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esd electronics, Inc. 525 Bernardston Road Greenfield, MA 01301
Controller Area Network
Presented byWilfred Voss
esd electronics, Inc.525 Bernardston Road
Greenfield, MA 01038http://www.esd-electronics-usa.com
Download/View this presentation at:
http://www.canseminar.com/Tutorials.html/
Serial Network Technology for Embedded Solutions
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Literature
Literature onController Area Network,CANopen and SAE J1939
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esd electronics, Inc.525 Bernardston RoadGreenfield, MA 01301
Tel.: 413-773-3170Fax: 413-773-3171
http://www.esd-electronics-usa.com
esd electronics provides:
CAN Hardware Interfaces PCI, cPCI, VME, PMC, PC104, ISA, and more
CAN Gateways USB, EtherNet, Bluetooth, IEEE488, and more
CAN Converters CANopen, DeviceNet, Profibus, and more
CAN Embedded Controllers
Drivers and APIs for various operating systems
Free CAN Analyzer software included with driver
esd Product Line
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What is CAN General Aspects
Serial Network Technology for Embedded Solutions
Network technology established among micro-controllers
Well suited for high speed/real-time applications
Replaces expensive Dual-Port RAM technology
CAN chips manufactured by Motorola, Philips, Intel, Infineon, andmore
600 Million CAN nodes used in 2007
Originally designed by Bosch forautomotive industry
Became very popular in industrialautomation
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What is CAN Technical Aspects
High-integrity serial data communications bus for real-timeapplications
Designed for max. performance & reliability
Operates at data rates up to 1 Mbit/sec
Uses short messages 8 bytes per message
Excellent error detection and fault confinement capabilities
Is an international standard: ISO 11898
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A Brief History of CAN - 1
1983 Start of Bosch internal project to develop in-vehicle network
1986 Official introduction of the CAN protocol
1987 First CAN controller chips by Intel & Philips
1991 Bosch publishes CAN specification 2.0
1992 CAN in Automation (CiA) established
1992 CAN Application Layer (CAL) protocol by CiA1992 First automobiles equipped with CAN (Mercedes Benz)
1993 ISO 11898 standard published
1994 First International CAN Conference (iCC)
1994 Allen Bradley introduces DeviceNet
1995 ISO 11898 amendment (extended frame format)
1995 CANopen protocol introduced
2000 Development of time-triggered CAN
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A Brief History of CAN - 2
2007
2006
2005
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Number of Million CAN Nodes sold:
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CAN Applications
CAN is used wherever two or more microprocessor units need tocommunicate with each other.
Passenger Cars (multiple separate CAN networks)
Trucks & Buses, Construction Vehicles, Agricultural Vehicles(SAE J1939 protocol)
Semiconductor Industry (Wafer Handlers, etc.)
Robotics, Motion Control Applications
Passenger/Cargo Trains (Brake Control, Wagon Communication)
Aircrafts (AC, Seat Adjustment)
Elevators (e.g. Otis)
Building Technologies (Light & Door Control Systems, Sensors, etc.)
Medical Equipment (X-Ray, CAT scanners, etc.)
Household Utilities (Coffee Machine, Washer, etc.)
Aerospace (Satellites)
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CiA CAN in Automation
International Users and Manufacturers Organization Develops, supports CAN Standards and CAN based higher layer
protocols All activities are based on CiA members interest
http://www.can-cia.org
CAN Newsletter
To subscribe log on to:
http://www.can-cia.org/newsletter/
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Main Characteristics
Multi-Master Bus Access
Message Broadcasting
Message Priority (No Node IDs)
Limited Data Length (08 bytes)
1 Mbit/sec Data Rate
Excellent Error Detection & Fault Confinement
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Benefits of Using CAN
Main Benefit:
Physical and Data Link Layer implemented in Silicon
SW Development Engineer is not involved with writingprotocol features
Low Cost Implementation
Be aware! Whenever you attempt to add software functions between the CAN Data Link Layer and the Application Layer, you will be
adding functionalities that are already covered by off- the-shelf available higher layer protocols such as CANopen and DeviceNet.
