as the voltage range of +3V to +15V i.e. low level voltage is logic ‘1’ and high level
voltage is logic ‘0’.
Slew Rate
The other important electrical characteristic is the rate of change of signal levels i.e. the Slew Rate.
The maximum slew rate in RS232 is limited to 30V/µs. Also, a maximum bit rate of 20 Kbps is also
defined.
These limitations of the standard help in reducing the cross – talk with adjacent signals.
Line Impedance
The line impedance i.e. impedance of the wire between the DTE and DCE devices is specified to be
around 3Ω to 7Ω.
Also, the original RS232 standard specifies the maximum length of the cable as 15 meters but the revised
standards specify the maximum length in terms of capacitance per unit length.

How RS232 Works?
• RS232 works on the two-way communication that exchanges data to one another. There are
two devices connected to each other, (DTE) Data Transmission Equipment& (DCE) Data
Communication Equipment which has the pins like TXD, RXD, and RTS& CTS
• Now, from DTE source, the RTS generates the request to send the data. Then from the other
side DCE, the CTS, clears the path for receiving the data. After clearing a path, it will give a
signal to RTS of the DTE source to send the signal. Then the bits are transmitted from DTE to
DCE.
• Now again from DCE source, the request can be generated by RTS and CTS of DTE sources
clears the path for receiving the data and gives a signal to send the data. This is the whole
process through which data transmission takes place.
TXD - TRANSMITTER
RXD - RECEIVER
RTS - REQUEST TO SEND
CTS - CLEAR TO SEND
GND - GROUND
DCD - DATA CARRIER DETECTIOR
DTR - DATA TERMINAL READY
DSR - DATA SET READY

Working Example:
• The signals set to logic 1, i.e., -12V. The data transmission starts from next bit and to inform this,
DTE sends start bit to DCE.
• The start bit is always ‘0’, i.e., +12 V & next 5 to 9 characters is data bits.
• If we use parity bit, then 8 bits data can be transmitted whereas if parity doesn’t use, then 9 bits
are being transmitted.
• The stop bits are sent by the transmitter whose values are 1, 1.5 or 2 bits after the data
transmission

Advantages
• Very widely used
• Low complexity
• Supports full duplex
Disadvantages
• Only supports communication between two devices
• Only works over short distances
• Relatively susceptible to noise
• If there is an increase in baud rate and length of the cable, there is a chance of cross talk introduced by the
capacitance between the cables
Applications
▪ RS232 serial communication is used in old generation PCs for connecting the peripheral devices like mouse,
printers, modem etc.
▪ Nowadays, RS232 is replaced by advanced USB.
▪ It is also used in PLC machines, CNC machines, and servo controllers because it is far cheaper.
▪ It is still used by some microcontroller boards, receipt printers, point of sale system (PoS), etc

RS232 null modem cables RS232 serial printer cable RS232 spy cable (monitor cable)
DB9 RS232C Humidity and Temperature
Sensor
with RS232 signal level
converter
USB to RS-232 Adapter

RS 422
• RS-422. Recommended Standard 422
• RS 422 is a telecommunications standard for binary serial communications between devices.
• RS 422 is an updated version of the original serial protocol known as RS-232.
• One device will be known as the data terminal equipment (DTE) and the other device is
known as data communications equipment (DCE).
• Example is a serial link between the computer and printer, the computer is the DTE device
and the printer is the DCE device.
• RS-422 is a balanced four wire system.
• Two wire is for DTE transmit signal to DCE, and other two wire is for DCE transmit signal to
DTE.

• RS422 is able to provide data rates of up to 10 Mbps at distances up to 50 feet (15.24 meters). However
using reduced data rates, RS422 is able to transmit data over distances of 4000 feet (~1220 meters): the
maximum is 100 kbps at this distance.
• The key reason why RS422 is able to achieve these improvements results from the use of differential or
balanced transmission techniques.
• The differential transmission method uses two signal lines to flow opposite-phase currents, and performs
transmission using the potential difference between the signal lines. External noise affects the + side and -
side signal lines equally, and differential transmission considers only the potential difference between the
signal lines, so the effect of the noise is canceled, making it more difficult for operation errors to occur.

• Lower voltage line levels are used for RS422: A space is represented by a line voltage level in the band between
+2 and +6 volts while a mark is represented by a voltage in the range -2 to -6 volts. The range between +2 and -2
volts provides a good noise margin for the system.
• The RS422 standard allows for line impedances down to 50 ohms while supporting the high data rates.
Specification of RS-422

Advantages of RS-422:
• High data rates
• Less subject to noise
• Longer cable lengths
Disadvantages of RS-422:
• Not as commonly used
• Unidirectional
• For most applications, only one transmitter is used
Applications:
• These connectors were used both to support RS-232 devices like modems, as well as AppleTalk networking,
RS-422 printers, and other peripherals.
• RS-422 is a common transport mechanism for RS-232 extenders. These consist of RS-232 ports on either end
of an RS-422 connection

RS 422 DB44 pin serial card adapter
RS 422 DB9 pin connector USB to RS 422 converter

RS-485
• RS232 is an interface to connect one DTE, data terminal equipment to one DCE, data
communication equipment at a maximum speed of 20 kbps with a maximum cable length of 50
feet.
• This was sufficient in the old days where almost all computer equipment were connected using
modems, but soon after people started to look for interfaces capable of one or more of the
following:
•Connect DTE's directly without the need of modems
•Connect several DTE's in a network structure
•Ability to communicate over longer distances
•Ability to communicate at faster communication rates
• RS485 is the most versatile communication standard in the standard series defined by the EIA, as
it performs well on all four points. That is why RS485 is currently a widely used communication
interface in data acquisition and control applications where multiple nodes communicate with
each other.

Electrical specifications
• The RS-485 standard specifies differential signaling on two lines. A logic 1 is a level greater than –200 mV, and a logic 0 is a
level greater than +200 mV
• The standard transmission medium is twisted-pair cable. Cable length defines the upper data rate. But because of the
lower logic voltage levels and the differential connection, data rates can exceed 10 Mbits/s depending on cable length.
• Maximum cable length is commonly defined as 1200 meters or about 4000 feet. The typical maximum data rate at 4000
feet is 100 kbits/s
RS485 SPECIFICATIONS
ATTRIBUTE SPECIFICATION
Cabling Multi-drop
Number of devices 32 transmitters
32 receivers
Communications modes half duplex
Maximum distance 4000 feet @ 100 kbps
Maximum data rate 10 Mbps @ 50 feet
Signalling Balanced/Differential
Driver output current capability 250 mA

Advantages of RS-485
➨Due to use of differential signaling, maximum data transmission speed (100 Kbps) and distance upto 1200 meters (i.e.
4000 ft) are supported .
➨Due to differential signaling RS485 interface is immune to noise.
➨It supports single master and multiple slaves (i.e. multi-stations) due to balanced transmission line.
➨It is considered to be lower signal level interface.
➨Response time between reader and software is short when less than 32 controllers (or readers) are communicating on
same data line.
Disadvantages of RS-485
➨In RS485 mode, only single mode can transmit data at a time.
➨The RS485 interface requires special type of cables and ordinary cables can not be used. Moreover it is expensive.
➨It requires 4 wires to communicate in multi-drop mode unlike RS232 which requires only 2 wires to communicate
between master and slave in point to point mode.
➨RS485 is not suitable to transfer large amount of data at 115.2 Kbps speed. This is due to occurrence of data loss at
such high speed. Data transfer at 56.2 Kbps is stable but takes longer time.
➨In RS485, backing up of system is difficult. This is because special switches and configurations are needed to build
redundant host PC

Other types:
• RS-366 interface
• RS-423 (TIA/EIA-423-B) serial interface
• RS-449 (EIA-449) interface
• RS-449 (EIA-449) Secondary
• RS-530 (EIA530) interface
• RS232 to RS422 cable
• RS232 to RS485 cable
• RS232 serial to USB converter

Introduction
USB System Architecture
Bus Topology
USB host
USB Devices
USB System overview
History of USB
Key Features of USB
USB Connector properties
USB Connector types
Difference between connector type
A,B,C
USB Evolution
USB Protocol layer
Token packets
Data packets
Handshake packets
Start of frame packets
Enumeration Steps
Advantages of USB
Disadvantages of USB
2.Universal Serial Bus (USB) - contents

2. Universal Serial Bus (USB)
• USB stands for Universal Serial Bus
• It Provides an expandable, fast, bi-directional, low cost, hot pluggable
Plug and Play serial hardware interface
• It Allows users to connect a wide variety of peripherals to a computer
and have them automatically configured and ready to use.
• It is Implemented to provide a replacement for legacy ports to make the
addition of peripheral devices quick and easy for the end use

USB System Architecture
A USB system is described by three definitional areas:
1. USB interconnect
2. USB host.
3. USB devices
1. USB interconnect
The USB interconnect is the manner in which USB devices are connected to and communicate with the host.
This includes the following:
Bus Topology: Connection model between USB devices and the host. Inter-layer Relationships: In terms of a capability
stack, the USB tasks that are performed at each layer in the system.
Data Flow Models: The manner in which data moves in the system over the USB between producers and consumers.
USB Schedule: The USB provides a shared interconnect. Access to the interconnect is scheduled in order to support
isochronous data transfers and to eliminate arbitration overhead.

