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CONTROLLER AREA NETWORK
( CAN BUS)
AHMAD SHAMMURI BIN MOHD NISAB INSTITUT KEMAHIRAN BELIA NEGARA KUALA
[email protected] PERLIS
Penyenggaraan kereta JALAN BUKIT KUBU
02000 KUALA PERLIS
PERLIS INDERA KAYANGAN
TRAINER PROFILE
AHMAD SHAMMURI BIN MOHD NISAB
JITRA,KEDAH
PENGAJAR DI IKBN KUALA PERLIS
JABATAN
AUTOMOTIF,PENYENGGARAAN KERETA
INSTITUT KEMAHIRAN BELIA NEGARA
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EDUCATION
UTM , BACHELOR OF ENGINEERING(MECHANICAL)
CIAST/ILP KL , DIPLOMA PENGAJAR VOKASIONAL(NITP)
POLISAS , SIJIL KEJURUTERAAN MEKANIKAL (AUTOMOTIF)
DKM , TEKNOLOGI AUTOMOTIF-SERVICE SELEPAS JUALAN
SKM 3 , SERVICE KERETA ELEKTRIK DAN HIDBRID
SEK MEN TEKNIK ARAU
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EXPERIENCE
• INSTITUT KEMAHIRAN BELIA NEGARA KUALA PERLIS
• DRB HICOM UNIVERSITY OF AUTOMOTIVE MALAYSIA , 9 YEARS
• SLC AUTO ACADEMY , 1 YEARS
• NATIONAL TRAINER , ASC KUALA LUMPUR 2016
• NATIONAL TRAINER , WSC ABU DHABI 2017
• TRAINER WSMB SINCE 2010
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CAN Bus systems
The abbreviation "CAN" means
Controller Area Network.
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The CAN (Controller Area Network)
(History)
Origin of the CAN system :
1. Created in 1980, developed by Robert BOSCH
company
2. First components in 1985
3. ISO certification achieved in 1991, follow by
modifications in 1993 and 1995
4. First application on vehicle in 1992 with
Mercedes Benz
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Introduction:
1. According to the increase of equipments and
convenient parts in the car, including the safety
for both driver and passenger which all of these
require a lot of wires and harnesses.
2. In order to reduce amount of wires and harnesses.
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What is a bus system?
A bus system is a network, in which data between different
devices (e.g ECU´s) is transmitted by a coded ( logical ) signal.
Because of the coding, it is possible to connect all devices by a
minimum amount of wiring. Other reasons to use bus systems ?
1. Less wiring / devices (saves weight and cost)
2. More safety against system failure
3. Easier Implementation of Complex functions
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STANDARD CONFIGURATION
SERIES CONFIGURATION
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THE PRINCIPLE OF DATA BUS
A subscriber (control unit) ”speaks“ data into the line network while
the other subscribers ”listen in“ to this data. Some subscribers will be
interested in this data and will utilise it. The other subscribers will
choose to ignore this data.
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Outline of Multiplex
Communication
“How are you doing?” “It will get hot today.”
“Where are we going “Is there anybody want to go to
today?” mountain?”
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Outline of Multiplex
Communication
“How are you doing?”
“Excellent!”
“Where are we going today?”
“Let’s go to a mountain”
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NETWORK LAYOUTS
HUMAN NETWORK COMPUTER NETWORK
COMMUNICATION NETWORK
RING BUS
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From a central control unit to
a networked system
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Car with 3 control units
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Vehicle with 3 control units
and bus system
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Vehicle with 3 control units
and bus system
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CAN Connection (Physical Layer)
When connecting between ECUs using CAN,
only 2 wires are needed between all of them.
Main Line CAN_H → Terminal
CAN_L Resistance
Branch 1.51m.5m
ECU Line 120Ω ECU
ECUs
CAN has differential-2-line system. It consists of CAN_H for higher
voltage and CAN_L for lower voltage.
Main Line…Main communication line for CAN
Branch Line…Wiring for connecting with other ECUs.
Terminal Resistance…Resistances attached on the ends of Main line.
Copy RHighat®rRneesesrsveiAmkadpeemidSaagna c/ EeonisBe1r2ha0d ohm. INSTITUT KEMAHIRAN BELIA NEGARA
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CAN Bus systems
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Basic CAN-Bus System
What is CAN-Bus?
