Nowadays mankind increasingly simplifies the processes related to life. The sphere of automotive industry is not an exception. If earlier the first vehicles were dispensed with a generator and a battery (the ignition was powered by magneto), and the electrician's equipment system was close to light aviation, now the auto is still a complicated technical system. Nevertheless, with the development of digital technologies, the electronic equipment of the vehicle has become much simpler.
In the early 90's, BOSCH and INTEL developed a CAN network interface that integrated the aggregate management system into a single network. Afterwards, this algorithm was called CAN bus.
CAN-bus is a special network which data is transmitted and exchanged between various control nodes that are physically located in different places of the truck. Each node consists of a microprocessor (CPU) and a CAN-controller whereby the executable protocol is implemented and interaction with the vehicle network is provided.
Normally, the CAN bus is a pair of twisted wires interconnected (CAN High and CAN Low). Moreover, the transceiver allows data transfer on different speeds and control of data integrity. Also modern transceivers have a number of additional features: protection against short circuit, thermal protection, etc.
CAN bus allows to exchange data for such units as the engine, gearbox, braking system, controller and also allows the semitrailer or trailer brake system to work together with the main truck system as a single network.
The J1939 uses the CAN protocol to allow any device to transmit a message by the network at the time the bus is not loaded. Each message includes an identifier that determines the priority of the message, information about the sender of the data, information which is enclosed message. Conflicts are avoided because of the arbitration mechanism, which is activated with the transfer of the identifier (a secure arbitration scheme is used). This allows messages with the highest priority to be transmitted with the lowest latency, due to equal access to the bus by any of the network devices.
Advantages of CAN:
• Accessibility for the consumer.
CAN protocol has been successfully used for more than 15 years, since 1986. There is a wide choice of CAN products and devices in open sale.
• Implementation of the protocol at the hardware level.
The protocol is based on the hardware level. This makes it possible to combine the ability to recognize and control errors with the ability of high-speed data transmission.
• Primitive transmission line
The data line is, in most cases, a twisted pair. But CAN communication can also be carried out by one wire. In various cases it is possible to use the most suitable communication channels, optical or radio channel.
• Excellent ability to detect errors and failures and localize faults.
The ability to detect errors and failures is a significant advantage of the CAN protocol. The error detection mechanism is built on an extensive principle, the system for checking and confirming errors and failures is also reliable and well developed. The fault detection and retransmission system is performed automatically at the hardware level.
• The system of detection and verification of malfunctions
A faulty source in the system is capable of disrupting the whole system, i.e. to occupy all communication channels. The CAN protocol has a built-in capability that protects the system from a malfunction source. The source of the error is removed from receiving and transmitting data over the CAN bus.
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