Bus Topology:
The USB connects USB devices with the USB host. The USB physical interconnect is a tiered star topology. A hub is at
the center of each star. Each wire segment is a point-to-point connection between the host and a hub or function, or
a hub connected to another hub or function.
Figure illustrates the topology of the USB

2.USB host.
There is only one host in any USB system. The USB interface to the host computer system is referred to as the
Host Controller. The Host Controller may be implemented in a combination of hardware, firmware, or software.
A root hub is integrated within the host system to provide one or more attachment point
The USB host interacts with USB devices through the Host Controller. The host is responsible for the following:
• Detecting the attachment and removal of USB devices
• Managing control flow between the host and USB devices
• Managing data flow between the host and USB devices
• Collecting status and activity statistics
• Providing power to attached USB devices
The USB System Software on the host manages interactions between USB devices and host based device
software.
There are five areas of interactions between the USB System Software and device software:
• Device enumeration and configuration
• Isochronous data transfers
• Asynchronous data transfers
• Power management
• Device and bus management information

USB devices are one of the following:
• Hubs, which provide additional attachment points to the USB
• Functions, which provide capabilities to the system, such as an ISDN connection, a digital
joystick, or speakers, cameras
USB devices present a standard USB interface in terms of the following:
• Their comprehension of the USB protocol
• Their response to standard USB operations, such as configuration and reset
• Their standard capability descriptive information.
3 USB Devices

• USB 0.7: Released in November 1994.
• USB 0.8: Released in December 1994.
• USB 0.9: Released in April 1995.
• USB 0.99: Released in August 1995.
• USB 1.0: Released in November 1995
There have been three versions released prior to 3.0
• USB 1.0 in January 1996 – data rates of 1.5 Mbps up to 12 Mbps
• USB 1.1 in September 1998 – first widely used version of USB
• USB 2.0 in April 2000 Major feature revision was the addition of a high speed transfer rate
of 480 Mbps.
USB 3.0
• On Nov 17,2008 It was Developed
• It is called as “SUPER SPEED” Technology
• Transfer Mode of Up to 4.8 Gbps
USB 4.0? RELEASED 2019, THUNDERBOLT MODE
History of USB

Key Features of USB
• Single connector type
Replaces all different legacy connectors with one well defined standardized USB connector for all
USB peripheral devices
• Hot swappable
Devices can be safely plugged and unplugged as needed while the computer is running (no need to
reboot)
• Plug and Play
OS software automatically identifies, configures, and loads the appropriate driver when connection
is made
• High performance
USB offers data transfer speeds at up to 4.8 Gbps
• Expandability
Up to 127 different peripheral devices may theoretically be connected to a single bus at one time
• Bus-supplied power
USB distributes the power to all connected devices, eliminating the need for an external power
source for low power devices (flash drives, memory cards, Bluetooth)

USB Connector properties
• Availability
Consumer Products are always available.
• Usability
Most connectors cannot be plugged in upside down
• Durability
The standard connectors were designed to be robust
• Compatibility
Two-way communication is also possible. In USB 3.0, full-duplex
communications are done when using Super Speed (USB 3.0) transfer

USB Protocol layer
During USB communication, data is transmitted as packets. Initially, all packets are
sent from the host via the root hub, and possibly more hubs, to devices. Some of
those packets direct a device to send some packets in reply.
USB has 4 different type of packets
Token packets - indicate the type of transaction to follow.
Data packets - contain the payload.
Handshake packets - are used for acknowledging data or reporting errors.
Start of frame packets - indicate the start of a new frame.

TOKEN PACKETS
There are three types of token packets:-
• In - Informs the USB device that the host wishes to read information.
• Out - Informs the USB device that the host wishes to send information.
• Setup - Used to begin control transfers.
• Token Packets must conform to the following format.
SYNC-SYNCHRONIZATION FIELD PID-PACKET IDENTIFIER ADDR-ADDRESS FIELD
ENDP-ENDPOINT FIELD CRC-CYCLIC REDUNDANCY CHECK EOP-END OF PACKET

DATA PACKET
There are two types of data packets each capable of transmitting up to 1024 bytes
of data.
• DATA0
• DATA1
• High Speed mode defines another two data PIDs, DATA2 and MDATA.
• Maximum data payload size for low-speed devices is 8 bytes.
• Maximum data payload size for full-speed devices is 1023 bytes. Maximum data
payload size for high-speed devices is 1024 bytes.
• Data must be sent in multiples of bytes (integral number).
Data packets have the following format

HANDSHAKE PACKETS
There are 3 types of handshake packets which consist simply of the PID
• ACK - Acknowledgment that the packet has been successfully received.
• NAK - Reports that the device temporary cannot send/receive data. Also used during
interrupt transactions to inform the host there is no data to send.
• STALL - The device finds its in a state that it requires intervention from the host.
Handshake Packets have the following format

The SOF packet consisting of an 11-bit frame number is sent by the host every 1ms ±
500ns on a full speed bus or every 125 µs ± 0.0625 µs on a high speed bus.
START OF FRAME PACKETS (SOF)

1. The system has a new device.
2. The hub detects the device
3. The host learns of the new device.
4. The hub detects whether a device is low or full speed.
5. The hub resets the device.
6. The host learns if a full-speed device supports high speed.
7. The hub establishes a signal path between the device and the bus.
8. The host sends a Get Descriptor request to learn the maximum packet size of
the default pipe.
9. The host assigns an address.
10.The host learns about the device’s abilities.
11.The host assigns and loads a device driver (client).
12.The host’s device driver selects a configuration.
Enumeration Steps

Advantages of USB
• The universal serial bus is easy to use.
• It has robust connector system.
• It has low cost.
• It has variety of connector types and size available.
• It has true plug and play nature.
• It has Low power consumption.
• Daisy chain up to 127 USB components / peripherals at the same time to one PC.
• Fits almost all devices that have a USB port
Disadvantages of USB
➨Though the speed supported is higher in latest USB variants of USB V3 and V4, it is lower compare to gigabit
Ethernet and Fire-wire interfaces.
➨USB supports peer to peer communication. In this type of interface, communication takes place between
host and peripheral and not between two hosts (or peripherals). Using OTG (On the Go) version of USB, this
issue is avoided. In OTG device can function both as peripheral and host.
➨USB standards support cables with length up to 5 meters. Beyond this, USB hubs are required to expand
connectivity.
➨Broadcasting is not possible in USB and communication of messages take place between host and peripheral
only.

3.INFRARED - contents
Introduction
IR transmission
IR Reception
Infrared Data Association(IrDA)
IrDA protocol
IrDA- phy layer Performance
IrDA Advantages
IrDA dis-advantages
IrDA- Applications

3.INFRARED
• IR, or infrared, communication is a common, inexpensive, and easy to use wireless
communication technology. IR light is very similar to visible light, except that it has a
slightly longer wavelength.
• The discovery of infrared radiation is ascribed to William Herschel, @1800 and Infra
means “Below”. The light which is below the Red light “Infrared”
• This means IR is undetectable to the human eye - perfect for wireless communication.
• Infrared band of the electromagnet corresponds to 430THz to 300GHz and a
wavelength of 980nm.
• The propagation of light waves in this band can be used for a communication system
(for transmission and reception) of data.
• This communication can be between two portable devices or between a portable
device and a fixed device.

IR transmission:
• The transmitter of an IR LED inside its circuit, which emits infrared light for every
electric pulse given to it.
• This pulse is generated as a button on the remote is pressed, thus completing the
circuit, providing bias to the LED.
• The LED on being biased emits light of the wavelength of 940nm as a series of pulses,
corresponding to the button pressed.
• However, since along with the IR LED many other sources of infrared light such as us
human beings, light bulbs, sun, etc, the transmitted information can be interfered. A
solution to this problem is by modulation.
• The transmitted signal is modulated using a carrier frequency of 38 KHz (or any other
frequency between 36 to 46 KHz).
• The IR LED is made to oscillate at this frequency for the time duration of the pulse. The
information or the light signals are pulse width modulated and are contained in the 38
KHz frequency

IR Reception
• The receiver consists of a photo-detector which develops an output electrical signal as
light is incident on it.
• The output of the detector is filtered using a narrow band filter that discards all the
frequencies below or above the carrier frequency (38 KHz in this case).
• The filtered output is then given to the suitable device like a Microcontroller or a
Microprocessor which controls devices like a PC or a Robot.
• The output from the filters can also be connected to the Oscilloscope to read the pulses.

Infrared Data Association(IrDA)
• Infrared Data Association, a group of device manufacturers that developed
a standard for transmitting data via infrared light waves.
• Increasingly, computers and other devices (such as printers) come with
IrDA ports.
• This enables you to transfer data from one device to another without any
cables.
• For example, if both your laptop computer and printer have IrDA ports, you
can simply put your computer in front of the printer and output a document,
without needing to connect the two with a cable.
• IrDA ports support roughly the same transmission rates as traditional parallel
ports.
• The only restrictions on their use is that the two devices must be within a few
feet of each other and there must be a clear line of sight between them.

