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AFDZP0BA – VCM Zapi 2uC - User Manual
6.2.1 Wirings: CAN connections and possible interferences
4
CAN stands for Controller Area Network. It is a communication protocol for real
time control applications. CAN operates at data rate of up to 1 Megabits per
second.
It was invented by the German company Bosch to be used in the car industry to
permit communication among the various electronic modules of a vehicle,
connected as illustrated in this image:
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The correct operation of the CANbus is of critical importance for the CAN I/O
because all functional messages and safety-related messages pass through
CAN wires. Moreover the CAN is used to interface master and slave
microcontrollers: an incorrect CAN communication will create mismatches
between the two microcontrollers and will lead to a stop of all functions.
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The best cable for can connections is the twisted pair; if it is necessary to
increase the immunity of the system to disturbances, a good choice would be
to use a cable with a shield connected to the frame of the truck. Sometimes it
is sufficient a simple double wire cable or a duplex cable not shielded.
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In a system like an industrial truck, where power cables carry hundreds of
Ampere, there are voltage drops due to the impedance of the cables, and
that could cause errors on the data transmitted through the can wires. In the
following figures there is an overview of wrong and right layouts of the cables
routing.
U
Wrong Layout:
Module
1
Module
3
Module
2
R
R
Can Bus
Power cables
