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Connection to the CAN bus

ASU modules are equipped with a high-speed CAN interface that supports CAN 2.0A and CAN 2.0B specifications. In addition, the ASU modules support higher-level protocols like CANopen orJ1939.
Note: the standard version of the ACS modules does not have CAN terminators (terminating resistors). It is assumed that they are already present on the car tire.


The following items are required to connect to the CAN bus:

  • CAN network involves the use of a bus topology with a cable connecting of all devices on the network.
  • The cable should have a length not exceeding 40 meters and have 120 Ohm terminators at both ends of the bus.
  • Terminators are necessary to eliminate the reflection of signals from the ends of the line and to provide the required voltage levels with an inactive bus.
  • Shielded twisted pair cable should be used as connecting cable.
 

Branches from the CAN bus:

  • The length of each branch from the bus should not exceed 1 meter. In addition, all branches must have different lengths to prevent re-reflections of the signals and to provide the required voltage levels with an inactive bus.
  • The CAN bus is susceptible to noise levels, for this reason the CAN Shield line must be connected with a number of rules:
    • The CAN Shield line should be connected to the potential with the least noise level, as a rule, this is the car body.
    • The line should have the lowest possible resistance.
    • CAN Shield connection is recommended at the center point of the CAN bus.
    • CAN Shield must be connected at one point to avoid stray loops.

The picture below shows the standard CAN bus structure.