What is CAN-bus protocol and what are its advantages?

The CAN-bus (Controller Area Network) system is a serial fieldbus standard devised in the 1980s in Germany by Robert Bosh GmbH for the purpose of connecting various ECUs (electronic control units).

Primarily created for use in the automotive environment, the CAN-bus protocol was expressly designed to operate in environments highly disturbed by the presence of electromagnetic waves and is currently used in many industrial embedded applications where a high level of noise immunity is required.

The CAN communication protocol is standardized ISO 11898-1 (2015) and consists of a layer/layers used for data exchange (data link layer), which in turn is structured by an underlying "logical" layer (Logical Link Control or LLC) and the underlying Media Access Control (MAC) layer. It is also possible to associate another set of layers as the "physical" layers, left to the free choice of the network designer.

Bus and data transmission in industry

The term bus identifies a series of communication channels that allow the exchange of data and information between peripherals and components within a computer or electronic system. A bus offers the possibility of connecting different devices to each other, either through parallel (ISA, PCI, AGP...) or serial (SATA, SPI, PCI Express, USB, PROFIBUS, CAN...) transmission.

The CAN standard defines four different types of messages or frames, characterized by a maximum load of 94 bits and marked by a specific priority (Arbitration Field).

• Data frames: represent the most common message and are used for data transmission. They consist of several fields including the arbitration field, acknowledgment field, data field and CRC field;
• Error frame: is a special message and is sent when a node detects an error within the communication;
• Overload frame: results much like the Error frame and is transmitted by a node that becomes too busy; with the development of increasingly intelligent CAN controllers, this type of frame is not used very often;
• Remote frame: is little used and typically requires information from a specific identifier.

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Why use a CAN-bus system? Benefits and fields of application

We have learned the main features and functions of the CAN-bus standard; however, what are its main benefits and within what applications can its peculiarities be enhanced?

Reliability

The possibility of losing data during message transmission is practically nil, and thanks to the various possibilities for error detection, the CAN bus standard is ideal for applications requiring a high degree of security and reliability.

Economic savings

Reducing weight, wiring and production costs was the main goal for the emergence of the CAN-bus standard in the automotive field, simplifying not only its assembly but also its maintenance.

Flexibility

The CAN-bus protocol is message-based, not node-based; this feature allows new electronic devices to be added and integrated without specific programming.

Speed

In fact, the real-time sharing between network nodes and the shared data processing capability gives high speed to the entire network.

Efficiency

The ability to manage the degree of priority based on ID, allows the management of various frames to be kept smooth and ensuring efficiency for the entire network.

The specific feature of the CAN-bus system that meet needs in the automotive field should not be misleading; in fact, the possible applications are countless and are concentrated within industries and environments where high resistance to interference are required. Here are some examples:

• Industrial automation
• Smart building and home automation
• Railway applications
• Human Interface Machine

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