CAN bus signal monitoring using the DL850V Yokogawa Meters & Instruments Corporation

CAN bus signal monitoring using the DL850V

Yokogawa Meters & Instruments Corporation

Leading-edge TechnologiesFORESIGHT

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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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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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(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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(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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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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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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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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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

１１

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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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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Tool lineup for CAN bus

ECUECU

ECUECU

CAN busFRAME

CANalyzer (Vector)

DLM2000SB5000

WE7000 DL850V


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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

ＩＤＤＡＴＡ


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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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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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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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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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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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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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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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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.

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CAN bus signal monitoring using the DL850V Yokogawa Meters & Instruments Corporation