Automotive Engineering Section, UniKLMFI - Autotronic 2 · Codage de la vitesse Engine speed sensor...

Why do we use multiplexing on cars ?

Automotive Engineering Section, UniKLMFI - Autotronic 2

(multiplexing)

After 1995, the target for car builders was to reduce the size of

harness.

MCN001

LA DIMINUTION DU VOLUME DU CABLAGE : ENJEU MAJEUR 95 -2000

EVOLUTION DU CABLAGE

1960 1985 1995

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1960 1985 1995

NOMBRE D’INTERCONNEXIONS

1960 1985 1995

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1960 1985 1995

METRES (longueur de cablage)

Automotive Engineering Section, UniKLMFI - Autotronic 2 (multiplexing)

One way of communication ( the bus) is shared between

several users ( the stations).

In concrete terms :

More simple harness.

- réduce the cost,

- réduce the volume of the harness,

- réduce the number of connectors.

Possibility to exchange data between all the ECU in the car.

- increase driving pleasure,

- reduce the number of sensors.

Définition :


• The data exchange between all the stations in the car are sent on the bus in « numeric form ».

What is MULTIPLEXING ?

Station A

Station C

Station B


Data gives information coded in binary system, that means

with 0 or 1 .

0 or 1 is called « a bit ».

A group of 8 bits is called « a BYTE ».

It is possible to translate decimal numbers in binary code.

example : 8 => 00001000.

THE BINARY NOTATION


For example :

O or 1 are corresponding to a certain

level of voltage on a wire.

1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit 1 Bit

« 01010110 » : 8 Bits = 1 BYTE

« 0 » « 1 » « 0 » « 1 » « 0 » « 1 » « 1 » « 0 » « 0 » « 1 »

THE BINARY NOTATION


THE BINARY NOTATION

DATA are converted in a series of BITS called « A FRAME » on the

BUS.


The serial transmission

01001011

FRAME

Station B

BYTE to

transmit:

01001011

Station A

On cars, the FRAME is transmitted in SERIAL MODE

on the BUS.


Station A Station DStation CStation B Station E

The BUS

The role of the bus is to allow the exchange of data between

all the stations ( ECU in the car)

Like that, the bus links all the ECU together.

- THE BUS


- The wired bus.

The bus is composed of 2

isolated copper wires ( small

section ( 0,6mm²).

For safety, the frame is

driven by one wire and the

opposite of the frame is

driven by the other wire.

The 2 wires of the bus

are twisted ( to avoid

electromagnetic problems)


For some applications, the bus is composed of :

One wire only ( economic solution).

Optical fiber ( high speed of transfer).

Radio signal ( easy to fit)


BUS

ECU

Inputs

outputs

ECU

of the

system

Multiplexing interface

Translator

- The multiplexing interface in each ECU connected to

the bus :

Sender

Reads information

Send orders Translates information from

ECU to multiplexing language

Emits or receive the

frames.Automotive Engineering Section, UniKLMFI - Autotronic 2 (multiplexing)

The frames are sent one by one on the bus.

The space between two frames is called « INTER

FRAME SPACE »


- THE FRAME STRUCTURE

The frame structure is defined by the communication procedure.

DATA DATA

01101100 00101100 01001100 01101110 11101100

The frame is composed with several parts called « FIELDS »

40 bits = 5 bytes


SOF : start of frame (envelope)

IDENT : identification (12 bits) (address)

Com. : command field (4 bits) (recorded delivery

DATA : information field (letter)

Control : control field (15 bits) (signing)

Ack : acknowledgement (recorded delivery response)

EOF : end of frame

Station A Station B Station C

A1, A2,A3,A4;B1,B2,B3;C1,C2

Example of frame language ( with 7 fields) on the bus

sof Ident. Com. data control eofack

THE FRAME


- The Frame.

SOF IDENT. COM. DATA CTRL ACK. EOF

Permits to fix the priority

level and to identify the

sender of the frame.

Permits to inform the stations

connected to the bus on the length

of the following field ( data).

Permits to synchronize

The ECU clocks.


-The frame.

