Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Introduction to CAN Bus Technology


Published on

In this CAN Bus Technology introduction learn about the history and applications of the technology.

Published in: Technology

Introduction to CAN Bus Technology

  1. 1. CAN Bus Technology
  2. 2. CAN Bus Introduction <ul><li>Controller Area Network (CAN) </li></ul><ul><li>Originally developed by Robert Bosch for automobile in-vehicle network </li></ul><ul><li>Multi-drop, Multi-master serial bus provides communications between controllers, sensors, and actuators. </li></ul><ul><li>Very reliable and robust, well proven technology (introduced mid 1980s) </li></ul><ul><li>Inexpensive </li></ul>
  3. 3. CAN Bus Introduction <ul><li>CAN 2.0 A </li></ul><ul><ul><li>Standard format </li></ul></ul><ul><li>CAN 2.0 B </li></ul><ul><ul><li>Extended format </li></ul></ul><ul><li>International Standard ISO 11898 </li></ul><ul><ul><li>ISO 11898-2 High speed applications up to 1 Mbps </li></ul></ul><ul><ul><li>ISO 11898-3 Low speed applications up to 125 Kbps </li></ul></ul>
  4. 4. CAN Bus Introduction <ul><li>CAN Applications </li></ul><ul><li>Automotive </li></ul><ul><li>Military vehicles </li></ul><ul><li>Industrial machinery </li></ul><ul><li>Medical systems </li></ul><ul><li>Agricultural machinery </li></ul><ul><li>Marine control and navigation </li></ul><ul><li>Elevator control systems </li></ul>
  5. 5. CAN Bus Introduction <ul><li>Network Layered Model </li></ul>Application Presentation Session Transport Network Data Link Physical CAN defines most of the lowest two layers Higher layer protocols defined by various industry standards: DeviceNet, CANOpen, CANaerospace, MilCAN, SAE J1939, ISO1192 and others
  6. 6. CAN Bus Introduction <ul><li>CAN Characteristics </li></ul><ul><li>All messages are broadcast </li></ul><ul><li>Any node is allowed to broadcast a message </li></ul><ul><li>Each message contains an ID that identifies the source or content of a message </li></ul><ul><li>Each receiver decides to process or ignore each message </li></ul>
  7. 7. CAN Bus Introduction <ul><li>CAN Characteristics </li></ul><ul><li>Bus length / Bit rate tradeoff </li></ul><ul><li>1M bit/sec 40 meters (131 feet) </li></ul><ul><li> 500K bit/sec 100 meters (328 feet) </li></ul><ul><li> 250K bit/sec 200 meters (656 feet) </li></ul><ul><li> 125K bit/sec 500 meters (1640 feet) </li></ul>
  8. 8. CAN Bus Introduction <ul><li>CAN characteristics – Physical Medium </li></ul><ul><li>Single twisted pair wire terminated on each end </li></ul>Node A Node B 120 Ω 120 Ω
  9. 9. CAN Bus Introduction <ul><li>CAN characteristics – Signal Levels </li></ul><ul><li>Differential signaling </li></ul>Volts 3.5 2.5 1.5 CAN H CAN L recessive1 dominant 0 recessive 1
  10. 10. CAN Bus Introduction <ul><li>CAN characteristics – Bit timing </li></ul>previous bit next bit Nominal bit time sync prop phase 1 phase 2 sample point Time Quanta Local timing logic re-synchronizes with bus on each recessive to dominant transition
  11. 11. CAN Bus Introduction <ul><li>CAN Characteristics </li></ul><ul><li>Network Size </li></ul><ul><li>The maximum number of nodes is not specified. </li></ul><ul><li>Networks are limited by electrical loading, up to 64 nodes is normal </li></ul>
  12. 12. CAN Bus Introduction <ul><li>Four Message Types </li></ul><ul><li>Data Frame </li></ul><ul><ul><li>Used to transmit data </li></ul></ul><ul><li>Remote Frame </li></ul><ul><ul><li>Used to request data transmission </li></ul></ul><ul><li>Error Frame </li></ul><ul><ul><li>Sent by a node that detects an error </li></ul></ul><ul><li>Overload Frame </li></ul><ul><ul><li>Sent by a node to request a delay in transmission </li></ul></ul>
  13. 13. CAN Bus Introduction <ul><li>Message Format (standard) </li></ul>0 – 64 Data field 0 – 8 bytes 1 Start of frame 7 End of frame 4 Data length code 1 ACK delimiter 1 Reserved 1 ACK slot 1 ID extension 1 CRC delimiter 1 Remote trans. 15 CRC 11 Identifier Bits Field Bits Field
  14. 14. CAN Bus Introduction <ul><li>Message Collision Detection / Arbitration </li></ul><ul><li>All nodes must wait for an idle bus condition </li></ul><ul><li>If two nodes begin transmitting simultaneously, they then participate in a non-destructive arbitration sequence </li></ul><ul><li>The node with the lower ID number wins the arbitration and continues transmitting its message </li></ul><ul><li>The loser of the arbitration backs off and re-tries </li></ul>
  15. 15. CAN Bus Introduction <ul><li>Error Detection Capabilities </li></ul><ul><li>Bit error </li></ul><ul><li>Acknowledge error </li></ul><ul><li>Form error </li></ul><ul><li>CRC errors </li></ul><ul><li>Stuff error </li></ul>
  16. 16. CAN Bus Introduction <ul><li>Error States </li></ul><ul><li>Error-active </li></ul><ul><ul><li>Normal operating mode, node participates in communications and error reporting </li></ul></ul><ul><li>Error-passive </li></ul><ul><ul><li>Node switches to passive error reporting </li></ul></ul><ul><li>Bus-off </li></ul><ul><ul><li>Node has detected too many transmit errors, stops transmitting (fault containment) </li></ul></ul>
  17. 17. CAN Bus Introduction <ul><li>End of presentation </li></ul>