CAN bus in 2024: Operation, Advantages and Recent Developments

Introduction

Imagine a highway where each vehicle communicates harmoniously with the others, thus avoiding traffic jams and accidents. This is exactly the role of the CAN bus (Controller Area Network). This vital communications system connects vehicle components, such as the speed sensor transmitting information to the dashboard, and also finds applications in industrial automation, aviation and medical equipment.

Originally developed by Bosch in the 1980s for the automotive industry, the CAN bus has radically changed the way electronic systems communicate. It has been established as an essential component in many industries thanks to its ability to simplify complex cabling networks. It also ensures reliable and secure data transmission.

In this article, we dive into the world of the CAN bus, exploring its operating principles, its benefits and varied applications, and discovering the innovations and future prospects of this key technology.

History and Evolution of the CAN Bus

The history of the CAN bus is a testament to continued innovation and technological adaptability, particularly in the automotive field.

30 years ago (Early 1990s):

  • Electronic Control Units (ECU): Cars of this era were equipped with a relatively limited number of ECUs, often just a few, handling essential functions like engine control, transmission and sometimes the anti-lock braking system (ABS).
  • Message Volume: The CAN bus, at that time, transmitted a limited number of messages, reflecting the relative simplicity of on-board systems of the time. These messages mainly focused on basic critical functions.

In Modern Cars:

  • Number of ECUs: With the advancement of technology, modern vehicles can integrate more than 70 ECUs. This reflects the increased complexity of systems for passenger comfort, safety, infotainment and energy management.
  • Message Volume: The volume of messages exchanged over the CAN bus has increased exponentially, covering a vast range of functions from vehicle health monitoring to advanced driver assistance systems (ADAS).
  • Multiplicity of CAN Networks: Today's cars often use multiple CAN networks, each dedicated to specific aspects of the vehicle, such as the powertrain, infotainment or comfort systems.

The evolution of the CAN bus illustrates technological advances in automobiles and its ability to adapt to the growing needs for communication and data management in modern vehicles.

How does the CAN bus manage to connect complex systems so efficiently? The next chapter, “CAN Technology Explained,” will answer this question by revealing the technical principles and unique structure of this essential technology.

I. CAN Technology Explained

a) Principles of CAN Bus Operation

Imagine a meeting at a round table, where everyone has the same right to speak, without a central authority figure directing the conversation. Similarly, this image reflects the unique democratic structure of the CAN bus. In this system, there is no ‘master’ or ‘slave’ device. In this regard, each unit, whether sensor, actuator or controller, can initiate communication. This situation is comparable to a round table where each participant freely shares their ideas. Ultimately, each node in the CAN network transmits and receives data, promoting fluid and democratic communication.

Democratic Structure:
  • No Master-Slave Hierarchy: Unlike many other communications protocols, the CAN bus does not operate on a master-slave model. There is no central device that controls communication. Instead, each unit on the network (whether a sensor, actuator, or control unit) has the ability to initiate communication.
  • Collaborative Communication: Each node can send information when needed, without waiting for a command or authorization from a central device, improving overall system responsiveness.
Equality of Devices:

Equal Communication Rights:

In a CAN network, all devices are equal in terms of communication rights. Each node can transmit data and listen to transmissions from other nodes.

Practical Advantages: This equality is particularly beneficial in environments where speed of response and coordination between multiple systems are critical. For example, in a vehicle, this allows effective communication between the braking system, engine, and safety sensors, ensuring optimal performance and safety.

Simplicity and Efficiency:

Reduction of Network Complexity: The CAN bus simplifies network architecture by minimizing the need for complex cabling. A single CAN network can replace multiple communication lines, reducing complexity and cost.