SOF IDENT. COM. DATA CTRL ACK. EOF

The transmitter waits in this field for the response

of the receptor ( to know if the frame has been

correctly received).

Indicates the end

of the frame.

Permits the receptor to

check if the frame has

been received completely.


SOF 0001 0001 1111 Com. DATA station A CTRL Ack. EOF

SOF 0001 0000 0101 Com. DATA station B CTRL Ack. EOF

SOF 0001 0000 0000 Com. DATA station C CTRL Ack. EOF

station C

station B

station A

The bus can accept only one frame at a same time. So each frame is

given by a priority level to avoid « bugs »

0 is DOMINANT 1 is RECESSIVE

SOF Com. DATA station C CTRL Ack. EOF

On the Bus

0001 0000

- THE PRIORITY LEVEL


Début 0001 0001 1111 Com. Informations de A Contrôle Ack. Fin

SOF 0001 0000 0101 Com. DATA station B CTRL Ack. EOF

SOF 0001 0000 0000 Com. DATA station C CTRL Ack. EOF

Station C

Station B

Station A

SOF Com. DATA station C CTRL Ack. EOF

On the Bus

0001 0000 00

- priority level.


Début 0001 0001 1111 Com. Informations de A Contrôle Ack. Fin

Début 0001 0000 0101 Com. Informations de B Contrôle Ack. Fin

Début 0001 0000 0000 Com. DATA station C CTRL Ack. EOF

Station C

Station B

station A

Début Com. DATA station C CTRL Ack. EOF

Station C has the highest priority level on the bus

0001 0000 0000

- priority level


A car is fitted with several different buses.

(ECU with the same level of performance are grouped on the same bus).

More performant.

More reliable.


BUS CAN

I/S

ABS wheel sensor

7000

7005

(x tops par tour)

1010 1100 0100 1010

Engine speed sensor

1010 1100 0100 1010

Engine speed

encoding

INTERFACE

INTERFACE

1313

7800ESP

1320Injection ECU

- EXCHANGE OF DATA ON THE SAME BUS.


BUS CAN

I/S

ABS wheel sensor

7000

70050100 1111 0101 0011

1010 1100 0100 1010

Codage de la vitesse

Engine speed sensor

1010 1100 0100 1010

Engine speed

encoding

INTERFACE

INTERFACE

1313

7800ESP

1320Injection ECU


BUS CAN

I/S

ABS wheel sensor

7000

70050100 1111 0101 0011

1010 1100 0100 1010


Engine speed sensor 0100 1111 0101 0011

1010 1100 0100 1010

Engine speed

encoding

INTERFACE

INTERFACE

1313

7800ESP

1320injection ECU - DATA is shared.


INTERFACE

1010 1100 0100 1010

BUS CAN

I/S

1630BVA

ABS wheel sensor

7000

70050100 1111 0101 0011

1010 1100 0100 1010



1010 1100 0100 1010

Engine speed

encoding

INTERFACE

INTERFACE

1313

7800ESP

1320Injection ECU


INTERFACE

1010 1100 0100 1010

BUS CAN

I/S

1630

automatic

gear box

ABS wheel sensor

7000

70050100 1111 0101 0011

1010 1100 0100 1010



1010 1100 0100 1010

Engine speed

encoding

INTERFACE

INTERFACE

1313

7800ESP

1320injection ECU

INTERFACE

0100 1111 0101 0011

1010 1100 0100 1010

BSI


INTERFACE

1010 1100 0100 1010

BUS CAN

I/S

1630Automatic gear

box

ABS wheel sensor

7000

70050100 1111 0101 0011

1010 1100 0100 1010



1010 1100 0100 1010

Engine speed

encoding

INTERFACE

INTERFACE

1313

7800ESP

1320Engine ECU

INTERFACE

0100 1111 0101 0011

1010 1100 0100 1010

BSI

0004Instrument

panel

INTERFACE

0100 1111 0101 0011

1010 1100 0100 1010

BUS VAN COMFORT

INTERFACE

- EXCHANGE OF DATA ON TWO DIFFERENT BUSES.

