CAN Bus – Informatie
CAN Bus, stand for Controller Area Network, is one type of serial communication that usually used in industrial and automotive environments. The real example of CAN Bus application can be found in speed car data sensor that can be transferred to the rpm indicator.
CAN Bus is a message based protocol that can be used for multiple device communication. The figure below represents that when several CAN devices are connected together like a network, each device can communicate with other devices in the node. In general, CAN communication range is in range 50Kbps to 1Mbps, with the distance range is 40 meters (at 1 Mbps) to 1000 meters (at 50 kbps).
Bit rate Bus length
1 Mbit/s 25 m
800 kbit/s 50 m
500 kbit/s 100 m
250 kbit/s 250 m
125 kbit/s 500 m
50 kbit/s 1000 m
20 kbit/s 2500 m
10 kbit/s 5000 m
In this communication, data is transferred in a certain message format. Each message consists of many segments, but there are two main segments: Identifier and Data. Identifier or CAN ID, or known as Parameter Group Number (PGN) is used to identify the CAN device in the CAN network, usually in 11 (Standard CAN) or 29 bit (Extended CAN) length, based on the CAN protocol. While Data is the message content to be sent, usually in 0 to 8 bytes length.
CAN Protocol itself is limited to a maximum payload of 8 bytes. You will not be able to send a payload of greater than 8 bytes in one frame while working with CAN Protocol.
CAN Protocol consists of two wires : CAN_H and CAN_L to send and receive the message. This two wires act as a differential line where CAN signal is represented with the potential difference between them. If the difference is positive and larger than a certain minimum voltage, then the signal is 1, and if the difference between them is negative, it will be 0.
Usually, in CAN communication, twisted pair cable is used. And at the ends of the CAN networks, a single 120-ohm resistor is used. It is because the line should be balanced and tied to the same potential.