CAN

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Chances and challenges

Holger Zeltwanger

CAN FD for commercial vehicles

CAN

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Commercial vehicles

CAN

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CAN in mobile machinery

CAN

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Truck network architecture GPS Radio GSM

Internet / Car PC

CAN (FD) + Ethernet/Most

Body & chassis, lights

CAN (FD)

Doors Trunk, fuel

Climate HVAC

Switches

Seats

Body train (62,5 or 125 kbit/s)

Engine management controller

ABS EBS

Gearbox Transmission

CAN (FD)

Power train (250 or 500 kit/s)

Cluster gauges display

Dashboard Switches

CAN (FD)

Instrumentation train (125 or 250 kbit/s)

Tacho-graph

Diagnostics interface (e.g. K-line with KWP 2000 or CAN with ISO 15765 or J1939-81))

Infotainment train (CAN 250 or 500 kbit/s)

Gateway

CAN

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Truck network topology

Central gateway

Doors

HVAC

Seats

Lights

etc.

Engine

ABS/EBS

Gearbox

etc.

Dash-board

Tacho-graph

Display cluster

Engine-train network (e.g. J1939)

Body-train network

(e.g. J1939)

Instrument-train network (e.g. J1939

or ISO 16844)

Infotainment-train network (non-CAN plus optional CAN)

FMS

net

wor

k (J

1939

)

OB

D li

nk (I

SO

ISO

157

65-4

)

Bod

y bu

ilder

net

wor

k (C

AN

open

) Tr

uck/

traile

r lin

k (IS

O 1

1992

CAN

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Trucks and body application

J1939 ECU 1

J1939 ECU n

Truck chassis

CAN-based J1939 (CiA 602) network

Gateway

CANopen device 1

CANopen device n

CANopen (FD)-based body-builder network

CAN

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Gateway with PLC function

CAN

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Future requirements

  Semi- and automated driving

  Improved availability and reliability

  Improved vehicle and traffic safety

  Reduced vehicle cost over lifetime

CAN

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CAN FD data frames

SOFArbitration

fieldControl field Data field

CRC field

ACK field EOF IMF

Arbitration phase Data phase Arbitration phase

  CAN FD enables higher bit-rates than 1 Mbit/s in the data phase.

  The up to 64-byte data-field enables a higher protocol efficiency.

  The CAN FD protocol supports 11-bit and 29-bit identifiers.

KEYSOF = start-of-frameCRC = cyclic redundancy checkACK = acknowledgementEOF = end-of-frameIMF = intermission field

CAN

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CAN FD and HLPs 7: Application layer

6: Presentation layer

5: Session layer

4: Transport layer

3: Network layer

2: Data link layer

1: Physical layer

Higher-layerprotocols (HLP): J1939, ISO 11783, CANopen

Lower-layerprotocols (LLP)

CAN

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A perfect CAN (FD) topology

Node 1 Node 2 Node n

RT RT

 Short not terminated stub lines on the PCB (e.g. daisy-chain) The very same impedance from one end to the other end  Impedance matching termination resistors (RT) at both ends This will work without problems up to 10 Mbit/s at 100-m network length System (owners) designers often use star and hybrid topologies A careful physical layer design is required at higher transmission rates

// // // //

CAN

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CiA 602-1 (preliminary)   Line topology with CAN-in and CAN-out based on J1939-14 (no stub lines)  Termination resistor tolerance (2 x 60 Ω ±1 %)  Star topology option with 2-m branches and 60-Ω termination at the star center with ferrites for 2 Mbit/s  Specified temperature ranges (-40 °C to +85 °C resp. +150 °C) for transceiver, cables, and connectors  40-MHz or 80-MHz oscillator frequency  Bit-rates for arbitration phase and data phase (500 kbit/s and 1 Mbit/s or 500 kbit/s and 2 Mbit/s or 667 kbit/s and 2 Mbit/s)  Detailed bit-timing setting (time-quanta per segments)  Secondary sample point (SSP) at 60 % of the nominal bit-time (also with detailed bit-timing settings)  Transmitter delay compensation is mandatory  Connector specification similar to Flexray

CAN

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Arbitration bit-timing Bit-rate

kbit/sClockMHz

BRPSync

No of tqProp

No of tqPhase 1No of tq

Phase 2No of tq

SJWNo of tq

50040 1 1 47 16 16 16

80 2 1 47 16 16 16

66740 1 1 41 9 9 9

80 2 1 41 9 9 9

CAN

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Data phase bit-timing Bit-rateMbit/s

ClockMHz

BRPSync

No of tqPhase 1No of tq

Phase 2No of tq

SJWNo of tq

140 1 1 22 16 16

80 1 1 22 32 32

240 1 1 11 8 8

80 2 1 11 8 8

The transmitter delay compensation (TDC) is mandatory. The secondary sample point (SSP) shall be at 60 % of the nominal bit-time.