ISO 11898 7-Layer Reference
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Message Frames
Data Frame Broadcasts a message to the CAN bus
Remote Frame Requests transmission of message
Error Frame Signals error condition
Overload Frame Special Error Frame
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Remote Transmission Request
Data Frame Broadcasts a message to the CAN bus
Remote Frame Requests transmission of message
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Message Broadcasting with Data Frames
Node A transmits a message Nodes B, C and D receive the message Nodes B and D accept the message, Node C declines
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Message Request with Remote Frames - 1
Node A sends a remote frame (request)
Node B, C, D receive message
Node D accepts, Nodes B & C decline message
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Message Request with Remote Frames - 2
Node D sends requested message
Nodes A, B, C receive requested message
Nodes A, B accept requested message, Node C declines
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Message Frame Format - 1
Data Frame
Remote Frame
Error/Overload Frame
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Message Frame Format - 2
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Extended CAN Protocol
Standard Format: 11 Bit Message Identifier
Extended Format: 29 Bit Message Identifier
Both formats, Standard and Extended, may co-exist on the same CANbus
The distinction between both formats is managed by IdentifierExtension Bit (IDE)
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Dominant/Recessive Bus Level
Node Output and Resulting Bus Level
Bi M i i
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Bit Monitoring
Each transmitting node monitors the Bit level on the bus,compares it to transmitted level.
Used during arbitration process.
Provides immediate detection of all bus-wide and local transmissionerrors.
B A bit ti P i i l 1
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Bus Arbitration Principle - 1
B A bit ti P i i l 2
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Bus Arbitration Principle - 2
B A bit ti P i i l 3
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Bus Arbitration Principle - 3
Main Rules of Bus Arbitration
Bus is considered idle after transmitted message plus IntermissionField
Node that transmits message with lowest ID (highest priority) winsarbitration, continues to transmit. Competing nodes switch toreceiving mode.
Nodes that lost arbitration will start new arbitration as soon as bus is
free for access again => No message gets lost
D t T f S h i ti 1
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Data Transfer Synchronization - 1
Bit Coding
Bit coding according to Non-Return-to-Zero principle
NRZ provides highest transport capacity
Constant Bit level over Bit time
Insufficient signal edges for synchronization of Bit stream
Bit Stuffing required
D t T f S h i ti 2
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Data Transfer Synchronization - 2
Bit Stuffing
Sender inserts complementary Bit (Stuff Bit) after 5 successive Bitsof same polarity
Receiver filters the complementary Bit
1. Bit sequence to betransmitted
2. Transmitted Bit sequence onbus after bit stuffing
3. Bit sequence at receiverafter filtering Stuff Bit
D t T f S h i ti 3
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Data Transfer Synchronization - 3
Bit Stuffing
Provides additional signal edges for data synchronization
No Bit Stuffing in static format fields of message frame
Special case: Stuff Bit contributes to 5 Bit sequence
Further Bit Synchronization through
Programmable Phase Buffers
Resynchronization Jump Width
Bit St ffi R
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Bit Stuffing Range
Frame Length Due to Bit Stuffing
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Frame Length Due to Bit Stuffing
Frame length varies due to bit stuffing
Based on 11-Bit Identifier
Average bit stuffing determined per mathematical model
Data Field0 Bytes
Data Field8 Bytes
No bit stuffing 47 bits 111 bits
Max. bit stuffing
(worst case scenario)
55 bits 135 bits
Average bit stuffing 49 bits 114 bits
Bit Monitoring 1
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Bit Monitoring - 1
When exactly does a receiving CAN node read the
bit information ?
Bit Rate[kBit/sec]
Nominal Bit-Time[sec]
1000 1
500 2
250 4
125 8
Bit Monitoring 2
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Bit Monitoring - 2
Partitioning of CAN Bit Time into Four Segments
Sync_Seg: Signal edge is expected here. Any deviationwill affect Phase Buffer lengths.
Prop_Seg: Compensates for signal propagation times
within the network.Phase_Seg1/2: Compensate for signal edge phaseerrors by adjusting their length.
Resynchronization Jump Width: Defines the upperlimit to adjust phase buffer lengths.
Hard Synchronization
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Hard Synchronization
Hard Synchronization at Start of Frame (SOF)
Resets internal timing of receiving node
Bit Synchronization
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Bit Synchronization
Bit Synchronization within a frame
Phase_Seg1 and Phase_Seg2 correct position ofbit sample point according to phase error
Ideal Bit Timing
Phase Errors
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Phase Errors
Positive Phase Error
Negative Phase Error
Compensation of Phase Errors
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Compensation of Phase Errors
Compensation of Positive Phase Error
Compensation of Negative Phase Error
Error Detection Method
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Error Detection Method
Bit Monitoring
Each transmitting node monitors the Bit level on the bus, compares it totransmitted level. Provides immediate detection of all bus-wide and localtransmission errors.
Stuff Error
More than 5 Bits of same polarity outside of bit-stuffed segment
CRC Error
Comparison of received CRC sequence and calculated CRC. Providesdetection of local receiver errors.
Form Error
Violation of fixed format Bit fields Acknowledgement Error
Transmitted message receives no acknowledgement. ACK confirms onlythe successful transmission. Is used for error confinement.
