Chances and challenges

Transcription

1 Chances and challenges CAN FD for commercial vehicles Holger Zeltwanger

2 Commercial vehicles

3 CAN in mobile machinery

4 Truck network architecture Trunk, fuel Switches CAN (FD) Instrumentation train (125 or 250 kbit/s) Doors Dashboard Switches Gateway Cluster gauges display GPS Radio GSM Tachograph Internet / Car PC Engine management controller CAN (FD) + Ethernet/Most Infotainment train (CAN 250 or 500 kbit/s) ABS EBS Climate HVAC Seats Body & chassis, lights Gearbox Transmission CAN (FD) Power train (250 or 500 kit/ s) CAN (FD) Body train (62,5 or 125 kbit/s) Diagnostics interface (e.g. K-line with KWP 2000 or CAN with ISO or J ))

5 Truck network topology Instrument-train network (e.g. J1939 or ISO 16844) Dashboard Tachograph Display cluster Infotainment-train network (non-can plus optional CAN) Doors HVAC Central gateway Engine ABS/EBS Seats Gearbox Lights etc. Body-train network (e.g. J1939) FMS network (J1939) OBD link (ISO ISO ) Body builder network (CANopen) Truck/trailer link (ISO etc. Engine-train network (e.g. J1939)

6 Trucks and body application CAN-based J1939 (CiA 602) network CANopen (FD)-based body-builder network J1939 ECU 1 CANopen device 1 Gateway J1939 ECU n CANopen device n Truck chassis

7 Gateway with PLC function

8 Future requirements Semi- and automated driving Improved availability and reliability Improved vehicle and traffic safety Reduced vehicle cost over lifetime

9 CAN FD data frames SOF Arbitration field Control field Data field CRC field ACK field EOF IMF Arbitration phase Data phase Arbitration phase KEY SOF = start-of-frame CRC = cyclic redundancy check ACK = acknowledgement EOF = end-of-frame IMF = intermission field 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.

10 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-layer protocols (HLP): J1939, ISO 11783, CANopen Lower-layer protocols (LLP)

11 A perfect CAN (FD) topology Node 1 Node 2 Node n R T // // // // R T 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 (R T ) 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

12 CiA (preliminary) Line topology with CAN-in and CAN-out based on J (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 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 bittime (also with detailed bit-timing settings) Transmitter delay compensation is mandatory Connector specification similar to Flexray

13 Arbitration bit-timing Bit-rate kbit/s Clock MHz BRP Sync No of tq Prop No of tq Phase 1 No of tq Phase 2 No of tq SJW No of tq

14 Data phase bit-timing Bit-rate Mbit/s Clock MHz BRP Sync No of tq Phase 1 No of tq Phase 2 No of tq SJW No of tq The transmitter delay compensation (TDC) is mandatory. The secondary sample point (SSP) shall be at 60 % of the nominal bit-time.

15 CiA (preliminary) FD base frame format (FBFF) or FD extended frame format format (FEFF) CAN-ID 29 or 11 bit Data field (5 to 64 byte) L-PDU i-pdu 1 i-pdu 2 i-pdu n n {1 to 13} 21 or 4 bit SA (J1939) KEY L-PDU (large protocol data unit); i-pdu (internal protocol data unit); SA (source address) NOTE Using todays J byte PGs you are limited to six i-pdus; in the future the PGs may have different lengths.

16 J1939 mapping i-pdu MSB LSB TOS a TL i-pdu short header (4 byte) Data page 24-bit ID PDU format Group ext./da Payload length Payload (e.g. J1939 PG) (Safety/ security) trailer 4 bit 2 bit 2 bit 8 bit 8 bit 8 bit 1 to 60 byte 0, 4 or 8 byte KEY DA (destination address); (J1939) PDU (protocol data unit); PG (parameter group); SA (source address); TL (trailer length); TOS (type of service) a 0001 b 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.

17 Padding i-pdu MSB LSB TOS (0000 b ) 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.

18 From J to CiA Legacy J1939 ECU#1 Legacy J1939 ECU#2 Legacy J1939 ECU#3 Legacy J1939 ECU#4 Legacy J1939 ECU#5 First evaluation: Busload ratio 3:1 (Vector s J1939 demo) Transparent gateway (250) or 500 kbit/s 500 kbit/s and (1) or 2 Mbit/s) CiA ECU#I with J1939 ECU#6 CiA ECU#II with J1939 ECU#7 CiA ECU#III with J1939 ECU#8

19 Mixed communication When you transmit CiA frames and J 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 ) 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.

20 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) KEY COB = 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).

21 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: 55 h or AA h with as less as possible stuff-bits).

22 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 timestamping 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.

23 Questions and answers?!