Robust design: Designed to be resistant to electromagnetic interference, the CAN bus ensures reliable and stable communication, even in environments subject to high disturbances.

b) Topology and Physical Architecture of the CAN Bus

The CAN bus topology can be compared to an efficient metro system. Indeed, imagine a metro network where each station is connected by a single main line. In this analogy, each station (node) on this line, similar to the CAN bus, has direct access. Additionally, it can communicate with all other stations on the line. Therefore, this simple and efficient structure of the CAN bus enables rapid and direct coordination and transmission of data between network nodes. This is particularly important in complex systems such as vehicles and industrial plants.

Linear Network Configuration

In the CAN bus, the topology is typically linear, similar to a subway line that connects all stations. This allows for simplified and direct communication, with each node connected to this common path.

Bus Terminations

Signal Stabilization: CAN bus terminals, similar to metro terminals, are located at the ends of the network. Generally 120 ohm resistors, they stabilize the signal on the network. This ensures reliable and consistent data transmission.

120 ohm termination resistors reduce signal reflections. They ensure stable and reliable data transmission. They eliminate potential disruptions due to a lack of proper termination. This function is crucial for the performance and efficiency of communication in the CAN network. It is particularly important in environments requiring data accuracy and reliability.

Connection and Communication of Nodes

Each CAN bus node, whether sensor, actuator or control unit, connects to the linear configuration of the network. A distinctive aspect of the CAN bus is that all nodes have equal communication rights. This democratic structure allows each node to initiate communication, providing increased flexibility and responsiveness to the network.

CAN High and CAN Low lines

The CAN High and CAN Low lines are crucial for signal transmission in the CAN bus architecture. These lines operate in tandem using differential signaling. This method is essential for robust and reliable communication in interference-prone environments.

  • CAN High: The CAN High line is usually yellow or orange in color. It transmits signals at a higher voltage level when a dominant bit (0) is sent.
  • CAN Low: The CAN Low line is often colored green. When sending a recessive bit (1), it transmits signals at a lower voltage level compared to the CAN High line.

This configuration allows the CAN bus to effectively minimize electromagnetic interference. It ensures reliable data transmission, even in contexts where electromagnetic disturbances are frequent. Differential signaling is based on the voltage difference between the CAN High and CAN Low lines. This method is a fundamental characteristic of its robustness.

Advantages of Twisted Cables

To maximize signal transmission efficiency, the CAN bus often uses twisted cables. These cables, where pairs of wires are wrapped around each other, are excellent for minimizing electromagnetic interference. This cabling is advantageous for systems where cables run long distances. In vehicles or large industrial machines, it preserves signal integrity over its entire length.

Imagine a scenario where your CAN cable is installed near a power source, such as the alternator in a vehicle, that generates significant electromagnetic noise. Normally, this noise could disrupt and distort communication signals. However, the CAN bus uses an ingenious system of differential signaling between the CAN High and CAN Low lines. This means that any disturbing signal affecting one line also affects the other in a similar way, allowing the system to cancel each other out. Thus, even in the presence of significant noise, the transmitted data remains clear and uncorrupted. This characteristic is shared with systems like Ethernet.

A detailed understanding of CAN bus architecture and signals leads us to a key step. We will explore the data transmission protocols and communication mechanisms that make the CAN bus efficient and reliable.

c) Protocol and Format of CAN Frames

Dominant and Recessive Bits in the CAN Bus

The CAN bus employs a system of dominant and recessive bits to control data transmission. This distinction is essential to ensure effective and reliable communication.

  • CAN High Speed : In high speed CAN, commonly used in applications requiring rapid transmission, the recessive state (1) corresponds to an absence of significant voltage between the CAN High and CAN Low lines. A dominant bit (0) creates a clear voltage difference, allowing clear communication even at high speeds.
  • CAN Low Speed : The low speed CAN, suitable for less demanding applications, uses voltages of 4 volts for CAN High and 2 volts for CAN Low in recessive state. This configuration provides increased resilience to interference in less critical environments.
  • Arbitration and Conflict Management : The CAN protocol has a key arbitration system based on the message identifier. This identifier determines the transmission priority. When several nodes communicate at the same time, the CAN bus uses these identifiers to avoid collisions. This ensures orderly data transmission. This feature will be explored in detail in the next section.
  • Importance in the CAN Network : This signaling technique is crucial for the CAN bus. It ensures efficient and structured management of data traffic. This is essential in systems where many devices communicate reliably.
Structure of a CAN Frame