Infrared physical layer (IrPHY)
This specification is intended to facilitate point-to-point communication between electronic devices.
It specifies the optical media interfaces for Serial Infrared (SIR) data transmission and is part of the first layer of
the OSI model.
Infrared link access protocol (IrLAP)
This specification is part of the second layer of IrDA specifications. It lies on top of the IrPHY layer and below the
IrLMP layer. It represents the data link layer.
Infrared link management protocol (IrLMP)
It is the third layer of IrDA specifications. It defines link management multiplexer and link management
information access service.
Transport protocol (TinyTP)
This optional protocol specified in the fourth layer lies on top of the IrLMP layer.
Infrared communication protocol (IrCOMM)
The IrCOMM protocol specified in the fifth layer lets the infrared device act like either a serial or parallel port.
Infrared Financial Messaging (IrFM)
This protocol specified in the sixth layer is a wireless payment standard developed by the Infrared Data
Association.

Low power requirements:
Therefore ideal for laptops, telephones, personal digital assistants
Low circuitry costs:
$2-$5 for the entire coding/decoding circuitry
Simple circuitry:
No special or proprietary hardware is required, can be incorporated into the integrated
circuit of a product
Higher security:
Directionality of the beam helps ensure that data isn't leaked or spilled to nearby devices
as it's transmitted Portable
Few international regulatory constraints:
IrDA (Infrared Data Association) functional devices will ideally be usable by international
travelers.
High noise immunity:
Not as likely to have interference from signals from other devices
ADVANTAGES

Line of sight:
Transmitters and receivers must be almost directly aligned (i.e. able to see each
other) to communicate
Blocked by common materials:
people, walls, plants, etc. can block transmission
Short range:
performance drops off with longer distances
Light, weather sensitive:
direct sunlight, rain, fog, dust, pollution can affect transmission
Speed:
data rate transmission is lower than typical wired transmission
DISADVANTAGES

Medicine: -
Doctors use infrared lamps to treat skin diseases and relieve the pain of sore muscles.
Military:
Infrared imaging is used extensively in military for target acquisition, surveillance, wireless
communication, night vision, homing and tracking.
Science:
Infrared have allowed buildings to keep cool even in the summer. Gold transparent films
in the windows of large office buildings reflect infrared and help to keep temperatures
cool.
Consumer Goods:
Photographers use film that is sensitive to infrared rays to take pictures in places where
there is no visible light. - TVs, VCRs and CD players also use infrared.
Industry:
Infrared is used extensively in specially-designed ovens for drying painted and enameled
surfaces, leather, metals, papers and textiles.
Applications

• Spectroscopy
Infrared vibrational spectroscopy is a technique that can be used to identify molecules by analysis of their
constituent bonds. The vibrational frequencies of most molecules correspond to the frequencies of infrared light.
Typically, the technique is used to study organic compounds using light radiation.
• Thin film metrology
In the semiconductor industry, infrared light can be used to characterize materials such as thin films and periodic
trench structures.
• Meteorology
Weather satellites equipped with scanning radiometers produce thermal or infrared images, which can then enable
a trained analyst to determine cloud heights and types, to calculate land and surface water temperatures, and to
locate ocean surface features.
• Climatology
In the field of climatology, atmospheric infrared radiation is monitored to detect trends in the energy exchange
between the earth and the atmosphere. These trends provide information on long-term changes in Earth's climate.
It is one of the primary parameters studied in research into global warming, together with solar radiation.
• Art conservation and analysis
Infrared reflectography can be applied to paintings to reveal underlying layers in a non-destructive manner, in
particular the artist's underdrawing or outline drawn as a guide

4.Bluetooth -contents
 Bluetooth
 Introduction
 The Name
 History
 How Bluetooth wireless technology works
 BWT network topologies
 pico-net
 scatter-net
 Bluetooth Connection Process
 Bluetooth Protocol
 core protocols
 cable replacement protocols
 telephony control protocols
 adopted protocols
 Bluetooth – chip
 Comparison between Bluetooth versions
 Advantages of Bluetooth
 Dis-Advantages of Bluetooth
 Applications of Bluetooth

• Bluetooth is a short-range and low power wireless technology originally
developed for exchanging data over short distances from fixed and mobile
devices, creating personal area networks (PANs).
• Short-range radio frequency technology that operates at 2.4 GHz on an
unlicensed Industrial Scientific Medical (ISM) band.
• Effective range of Bluetooth devices is 10 meters.
• Bluetooth can connect up to “eight devices” simultaneously and each device
offers a unique 48 bit address from the IEEE 802 standard with the
connections being made point to point or multipoint.
• It was originally conceived as a wireless alternative to data cables
4.Bluetooth - Introduction

Bluetooth: The Name
The word "Bluetooth" is taken from the 10th century Danish Viking King
Harald Gormsson, he had been influential in uniting Scandinavian tribes
into a single kingdom.
• Likes to eat blueberries
• King of Denmark and Norway
• Aka. Harald Blåtand (Harald Bluetooth))
Bluetooth was named so because
1) Bluetooth technology was developed in Scandinavia.
2) Bluetooth technology is able to unite differing industries such as the cell
phone, computing, and automotive markets

• 1994 : Ericsson study complete / vision
• 1995 : Engineering work begins
• 1997 : Intel agrees to collaborate
• 1998 : Bluetooth SIG formed: Ericsson, Intel, IBM, Nokia & Toshiba
• 1999 : Bluetooth Specification 1.0A SIG promoter group expanded: 3Com, Lucent, Microsoft
& Motorola
• 2000 : Bluetooth Specification 1.0B, 2000+ adopters
• 2001 : First retail products released, Specification 1.1
• 2003 : Bluetooth Specification 1.2
• 2004: Bluetooth 2.0 + EDR
• 2007: Bluetooth 2.1
• 2009: Bluetooth 3.0 + HS
• 2016: Bluetooth 5
Bluetooth History

How Bluetooth wireless technology works
• BWT-enabled devices operate in the unrestricted 2.4-gigahertz (GHz) Industrial, Science, Medical (ISM)
band. The ISM band ranges between 2.400 GHz and 2.483 GHz
• BWT-enabled devices use a technique called frequency hopping to minimize eavesdropping and
interference from other networks that use the ISM band. With frequency hopping, the data is divided into
small pieces called packets. The transmitter and receiver exchange a data packet at one frequency, and
then they hop to another frequency to exchange another packet. They repeat this process until all the
data is transmitted.
• BWT devices randomly hop between frequencies up to 1600 times per second—much faster than other
types of devices that use the ISM band. This gives BWT networks a high immunity to interference from
other 2.4-GHz devices.
• There are three classes of BWT radio devices, each with a different maximum range: Class 1 (100 meters);
Class 2 (50 meters); and Class 3 (10 meters)

BWT network topologies
• BWT-enabled devices form network topologies called Pico-nets and scatter-nets.
• A pico-net consists of up to eight BWT-enabled devices
• When a pico-net is established, one device sets the frequency-hopping pattern and the other
devices synchronize their signals to the same pattern.
• The device that sets the frequency-hopping pattern is called the primary device and the
other devices are called secondary devices. Each pico-net has a different frequency-hopping
pattern to differentiate its signals from the signals of other pico-nets

• A scatter-net is formed when two or more pico-nets are linked by a common BWT-
enabled device.
• When a device is present in multiple pico-nets, it synchronizes to the master of each
pico-net with which it is currently communicating and sets the hopping pattern of the
pico-net in which it is the master

Bluetooth Connection Process
Creating a Bluetooth connection between two devices is a multi-step process involving three progressive states:
• Inquiry – If two Bluetooth devices know absolutely nothing about each other, one must run an inquiry to try
to discover the other. One device sends out the inquiry request, and any device listening for such a request
will respond with its address, and possibly its name and other information.
• Paging (Connecting) – Paging is the process of forming a connection between two Bluetooth devices. Before
this connection can be initiated, each device needs to know the address of the other (found in the inquiry
process)
• Connection – After a device has completed the paging process, it enters the connection state. While
connected, a device can either be actively participating or it can be put into a low power sleep mode
• Active Mode – This is the regular connected mode, where the device is actively transmitting or
receiving data.
• Sniff Mode – This is a power-saving mode, where the device is less active. It’ll sleep and only listen
for transmissions at a set interval (e.g. every 100ms).
• Hold Mode – Hold mode is a temporary, power-saving mode where a device sleeps for a defined
period and then returns back to active mode when that interval has passed. The master can
command a slave device to hold.
• Park Mode – Park is the deepest of sleep modes. A master can command a slave to “park”, and that
slave will become inactive until the master tells it to wake back up

Bluetooth is defined as a layer protocol architecture consisting of
• core protocols
• Radio (RF) layer, Baseband Link layer, Link Manager protocol layer
Logical Link Control and Adaption protocol layer, Service Discovery
Protocol
• cable replacement protocols
• RF comm layer
• telephony control protocols
• telephony service
• adopted protocols
• Point-to-Point Protocol, TCP/IP/UDP, Object Exchange Protocol, Wireless
Application Environment/Wireless Application Protocol
Bluetooth Protocol architecture

Bluetooth protocol Architecture - core protocols
• Radio (RF) layer:
It performs modulation/demodulation of the data into RF signals. It defines the physical
characteristics of Bluetooth transceiver. It specifies the usage frequency hopping.
• Baseband Link layer:
It performs the connection establishment within a piconet. Addressing scheme, packet frame
format , timing and power control algorithms required for establishing connection between Bluetooth
devices within piconet defined in this part of protocol specification.
• Link Manager protocol:
It is responsible to establish link between Bluetooth devices and to maintain the link between
them. This protocol also includes authentication and encryption specifications. Negotiation of packet
sizes between devices can be taken care by this.
• Logical link control and adaptation protocol:
This L2CAP protocol adapts upper layer frame to baseband layer frame format and vice versa.
L2CAP take care of both connection oriented and connectionless services.
• Service discovery protocol:
Service related queries including device information can be taken care at this protocol so that
connection can be established between Bluetooth devices.

