CAN FD. An Introduction V

Transcription

1 CAN FD An Introdction V

2 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 2

3 Why CAN FD? Many CAN bses have reached 50 % 95 % network load level. Network speed limited to Mbit/s (typical 500 kbit/s) Limited by physical characteristics of in-vehicle wiring de to the In-Frame response mechanism: ACK generation delay in CAN controller Propagation delay throgh the transceiver Propagation delay over wire CAN ECU CAN ECU CAN_H CAN_L R T 2. CAN messages contain 50 % overhead Other protocols have less overhead Ethernet UDP ~500 bytes/datagram, 64 bytes overhead (IPv4) FlexRay 254 bytes/frame, 8 bytes of overhead 3

4 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 4

5 What is CAN FD? CAN FD is an improved CAN protocol (based on CAN 2.0) Two featres added: Changes limited to CAN controller hardware. Spport dal bit rates within a message Arbitration Phase: same bit rate as standard CAN Data Phase: bit rates p to 5 Mbit/s depending on the application small software change needed (de to change of timing) 2. Spport larger payload (data length) Up to 64 bytes/message larger software change needed 6

6 What is CAN FD? System cost similar to standard CAN Controller, crystal, transceiver, node interconnection cost Existing CAN transceivers sable p to 2-5 Mbit/s depending on the application Well known technology: Event triggered system Smooth migration at reasonable cost possible Classic CAN and CAN FD ECUs can be mixed nder certain conditions 7

7 What is CAN FD? Combining CAN and CAN FD Scenario Some nodes are not CAN FD capable: Commnicate only with classic CAN messages or switch off the notcapable nodes (e.g. dring flashing) > Partial network transceiver > Sophisticated filter transceivers (e.g. NXP Shield Transceiver) Scenario 2 All nodes are CAN FD capable: Classic and FD messages can be mixed 8

8 What is CAN FD? Combining CAN and CAN FD Transmit Classical Receive FD Classical FD 9

9 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 0

10 CAN FD Use Cases Faster software download Avoid split of data into several frames Decrease bs load of an existing bs Increase no. of ECUs on the bs Avoid split of networks Accelerate commnication on long bs lines (trck/bs)

11 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 2

12 Atomotive Application Domains Bandwidth and Cost Ethernet, BroadR-Reach, IEEE RTPGE Data rate CAN FD FlexRay Driver Assistance Assistance & X-by-wire MOST50 Infotainment CAN HS Powertrain & chassis CAN LS Convenience LIN Sensors & actators Implementation cost 3

13 Atomotive Application Domains CAN FD vs. FlexRay CAN FD closes the gap between classic CAN ( MBit/s) and FlexRay (0 MBit/s) bt Higher effort for FlexRay migration FlexRay is less flexible bt offers high predictability (bs load, ) FlexRay is not efficient for ECU flashing CAN FD vs. Ethernet Ethernet provides the necessary bandwidth e.g. for Car2x, and camera applications Higher effort for Ethernet migration Ethernet (UDP) more efficient for streaming applications Event triggered system vs. switched network 4

14 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 5

15 SOF SRR IDE RRS FDF res BRS ESI CRC Delimiter ACK ACK Delimiter SOF RRS IDE FDF res BRS ESI CRC Delimiter ACK ACK Delimiter Arbitration Phase and Data Phase Identifier DLC Data Stff CRC EOF IFS Cont / Arbitration Phase (standard bit rate) Data Phase (optional high bit rate) Arbitration Phase (standard bit rate) CAN FD Extended Frame Identifier Extended DLC Data Stff CRC EOF IFS Identifier Cont / Arbitration Phase Data Phase Arbitration Phase 6

16 SOF RRS IDE FDF res BRS ESI CRC Delimiter ACK ACK Delimiter Fields and seven different bit fields SOF, Arbitration, Control, Data, CRC (Stff Cont + CRC Seqence), ACK, EOF Identifier DLC Data Stff CRC EOF IFS Cont / Start Arbitration Control Data Field CRC ACK End Of Field Field Field Field Of Frame Frame 7

