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Jonathan Meed Alexander Basil

Jonathan Meed Alexander Basil. What is CAN (Controller Area Network). CAN is a multi-master serial bus Developed by Bosch for automotive applications in early 1980s Released publicly in 1986 Became ISO standard in 1993 Is now required in all cars in the USA

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Jonathan Meed Alexander Basil

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  1. Jonathan Meed Alexander Basil

  2. What is CAN (Controller Area Network) • CAN is a multi-master serial bus • Developed by Bosch for automotive applications in early 1980s • Released publicly in 1986 • Became ISO standard in 1993 • Is now required in all cars in the USA • Used for connecting multiple separate electronic systems

  3. Figure 1 - Typical CAN implementation in a car [1]

  4. All the places CAN can go Solar car Plane Heavy machinery Boats

  5. What CAN looks like Figure 3 - RS-435 Wire Specification [3]

  6. Low-Voltage Differential Signaling Figure 2 - Diagram of LVDS [2]

  7. U CAN 2 CAN implementation often requires additional hardware to generate LVDS MCP2551

  8. Stack Frame Message for CAN 2.0A Figure 4. CAN Message bit partitioning. Bus Idle Bus Idle S O F S O F Address Field Address Field Control Field Control Field Data Field Data Field CRC Field CRC Field ACK Field ACK Field E O F E O F Inter-mission Inter-mission 1 bit 12 bits 6 bits 0-8 bytes 16 bits 2 bits 7 bits • Start of frame (low bit) • Address (arbitration) • Control (data length, reserved bits) • Data • Cyclic Redundancy Check (error checking) • Acknowledge • End of frame • Intermission (time between frames)

  9. Message Arbitration (same as I2C) • Message includes 11-bit target address and a remote transmission bit • Lower target address value = higher priority • Node transmits the target address bit-by-bit and receives other transmitted addresses • If it transmits a 1 and receives a 0, it loses arbitration Figure 5 - Arbitration example. [4]

  10. Pros and Cons • Pros • Long transmission distance and low weight • Multiple masters with arbitration • Great for inter-board communication • The bus is not clocked (but requires each device on the bus to run at the same clock speed) • Cons • Complex for single board or single device communications • I2C and SPI are more suited for this environment • Higher cost – overhead bits and additional hardware

  11. Questions

  12. References [1] Cook, Jeff, and Jim Freudenberg. "Controller Area Network (CAN)." (2008): Web. <http://www.eecs.umich.edu/courses/eecs461/doc/CAN_notes.pdf>. [2] "Low-voltage differential signaling." Wikipedia. N.p.. Web. 21 Feb 2013. <http://en.wikipedia.org/wiki/Low-voltage_differential_signaling>. [3] Kugelstadt, Thomas. "Isolated CAN Transceiver Assures Robust Fieldbus Design." ECN. Texas Instruments. Web. 21 Feb 2013. <http://www.ecnmag.com/articles/2009/10/isolated-can-transceiver-assures-robust -fieldbus-design>. [4] Bitwise arbitration in CAN networks. TechnologyUK. Web. <http://www.technologyuk.net/telecommunications/industrial_networks/can. shtml>.

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