Bluetooth protocol Architecture - cable replacement protocols
Radio Frequency Communications (RFCOMM)
• RFCOMM is a cable replacement protocol used for generating a virtual serial
data stream.
• Serial ports are popular to provide serial communication between devices.
Bluetooth uses RFCOMM as cable replacement protocol.
• RFCOMM functions as virtual serial port and does transport of binary digital
data bits.
• It basically emulates RS232 specifications over Bluetooth physical layer.

Bluetooth protocol Architecture - telephony control protocols
The Telephony Control Protocol – Binary
• TCS BIN is the bit-oriented protocol that defines the call control signaling for the
establishment of voice and data calls between Bluetooth devices.
• Additionally, "TCS BIN defines mobility management procedures for handling groups of
Bluetooth TCS devices."
• TCS-BIN is only used by the cordless telephony profile, which failed to attract
implementers.

Bluetooth protocol Architecture-adopted protocols
These protocols are already defined by other standard bodies which are incorporate without any change in the
Bluetooth protocol stack architecture.
point to point protocol(PPP)
Internet standard protocol for transporting IP datagrams over a point-to-point link.
TCP/UDP and IP
Foundation Protocols for TCP/IP protocol suite
object exchange protocol
OBEX is a object exchange protocol developed by IrDA and it is similar to HTTP. It is a session level protocol.
Wireless Application Environment/Wireless Application Protocol (WAE/WAP)
WAE specifies an application framework for wireless devices and WAP is an open standard to provide mobile
users access to telephony and information services
The Audio/Video Control Transport Protocol
AVCTP is used by the remote control profile to transfer AV/C commands over an L2CAP channel. The music
control buttons on a stereo headset use this protocol to control the music player.

Bluetooth – chip
Bluetooth devices are fabricated on RF CMOS integrated circuit (RF circuit) chips.
Hardware
• The hardware that makes up the Bluetooth device is made up of, logically, two parts;
• A radio device, responsible for modulating and transmitting the signal; and
• The digital controller is likely a CPU, one of whose functions is to run a Link Controller; and interfaces
with the host device.
• The CPU of the device is responsible for attending the instructions related to Bluetooth of the host
device, in order to simplify its operation.
Software
• Seeking to extend the compatibility of Bluetooth devices, the devices that adhere to the standard use
an interface called HCI (Host Controller Interface) between the host device (e.g. laptop, phone) and
the Bluetooth device (e.g. Bluetooth wireless headset).
• High-level protocols such as the SDP, RFCOMM (Protocol used to emulate serial port connections) and
TCS (Telephony control protocol) interact with the baseband controller through the L2CAP Protocol
(Logical Link Control and Adaptation Protocol).

Bluetooth 1.0
1998 – 2003
• “Base Rate”
• 1Mbps data rate
• Gaussian Frequency Shift Keying
• V1.0 ‐ Draft
• V1.0A ‐ published on 1999
• V1.0B Enhanced Interoperability
• V1.1 ‐ IEEE 802.15.1
• V1.2 Enhanced the compatibility
Bluetooth 2.0 + EDR
2004– 2007.
• “Enhanced Data Rate”
• Higher ordered modulation for
data payload
• 2Mbps or 3Mbps physical data rate
• DQPSK/DPSK
• V2.0
• V2.1
Bluetooth 3.0 + HS
2009
• “HS Mode”
• AMP- Alternative MAC/PHY
• Implement high data rate by
using 802.11 protocols.
• 24 Mbps of data transfer
• Facing the Challenge from Wi‐Fi
• V3.0
Bluetooth 4.0
2010 – 2014
• “Low Energy”
• Facing the IoT application
• Changed the protocol greatly,
almost a new technology
• LE Link Layer Topology
• 1Mbps data transfer
• V4.0
• V4.1
Bluetooth 5.0
2016 on-words
• “Low Energy”
• IoT applications
• 2Mbps, 1Mbps, 500kbps,
125kbps
• Mesh-based model hierarchy
• V5.0
• V5.1
• V5.2

Advantages of Bluetooth
➨It creates ad-hoc connection immediately without any wires. Connection establishment is very
quick. User only need to pair the Bluetooth PAN connection between two devices.
➨It has low power consumption.
➨It can pass through walls.
➨It has range better than Infrared communication.
➨It has been managed by Bluetooth SIG and hence products from large companies are available and
there is no issue of interoperability among different Bluetooth vendor products.
➨It is used for voice and data transfer.
➨It uses FHSS and hence data communication is more secure.
➨The technology is adopted in many products such as head set, in car system, printer, web cam, GPS
system, keyboard and mouse.
➨Due to availability of Bluetooth headphones, calls can be taken on phone even while driving and
doing some other activity simultaneously. This hands free operation relieves great strain.
➨Bluetooth devices are available at very cheap cost.
➨It has less interference compare to other wireless technologies due to use of FHSS technique

Disadvantages of Bluetooth
➨One of the big disadvantages of Bluetooth is security. This is due to the fact that it operates on
Radio frequency and hence can penetrate through walls. It is advisable not to use it for critical
business or personal data transfer.
➨As Home RF technology operates on same frequency, It has interference from it.
➨The bandwidth is lower compare to Wi-Fi.
➨Battery usage is more compare to the condition when Bluetooth is powered OFF. The new
technology known as BLE or Bluetooth low energy or Bluetooth smart is developed to enhance the
battery life further
➨ Limited Operational Range- Enabled devices can only establish and maintain wireless
communication as long as they are within the range limit

4.Wi-Fi – contents
 Computer Networks - Introduction
 The OSI Reference model
 Wi-Fi (wireless fidelity)
 Introduction
 Naming and Logo
 History
 Elements of a WI-FI Network
 How a Wi-Fi Network Works
 IEEE 802.11 Protocol Architecture
 IEEE 802.11 Physical Layers
 IEEE 802.11 Data Link Layer
 Wi-Fi Technology Standards
 Advantages of Wi-Fi
 Dis-advantages of Wi-Fi
 Applications of Wi-Fi

4.WiFi (wireless fidelity)
Computer Networks
A computer network is two or more computers connected together using a telecommunication system
for the purpose of communicating and sharing resources
Goal: Universal Communication (any to any)
Type of Networks
• PAN: a personal area network is a computer network (CN) used for communication among computer
devices (including telephones and personal digital assistants) close to one person
Technologies: USB and Fire-wire (wired), IrDA and Bluetooth (wireless)
• LAN: a local area network is a CN covering a small geographic area, like a home, office, or group of
buildings
Technologies: Ethernet (wired) or Wi-Fi (wireless)
• MAN: Metropolitan Area Networks are large CNs usually spanning a city
Technologies: Ethernet (wired) or WiMAX (wireless)
• WAN: Wide Area Network is a CN that covers a broad area, e.g., cross metropolitan, regional, or national
boundaries
Examples: Internet
Wireless Technologies: HSDPA, EDGE, GPRS, GSM.

• Wireless Technology is an alternative to Wired Technology, which is commonly used, for
connecting devices in wireless mode.
• Wi-Fi uses a radio technology, which can transmit data over short distances using high
frequencies
• Wi-Fi (Wireless Fidelity) is a generic term that refers to the IEEE 802.11 communications
standard for Wireless Local Area Networks (WLANs).
• The 802.11 standard provides several distinct radio frequency ranges for use in Wi-Fi
communications: 900 MHz, 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 5.9 GHz and 60 GHz bands.
• Wi-Fi Network connect computers to each other, to the internet and to the wired network.
• Wi-Fi works on physical and data link layer.
• The purpose of Wi-Fi is to hide complexity by enabling wireless access to applications and data,
media and streams.
• The main aims of Wi-Fi are the following:
• make access to information easier
• ensure compatibility and co-existence of devices
• eliminate cabling and wiring
• eliminate switches, adapters, plugs, pins and connectors
WiFi (wireless fidelity)

• In 1999 Wi-Fi alliance was formed and it took help of a brand building
company to come up with a catchy name. It just came up with the play of
words rhyming similar to Hi-Fi (a term for high-quality audio technology).
Later to that the alliance used the punch line "The standard for Wireless
Fidelity" and this lead to the misconception that Wi-Fi is Wireless Fidelity.
• Phil Belanger who is the founding member of the Wi-Fi Alliance states that
term Wi-Fi was never supposed to mean anything at all
• The exact technical name of Wi-Fi is “IEEE 802.11b Direct Sequence”
• The “yin-yang” logo indicates the certification of a product for
interoperability.
WiFi (wireless fidelity) – Naming and Logo