17 SOF r IDE FDF r0 BRS ESI SOF RTR IDE r0 Start of Frame CAN and CAN FD se the same SOF a single dominant bit CAN frame Recessive Identifier DLC Data Bit state Dominant CAN FD frame Recessive Identifier DLC Data Bit state Dominant

18 SOF RRS IDE FDF res BRS ESI SOF RTR r r0 Arbitration Field Little difference between CAN and CAN FD arbitration fields Both share the same addressing for Standard and Extended formats CAN FD removes the RTR bit and maintains an always dominant RRS bit Identifier DLC Data CAN frame Identifier DLC Data CAN FD frame

19 SOF RRS IDE FDF res BRS ESI Control Field CAN and CAN FD share the following bits: IDE, res and the DLC bits Identifier DLC Data CAN FD adds the following bits to the control field: FDF FD Format Determines if CAN (dominant) or CAN FD (recessive) BRS Bit Rate Switch Separates Arbitration Phase from Data Phase in CAN FD Clock rate switches when BRS is recessive ESI Error State Indicator (error active/passive) 20

20 SOF RRS IDE FDF res BRS ESI CRC Delimiter ACK ACK Delimiter Control Field: DLC Data Length Code (DLC) 4 bits sed for both formats CAN FD compatible with CAN at data lengths 7 CAN ignores 3 lsb if DLC = 8, CAN FD does not For lengths 8, CAN FD ses the following DLCs: 000 = 8 00 = = 2 0 = = 6 0 = 48 0 = 20 = 64 Identifier DLC Data Stff CRC EOF IFS 0-8, 2, 6, 20, 24 Cont 32, 48, or 64 bytes /

21 SOF RRS IDE FDF res BRS ESI CRC Delimiter ACK ACK Delimiter Data Field 0-8 bytes in CAN 0-8, 2, 6, 20, 24, 32, 48, or 64 bytes in CAN FD Bytes are transferred msb first No data field if DLC = 0 Identifier DLC Data Stff CRC EOF IFS 0-8, 2, 6, 20, 24 Cont 32, 48, or 64 bytes /

22 Bit 2 Bit Bit 0 Parity CRC Delimiter ACK ACK Delimiter CRC Field: Stff Cont Data Stff CRC EOF IFS Cont / Preceding stff bits are inclded in the CAN FD CRC calclation CAN does not se stff bits in the CRC calclation This makes it necessary to transmit the total nmber of bits. Therefore the nmber of dynamic stff bits is inclded into the frame format (stff bit cont modlo 8). Two safegards for the Stff Cont are implemented:. Adding a parity-bit (even parity) 2. Gray-coding the stff bit cont (Bit0-2)

23 CRC Delimiter ACK ACK Delimiter CRC Field: CRC Seqence Data Stff CRC EOF IFS Cont / Size of CRC differs based on CAN/CAN FD and length of DLC 5 bits for CAN 7 bits for CAN FD where data field 6 bytes 2 bits for CAN FD where data field > 6 bytes CAN FD CRC delimiter is always transmitted as bit, bt de to phase shift between nodes a transmitter accepts p to 2 bit times Data Phase of CAN FD frame ends with the sample point of the first bit of the CRC delimiter 24

24 CRC Delimiter ACK ACK Delimiter ACK Field Data Stff CRC EOF IFS Cont / ACK sent at the end of the CRC delimiter bit Slight difference in the format between CAN and CAN FD CAN FD nodes recognize p to two bit times as a valid ACK extra bit time allowed to compensate for transceiver phase shift and bs propagation delay de to the switch from a high Data Phase clock to a low Arbitration Phase clock End of Frame Frames are delimited by a grop of 7 recessive bits 25

25 CAN FD Oscilloscope Trace Arbitration Phase Data Phase Arbitration Phase 26

26 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 27

27 CAN FD Controller Controller allows for dynamic switching between CAN CAN FD For Frame Formats: CAN base format bit identifier and fixed bit rate CAN extended format 29 bit identifier and fixed bit rate CAN FD base format bit identifier and dal bit rate CAN FD extended format 29 bit identifier and dal bit rate Error Frame: Identical to CAN error frame Error frame is always sent with arbitration bit rate Controller switches atomatically to arbitration bit rate 28

