Communication protocols - Embedded Systems

Team Emertxe

Communication Protocols 1

CommunicationProtocols I

● Introduction

● UART

● SPI

● I²C

● CAN

● USB

Introduction

Introduction

● What do mean by Communication?

● Mode of Communications

● Type of Communications

● Why Protocols?

IntroductionModes of Communication

● Simplex

● Half Duplex

● Duplex

UART

UART

Serial Peripheral Interface

SPI

● Introduction

● Interface

● Hardware Configurations

● Data Transmission

– Data Propagation

– Data Validity

SPIIntroduction

● Synchronous

● Full Duplex

● Master / Slave

SPIInterface

● SCLK● MOSI● MISO● nSS

SPIHardware Configuration



SPIData Transmission









SPIData Validity

Inter Integrated Circuits

● Introduction to I²C

● I²C Bus Features

● The I²C Bus Protocol

● Bus Speeds

I2C

● Synchronous

● Half Duplex

● Multi Master / Slave

I2CIntroduction

● Two Line Interface

● Software Addressable

● Multi Master with CD

● Serial, 8 bit Oriented, Bidirectional with 4 Modes

● On Chip Filtering

I2CBus Features

● Example

● Signals

● A Complete Data Transfer

I2CProtocol

I2CExample

● Two-wired Interface

– SDA

– SCL● Wired-AND

● Conditions and Data Validity

● Transmission

I2CSignals

I2CSignals – Wired-AND

I2CSignals – Conditions and Data Validity

I2CSignals – Transmission

● Data on SDA

● Clocking on SCL

● Clock Synchronization

● Data Arbitration

I2CSignals – Data on SDA





I2CSignals – Clocking on SCL

I2CSignals – Clock Synchronization

I2CSignals – Data Arbitration

I2CA Complete Data Transfer

I2CBus 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)

Controller Area Network

● 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

CANIntroduction

● 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

CANBasic Concepts

CANBasic Concepts - Example

CANBasic Concepts - Versions

NOMENCLATURE STANDARDMAX 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

CANBasic Concepts - Properties

CANBasic Concepts - Layered Architecture



CANMessage 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

CANMessage Transfer - Frame Formats

CANMessage Transfer – Data Frame

● A data frame consists of seven fields: start-of-frame, arbitration, control, data, CRC, ACK, and end-of-frame.

CANMessage 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.

CANMessage 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.

CANMessage 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

CANMessage 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).

CANFrame 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.

CANFrame Fields – Arbitration Field

● May contain 0 to 8 bytes of data

CANFrame Fields – Data Field

● It contains the 16-bit CRC sequence including CRC delimiter.

● The CRC delimiter is a single recessive bit.

CANFrame 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.

CANFrame Fields – Ack Field

CANError Handling

● Error Detection

– Bit Error

– Stuff Error

– CRC Error

– Form Error

– Acknowledgment Error● Error Signaling

CANFault Confinement

● Counters– Transmit Error Counter & Receive Error Counter

Universal Serial Bus

● 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

USBIntroduction

● 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

USBTechnical Overview

● USB 1.X and 2.0

– Vcc

– D-

– D+

– GND

● USB 3.0

– Older USB interface line plus

– SSTX+/-

– SSRX+/-

USBInterfaces

● Follows a Tiered star Topology and consists of

– Host controller

– Hubs

– Peripherals

USBArchitecture

USBArchitecture - 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

USBArchitecture - 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.

USBArchitecture - Hubs

● Receive and respond to the commands from the host. E.g. Mice, Keyboard, Joysticks

● Two types of Peripherals – Standalone– Compound Device

USBArchitecture - 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

USBPower 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

USBCommunication 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 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 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

USBExtensions

● 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

USBOTG

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

USBOTG

● 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

USBWireless

Thank You