• 1971: ALOHA net connected the Hawaiian Islands with a UHF wireless packet network. ALOHA net and the ALOHA protocol were
early forerunners to Ethernet, and later the IEEE 802.11 protocols, respectively.
• 1974: Vic Hayes is often regarded as the “father of Wi-Fi.” He started such work in 1974 when he joined NCR Corp.
• 1985 The U.S. Federal Communications Commission released the ISM band for unlicensed use.
• 1991: NCR Corporation with AT&T Corporation invented the precursor to 802.11, intended for use in cashier systems. The first
wireless products were under the name WaveLAN
• 1992 and 1996:CSIRO obtained patentsfor a method later used in Wi-Fi to "unsmear" the signal.
• 1997:The first version of the 802.11 protocol was released , and provided up to 2 Mbit/s link speeds.
• 1999: This was updated with 802.11b to permit 11 Mbit/s link speeds, and this proved to be popular as WiFi 1
• 1999:Wi-Fi Alliance formed as a trade association to hold the Wi-Fi trademark under which most products are sold.
IEEE 802.11a– WiFi 2
• 2003: IEEE 802.11g – WiFi 3
• 2007: IEEE 802.11REVma created a single document that merged 8 amendments (802.11a, b, d, e, g, h, i, j) with the base standard.
• 2009: IEEE 802.11n – WiFi 4
• 2012: IEEE802.11REVmB created a single document that merged ten amendments (802.11k, r, y, n, w, p, z, v, u, s) with the 2007
base standard
• 2013:IEEE 802.11ac &IEEE 802.11ad – WiFi 5
• 2014:IEEE 802.11af, also referred to as "White-Fi" and "Super Wi-Fi“
• 2016:IEEE 802.11 REVmc, is a revision based on IEEE 802.11-2012, incorporating 5 amendments (11ae, 11aa, 11ad, 11ac, 11af)
• 2017:IEEE 802.11af
• 2019:IEEE 802.11ax- WiFi-6
• 2023: IEEE 802.11be –WiFi 7
WiFi - History

Elements of a WI-FI Network
Access Point (AP) - The AP is a wireless LAN transceiver or “base station” that can connect one or many
wireless devices simultaneously to the Internet.
A wireless router is a device that enables wireless network packet forwarding and routing, and serves as an
access point in a local area network. It works much like a wired router but replaces wires with wireless radio
signals to communicate within and to external network environments. It can function as a switch and as an
Internet router and access point.
Wi-Fi cards - They accept the wireless signal and relay information. They can be internal and external.(e.g
PCMCIA Card for Laptop and PCI Card for Desktop PC)
Antennae
Most antennae for wireless LANs are omnidirectional and have low gain. Nearly all access points, routers, and
repeaters come standard with omnidirectional antennae. Omnidirectional antennae satisfy most coverage
requirements; however, consider the use of optional directive antennae to cover a long, narrow area. In some
cases, the antenna is integrated within a radio card or access point and there is no choice to make. If a need
exists to use a directive antenna (higher gain), ensure that the radio card or access point has an external
antenna connector

IEEE 802.11 Physical Layers
IEEE 802.11 Frequency Hopping Spread Spectrum (FHSS)
• Frequency hopping works by modulating a data signal with a carrier signal that hops from frequency to
frequency as a function of time over a wide band of frequencies.
• With 802.11 FHSS, the carrier frequency hops over the 2.4GHz frequency band between 2.4GHz and 2.483GHz.
• Advantage: Capability to operate up to 10 collocated access points without significant interference
IEEE 802.11 Direct Sequence Spread Spectrum (DSSS)
• IEEE 802.11 DSSS combines a data signal at the sending station with a higher data rate bit sequence, which
many refer to as a chipping code.
• The IEEE 802.11 Working Group has set its minimum processing gain requirements at 11, which means that the
chipping code multiplies the data signal by 11.
• Direct sequence spread spectrum sends a specific string of bits for each data bit sent.
• A chipping code is assigned to represent logic 1 and 0 data bits. As the data stream is transmitted, the
corresponding code is actually sent.
• For example, the transmission of a data bit equal to 1 would result in the sequence 00010011100 being sent.
• Advantage: Highest potential data rates from individual physical layers, which is why DSSS was chosen for a
higher-rate 802.11 physical layer (802.11b)

IEEE 802.11b High-Rate Direct Sequence Spread Spectrum (HR-DSSS)
• IEEE 802.11 HR-DSSS The IEEE 802.11b version of the standard is a data rate extension of the initial
802.11 DSSS, providing operation in the 2.4GHz band with additional data rates of 5.5 and 11Mbps.
• All primary wireless LAN vendors offer 802.11b radio cards and access points.
• In addition, the IEEE 802.11 working group is considering an enhancement of the standard to double this
data rate to 22Mbps.
IEEE 802.11a Orthogonal Frequency Division Multiplexing (OFDM)
• The IEEE 802.11a standard specifies a modulation that divides a high-speed serial information signal into
multiple lower-speed "sub-signals" that the system transmits simultaneously at different frequencies in
parallel over a 20MHz channel located in the 5GHz frequency band.
• This parallel form of transmission over multiple subcarriers enables OFDM-based wireless LANs to
operate at higher aggregate data rates. 802.11a has a wide variety of high-speed data rates available: 6, 9,
12, 18, 24, 36, 48, and 54Mbps.
• The 6, 12, and 24Mbps rates are mandatory for all products.
IEEE 802.11 Physical Layers

This Data Link Layer is divided into two sub-layers:
•Logical Link Control (LLC). This sub-layer is responsible for the data transmission between computers or devices
on a network.
•Media Access Control (MAC). On a network, the network interface card (NIC) has an unique hardware address
which identifies a computer or device. The physical address is utilized for the MAC sub-layer addressing.
•The function of the Logical Link Control (LLC) is to manage and ensure the integrity of data transmissions.
•The LLC provides Data Link Layer links to services for the Network Layer protocols.
•This is accomplished by the LLC Service Access Points (SAPs) for the services residing on network computers.
Also, there is a LLC Control field for delivery requests or services.
The Logical Link Control (LLC) has several service types:
Service type 1, is a connectionless service with no establishment of a connection, and an unacknowledged
delivery.
Service type 2, is a connection logical service with an acknowledgement of delivery.
Service type 3, is a connectionless service with an acknowledgement of deliver
IEEE 802.11 Data Link Layer

MAC layer provides functionality for several tasks like control medium access, can also offer support for
roaming, authentication, and power conservation.
The basic services provided by MAC are the mandatory asynchronous data service and an optional time-
bounded service.
IEEE 802.11 defines two MAC sub-layers :-
1.Distributed Coordination Function (DCF) –
DCF uses CSMA/CD as access method as wireless LAN can’t implement CSMA/CD. It only offers
asynchronous service.
2.Point Coordination Function (PCF) –
PCP is implemented on top of DCF and mostly used for time-service transmission. It uses a centralized,
contention-free polling access method. It offers both asynchronous and time-bounded service
Media Access Control (MAC).

Wi-Fi Technology Standards
• The IEEE develops and maintains a large number of standards associated with the electrical and
electronics industries - not only do these include the Wi-Fi 802.11 series of standards, but also many
others including those for Ethernet, IEEE 802.3.
• All the Wi-Fi standards come under the IEEE 802 umbrella for local area and metropolitan area
networking, LAN / MAN. The Wi-Fi standards come under the IEEE 802.11 series.
• The most common set of wireless standards are
• IEEE 802.11b (WiFi 1)
• IEEE 802.11a (WiFi 2)
• IEEE 802.11g (WiFi 3)
• IEEE 802.11n (WiFi 4)
• IEEE 802.11ac (WiFi 5)
• IEEE 802.11ax (WiFi 6)
• IEEE 802.11be (WiFi 7)

• Appears in late 1999
• Operates at 2.44Ghz radio spectrum
• 11Mbps (theoretical speed)- within 30
meter Range
• 4-6 Mbps Actual Speed
• 100-150 feet range
• Limits the number of access points in
range of each other to three
• Most Popular , Least Expensive
• Interference from Mobile Phones and
Bluetooth device which can reduce
transmission speed
• Uses direct-sequence spread-spectrum
technology
1.IEEE 802.11b Standard
• Introduce in 2001
• Operates at 5GHz
• Less popular and Less interfered
• 54 Mbps (theoretical Speed)
• 15-20 Mbps (Actual Speed)
• More Expensive
• Highly Obstructed
• Not Compatible with 802.11b
• Uses frequency division multiplexing
2.IEEE 802.11a Standard

3. IEEE 802.11g Standard
• Introduce in 2003
• Combine features of both a and b
• 54 Mbps (theoretical speed)
• 20-25 Mbps (actual Speed)
• 2.4 GHz radio frequency
• Compatible with b
• Uses frequency division multiplexing
4. IEEE 802.11n Standard
• 802.11n also known as Wireless N
• 802.11n Ratified in 2009
• 802.11n builds upon previous 802.11
standards by adding multiple-input multiple-
output (MIMO).
• Operates on Both 2.4Ghz and 5Ghz
• Provide Bandwidth up to 300Mbps
• Backward-compatible with 802.11b/g gear
• Increased Speed and range

