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CAN bus signal monitoring using the DL850V
Yokogawa Meters & Instruments Corporation
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Page Page 22
What is CAN?
Controller Area Network Developed by BOSCH in 1983. It is a de facto standard protocol, being used for communication between ECUs in a vehicle.
• It is used for data communication such as speed, RPM, break status, diagnosis information.
• It is widely being used for not only for vehicle but also power, vessel, railroad, medical equipment, FA, elevator, etc.
Serial communication
Master Slave
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Page Page 33
Merit of using CAN
Cutting Harness………low-cost, simple-designCutting weight………..more economicalDifferential signal……noise reduction (safety)Error detection……….higher reliability
Wire Harness
Using CAN
SimpleLight weight
complicated
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Page Page 44
(Reference) Example of in-vehicle network
The source: Renesas Electronics Corporation (Japan)
For Multi-Media
For Fault-diagnosis (controlled legally) Fault-diagnosis “CAN”
diagnosis tool
Sub-Network
For Power Train Chassis
MD/CDchanger
LampInstrument panel Keyless
Door
Switch SwitchSensor Sensor
Squibb Squibb
Air-bag Control
For SafetyFor Body Control
Sub-Network
Gateway
Sub-Network
Tire Pressure
Engine Steering
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Page Page 55
(Reference) CAN regulation
OSI basic reference model
Both datalink layer and Physical layer are defined.
In addition to ISO-defined standards, there are some other CAN-regulated standards such as SAE J2284, J2411.
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
LLC
Physical Layer
Data Link Layer (ISO11898, ISO11519-2)
MAC
Acceptance, Filtering (1:1, 1:n communication)Overload (not ready yet) NoticeResend when an error is occurredFrame Generation (Data, Remote, Error, Overload frame)Bus monitoring, Error detection and noticeAcknowledgementArbitration
Data Link LayerPhysical Layer (ISO11898, ISO11519-2)Bit, Timing, Synchronization, Resynchronization, Communication speed
Bus characteristic, Driver, etc.Controlled by Software
Controlled by Hardware
Processed by CAN controller
Processed by CANTransceiver
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Page Page 66
CAN bus and Node(s)
ECUECU
ECUECU
CAN bus= Two wire
Max. 30 nodes
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Signal flow in the CAN….1
Packet signal, called “FRAME”, carried and received.
ECUECU
ECUECU
CAN busFRAME
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Each node can send a frame freely, also can receive a frame freely.
Signal flow in the CAN….2
ECUECU
ECUECU
CAN busFRAME FRAME
FRAME
Multi-master
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Page Page 99
Features of CAN Differential Signal Multi-master
Any node can send out a message when the bus is open.
The order of priority for sendingIdentifier field in a message determines the order of priority.
System flexibilityEach node has no specific address, so easy for “adding” and “removing”.
Flexibility for communication speedIt can be set according as a scale of network, function of system.
Advanced error handlingExcellent in error detection, notice and recovery
Data requestAny node can generate data output request for the other node.
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Page Page 1010
ECU (Node) connection
Differential signal
Node N(max.30)
Node 1
∬
∬
CAN_H
CAN_L
CAN Bus LineTerminator
120 ohm
Node 2Terminator
120 ohm
CPU
CAN Controller TX0 TX1 RX0 RX1
Transceiver
Communicate via differential signal (CAN_H/CAN_L) Max. 30 nodes can be connected. Terminators must be placed at the end of bus line. It is classified into two type of standards, Hi-speed C
AN and Low-speed CAN. The boundary is 125kbps. The figure below shows an example of Hi-speed CAN.(Terminated by 120 ohm)
Each node is connected to CAN bus via the CAN Controller and CAN Transceiver.
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Page Page 1111
CAN Topology
The “Bus type” is typically being used.
1. Bus type
2. Star type 3. Ring type
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A variety of framesData Frame A DATA FRAME carries data from a transmitter to the receivers.