Control Area Network-Bus Electrical System
Maximum communication speed is 1Mbps
but PROTON only use 500kbps
CAN-H CAN-BUS Communication
CAN-L
BCM EMS 700
ABS TCU Meter
Cluster
SRS K-Line Communication PADT-07
Airbags
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Twisted pair,
CAN high and CAN low wire
Data is exchanged between the control units via both of
these wires.
The data comes in the form of engine speed, tank fill level
and road speed, for example.
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The features of the CAN
data bus.
The data bus comprises two
lines along which
information is sent.
To avoid electromagnetic
interference and radiation
emission, the two data bus
lines are twisted together.
Note twist length.
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Twisted Wire
2.5V 3.5V
Twisted wire
1.5V
CAN-H
CAN-L
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CAN signal 0 1 Logical signal
V1
Can high Tension
5 Can low
3 120 ohm
2
1 INSTITUT KEMAHIRAN BELIA NEGARA
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120 ohm
Communication Methods
(Reception)
• Broadcast: All ECUs are able to receive transmission data.
• ID Filtering: Receiver ECUs decide whether it should receive the
data or not depending on the ID.
I need ID1 I don’t
need ID1
ECU1 ECU2 ECU3
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Signal Types
Parallel signal Digital signal
44 41
xx xx
11 14
bit bit bit bit
Dataframe
start end
The data frame is necessary to identify one specific message! It contains all
necessary information such as start, address , message, priority, end, etc.
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Contents of CAN Data Frame
Protocol Characteristics
SSOOFF ID ID RTR Control DATA CRC ACKK EEOOFF
1bit 11bit 1bit 6bit 0-64bit => 0-8byte 16bit 2bit 7bit
SOF Start of frame DATA Data bit (s).
ID The Identifier gives different CRC Cyclic redundancy check
priorities
RTR Remote transmission request ACK Acknowledge signal when
the data is received
Control gives the amount of bits send EOF End of frame bit
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The processing of the data are defined by the so called protocol.
The different network layouts have different protocols which are defined
by ISO or SAE or others.
0
0 0 0 0
1 1 1 1
11 1 1 1
0 0 0 0
1 01 1 0
1
0
V arian Maklumat V arian Maklumat V arian Maklumat
dengan 1 yang dengan 2 yang dengan 3 yang
bit mungkin bit mungkin bit mungkin
0V 10°C 0V ,0V 10°C 0V ,0V ,0V 10°C
0V ,0V ,5V 20°C
5V 20°C 0V ,5V 20°C 0V ,5V ,0V 30°C
0V ,5V ,5V 40°C
5V ,0V 30°C 5V ,0V ,0V 50°C
5V ,0V ,5V 60°C
5V ,5V 40°C 5V ,5V ,0V 70°C
5V ,5V ,5V 80°C
1 2 3 4 5 6 7 8 bit = 1 bait = 256 Information
Example:
000100110100010011001000010I1NSTITUT KEMAHIRAN BELIA NEGARA
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CAN DATA BUS
A separate wire is required for each item of information. As the volume of additional information
increases, so does the number of wires and the number of pins on the control units. Therefore, this
data transfer mode is only suitable for exchanging a limited volume of information.
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With this data transfer mode, all information is transferred along two wires regardless of the number of
participating control units and the volume of information involved. Data transfer with the CAN data bus would
therefore make sense if a large volume of information is exchanged between control units.
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THE CAN DATA BUS
The following components in The following components in the
the drive train form an convenience system form an
integrated system: integrated system:
• the engine control unit, • the central control unit and
• the automatic gearbox • the door control units
control unit and
• the ABS control unit
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BENEFITS OF THE DATA BUS:
• If the data protocol is extended to • High-speed data transfer is
include additional information, only
software modifications are necessary. possible between control units.
• More space available through
• Low error rate through continuous
verification of the transmitted smaller control units and smaller
information by the control units as
well as additional safeguards in the control unit plugs.
data protocols. • The CAN data bus conforms to
• Fewer sensors and signal lines international standards and
through the multiple use of a sensor
signal. therefore facilitates data
interchange between different
makes of control unit.
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WHAT COMPONENTS MAKE UP A CAN DATA BUS?