5.IEEE 802.11ac Standard
• Builds on 802.11n ,Published in 2013
• The addition of Multi-user MIMO (MU-
MIMO)
• Utilizes dual band wireless technology
• Support Connection both 2.4 GHz and
5GHz
• Backward compatibility to 802.11b/g/n
• Bandwidth rated up to 1300 Mbps on
the 5 GHz
• bandwidth rated up to 450 Mbps on the
2.4 GHz
• Builds on 802.11n ,Published in 2019
• IEEE 802.11ax, marketed as Wi-Fi 6 by Wi-Fi
Alliance, is a current generation Wi-Fi
specification standard
• 802.11ax addresses frequency bands between
1 GHz and 6 GHz
• Supports orthogonal frequency-division multiple
access (OFDMA), higher order 1024-QAM.
• The addition of MIMO and Multi-user MIMO
(MU-MIMO)
• Frequency bands - 2.4 GHz and 5GHz
6 GHz for Wi-Fi 6E as spectrum is allocated
globally
• Bandwidth rated up to
600.4 Mbps ( 80 MHz channel & 1 SS *)
9607.8 Mbps (160 MHz channel & 8SS *)
6.IEEE 802.11ax Standard

7.IEEE 802.11be Standard
• WiFi 7: the next generation of WiFi technology
• IEEE 802.11be Extremely High Throughput (EHT) is the potential next amendment of
the 802.11 IEEE standard
• Mainly focusing on WLAN indoor and outdoor operation with stationary and pedestrian speeds in the
2.4, 5 and 6 GHz frequency. the Wi-Fi Alliance will most likely certify it as Wi-Fi 7
Features:
• 320 MHz bandwidth and more efficient utilization of non-contiguous spectrum,
• Multi-band/multi-channel aggregation and operation,
• 16 spatial streams and Multiple Input Multiple Output (MIMO) protocols enhancements,
• Multi-Access Point (AP) Coordination (e.g. coordinated and joint transmission),
• Enhanced link adaptation and retransmission protocol (e.g. Hybrid Automatic Repeat Request (HARQ)),
• If needed, adaptation to regulatory rules specific to 6 GHz spectrum.
• Integrating Time-Sensitive Networking (TSN) extensions for low-latency real-time traffic (IEEE 802.11aa)

Standard Year Frequency
band
Bandwidth Transmission
Scheme
Modulation
scheme
MIMO Max Data
rate
Maximum
Range
IEEE 802.11b 1999 2.4GHz 20MHz DSSS QPSK No 11Mbps 450ft.
IEEE 802.11a 2001 5GHz 20MHz OFDM QPSK No 54Mbps 400ft.
IEEE 802.11g 2003 2.4GHz 20MHz DSSS,OFDM 64QAM No 54Mbps 450ft.
IEEE 802.11n 2009 2.4GHz
5GHz
20MHz
40MHz
OFDM 64QAM Yes 600Mbps 825ft.
IEEE 802.11ac 2013 2.4GHz
5GHz
20MHz
40MHz
80MHz
160MHz
OFDM 64QAM Yes 1300Mbps 1000ft.
IEEE 802.11ax 2019 2.4GHz
6GHz
20MHz
40MHz
80MHz
160MHz
OFDM 1024QAM Yes 10Gbps 1000ft.
IEEE 802.11be 2022 2.4GHz
5GHz
6GHz
20MHz
40MHz
80MHz
---- ---- Yes ---- ---

➨It is easy to add or move wifi clients or wifi stations to the wifi network created by AP
(Access Point).
➨Installation is very quick and easy. It does not require technical knowledge of wifi or
wlan system and its protocols.
➨Access to the wifi network can be availed from anywhere within the wifi AP (Access
point) coverage range.
➨WiFi enabled USB dongles are available at very affordable rates from TP-Link, D-Link,
Tenda etc.
➨Latest wifi standard versions such as 11n and 11ac deliver fast data connection rates
e.g. 300 Mbps and higher.
➨As it is easy to integrate wifi functionality in the mobile computing devices; it is now
being used by millions of people using various devices such as PCs, laptops, PDAs,
Printers, Cameras, Games, MP3 players, smartphones etc
Advantages of WiFi

➨Data transfer rate decreases (to individual computer) when number of clients or computers
connected with wifi network increases.
➨Full security is difficult to achieve due to wifi connection being wireless in nature. It requires
proper security authentication protocols and configurations.
➨Wifi devices operate in full functionality and without any interruptions when they are within the
range of AP and receiving good signal strength. WiFi access is limited to about 30 to 100 meters
(i.e. 100 to 300 feet).
➨In case wifi connection does not work, minimal troubleshooting are needed. This requires one to
understand basics of wifi device from user manual provided by the manufacturer.
➨Before using wifi device, one need to install software from the CD provided by the manufacturer
in the desktop or laptop.
Disadvantages of WiFi

Applications
• Internet Access
• Voice over Wireless
• Inventory Control
• Health Care
• Education
• Real Estate
• Public Networks
• Vending
• Field Sales

6.Ethernet- contents
 Ethernet
 Introduction
 History
 IEEE Ethernet standards
 Types of Ethernet Networks
 Ethernet- Protocol stack
 How does Ethernet work?
 IEEE 802.3 Physical layer
 Ethernet MAC layer
 Data Frame format
 The CSMA/CD protocol
 Wireless Ethernet
 Advantages and disadvantages

Ethernet – Introduction
• Ethernet, pronounced "E-thernet" (with a long "e"), is the standard way to connect
computers on a network over a wired connection.
• It provides a simple interface and for connecting multiple devices, such
computers, routers, and switches. With a single router and a few Ethernet cables,
you can create a LAN which allows all connected devices to communicate with each
other
• Ethernet is a family of computer networking technologies commonly used in local
area networks (LAN), metropolitan area networks (MAN) and wide area
networks (WAN).
• It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3
• Over time, Ethernet has largely replaced competing wired LAN technologies such
as Token Ring, FDDI and ARCNET.
• The Ethernet technology mainly works with the fiber optic cables that connect
devices within a distance of 10 km

Ethernet-History
• 1968: Norman Abramson pioneered the precepts of Ethernet by developing this packet radio networking
system that ran at 4800 bps and 9600 bps.
• 1973: Robert Metcalfe and David Boggs at Xerox Corporation in Palo Alto, CA applied the ALHOA network
principles and created the world’s first Local Area Network (LAN). Initially named ALTO ALOHA, the name
was later changed to Ethernet. This first version of Ethernet ran at speeds up to 2.94 Mbps.
• 1980: The first commercial release of Ethernet was by DEC, Intel, and Xerox (DIX) in 1980 as Ethernet,
Version 1. It was commonly referred to as Ethernet DIX80.
• 1982: The second revision release, Ethernet, Version 2, was released. It was commonly referred to as
Ethernet DIX82. Ethernet, Version 2 is the standard of Ethernet technology that is in use today.
• In 1980, the IEEE formed Project 802 to provide a framework for the standardization of LAN technology.
• 1983: Novell released Novell Netware ’86 , which used a proprietary frame format based on a preliminary
specification of the IEEE 802.3 standard. This is the same Novell software that is used today to manage
printers and servers.
• In 1983, the IEEE approved the IEEE 802.3 standard, which included IEEE 802.2 Logical Link Control (LLC).
This made Novell Netware’s proprietary format incompatible with the latest technology.
• In the late 1980s, SynOptics Communications developed a mechanism for transmitting 10 Mbps Ethernet
signals over twisted-pair cables.
• The Ethernet-over-twisted-pair specification (10 BASE-T) was approved by the IEEE in 1990 as the IEEE
802.3i standard. It quickly became the preferred Ethernet media type.

IEEE Ethernet standards
Ethernet is defined in a number of IEEE 802.3 standards. These standards define the physical and
data-link layer specifications for Ethernet. The most important 802.3 standards are:
10Base-T (IEEE 802.3) –
• 10 Mbps with category 3 unshielded twisted pair (UTP) wiring, up to 100 meters long.
• The cable is thinner and more flexible than the coaxial cable used for the 10Base-2 or 10Base-5 standards.
• Cables in the 10Base-T system connect with RJ-45 connectors. A star topology is common with 12 or more
computers connected directly to a hub.
100Base-TX (IEEE 802.3u) – known as Fast Ethernet,
• This has either two pairs of unshielded twisted pairs (UTP) category 5 wires or two shielded twisted pairs (STP)
type 1 wires.
• One of these pairs transmits frames from hub to the device and the other pair transmits from device to hub, thus
providing full-duplex communication
• Each network segment can have maximum length of 100m (328ft)
100Base-FX (IEEE 802.3u) – a version of Fast Ethernet that uses multi-mode optical fiber.
• This has two pairs of optical fibers. One pair transmits frames from hub to the device and the other from device
to hub.
• Maximum distance between hub and station is 2000m.
***Note:1000Base-T means that the speed of the network is up to 1000 Mbps, baseband signaling is used, and the
twisted-pair cabling will be used (T stands for twisted-pair).