Remote Frame A REMOTE FRAME is transmitted by a bus
unit to request the transmission of the DATA FRAME with the same IDENTIFIER.
Error Frame An ERROR FRAME is transmitted by any unit
on detecting a bus error.
Overload FrameAn OVERLOAD FRAME is used to provide for an extra delay between the preceding and the succeeding DATA or REMOTE FRAMEs.
The DL850V can monitor only a data frame. Start of Frame
Arbitration Field
Control Field
Data Field
CRC Field
ACK Field
EndofFrame
Start of Frame
Arbitration Field
Control Field
CRC Field
ACK Field
EndofFrame
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Data Frame format (Packet structure)
ACKCRCDataControlField
ArbitrationFieldRecessive
Dominant
SOF
1 4
ID
11 Bit
RTR
1 1
r
1
0-64
(0-8 byte) 15 1 1 1
EOF
7 3
Start of Frame: Marks the beginning of DATA FRAMES and REMOTE FRAMEs.Identifier Field: Indicates the contents of message, also can be used for the order of priority for bus acce
ss. Standard format:11bit / Extended format:29bit (DL850V supports both.)RTR: Remote Transmission Request BIT. In DATA FRAMEs the RTR BIT has to be ’dominant’. Within a RE
MOTE FRAME the RTR BIT has to be ’recessive’.Control Field: It includes the DATA LENGTH CODE and two bits reserved for future expansion.Data Field: The DATA FIELD consists of the data to be transferred within a DATA FRAME. (Max. 8-byte(6
4-bit))CRC Sequence & CRC Delimiter : It is the frame check sequence. The CRC SEQUENCE is followed by the CRC DELIMITER which
consists of a single ’recessive’ bit.Ack Slot & Ack Delemiter : All nodes having received the matching CRC SEQUENCE report this within the ACK SLOT by
superscribing the ’recessive’ bit of the TRANSMITTER by a ’dominant’ bit.End Of Frame: A flag sequence consisting of seven ’recessive’ bits.
DLCr
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Page Page 1414
CAN data frame and physical data
142h
b0 - - - -15 16 17
0006h 2468h 0302h
32 - - 47 48 - - 63
RPMIntegratingrevolutioncounter
Oilpressure
Identifier Field Data Field
Air cond.ON/OFF
1
High beam indicator
0
With CAN data frames, multiple data (physical data) are carried and received under a single ID.
Ex.)
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Page Page 1515
Tool lineup for CAN bus
ECUECU
ECUECU
CAN busFRAME
CANalyzer (Vector)
DLM2000SB5000
WE7000 DL850V
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Page Page 1616
Measurement targets of the CAN tools
DLM2000 CANalyzerWE7000DL850V
Physical layer wavefoem observation ○Protocaol Analysis △ ○ △Signal trend waveformobservation ○
TargetModel
Mainly for CAN hardware design
Mainly for CAN software design
ID DATA
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The difference of observed “waveform”
DLM2000, SB5000
“waveform” = Trend of “voltage signal” of the CAN bus
DL850V
“waveform” = Trend of “physical value(signal)” that is transmitted on the CAN bus
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Page Page 1818
Simultaneous observation of CAN data and the analog signal(s)
Analog signals
Engine Transmission BrakeStraingauge
Acceleration Sensor
Pressure sensor
ECU ECUECU
Analog Signals
CAN bus
thermocouple
DL850V
CAN data
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Page Page 1919
CAN bus data monitoring
E/G RPM Vehicle speed
Data Data
Trend of RPM
Trend of speed
CAN Frame
720240
You can check physical value trends of CAN bus data and the corresponding actually measured waveforms on the same screen at once.
Multi kinds of data transmitted on the CAN bus can be monitored at the same time via a single wire.
ECU1ECU2
ECU3CAN
monitoring of CAN protocolcommunication data(signal) as an analog trend wafeform(s).
What is “CAN monitor” function?