Understanding the structure of a CAN frame is crucial to understanding how data is transmitted within this network. Here is a detailed overview of the different fields of a CAN frame:

  1. Start of Frame (SOF): A single bit that indicates the start of the frame.
  2. Field of Arbitration: Includes the message identifier (ID) that determines frame priority and the Remote Transmission Request (RTR) bit for remote requests.
  3. Field of Control: Includes DLC (Data Length Code) which indicates the number of bytes of data.
  4. Data Field: Contains the actual data of the frame, up to 8 bytes.
  5. CRC (Cyclic Redundancy Check) field: Used for error checking, it includes the CRC sequence and a CRC delimiter.
  6. Acknowledgment field (ACK): Includes the acknowledgment bit and an acknowledgment delimiter.
  7. End of Frame Field (EOF): Composed of 7 recessive bits, marking the end of the frame.
  8. Intermission: Sequence of three recessive bits after EOF, allowing a pause between frames.
  9. Error and Overload Indicators: Additional fields to report errors or manage network overload.

Thanks to this structure, the CAN bus efficiently manages data transmission. It uses mechanisms for arbitration, error detection and traffic management

d) CAN Bus Arbitration Mechanisms: A Key Process for Effective Communication

The CAN bus arbitration mechanism is similar to the priority given to emergency vehicles, such as ambulances or police cars, in traffic. Imagine a situation where several vehicles reach an intersection at the same time. Ambulances and police cars, with their priority signals, are allowed to go first. This is similar to messages with low priority identifiers in the CAN bus.

Principle of Arbitration:
  • Prioritization of Messages: Each message on the CAN bus has a unique identifier that determines its priority. Messages with lower priority IDs are like emergency vehicles having priority right of way. In case of simultaneous transmission, the message with the lowest identifier (and therefore highest priority) takes precedence and is transmitted first.
Conflict management :
  • Conflict Resolution Like a Boxing Match: Imagine a boxing match where two boxers (nodes) compete for victory (data transmission). The boxer (node) who succeeds in knocking out his opponent (other node) wins the right to transmit his message. This process avoids data conflicts and ensures smooth and orderly transmission.
Impact on Network Robustness:
  • Reliability in Dense Environments: The arbitration system maintains CAN bus reliability and efficiency in communication-heavy environments. Like emergency vehicles crossing traffic efficiently, priority messages on the CAN bus are transmitted without delay. This guarantees smooth and efficient communication.

With this introduction to CAN technology, we have shed light on its operating principles and reliability. This allows us to understand its crucial role in various applications. We will now explore the section “Advantages and Applications of CAN Bus“. Here we will discover why it is widely adopted and its multiple uses, from automotive to aviation and in industry.

e) Filtering management in the CAN Bus

The CAN bus uses a unique filtering mechanism for message handling. This approach reinforces its efficiency and flexibility. Understanding this functionality is crucial to grasp the interaction and processing of information by network nodes.

Filtering and Selection of Messages:

In a CAN network, each node independently chooses which messages to receive. This selection is made via a filtering process. Thus, each node establishes its own criteria to identify relevant messages, based on their identifier (ID). This system targets communication and minimizes unnecessary traffic. A node exclusively processes vital information, optimizing the overall efficiency of the system and lightening its processing load.

Importance of Filtering:

Filtering is particularly beneficial in complex systems where multiple nodes communicate simultaneously. It ensures that essential information reaches the appropriate recipients, without cluttering other nodes with non-essential data. This role is crucial in optimizing communication within dense CAN networks. These networks are common in modern vehicles, industrial control systems, and medical equipment.