Error Detection Analysis
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Error Detection Analysis
Probability of non-detected faulty CAN messages
Example:
1 Bit error each 0.7 sec
500 kBit/sec
8 h/day
365 days/year
Residual Error Probability :
1 undetected error in 1000 years
Error Detection
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Error Detection
Error Frame
Basic Error Frame
More realistic Error Frame
Error Recovery Time = Error Flag + Error Delimiter + Intermission Field = 12 + 8 + 3 = 23 Bits
Error Frame Super Positioning
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Error Frame Super Positioning
Fault Confinement - 1
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Fault Confinement - 1
Guarantees proper network operation even in cases wheremalfunctioning nodes produce continuous error condition
CAN error detection can pinpoint to perpetrator
Distinction between temporary and permanent node failures
Identification and removal (self-retirement) of malfunctioning nodesfrom the bus
Transmit/Receive Errors
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Transmit/Receive Errors
Possible error scenarios in a CAN network:
1. Transmit Error
A transmitting node sends a faulty message
ALL receiving nodes in the network respond with an error frame
Through majority vote the transmitting node is being flagged as theperpetrator
2. Receive Error
A transmitting node send a perfectly good message
Only ONE node in the network responds with an error frame
Through majority vote the error reporting node is being flagged asthe perpetrator
Fault Confinement - 2
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Fault Confinement 2
CAN Node Error States
Bus Medium
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Bus Medium
Physical media must support dominant and recessive bus level.Dominant level always overrules recessive level, especially during busarbitration.
Two-wire bus terminated with line impedance to avoid signalreflections
Bus Topology
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Bus Topology
Bus Topology according to ISO 11898
Bus Level - 1
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Bus Level 1
Bus Levels according to ISO 11898
Bus Level - 2
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Bus Level 2
Bus Levels according to ISO 11898
Bus Connection
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Bus Connection
Maximum Bus Length
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Maximum Bus Length
Bus Length is limited due to Bit Monitoring(Signal Propagation Time)
Wiring and Connections
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Wiring and Connections
Pin Signal Description
1 - Reserved
2 CAN_L CAN_L bus line (dominant low)
3 CAN_GND CAN Ground
4 - Reserved
5 CAN_SHLD Optional CAN shield
6 GND Optional CAN Ground
7 CAN_H CAN_H bus line (dominant high)
8 - Reserved (error line)
9 CAN_V+ Optional CAN external positive supply
CAN Controller Chips - 1
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C Co t o e C ps
Two different types of CAN applications:
Stand-Alone CAN Controller
Microprocessor with integrated CAN Controller
Many major semiconductor manufacturers, such as Motorola, Philips,Intel, Infineon, and many more, sell CAN chips.
Most semiconductor manufacturers who usually integrated a UART withtheir microprocessor design, in order to support serial communication forRS 232/485, nowadays tend to integrate CAN instead.
CAN Controller Chips - 2
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p
Basic CAN
One receive, one transmit message FIFO buffer
Low cost solution
Requires good CPU performance or low CAN data traffic
Full CAN
Several programmable receive and/or transmit message buffers
Most designs also provide Basic CAN features
Allows low CPU performance or high CAN data traffic
CAN Development Tools - 1
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p
What you need is
The regular tools such as cross-compiler, emulator, etc.
CAN Hardware Interface (Starter Kit)
For more information on CAN Starter Kits log on to:http://www.canstarterkit.com
CAN Development Tools - 2
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What you need is
CAN API for your own programming (should be included with HW)
CAN Analyzer Software
For more information on free CAN Analyzer software log on to:
http://www.canstarterkit.com or http://www.USBtoCAN.com
Higher Layer Protocols - 1
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g y
Why Higher Layer Protocols?
Data Transport of more than 8 bytes
Embedded Systems require appropriate communication model based onMaster/Slave configuration
Network Management (Network Start-Up, Node Monitoring, NodeSynchronization, etc.)
Higher Layer Protocols - 2
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g y
CANopen
Suited for embedded applications
Was originally designed for motion control
Developed/Maintained by CAN-in-Automation User Group
Manufacturer-Independent Protocol
http://www.can-cia.org
DeviceNet
Suited for industrial applications (floor automation) Developed by Allen Bradley/Rockwell
Maintained by Open DeviceNet Vendor Association (ODVA)
Standard controlled by Allen Bradley/Rockwell
http://www.odva.org
SAE J 1939
Communication for vehicle networks (trucks, buses, etc.)
Standard developed by Society of Automotive Engineers (SAE)
http://www.sae.org
More Info on CAN
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CAN-in-Automation (CiA)
http://www.can-cia.org
Open DeviceNet Vendor Association (ODVA)
http://www.odva.org
Society of Automotive Engineers (SAE)http://www.sae.org
Robert Bosch GmbH
http://www.semiconductors.bosch.de/en/20/can/index.asp
Literature
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Literature onController Area Network,CANopen and SAE J1939