Communication protocols - Embedded Systems

Team Emertxe
Communication Protocols 1

Communication
Protocols I
● Introduction
● UART
● SPI
● I²C
● CAN
● USB

Introduction
● What do mean by Communication?
● Mode of Communications
● Type of Communications
● Why Protocols?

Introduction
Modes of Communication
● Simplex
● Half Duplex
● Duplex

SPI
● Introduction
● Interface
● Hardware Configurations
● Data Transmission
– Data Propagation
– Data Validity

SPI
Introduction
● Synchronous
● Full Duplex
● Master / Slave

SPI
Interface
● SCLK
● MOSI
●
MISO
●
nSS

● Introduction to I²C
● I²C Bus Features
● The I²C Bus Protocol
● Bus Speeds
I2
C

● Synchronous
● Half Duplex
● Multi Master / Slave
I2
C
Introduction

● Two Line Interface
● Software Addressable
● Multi Master with CD
● Serial, 8 bit Oriented, Bidirectional with 4 Modes
● On Chip Filtering
I2
C
Bus Features

● Example
● Signals
● A Complete Data Transfer
I2
C
Protocol

● Two-wired Interface
– SDA
– SCL
● Wired-AND
● Conditions and Data Validity
● Transmission
I2
C
Signals

I2
C
Signals – Conditions and Data Validity

I2
C
Signals – Transmission
● Data on SDA
● Clocking on SCL
● Clock Synchronization
● Data Arbitration

I2
C
Signals – Clocking on SCL

I2
C
Signals – Clock Synchronization

I2
C
Signals – Data Arbitration

I2
C
Bus Speeds
● Bidirectional Bus
– Standard Mode - 100 Kbit/s
– Fast Mode - 400 Kbits/s
– Fast Mode Plus - 1 Mbits/s
– High Speed Mode - 3.4 Mbits/s
● Unidirectional Bus
– Ultra Fast Mode – 5 Mbits/s
● Uses Push-Pull Drivers (No Pullups)

●
Introduction to CAN
●
Basic Concepts
●
Message Transfer
●
Message Filtering
●
Message Validation
●
Coding
●
Error Handling
●
Fault Confinement
●
Oscillator Tolerance
●
Bit Timing Requirement
Controller Area Network

●
Asynchronous
●
Half Duplex
●
Multi Master / Slave
CAN
Introduction

● Example
● Versions
● Absence of node addressing
– Message identifier specifies contents and priority
– Lowest message identifier has highest priority
● Non-destructive arbitration system by CSMA with collision
detection
● Simple Transmission Medium
– Twisted pair – CAN H and CAN L
● Properties
● Layered Architecture
CAN
Basic Concepts

CAN
Basic Concepts - Versions
NOMENCLATURE STANDARD
MAX SIGNALING
RATE
IDENTIFIER
Low Speed CAN ISO 11519 125 kbps 11 bit
CAN 2.0A ISO 11898:1993 1 Mbps 11 bit
CAN 2.0B ISO 11898:1995 1 Mbps 29 bit

● Prioritization of Messages
● Guarantee of Latency Times
● Configuration of Flexibility
● Multicast Reception with Time Synchronization
● System wide Data Consistency
● Multi master
● Error Detection and Error Signaling
● Automatic Retransmission
● Distinction between temporary errors and permanent failures
of nodes and autonomous switching off of defect nodes
CAN
Basic Concepts - Properties

CAN
Basic Concepts - Layered Architecture

CAN
Message Transfer
● Frame Formats
– Standard Frame - 11 bits Identifiers
– Extended Frame - 29 bits Identifiers
● Frame Types
– Data Frame
– Remote Frame
– Error Frame
– Overload Frame
● Frame Fields

CAN
Message Transfer - Frame Formats

CAN
Message Transfer – Data Frame
● A data frame consists of seven fields: start-of-frame, arbitration,
control, data, CRC, ACK, and end-of-frame.

CAN
Message Transfer – Remote Frame
● Used by a node to request other nodes to send certain
type of messages
● Has six fields as shown in above figure
– These fields are identical to those of a data frame
with the exception that the RTR bit in the arbitration
field is recessive in the remote frame.

CAN
Message Transfer – Error Frame
● This frame consists of two fields.
– The first field is given by the superposition of error flags
contributed from different nodes.
– The second field is the error delimiter.
● Error flag can be either active-error flag or passive-error flag.
– Active error flag consists of six consecutive dominant bits.
– Passive error flag consists of six consecutive recessive bits.
● The error delimiter consists of eight recessive bits.

CAN
Message Transfer – Overload Frame
● Consists of two bit fields: overload flag and overload delimiter
● Three different overload conditions lead to the transmission of the
overload frame:
– Internal conditions of a receiver require a delay of the next data frame or
remote frame.
– At least one node detects a dominant bit during intermission.
– A CAN node samples a dominant bit at the eighth bit (i.e., the last bit) of an
error delimiter or overload delimiter.
● Format of the overload frame is shown in above fig
● The overload flag consists of six dominant bits.
● The overload delimiter consists of eight recessive bits.