Comparison and verification of actually measured signals and CAN bus signals
Trend display
Each signal(s) can be “extracted” from a single CAN bus line.
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Page Page 2020
Sampled Data and Displayed Waveforms
Extracted data is stored in memory at up to 100 ks/s while simultaneously being displayed on screen as trends.
Sampled data (trend waveform data) can be saved into files.
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Page Page 2121
Pressure sensor(analog)
CAN signal(Physical layer)
Current(CAN monitor waveform 1)
CAN bus 1 frame
Two signals transmitted by a single frame are trend-displayed as two waveforms.
Observed waveform exampleYou can use Vector Informatik's CANdb database file (.dbc format) to indicate the field being monitored (acquired).
Pressure(CAN monitor waveform 2)
The timing of analog signal and CAN communication signal can be checked.
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Page Page 2222
Sub channel definition720240 Sub channel(s) means the signal definitions of target item(s)
142h
b0 - - - - - - - - - 31
00069012h 2468h 0302h
32 - - 47 48 - - 63
CH3CH1 CH2Number of
sub CHID Start bit Bit length
(Note)
1 142 0 32 Integrating revolutioncounter
2 142 32 16 Oil pressure
3 142 48 16 RPM
: : : : :
Up to 16CH(Signal)/port can be defined.
(sub-CH)
Note:Up to 16 of bit length can be defined by 720240 module.
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Sub channel definition display (Preliminary)
Factor, Offset, Unit:Scaling factor and unit for converting physical value.
Signal definition setting(see the previous page)
Import of setup configuration file
Port Setup(refer to the next page)
Byte Count :Target byte lengthStart Bit :Position of the start bit (counted from LSB)Bit Count :Target bit lengthByte Order : (Big): transmitted in “from upper byte to lower byte” order
(Little): transmitted in “from lower byte to upper byte” order
Note: The bit data in a byte is transmitted by MSB first.
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Port Setup ( Preliminary)
Terminator:When it turn to “ON”, the module-built-in terminator is inserted between CAN_H and CAN_L.
Bit Rate:Communication speed of the bus
Sample Point:Position for detecting dominant or recessive in a single bit.
Sync Jump Width:It can be used for correction of clock cycle in a single bit for re-synchronization.
Bit Sample Num:It can be used for designating the number of sample point(s).
Setup configuration for 720240 input port
Listen Only:When it turns to “ON”, any signal(Frame, Ack) is not outputted from the DL850V.
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*1 : The CANdb file(.dbc) is a signal definition database defined by CANdb or CANdb++ presented by Vector Informatik.
Using ”Symbol Editor” free software, a message and signal can be selected(imported) from CANdb, then export as the signal labels to the DL850V.
Drug & Drop
Edits
Usage of CAN db databaseSignal labels can be imported from CANdb database*1
CAN db fileimports
**.dbc
Definition file for exporting to the DL850V.
**.sbl
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Page Page 2626
Outputting Frame Data (Preliminary)
Single specified (defined) data frames or remote frames can be output (manually, at desired timing).
Setting the condition of frame output
A designated frame is output when “Execute” is set.
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Page Page 2727
Model 720240 CAN Bus Monitor module main specifications
Input ports: 2 (16 signals x 2 ports)Number of Channels : 16 signals/1portConnector type: D-sub 9 pin (male),
Isolated (across port and main unit, across each port)Supported protocols:
Physical layer: ISO-11898 (High Speed Communication)CAN in Automation: CAN2.0B (Standard & extended message format)
Bit rates: 10 k, 20 k, 33.3 k, 50 k, 62.5 k, 66.7 k, 83.3 k, 125 k, 250 k, 500 k, 800 k, 1 Mbps
Max. sampling rate: 100kS/s(when using 1signal/1port)
Max. 2 modules can be installed for the specified slot(s) in a single DL850V main frame.
There are some competitive memory recorders which has CAN monitoring capability. However, the DL850V has a certain advantages over them such as higher sampling rate, easy for handling and costs.