(BSI is a bridge between the buses)


0004Instrument

panel

INTERFACE

0100 1111 0101 0011

1010 1100 0100 1010

INTERFACE

BUS VAN COMFORT

ABS wheel sensor

7000

70050100 1111 0101 0011

1010 1100 0100 1010



1010 1100 0100 1010

Engine speed

encoding

INTERFACE

INTERFACE

INTERFACE

INTERFACE

0100 1111 0101 0011

1010 1100 0100 1010

1010 1100 0100 1010

1313

7800ESP

1630automatic gear

box

BSI1320Injection ECU

BUS CAN

I/S

BUS VAN

BODY

INTERFACE

0100 1111 0101 0011

1010 1100 0100 1010INTERFACE


B.S.I


MAIN NETWORKS USED ON

CITROËN CARS

CODE NAME CAR MODELS

VAN Vehicle Area Network Xsara, xsara picasso, C3, C2,C5…

CAN HS (I/S) Control Area Network

High Speed

( Inter / Systems)

Xsara, xsara picasso, C3, C2,C5…

CAN LS (FT) Control Area Network Low

Speed

( Fault Tolerant)

C3 II,C4,C4 picasso,C5 II, C6 …

LIN Local Interconnect Network C3 II,C4,C4 picasso,C5 II, C6 …

THE VAN NETWORK

VAN (Vehicle Area Network).

- Historical.

- 1985/86 Born of VAN,

- 1994 Test one model of car (XM),

- (…) Mass production

- 2004 End of production


- Example of architecture VAN CAN, (C3)

ECM

BVA

Combiné

Climatisation

Changeur

de CD

Calculateur

de navigation Afficheur multifonctions

Autoradio

Calculateur d’additivation

carburant

Capteur angle

volant

ESP ABS

Platines de portes

AVG et AVD

Calculateur Air-

bag

BSM

COM 2000

Boîtier Alarme anti-

effraction


VAN very well adapted to car environment.

ME

E

E

E

MM

M M

Maximum 16 ECU on the same bus.


Architecture CAN / VAN (C8)1

+ VAN


- Synoptic diagram (C8)


- Supply of the stations (C8) (+VAN).


- Electric signals on the bus VAN

2 wires on the bus called DATA and DATA/.

5 V4.5 V max

2.8 V

0.5 V mint

DATA

DATA /

DATA : 1 10t

Udiff

Udiff = V DATA – V DATA/ if Udiff > 0 the bit is 1 ( recessive)

if Udiff < 0 the bit is 0 ( dominant)Automotive Engineering Section, UniKLMFI - Autotronic 2 (multiplexing)

- Advantages of the differential reading :

- The data is not modified by electromagnetic perturbations

5 V4.5 V max

2.8 V

0.5 V mint

DATA

DATA /

Udiff


- FAULT TOLERANCE:

Short circuit to earth

Short circuit to + supply

Wire cut

With these faults, the VAN

still works ( in downgraded

mode).


- Characteristics of the VAN NETWORK :

Transfer speed :

250 KTs (Kilo time slot / second) maximum

125 KTs for VAN Comfort,

62.5 KTs for VAN Body.

Length of the data field 28 Bytes maximum.


Downgraded mode possible.

Very well adapted for car applications.


THE CAN

High Speed ( Inter/Systems)

NETWORK


CAN (Controller Area Network).

- Historical.

- 1980 : Born of CAN.

- 1992 : First vehicle fitted with CAN network

- 1993 : CAN High-Speed is standardized

(transfert speed 1 Mbit/s)

- 2000 : CAN Low-Speed Fault Tolerant is

standardized (transfert speed 125 Kbits/s)

- 2004 : CAN Low-Speed Fault Tolerant replace the

VAN network on CITROËN cars.


- Since 2004 all CITROËN carshave been FULL CAN

- The transfert speed of the VAN NETWORK was not

enough for high performance ECU.

- CAN became a standard for all car builders.

- CAN LS (FR) has the same qualities than the VAN.


-Electric signals on the bus CAN.

2 wires on the bus called CAN High and CAN Low.