28 CAN FD Controller Remote Frame: Remote frame in CAN base format Remote frame in CAN extended format Remote frames are ndefined in CAN FD format RTR bit removed from CAN FD bit-stream Overload Frame: Identical to CAN overload frame Overload frame is always send with arbitration bit rate 29

29 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 30

30 CAN FD Performance Basic calclation principles: Stff bits exclded Max CAN frame with bits Max CAN FD frames with 20/572 bits Frame Type No. Data Bytes Arb. Bit-Rate Opt. Bit-Rate Avg. Bit-Rate Frame Dration CAN Kbit/s s CAN FD Kbit/s 2 Mbit/s.6 Mbit/s 03.5 s CAN FD Kbit/s 5 Mbit/s.57 Mbit/s 76.2 s CAN FD can decrease bs loading significantly CAN FD Kbit/s 2 Mbit/s.74 Mbit/s s Data/Overhead ratio increases for 64 byte significantly CAN FD Kbit/s 5 Mbit/s 3.43 Mbit/s 66.6 s 3

31 CAN FD Performance CAN FD average bit rate converges de to Arbitration Phase Arbitration phase becomes dominant at a certain bad rate for the Data Phase. This means that the overall frame length becomes not mch smaller throgh a frther increase of the Data Phase bit rate. 32

32 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 33

33 CAN FD Devices CAN Controller MCUs with fll CAN FD spport available (ISO) Freescale, ST, Renesas, Spansion, Infineon CAN Transceiver Typical bit rates of atomotive transceivers for CAN FD Fnctional messages: 2 Mbit/s Reprogramming: 5 Mbit/s Transceivers for CAN FD operation available from different manfactrers Spport of 2 Mbit/s within crrent emission limits 34

34 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 35

35 CAN FD Standardization CAN ISO 898 CAN FD as part of ISO 898- (CAN Controller) > International Standard (IS 205) ISO (CAN Transceiver) > International Standard (IS 206) > Sbstittes the previos versions of part 2, part 5, and part 6. > Specifies the transceiver characteristics for bit-rates p to 5 Mbit/s. CAN ISO 6845 Upgrade of CAN controller conformance test ISO > International Standard (IS 206) Upgrade of CAN transceiver conformance test ISO > International Standard (IS 208) AUTOSAR CAN FD (8 byte) in Atosar 4.. CAN FD (64 byte) in Atosar 4.2. J939 CAN FD pgrade ongoing 36

36 CAN FD Standardization ISO : ISO TP ISO transport protocol spports the CAN FD data link layer with data fields p to 64 byte International Standard (IS 206) CANopen CiA SIG CANopen is pdating the CiA 30 application layer to spport the CAN FD data link layer 37

37 CAN FD Standardization Changes in ISO New Single Frame for payloads > 8 bytes Type Byte Bits 7-4 Byte Bits 0-3 Single Frame Length SF Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Escape Seqence New First Frame for Message Length > 4095 byte Type Byte Bits 7-4 Byte Bits 0-3 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 First Frame Message Length Escape Seqence 38

38 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 39

39 Smmary Serial commnication networks reqire increased bandwidth De to high bs load levels For flashing applications CAN FD can provide significantly increased bandwidth De to increased data clock rates De to larger data payloads CAN FD is an improvement of well known CAN technology Event triggered system Unchanged arbitration and acknowledge mechanism 40

40 Agenda Why CAN FD? What is CAN FD? CAN FD Use Cases Atomotive Application Domains CAN FD Controller CAN FD Performance CAN FD Devices CAN FD Standardization Smmary References 4

41 References Paper CAN with Flexible Data Rate Florian Hartwich, Robert Bosch GmbH;CAN in Atomation, icc 202, March 202 Presentation CAN FD CAN with Flexible Data Rate Florian Hartwich, Robert Bosch, GmbH; Feb. 5, M_CAN Controller Area Network User s Manal Papers abot bit timing reqirements and robstness of CAN FD networks Press Articles from Vector:

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