1000Base-CX (IEEE 802.3z)
• The initial standard for Gigabit Ethernet
• Uses shielded copper twisted-pair cabling with DE-9 or 8P8C connector
• Maximum segment length is 25 metres
1000Base-SX (IEEE 802.3z) –
• 1 Gigabit Ethernet running over multimode fiber-optic cable.
• Uses a pair of fibre optic cables of a shorter wavelength having 770 – 860 nm diameter
• The maximum segment length varies from 220 – 550 metres.
1000Base-LX (IEEE 802.3z) –
• 1 Gigabit Ethernet running over single-mode fiber
• Uses a pair of fibre optic cables of a longer wavelength having 1270 – 1355 nm diameter
• Can cover distances up to 5 km
1000Base-T (IEEE 802.3ab) –
• Gigabit Ethernet that uses Category 5 UTP wiring
• Uses a pair four lanes of twisted-pair cables (Cat-5, Cat-5e, Cat-6, Cat-7)
10G Base-T (802.3.an) –
• 10GBASE-T is a type of Ethernet signaling providing speeds over twisted-pair cabling that go beyond 1 Gigabit per
second (Gbps) for distances up to 100 meters.
• This IEEE 802.3an standard can reach 2.5 and 5 Gbps over Cat5e and Cat6 cabling. Depending upon the network
infrastructure, signals can potentially reach new speeds of up to 10 Gbps.

Types of Ethernet Networks
1.Fast Ethernet
• The fast Ethernet is a type of Ethernet network that can transfer data at a rate of 100 Mbps using a
twisted-pair cable or a fiber-optic cable.
• The older 10 Mbps Ethernet is still used, but such networks do not provide necessary bandwidth for some
network-based video applications.
• Fast Ethernet is based on the proven CSMA/CD Media Access Control (MAC) protocol, and uses existing
10BaseT cabling.
• Data can move from 10 Mbps to 100 Mbps without any protocol translation or changes to the application
and networking software
2.Gigabit Ethernet
• The Gigabit Ethernet is a type of Ethernet network capable of transferring data at a rate of 1000 Mbps
based on a twisted-pair or fiber optic cable, and it is very popular.
• The type of twisted-pair cables that support Gigabit Ethernet is Cat 5e cable, where all the four pairs of
twisted wires of the cable are used to achieve high data transfer rates.
• The 10 Gigabit Ethernet is a latest generation Ethernet capable of transferring data at a rate of 10 Gbps
using twisted-pair or fiber optic cable.

3. 10 Gigabit Ethernet
• 10 Gigabit Ethernet is the latest generation and delivers a data rate of 10 Gbit/s (10,000 Mbit/s), and a
fiber optic or twisted pair cable can be used.
• 10GBASE-LX4, 10GBASE-ER and 10GBASE-SR based on an optical fiber cable can be used to bridge
distances of up to 10,000 m (6.2 miles). With a twisted pair solution, a very high quality cable (Cat-6a
or Cat-7) is required.
• 10 Gbps Ethernet is mainly used for backbones in high-end applications that require high data rates.
4. Switch Ethernet
• Multiple network devices in a LAN require network equipment's such as a network switch or hub.
When using a network switch, a regular network cable is used instead of a crossover cable.
• The crossover cable consists of a transmission pair at one end and a receiving pair at the other end
• The network switch normally supports different data transfer rates. The most common data transfer
rates include 10 Mbps – 100 Mbps for fast Ethernet, and 1000 Mbps – 10 Gbps for the latest Ethernet.
• Switch Ethernet uses star topology, which is organized around a switch. The switch in a network uses a
filtering and switching mechanism similar to the one used by the gateways, in which these techniques
have been in use for a long time.

How does Ethernet work?
• When communicating over a data network, the Ethernet system divides the data
into a set of what are termed frames.
• These frames have a specific format and each one contains the source and
destination addresses.
• The frame also contains information for error checking so that any data that is
corrupted can be detected.
• If errors are detected then typically the higher layers of the protocol stack for the
system will discard the data and request a re-transmission.
• Ethernet adopts the OSI model for its protocol stack and in line with this,
Ethernet itself provides services up to Layer 3, the data link layer
• Ethernet has adopted the 48 bit MAC address format that has also been used by
other IEEE 802 standards

IEEE 802.3 Physical layer
Physical layer
10Base5/10base
2
10Base T
100Base TX/100
BASE FX
1000Base
CX/SX/LX/T
10G Base T
802.3 802.3 802.3u
802.3z and
802.3ab
802.3an
Ethernet
Fast
Ethernet
Gigabit
Ethernet
10Gigabit
Ethernet

Ethernet MAC data frame format
• The basic Ethernet frame in use today is referred to as the Ethernet type II frame. This is the frame format
developed by the layer 2 elements of the stack, and this is then passed to the layer 1 physical layer to put it
into the format for sending.
• The layer 2 format consists of the main elements of the data frame, but without some headers needed for
the actual sending of the overall data
• In order to send the data over the Ethernet link, some additional elements need to be added to
the basic MAC data frame so that the data can be pre-transmitted.

The basic frame consists of seven elements split between three main areas:-
Header
• Preamble / SFD: - this element within the header is added by the layer 1 part of the protocol stack. It enables
the receiver to synchronize and know that a data frame is about to be sent.
• Preamble (PRE) - This is seven bytes long and it consists of a pattern of alternating ones and zero, and this
informs the receiving stations that a frame is starting as well as enabling synchronization.
• Start of Frame Delimiter (SFD) - This consists of one byte and contains an alternating pattern of ones and
zero but ending in two ones.
• Destination Address (DA) - This field contains the address of station for which the data is intended. The left
most bit indicates whether the destination is an individual address or a group address. An individual address
is denoted by a zero, while a one indicates a group address. The next bit into the DA indicates whether the
address is globally administered, or local. If the address is globally administered the bit is a zero, and a one of
it is locally administered. There are then 46 remaining bits. These are used for the destination address itself.
• Source Address (SA) - The source address consists of six bytes, and it is used to identify the sending station.
As it is always an individual address the left most bit is always a zero.
• Length / Type - This field is two bytes in length. It provides MAC information and indicates the number of
client data types that are contained in the data field of the frame. It may also indicate the frame ID type if the
frame is assembled using an optional format.(IEEE 802.3 only).

•Payload
• User Data - This block contains the payload data and it may be up to 1500 bytes long. If the length of the field is
less than 46 bytes, then padding data is added to bring its length up to the required minimum of 46 bytes.
Later implementations allowed for so-called ‘jumbo’ frames up to 9,000 bytes long to facilitate certain types of
large traffic flows such as file transfers and video links.
•Trailer
• Frame Check Sequence (FCS) - This field is four bytes long. It contains a 32 bit Cyclic Redundancy Check (CRC)
which is generated over the DA, SA, Length / Type and Data fields.
After the Ethernet data frame itself there is an inter-frame gap of a minimum of 12 bytes of data. This acts as a delimiter
to ensure that the receiver knows the frame is complete before any further data is sent.
The CSMA/CD protocol
This access method involves the use of CSMA/CD and it was developed to enable several stations to
share the same transport medium without the need for switching, network controllers or assigned
time slots. Each station is able to determine when it is able to transmit and the network is self
organizing

• The CSMA/CD protocol used for Ethernet and a variety of other applications falls into three categories.
• The first is Carrier Sense. Here each station listens on the network for traffic and it can detect when the
network is quiet.
• The second is the Multiple Access aspect where the stations are able to determine for themselves whether
they should transmit.
• The final element is the Collision Detect element.
• Even though stations may find the network free, it is still possible that two stations will start to transmit at
virtually the same time.
• If this happens then the two sets of data being transmitted will collide.
• If this occurs then the stations can detect this and they will stop transmitting.
• They then back off a random amount of time before attempting a retransmission.
• The random delay is important as it prevents the two stations starting to transmit together a second time.

• The standard for wireless networking within a home or office. Also known as a "Wi-Fi" or "802.11"
network, wireless Ethernet is the wireless counterpart to regular, wired Ethernet, which is also the
standard for local networks.
• Ethernet networks can also be wireless. Rather than using Ethernet cable to connect the computers,
wireless NICs use radio waves for two-way communication with a wireless switch or hub. It consists of
Ethernet ports, wireless NICs, switches and hubs.
• Wireless network technology can be more flexible to use, but also require extra care in configuring
security.
Wireless Ethernet

Advantages of Ethernet connection:
➨It is inexpensive to form Ethernet based network of computers.
➨The nodes on Ethernet network have same privileges and do not follow client-server architecture.
➨It is easy to maintain and troubleshoot the Ethernet network.
➨The cables used in Ethernet connection are immune to noise and hence quality of connection is
maintained without any degradation.
➨With latest versions such as gigabit Ethernet and wireless Ethernet (IEEE 802.11ac/11ad) transfer
speeds in Gbps have become possible
Disadvantages of Ethernet connection:
➨As it is not designed to support real time voice and video traffic initially, it works best for traffic
consisting of data solely.
➨The Ethernet network does not prioritize traffic in order to support effective class of service.
➨The gigabit Ethernet is still not in use at many places and hence will take time for common man to
have benefits of this Ethernet version.
➨The 100Base-T4 version requires 4 pair of wiring to support data transfer. Moreover it can not support
full duplex data communication mode.

