CAN 2.0

wiki

  • A controller area network (CAN) is a vehicle bus standard designed to enable efficient communication primarily between electronic control units (ECUs)
  • We use High Speed CAN
  • Andn CAN 2.0B (Extended CAN)

Due to its legacy, CAN 2.0 is the most widely used protocol - maximum payload size of eight bytes - typical baud rate of 500 kbit/s

Classical CAN - includes - CAN 2.0A (Standard CAN) and - CAN 2.0B (Extended CAN) - primarily differs in identifier field lengths - CAN 2.0A uses an 11-bit identifier - CAN 2.0B employs a 29-bit identifier - allows for a greater number of unique message identifiers - beneficial in complex systems with many nodes and data types - increase in unique message identifiers also increases frame length - which in turn reduces the maximum data rate - provides finer control over message prioritization - due to more available identifier values - CAN 2.0A devices can generally communicate with CAN 2.0B devices, - but not vice versa because of potential errors in handling longer identifiers - High-speed CAN 2.0 supports bit rates from: - 40 kbit/s to 1 Mbit/s - is the basis for higher-layer protocols - Low-speed CAN 2.0 supports bit rates from: - 40 kbit/s to 125 kbit/s - and offers fault tolerance by allowing communication to continue despite a fault in one of the two wires, with each node maintaining its own termination

Two signals, CAN high (CANH) and CAN low (CANL) - High-speed CAN signaling drives the - CANH wire towards 3.5 V and - CANL wire towards 1.5 V

The CAN bus must be terminated - The termination resistors are needed to suppress reflections - return the bus to its recessive or idle state

High-speed CAN uses a 120 Ω resistor at each end of a linear bus. Low-speed CAN uses resistors at each node.

CAN data transmission uses a lossless bitwise arbitration method of contention resolution