CAN

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CiA 602-2 (preliminary) FD base frame format (FBFF) or FD extended frame format format (FEFF)

CAN-ID Data field (5 to 64 byte)

29 or 11 bit

L-PDU

i-PDU 1 i-PDU 2 … i-PDU n

21 or 4 bit SA (J1939)

KEYL-PDU (large protocol data unit); i-PDU (internal protocol data unit); SA (source address) N

OT

E

Usi

ng to

days

J19

39-7

1 8-

byte

PG

s yo

u ar

e lim

ited

to

six

i-PD

Us;

in th

e fu

ture

the

PG

s m

ay h

ave

diffe

rent

leng

ths.

n {1 to 13}

CAN

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J1939 mapping i-PDU MSB LSB

i-PDU short header (4 byte) Pay-load(e.g.

J1939PG)

(Safety/security)

trailer

24-bit ID Pay-load

lengthTO

Sa

TL Data

pagePDU

formatGroup ext./DA

4 bit

2 bit

2 bit 8 bit 8 bit 8 bit1 to 60

byte

0, 4 or 8 byte

KEYDA (destination address); (J1939) PDU (protocol data unit); PG (parameter group); SA (source address); TL (trailer length); TOS (type of service)

a 0001b

NOTE It is planned that PGs with other than 8-byte length will be defined. An i-PDU may also contain several segments of the BAM protocol, the lower layer of the receiver shall take care on the correct timing.

CAN

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Padding i-PDU MSB LSB

TOS(0000b)

Padding sub-field(4 bit to 116 bit)

NOTE Just the last i-PDU can be a padding i-PDU. The coding of the padding sub-field is manufacturer-specific. A coding starting with “1” followed by alternating bit-values avoids stuff-bits.

Padding i-PDUs are necessary, when the length of the sum of the J1939 i-PDUs does not match the data length of the CAN FD data frames.

CAN

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From J1939-21 to CiA 602-2 Legacy J1939 ECU#1

Legacy J1939 ECU#2

Legacy J1939 ECU#3

Legacy J1939 ECU#4

Legacy J1939 ECU#5

CiA 602-2 ECU#I with

J1939 ECU#6

CiA 602-2 ECU#II

with J1939 ECU#7

CiA 602-2

ECU#III with

J1939 ECU#8

Trans-parent

gateway

(250) or 500 kbit/s

500 kbit/s and (1) or 2 Mbit/s)

First evaluation: Busload ratio 3:1 (Vector’s J1939 demo)

CAN

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Mixed communication

 When you transmit CiA 602-2 frames and J1939-21 frames in the same network segment, you need to avoid double-use of CAN-IDs, if you use Autosar. (one option: use the FBFF format for CiA 602-2)  When using the ISO transport protocol (ISO 15765-2) in the same network segment, you also need to avoid double-use of CAN-IDs, if you use Autosar.   Proprietary legacy FBFF may need other CAN-IDs, or you have to limit the Source Addresses (SA), if you use Autosar.

CAN

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CANopen FD All COBs specified in CiA 301 version 5.0 are transmitted in FBFF (11-bit ID) by default:

  NMT protocol  Heartbeat protocol  TIME protocol  SYNC protocol  New: Universal “SDO” protocol (USDO)  PDO protocol  LSS protocols (CiA 305)  Flying NMT master (CiA 302)

KEYCOB = communication object, FBFF = FD base frame format, ID = identifier, LSS = layer setting services, NMT = network management, PDO = process data object, SDO = service data object

NOTE CANopen FD devices need to be conformance tested by CAN in Automation (CiA).

CAN

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PDO with up to 64 byte

 More process data can be mapped into a

single PDO. This could improve the throughput

even without higher data-phase bit-rates.

 Multiple commands to different nodes can be

transmitted in one PDO. This could avoid

synchronous RPDOs.

 Remotely requested PDOs are not supported.

 Bit-wise mapping is not more recommended,

(there are just 64 mapping entries).

 Existing CANopen (device) profiles need to be

updated.

  In some applications, padding of unused bytes

is necessary (proposal: 55h or AAh with as less

as possible stuff-bits).

CAN

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Summary   CAN FD based communication increases

the throughput sufficiently.

  The physical network design rules are

stricter compared to Classical CAN.

  There is a need for standardized time-

stamping in CAN FD networks.

  CAN FD enables more flexible PG (J1939)

and PDO (CANopen FD) definitions.

  CAN FD enables a future-proofed USDO

(CANopen FD) communication.

  CAN FD enables safety and security

extensions due to the 64-byte payload.

CAN

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Questions and answers

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