7.IEEE 1394 Fire wire - contents
 IEEE 1394 Fire wire
 Introduction
 History
 IEEE 1394 - Standards and versions
 How It Works
 Advantages
 Dis-Advantages
 Applications

7.IEEE 1394 Fire wire - Introduction
• IEEE 1394, High Performance Serial Bus, is an electronics standard for connecting devices to your
personal computer.
• IEEE 1394 provides a single plug-and-socket connection on which up to 63 devices can be
attached with data transfer speeds up to 400 Mbps.(latest 800Mbps)
• The standard describes a serial bus or pathway between one or more peripheral devices and
computer's microprocessor . Many peripheral devices now come equipped to meet IEEE 1394.
• Two popular implementations of IEEE 1394 are Apple's FireWire and Sony's i.LINK .
• IEEE 1394 implementations are expected to replace and consolidate today's serial and parallel
interfaces, including Centronics parallel , RS-232C , and Small Computer System Interface ( SCSI ).
The first products to be introduced with FireWire include digital camera s, digital video disks
( DVD s), digital video tapes, digital camcorders, and music systems.
• IEEE 1394 is a peer-to-peer interface, one camcorder can dub to another without being plugged
into a computer. With a computer equipped with the socket and bus capability, any device (for
example, a video camera) can be plugged in while the computer is running

• Michael Johas Teener, original chair and editor of the IEEE 1394 standards document,
and technical lead for Apple's FireWire team from 1990 until 1996
• The original FireWire project name was "Chefcat", the name of Michael Teener's favorite coffee cup
• FireWire is a trademark of Apple Computer, Inc. The trademark was filed in 1993. The "FireWire" name
was chosen by a group of engineers socializing before Comdex 1993, just before the project was about
to going to the public.
• It was developed by the IEEE P1394 Working Group, largely driven by contributions from Sony(102
patents), Apple (58 patents), and Panasonic (46 patents), in addition to contributions made by,
engineers from Philips, LG Electronics, Toshiba, Hitachi, Canon INMOS/SGS Thomson
(now STMicroelectronics) and Texas Instruments.
• In 2007, IEEE 1394 was a composite of four documents: the original IEEE Std. 1394–1995, the IEEE Std.
1394a-2000 amendment, the IEEE Std. 1394b-2002 amendment, and the IEEE Std. 1394c-
2006 amendment. On June 12, 2008, all these amendments as well as errata and some technical
updates were incorporated into a superseding standard, IEEE Std. 1394–2008.
• Sony's implementation of the system, i.LINK, used a smaller connector with only four signal conductors,
omitting the two conductors that provide power for devices in favor of a separate power connector. This
style was later added into the 1394a amendment. This port is sometimes labeled S100 or S400 to
indicate speed in Mbit/s.
IEEE 1394 Fire wire-History

FireWire 400 (IEEE 1394-1995)
• The original release of IEEE 1394-1995 specified what is now known as FireWire 400.
• It can transfer data between devices at 100, 200, or 400 Mbit/s half-duplex data rates.
• These different transfer modes are commonly referred to as S100, S200, and S400.
• Cable length is limited to 4.5 metres (14.8 ft), although up to 16 cables can be daisy chained using
active repeaters; external hubs or internal hubs are often present in FireWire equipment.
• The S400 standard limits any configuration's maximum cable length to 72 metres (236 ft).
FireWire 400 (IEEE 1394a-2000)
• An amendment, IEEE 1394a, was released in 2000, which clarified and improved the original specification. It
added support for asynchronous streaming, quicker bus reconfiguration, packet concatenation, and a power-
saving suspend mode.
• IEEE 1394a offers a couple of advantages over the original IEEE 1394–1995. 1394a is capable of arbitration
accelerations, allowing the bus to accelerate arbitration cycles to improve efficiency. It also allows for arbitrated
short bus reset, in which a node can be added or dropped without causing a big drop in isochronous
transmission.
• 1394a also standardized the 4-conductor alpha connector developed by Sony and trademarked as "i.LINK",
already widely in use on consumer devices such as camcorders, most PC laptops, a number of PC desktops, and
other small FireWire devices. The 4-conductor connector is fully data-compatible with 6-conductor alpha
interfaces but lacks power connectors.
IEEE 1394 - Standards and versions

FireWire 800 (IEEE 1394b-2002)
• IEEE 1394b-2002 introduced FireWire 800 (Apple's name for the 9-conductor "S800
bilingual" version of the IEEE 1394b standard)
• FireWire 800's connector, referred to as a beta connector, is different from FireWire 400's
alpha connectors, making legacy cables incompatible.
• The full IEEE 1394b specification supports data rates up 400Mbps over beta-mode or
optical connections up to 100 metres (330 ft) in length.
• The original 1394 and 1394a standards used data/strobe (D/S) encoding (renamed to alpha
mode) with the cables, while 1394b added a data encoding scheme called 8B10B referred
to as beta mode.
FireWire S800T (IEEE 1394c-2006)
• IEEE 1394c-2006 was published on June 8, 2007.
• It provided a major technical improvement, namely new port specification that provides 800 Mbit/s
over the same 8P8C (Ethernet) connectors with Category 5e cable, which is specified in IEEE 802.3
clause 40 (gigabit Ethernet over copper twisted pair) along with a corresponding automatic
negotiation that allows the same port to connect to either IEEE Std 1394 or IEEE 802.3 (Ethernet)
devices.

FireWire S1600 and S3200
• The 1394 Trade Association announced that products would be available before the end of 2008 using the
S1600 and S3200 modes that, for the most part, had already been defined in 1394b and were further clarified
in IEEE Std. 1394–2008.
• The 1.5 Gbit/s and 3 Gbit/s devices use the same 9-conductor beta connectors as the existing FireWire 800 and
are fully compatible with existing S400 and S800 devices. It competes with USB 3.0.
• S1600 (Sym-wave) and S3200 (Dap Technology) development units have been made, however because of FPGA
technology Dap-Technology targeted S1600 implementations first with S3200 not becoming commercially
available until 2012.
• Steve Jobs declared FireWire dead in 2008.As of 2012, there were few S1600 devices released, with a Sony
camera being the only notable user.
Future enhancements (including P1394d)
• A project named IEEE P1394d was formed by the IEEE on March 9, 2009 to add single mode fiber as an
additional transport medium to FireWire. The project was withdrawn in 2013.
• Other future iterations of FireWire were expected to increase speed to 6.4 Gbit/s and additional
connectors such as the small multimedia interface.

How It Works
• There are two levels of interface in IEEE 1394, one for the backplane bus within the computer
and another for the point-to-point interface between device and computer on the serial cable.
• The backplane bus supports 12.5, 25, or 50 megabits per second data transfer.
• The cable interface supports 100, 200, or 400 megabits per second. Each of these interfaces
can handle any of the possible data rates and change from one to another as needed.
• IEEE 1394 provides two types of data transfer: asynchronous and isochronous.
• Asynchronous is for traditional load-and-store applications where data transfer can be initiated
and an application interrupted as a given length of data arrives in a buffer.
• Isochronous data transfer ensures that data flows at a pre-set rate so that an application can
handle it in a timed way.
• For multimedia applications, this kind of data transfer reduces the need for buffering and helps
ensure a continuous presentation for the viewer.
• FireWire can work with the latest internal computer bus standard, Peripheral Component
Interconnect (PCI), but higher data transfer rates may require special design considerations to
minimize undesired buffering for transfer rate mismatches.

•Implementation cost of IEEE 1394 is low
•Cabling system is adaptable
•Provides higher bandwidth
•Transfer rates are high
•Very efficient
•Supports current versions of Windows
•Supports isochronous data transfer
•Supports customization
•Provides throughput of 400 megabits per second
•Provides low latency
•It is PC independent
•Easy to use
•Capability of Plug and play
•Most of them do not require external power supply
Advantages

disadvantages
• Slower data transfer rate - up to 400 Mbps for 1934a and up to 800
Mbps for 1394b (dependent on camera, IEEE 1394 interface hardware,
and operating system support)
• No onboard memory for saving images
• Less triggering support
• Difficult to synchronize with other devices
• Not all PCs come factory equipped with Fire-wire ports.
• Fire-wire devices are typically more expensive than USB devices

Consumer automobiles
IDB-1394 Customer Convenience Port (CCP) was the automotive version of the 1394 standard
Consumer audio and video
IEEE 1394 was the High-Definition Audio-Video Network Alliance (HANA) standard connection interface for A/V
(audio/visual) component communication and control.
Military and aerospace vehicles
SAE Aerospace standard AS5643 originally released in 2004 and reaffirmed in 2013 establishes IEEE-1394 standards as a
military and aerospace data-bus network in those vehicles.
General networking
FireWire can be used for ad-hoc (terminals only, no routers except where a FireWire hub is used) computer networks.
Specifically, RFC 2734 specifies how to run IPv4 over the FireWire interface, and RFC 3146 specifies how to run IPv6.
Instrumentation & Industrial Digital Camera
Digital Video (DV) is a standard protocol used by some digital camcorders
iPod and iPhone synchronization and charging
Applications

communication interfaces-Embedded real time systems

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