The CAN controller The CAN transceiver
receives the transfer data from the is a transmitter and receiver in one. It
microcomputer integrated in the control unit. converts
The CAN controller processes this data and the data which the CAN controller supplies
relays it to the CAN transceiver. into electrical signals and sends this data
Likewise, the CAN controller receives data over
from the CAN transceiver, processes it and the data bus lines.
relays it to the microcomputer integrated in Likewise, it receives data and converts this
the control unit. data for the CAN controller.
The data bus lines The data bus terminal
are bidirectional and transfer the data. is a resistor. It prevents
They are referred to as CAN High and CAN data sent from being
Low. reflected at the ends and
returning as an echo.
This would corrupt the data
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DATA TRANSFER PROCESS
Supplying the data
The control unit provides data to the CAN controller for transfer.
Sending data Checking data
The CAN The control units check
transceiver whether they require
receives data the data they have
from the received for their
CAN controller, functions or not.
converts it into
electrical Accepting data
signals and sends If the received data
them. is important, it is
accepted and
Receiving data processed. If not, it
All other control is ignored.
units networked
with the CAN INSTITUT KEMAHIRAN BELIA NEGARA
data bus become KUALA PERLIS
receivers.
What does the CAN data bus transfer?
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It transfers a data protocol between
the control units at short intervals. It
is subdivided into seven areas
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THE DATA PROTOCOL
comprises a long string of bits. The number of bits in a data
protocol depends on the size of the data field. The diagram
below shows the format of a data protocol. This format is
identical on both data bus lines. For simplicity’s sake, only one
data bus line will be shown in this Self-study Programme.
A bit is the smallest unit of information (one circuit state per
unit of time). In electronics, this information can only have the
value ”0“ or ”1“, i.e. ”yes“ or ”no“ .
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THE SEVEN AREAS
The start field marks the start of the data
protocol. A bit with approx. 5 Volts
(depending on system) is sent over the CAN
High Line and a bit with approx. 0 Volts is sent
over the CAN Low Line.
The status field defines the level of priority of the data
protocol. If, for instance, two control units want to send their
data protocol simultaneously, the control unit with the higher
priority takes precedence.
The check field displays the number of items of information
contained in the data field. This field allows any receiver to
check whether it has received all the information transferred to
it.
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In the data field, information is transferred to the
other control units.
The safety field detects transfer faults.
In the confirmation field, the receivers signal to the transmitter
that they have correctly received the data protocol. If an error
is detected, the receivers notify the transmitter of this
immediately. The transmitter then sends the data protocol
again.
The end field marks the end of the data protocol. This is the
last possibility to indicate errors which lead to a repeat transfer.
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HOW IS A DATA PROTOCOL PRODUCED?
The data protocol comprises a string of several bits. Each bit
can only have status or value “0“ or “1“.
Here is a simple example to explain how a status with the value
”0“ or ”1“ is generated:
The light switch
switches a light on or off. This means that the light switch can
have two different states.
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Status of the light switch with the value ”1“ Status of the light switch with the value ”0“
• Switch closed • Switch opened
• Lamp on • Lamp is not on
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In principle, the CAN data bus functions in
exactly the same way.
The transceiver can also generate two different bit states
Status of bit with the value ”1“ Status of the bit with the value ”0“
• Transceiver open, switches to 5 Volts in • Transceiver closed, switches to earth
• Voltage applied to data bus line: approx. 0 Volts
the convenience system (drive train:
approx. 2.5 Volts)
• Voltage applied to data bus line: approx. 5
Volts in the convenience system (drive
train: approx. 2.5 Volts)
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The transceiver CAN HS essentially comprises a:
• Transceiver (with its transistors) which converts the binary data in order to transmit
an electrical voltage on the CAN high and low wires.
• A receiver which links the voltages on the CAN high and low wires forming a
difference from them to send to the CAN controller. In this way everything taking
place on the bus is read continuously.
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Explanatory notes: If bits 1 and 2 are transmitted with 0 Volts, the information
in the table ”Electric windows now in motion“ or “Coolant temperature is
10°C“.
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The table below shows you how the number of items of information increases with each
additional bit.
The higher the number of bits, the more items of information can be transferred. The number of possible items of
information doubles with each additional bit.
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CAN DATA BUS ALLOCATION
How are allocations made?
Each bit has a value, and this value How is the priority of a data protocol recognised?
is assigned a weighing. There are
two possibilities: high weighting or A code comprising eleven bits is assigned to
low weighting. each data protocol depending on its priority in
the status field.
The priorities of three different data protocols
are shown in the table below.
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