2.  What is a Controller Area Network?  History of CAN  CAN communication protocol  Physical layer  ISO 11898  CiA  CANopen  DeviceNet  Applying CAN

3.  CAN = controller area network  ECU = electronically controlled unit  Dominant = 0  Recessive = 1

4.  CAN implements a vehicle bus to which all CAN devices are connected  Allows all devices to communicate with one another

5.  Cars, trucks, buses, off-road vehicles  Maritime electronics  Aircraft/aerospace electronics  Medical equipment and devices  Coffee machines  Elevators

6.  Developed in Germany in the 1980's by engineers working at Robert Bosch  More functionality while reducing the weight and complexity of the wiring between controllers.  Multi-processor system which has better performance, increased reliability and is more maintainable  No communication protocols at the time met the speed and reliability requirements so Bosch developed CAN specification 2.0

7.  Physical and data link layer are implemented in the CAN controllers  Standard CAN bypasses layers 3-6  (1) Physical layer = actual hardware  (2) Data link layer = connects data to the protocol  (7) Application layer = interacts with OS of CAN device

8.  Since CAN is so widely used CAN chips are cheap  Reliability and error resistance of CAN calculated in mathematical model shown to have only 1 undetected error in 1000 years  Has world wide acceptance  Higher layer protocols defined for data intensive applications

9.  Data frame – sends data  Remote frame – requests data  Error frame – reports an error  Overload frame – reports a node is overloaded

10.  SOF – 1 dominant bit  Arbitration Field – message ID + RTR

11.  Control Field -Length of the data field to follow -For remote frame DLC is ignored, data field is always zero

12.  CRC Field – CRC segment + delimiter bit  ACK Field – acknowledgement bit + delimiter bit

13.  SOF – 1 bit  Arbitration field – 12 or 32 bits  Control field – 6 bits  Data field – up to 8 bytes  CRC field – 16 bits  ACK field – 2 bits  EOF -7 bits  IFS – 3 bits

14.  Off-road vehicles require more messages  11 bit message ID -> 29 bit  Use IDE to determine format: › 0 = 11 bit › 1 = 29 bit  Extended frame has trade-offs: › Bus latency time is longer › More bandwidth required › Error detection performance decreased

15.  Error occurs: bit stuffing, CRC incorrect, etc.  Error flag set followed by recessive delimiter and interframe

16.  Errors are caught quickly and have short recovery times: Error Frame LengthBaud RateTotal error recovery time (error frame + interframe) 14 bits1 Mbit/sec14 + 3 uSec 14 bits500 kBit/sec28 + 6 uSec 14 bits250 kBit/sec56 + 12 uSec 20 bits1 Mbit/sec20 + 3 uSec 20 bits500 kBit/sec40 + 6 uSec 20 bits250 kBit/sec80 + 12 uSec

17.  Overload flag – 6 dominant bits so all nodes detect overload, messaging ceased

18.  Producer/consumer  All messages are acknowledged for consistency (error if inconsistent or unacknowledged)  Nodes can accept or decline message filitering

19.  CAN uses message ID of the node to prevent collisions – high priority first  Uses bitwise arbitration as follows: › Node sends SOF with dominant level  Non-sending nodes begin listening › Node sends next bit and compares output signal with actual bus level  If sent recessive, detects dominant, then begins listening, else sends next bit › Transmits the rest of the message if it transmits all arbitration bits

20.  Node A = 1000101100 (high priority)  Node B = 1110110000  B send a recessive, detects dominant, then listens 1 st arbitration bit2 nd arbitration bit3rd arbitration bit Node A100 Node B11listen Bus level100

21.  Errors detected by: › Bit monitoring › Checksum Check › Variable bit stuffing with a stuff width of 5 › Frame check › Acknowledge Check  Defective frames are aborted and retransmitted

22.  Malfunctions that would disrupt the system: › Transmitting Error from malfunctioning node › Receiving Error from malfunctioning node  CAN determines permanent vs. temporary malfunctions › Transmit error counter › Receive error counter

23.  Based on the counters, a node is in one of the following states: › Error Active  Transmit and receive counters <128 › Error Passive  Transmit or receive counters >127 › Bus-Off  Transmit error counter >255

24.  ISO 11898-2 is the most common standard for the physical layer  Nodes connected by 2 wires: CAN_H and CAN_L  Bus level determined by: › Vdiff = Vcan_h – Vcan_l › 2V for recessive, 0V for dominant  Bus terminated by 120 Ω resistors to suppress electrical reflections on the bus  Electromagnetic interferences are minimized with the differential voltage between CAN_H and CAN_L  At a maximum baud rate of 1 Mbit/sec a bus can be up to 40m long › At <10 kbit/sec can have up to 5000 m bus

25.  “Road vehicles – Controller area network (CAN)” 1993  Contains: › Data link layer and physical signaling › High speed medium access unit › Low speed fault tolerant medium dependant interface › Time triggered communication

26.  Users + manufacturers develop and support CAN  Based on participation and initiative  Represented at ISO and IEC committees

27.  Higher layer protocol adds: › Network management › Device monitoring › Communication between nodes  Requires CANopen nodes to have: › Communication unit › State machine › Object dictionary

28.  Application layer protocol adds 4 required objects: › Identity object › Connection object › Message router object › DeviceNet object

29.  Hewlett-Packard  Lockheed Martin  Boeing  NASA  GE Medical  Siemens Medical  John Deere

30.  Vehicle Spy (Vspy)  NETCAR-Analyzer  Volcano Network Architect (VNA)  Ability to: › Read bus signals › Transmit messages › Log data › Write to ECU memory

32.  ECU  TCU  CCU  SSM15  SSM25  CMU

33.  LIN-Bus (Local Interconnect Network)  Ethernet  RS232  Universal serial bus

34.  CAN specification 2.0 CAN specification 2.0 › A = standard format › B = extended format  ISO 11898 › Specific requirements on the sub layers of the data link layer and physical layer  CANopen specification CANopen specification  Book: A comprehensible guide to CAN  Book: Embedded networking with CAN and CANopen

36.  [1]Wilfried Voss. (2005). A Comprehensible Guide to Controller Area Network. Greenfield: Copperhill Technologies Corporation.  [2]Pazul Keith. (2002). Controller Area Network (CAN) Basics. In Microchip.  [3]CiA. (2001). Can physical layer. Retrieved 1 24, 2012, from http://www.can- cia.de/index.php?id=systemdesign-can-physicallayerhttp://www.can- cia.de/index.php?id=systemdesign-can-physicallayer  [4]International Standard ISO 11898. First edition 2003-12-01. Road vehicles - Controller area network (CAN).  [5]Robert Bosch. (1991). CAN Specification. Robert Bosch GmbH.  [6]National Instruments. (2012). Controller Area Network (CAN) Overview. Retrieved 2 2, 2012, from http://zone.ni.com/devzone/cda/tut/p/id/2732 http://zone.ni.com/devzone/cda/tut/p/id/2732  [7]Vehicle Spy. (2005-2012). Vehicle Spy Professional. Retrieved 2 4, 2012 from http://intrepidcs.com/VehicleSpy/ http://intrepidcs.com/VehicleSpy/  [8]CANopen. CANopen USA. Retrieved 2 4, 2012 from http://www.canopen.us/http://www.canopen.us/  [9]Real Time Automation. DeviceNet Introduction. Retrieved 2 4, 2012 from http://www.rtaautomation.com/devicenet/#2 http://www.rtaautomation.com/devicenet/#2