The automotive CAN bus, short for Controller Area Network, is a communication protocol that has become the backbone of vehicle communication systems. Originally developed by Robert Bosch GmbH in the 1980s, this standard has evolved to address the growing complexity of in-vehicle electronic systems. The CAN bus allows various electronic control units (ECUs) in a vehicle to communicate with each other, enabling seamless integration and coordination of different functionalities. In this article, let us have a look at the applications of CAN and the higher-level protocols being used in the automotive systems.
CAN Standard specifies the Physical Layer and Data Link layer of the standard OSI model. Running on 2 wires with necessary line-termination resistors, CAN uses differential signaling mechanism for a robust performance. CAN specifies detailed bit timing in terms of smaller time units called quanta. It also employs Bit stuffing as is an NRZ(Non-Return-to-Zero) encoding mechanism.
The CAN communication is organized as frames with 2 different variants – Standard Frame Format and Extended Frame Format. CRC checks are used along with acknowledgement mechanism to provide a reliable communication. Details of the CAN standard are captured in our technology insights pages - Introduction-to-Controller-Area-Network-CAN-Bus and CAN-Bus-Communication-CAN-Frame-Types-and-Throughput.
The automotive CAN bus finds extensive applications in modern vehicles. One of its primary uses is in the transmission of sensor data. Sensors located throughout the vehicle measure parameters such as engine speed, temperature, brake status, and tire pressure. The CAN bus facilitates the transmission of this data to the relevant ECUs, ensuring effective monitoring and control of the vehicle's performance. A typical CAN network in the automotive network looks as follows.
Each of the ECU’s in the system is assigned a unique node address and the ID is used to identify the originating party of the CAN frame.
In addition to sensor data, the CAN bus also enables communication between various ECUs responsible for different systems in the vehicle. For example, the engine control unit can communicate with the transmission control unit to optimize gear shifts, resulting in improved fuel efficiency and smoother driving experience. The CAN bus also allows for communication between safety systems, such as the anti-lock braking system (ABS) and the electronic stability control (ESC), enhancing vehicle safety.
While the CAN standard specifies only the lower layers, higher-level protocols are often utilized on the CAN Vehicle Communication to enable application specific functionalities. The most used protocol is the In-Vehicle Networking protocol where the ECUS communicates the values as Signals organized as Messages.The OBD-II (On-Board Diagnostics) protocol provides standardized access to diagnostic information in vehicles. It allows service technicians to retrieve fault codes, monitor vehicle performance, and perform emissions testing, aiding in vehicle maintenance and repair.
The Unified Diagnostics Services protocol is used for running vehicle diagnostics, end-of-line configuration etc. It is also used extensively during servicing and maintenance of the vehicle. Another higher-level protocol commonly for CAN Vehicle Communication used is the J1939 protocol, which is primarily employed in heavy-duty vehicles and off-road equipment. The J1939 protocol defines a set of standard parameter groups and messages, facilitating communication between different vehicle systems.
The CAN protocol has established itself as the dominant communication protocol in the automotive industry. Its widespread adoption can be attributed to its reliability, scalability, and cost-effectiveness. According to a report by Precedence Report, the global automotive communication technology market size was valued at USD 7.63 billion in 2020 with a majority of it dominated by CAN. It is expected to grow with a compound annual growth rate of 6.9%.
The market share of the CAN In-vehicle Network can be attributed to its ability to handle real-time data transmission, its robust error detection and correction mechanisms, and its low implementation cost. It is widely supported by automotive manufacturers, and its compatibility with a wide range of electronic components makes it an attractive choice for vehicle communication systems.
The CAN protocol offers several advantages in vehicle communication. Firstly, its low latency and high reliability make it suitable for real-time applications, such as engine control and active safety systems. The distributed nature of the protocol ensures that even if one ECU fails, the remaining ECUs can continue to communicate with each other, maintaining the overall functionality of the system.
Secondly, the CAN Vehicle Communication is highly scalable. It supports a hierarchical architecture, allowing for the addition of new ECUs without significant changes to the existing network. This flexibility enables the integration of new functionalities and systems as vehicles evolve, without the need for extensive rewiring or reprogramming.
Lastly, the CAN protocol has a low implementation cost compared to other communication protocols. Its simplicity and wide availability of compatible components make it a cost-effective choice for automotive manufacturers. The protocol's popularity also means that there is a vast ecosystem of tools and resources available for development and testing, further reducing implementation costs.
While the CAN protocol has many advantages, it also has some limitations. One of the primary drawbacks is its limited bandwidth. The original CAN protocol supports data rates up to 1 Mbps, which may not be sufficient for applications that require high-speed data transmission, such as high-definition video streaming or large software updates.
Another disadvantage is the lack of built-in security features. The CAN protocol does not include encryption or authentication mechanisms, making it susceptible to unauthorized access and potential security breaches. However, various solutions and best practices have been developed to address these security concerns, such as the use of secure gateways and intrusion detection systems.
CAN standard is evolved continuously to meet the growing needs of the automotive market with variants introduced on top of the classic 2.0. One such variant is the CAN-FD (Flexible Data Rate), which allows for increased data transmission rates, making it suitable for applications that require high bandwidth, such as advanced driver assistance systems (ADAS). The CAN XL (eXtra Long) aims to address the further increasing bandwidth requirements of modern vehicles by supporting data rates up to 20 Mbps.
Furthermore, the integration of the CAN protocol with other emerging technologies, such as Ethernet and wireless communication, is expected to further expand its capabilities. The combination of different communication protocols can enable the seamless integration of various systems, paving the way for advanced functionalities like autonomous driving and vehicle-to-vehicle communication.
The automotive CAN bus has revolutionized vehicle communication, providing a robust and cost-effective solution for integrating various electronic systems in vehicles. Its wide adoption and dominance in the automotive industry can be attributed to its reliability, scalability, and low implementation cost. While the CAN protocol has its limitations, ongoing advancements and developments are addressing these shortcomings and ensuring its relevance in the future of automotive bus systems.
As vehicles become more connected and autonomous, the importance of efficient and secure communication protocols like CAN will only increase. The CAN protocol, with its proven track record and continuous evolution, remains the backbone of vehicle communication, enabling the seamless integration of different systems and functionalities. With further advancements on the horizon, the future of the CAN Vehicle Communication looks promising. Get in touch with us to utilize Embien’s vast experience in automotive CAN communication system design and development including CAN In-vehicle Network stack development.
