For a speed of 500kbps:
– the length of the connection cable between the bus and the node must not exceed 30 cm.
– the maximum bus length is 100m
– the maximum number of nodes is 30
Regardless of the speed, the CAN bus must have 120 Ohm termination resistors at both ends.
Additionally, all connections within the bus must be made using twisted pair wires.
It is important that the data transfer speed on a bus is identical for all devices.
WARNING!
Failure to follow these rules will lead to a malfunctioning CAN bus and problems
with communication.
The CAN frame consists of an identifier (ID), the number of transmitted bytes (DLC), and the data.
Depending on the bus type, the identifier may be 11 bits (0x0-0x7ff) or 29 bit (0x0-0x1fffffff). The
number of data bytes may range from 0 to 8
ID DLC Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7
Below is a sample CAN frame from a CAN Switchboard device.
ID DLC Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7
0x666 8 Analog#1(mV) Analog#2 (mV) CALPOT 1 CAL POT 2 Switch mask Heartbeat
Parameter Description
Analog#1 The voltage for the analogue input #1 0-5000mV, big endian
Analog#2 The voltage for the analogue input #2 0-5000mV, big endian
Switch mask Bitmap of the pressed buttons (1 means pressed)
CAL POT #1 Discrete value of the position of the rotary switch connected to analogue input #1
CAL POT #2 Discrete value of the position of the rotary switch connected to analogue input #2
Heartbeat The counter increases its value by 1 after sending each frame
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General