5 V

3.5 V max

2.5 V

1.5 V min

t

CAN H

CAN L

DATA : 1 10t

Udiff

Udiff = V CAN H – V CAN L if Udiff ≥ 2 the bit is 0 ( dominant)

if Udiff = 0 the bit is 1 (recessive)Automotive Engineering Section, UniKLMFI - Autotronic 2 (multiplexing)

- - Advantages of the differential reading :

- The data is not affected by electromagnetic perturbations

5 V

3.5 V max

2.5 V

1.5 V min

t

CAN H

CAN L

Udiff


- FAULT TOLERANCE:

With these faults, the CAN cannot work.

(no downgraded mode)


CAN H

CAN L


CAN H

CAN L

Wire cut

CAN L

CAN H

Short circuit in the bus

CAN H

CAN L


- Architecture of the bus CAN.

40 m maxi

10 cm mini

1320 BSI

1630 7800 7715

- Maximum 8 ECU on the same BUS,

- 2 resistances at each end of the bus.


- Network Architecture.

The resistances are located in the BSI and in the injection ECU on

CITROËN cars.

BSI 1320

T T


Two possibilities to connect ECU on the CAN bus.

7600 7800

Daisy Chain ( serial)parallel


- Characteristics of the CAN High Speed (Inter

System) NETWORK:

2 resistances at the end of the bus.

Transfer speed :

1 MBit/s (Mega Bit / second) maxi

250 Kbits/s for CITROËN cars (Full MUX)

Length of the data field 8 Bytes maximum.


The bus can not « wake up » the ECUs with a frame.

No downgraded mode.


THE « FULL CAN »

ARCHITECTURE


1 network

CAN HS I/S

2 networks

CAN LS.

-Example C4


2

Example

new C5


THE CAN

Low Speed

(Fault Tolerant)

NETWORKAutomotive Engineering Section, UniKLMFI - Autotronic 2 (multiplexing)

- Electric signals on the bus CAN LS.

5 V4.8 V min

3.6 V max

2.5 V

1.4 V max

0.2 V maxt

DATA: 1 10t

CAN L

CAN H


- FAULT TOLERANCE:

With these faults, the CAN LS still works

( downgraded mode)


CAN H

CAN L


CAN H

CAN L

Wire cut

CAN L

CAN H

Short circuit in the bus

CAN H

CAN L


- Characteristics of the CAN LS NETWORK :

No resistance at the end of the bus.


Downgraded mode possible.

Transfer speed, 125 Kbits/s.

The bus CAN LS can wake up the ECUs with a

frame.


THE LIN

NETWORK


Characteristics of the LIN NETWORK:

- The bus is made of only 1 wire.

- Maximum 17 ECU on the same bus.

1 Master, 16 slaves

Response of the slaveQuestion of the master

- The response is in the same frame than the question.

5025 5030 PSF1

1 wire for the

bus


- THE FRAME STRUCTURE.

DataSOF CTRLSynchro Identification

Sent by the master Sent by the slave

9 dominant bits(0)

10 bits

1010101010

8 bits

8 octets

8 bits


The LIN FRAME


BSI BSM

master

wiper (slave 1)

CAN LS/Car LIN

wiper (slave 2)

+ CAN + LIN

Example of LIN

network


Front Windscreen-wipers C4 picasso


CAN I/S LIN

UC

Brakes

CMM

BSI (master)

Tank tap sensor +

fuel gauge

Interface MUX Pump

(slave)

Pump additive

sensor pump

C4 HDI FULL CAN

Example of LIN network


- Characteristics of the LIN NETWORK :

No Downgraded mode possible.

LIN network is used for many functions ( directionnal

head lamps, alternator remote control, …)

Transfert speed, 19,2 Kbits/s.


LEXICAL


Glossary.

VAN : Vehicle Area Network.

CAN : Controler Area Network.

LIN : Local Interconnect Network.

MOST : Media Oriented Systems Transport.

Bit : elementary Information in the binary language (1 or 0).

BYTE : Group of 8 bits.

Récessive : Bit = 1.

Dominant : Bit = 0

Frame : Information composed with a package of fields.

Transfer speed : number of bits transmitted in one second(Kb/s or

Kts/s).


Automotive Engineering Section, UniKLMFI - Autotronic 2 · Codage de la vitesse Engine speed sensor...

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