● Control Field
● Arbitration Field
● Data Field
● CRC Field
● ACK Field
CAN
Message Transfer – Frame Fields

● The first bit is IDE bit for the standard format but is
used as reserved bit r1 in extended format.
● r0 is reserved bit.
● DLC3…DLC0 stands for data length and can be from
0000 (0) to 1000 (8).
CAN
Frame Fields – Control Field

●
The identifier of the standard format corresponds to the base ID in the
extended format.
● The RTR bit is the remote transmission request and must be 0 in a data
frame.
● The SRR bit is the substitute remote request and is recessive.
● The IDE field indicates whether the identifier is extended and should
be recessive in the extended format.
● The extended format also contains the 18-bit extended identifier.
CAN
Frame Fields – Arbitration Field

● May contain 0 to 8 bytes of data
CAN
Frame Fields – Data Field

● It contains the 16-bit CRC sequence including CRC
delimiter.
● The CRC delimiter is a single recessive bit.
CAN
Frame Fields – CRC Field

●
Consists of two bits
●
The first bit is the acknowledgement bit.
●
This bit is set to recessive by the transmitter,
but will be reset to dominant if a receiver
acknowledges the data frame.
●
The second bit is the ACK delimiter and is
recessive.
CAN
Frame Fields – Ack Field

CAN
Error Handling
● Error Detection
– Bit Error
– Stuff Error
– CRC Error
– Form Error
– Acknowledgment Error
● Error Signaling

CAN
Fault Confinement
●
Counters
– Transmit Error Counter & Receive Error Counter

● Introduction
● Technical Overview
● Interfaces
● Architecture
● Power Managment
● Communication Overview
● Extensions
– OTG
– Wireless
Universal Serial Bus

● Asynchronous
● Half Duplex
● Master / Slave
● Offers simple connectivity
● Low cost
● Ease of use
● Manages power efficiently
● Supports all kinds of Data
USB
Introduction

● Upstream Connection and Downstream Connection
● Device Speeds
– Low Speed cables at 1.5 Mbps
– Full Speed cables at 12 Mbps and
– High Speed cables at 480 Mbps
– Super Speed upto 5.0 Gbps (Raw throughput)
● Two types of Connectors
– Type A and Type B
– Sizes
●
Standard, Mini, Micro
USB
Technical Overview

● USB 1.X and 2.0
– Vcc
– D-
– D+
– GND
● USB 3.0
– Older USB interface line plus
– SSTX+/-
– SSRX+/-
USB
Interfaces

● Follows a Tiered star Topology and consists of
– Host controller
– Hubs
– Peripherals
USB
Architecture

USB
Architecture - Bus Topology

● Host recognizes the peripheral through a process called
Enumerations
● Host communicates with the peripheral to learn its
identity and identifies which device driver is required
● Host supplies the peripheral with an address
● Host is the controller of the entire network. e.g. PC
USB
Architecture - Host

● Allows many USB devices to share a single USB port
● USB devices with some incorporated intelligence
● Increase the logical and physical fan out
●
Single upstream connection and one-many down stream
connection
●
Smart wire passing data between the peripheral and Host
●
Direct connection exists between host and peripherals
●
Two kinds of Hubs:
– Bus Powered Hub: Draws power from the host computers
USB interface
– Self Powered Hub: Has a built in power supply.
USB
Architecture - Hubs

● Receive and respond to the commands from the host. E.g.
Mice, Keyboard, Joysticks
●
Two types of Peripherals
– Standalone
– Compound Device
USB
Architecture - Peripherals

● Peripherals connected regardless of the power state
● A pair of wires to supply power to the peripherals
● Manage power by enabling and disabling power to
devices
● Removes electrically ill behaved systems from the
network
USB
Power Management

● End point is a unique point in the device which is the
source or the receiver of the data
● End point has a definite address associated with it
● Codes indicate the type of transfer
● 16 end points within each device each end point has a
4 bit address
● End point “0” reserved for control transfers
USB
Communication Overview

● Transactions between the host and end point take
place through virtual pipes
● Pipes are logical channels which connect the host to
the end points
● Once the communication is established the end points
return a descriptor
● Descriptor is a data structure tells the host about the
end points configuration and expectations
USB

USB supports four transfer types of data:
●
Control Transfers:
– Exchange information such as configuration, command
information , set up between host and end point
●
Bulk Transfers:
– Supports bulk amounts of data when timely delivery isn’t critical.
– e.g. Printers and Scanners
●
Isochronous transfers:
– Handle transfers like streaming data
●
Interrupt transfers:
– Poll devices to see if they need service
USB

● USB 2.0
● PictBridge Standard to communicate imaging devices
● Microsoft X box console
● IBM Ultraport
● USB 1.0 OTG
● USB 1.0a supplement OTG
● Wireless USB
USB
Extensions

● USB On-The-Go Technology is used to provide dual
role to the peripherals
● Enables direct communication between the hosts
without involving the processor
● Incorporates Mini A , Mini B, Mini AB plugs and
receptacles
● Highly complex design
USB
OTG

Advantages:
● Provides Dual Role Devices
● Introduces new connector types, Mini A, Mini B, Mini
AB
● Provides with Aggressive Power Management
On the Go Functionality of the USB can be implemented:
● Using a Full solution Approach
● Using a USB microcontroller
● Designing a custom IC
USB
OTG

● A Paradigm developed by Cypress that allows devices
to be connected but appear as if they are connected
to the host over normal USB connectivity
● Addresses many of the Design issues of Wireless
networking
● An evolution that relies on familiar and existing
technologies
● Desirable for point to point devices
● Features of Wireless USB are its Ease of use, simple
connectivity and conservation of the battery power
USB
Wireless

Communication protocols - Embedded Systems

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Semelhante a Communication protocols - Embedded Systems

Semelhante a Communication protocols - Embedded Systems (20)

Mais de Emertxe Information Technologies Pvt Ltd

Mais de Emertxe Information Technologies Pvt Ltd (20)

Último

Último (20)

Communication protocols - Embedded Systems