II. CAN Bus Components and Integration

a) Essential CAN Bus Components

  • CAN transceivers:
    • Function: The CAN transceiver is a crucial component that acts as a bridge between the microcontroller and the physical CAN network. It converts logic signals from the microcontroller into CAN signals suitable for transmission over the network, and vice versa.
    • Features: CAN transceivers are designed to handle high voltages and electromagnetic disturbances typical in automotive and industrial environments, ensuring reliable and robust communication.
  • Microcontrollers with CAN Interface:
    • Integration of the CAN Interface: Many modern microcontrollers come with built-in CAN interfaces, allowing direct communication with the CAN network without requiring additional external components.
    • Role and Benefits: These microcontrollers facilitate the design of embedded systems by reducing hardware complexity and improving communication efficiency. They are ideal for applications where space is limited and reliability is critical.
  • CAN modules:
    • External CAN Modules: Systems without an integrated CAN interface can use external CAN modules. These modules usually include a CAN transceiver and sometimes a microcontroller with an integrated CAN interface.
    • Usage : These modules provide a flexible solution for adding CAN capabilities to systems such as basic microcontrollers, single board computers like the Raspberry Pi, or even PCs.
  • Choice of Components:
    • Selection criteria : When selecting CAN components, it is important to consider factors such as network speed, communication distance, environmental conditions and size constraints.
    • Compatibility: Make sure the selected components are compatible with each other and the overall system to ensure smooth, error-free communication.

b) Adaptations and Communication Interfaces for Systems without Native CAN Interface

  • Introduction:
    • Context: Many popular systems like Arduinos and Raspberry Pis do not have built-in CAN capabilities. The integration of the CAN bus into these systems therefore requires specific adaptations.
    • Importance: This integration allows the use of the CAN bus to be extended to a wider variety of applications, making these platforms more versatile.
  • Adaptations with Shields and HATs:
    • CAN Shields for Arduino: CAN shields plug directly into the expansion pins of an Arduino, adding CAN functionality via an SPI, I2C, or UART interface.
    • CAN HATs for Raspberry Pi: HATs connect to the Raspberry Pi's GPIO port and typically use SPI or I2C for communication.
    • Examples: These extensions are available from different manufacturers and may include additional features such as electrical isolation or advanced programming interfaces.
  • Integration and Configuration:
    • Physical Installation: Connecting shields or HATs is generally simple, requiring little or no soldering.
    • Software Configuration: Configuration usually involves installing specific libraries and programming the microcontroller or Raspberry Pi to communicate with the CAN network.
  • Technical Considerations:
    • Selection of Components: The choice of shields or HATs depends on the specific needs of the project, such as CAN network speed, communications distance and power requirements.
    • Compatibility and Performance: It is essential to ensure that the extensions chosen are compatible with existing hardware.

III. Various Sectors of Use of the CAN Bus

The scope of CAN bus applications continues to expand. It touches a variety of sectors far beyond its automotive roots. This versatility demonstrates its ability to adapt to the communication needs of different areas.

  1. Automotive : The CAN bus is a fundamental component in vehicles, where it manages communication between various systems, such as engine control, braking and safety systems, and more. Its ability to reduce the amount of cabling while facilitating interoperable communication is invaluable in this industry.
  2. Manufacturing : In the industrial sector, the CAN bus plays an essential role in automation. It connects machines, sensors and controllers for smooth, integrated operation.
  3. Aviation : The CAN bus, used in aviation for communication between navigation, flight management and other critical systems, demonstrates its reliability even in extreme conditions.
  4. Soft Electric Mobility : Soft electric mobility, notably electric bikes and, to a lesser extent, scooters, is starting to adopt the CAN bus for its ability to make vehicles more connected, allowing geolocation, remote maintenance, and increased security for users​.

This exploration of the various applications of the CAN bus perfectly illustrates its versatility and effectiveness across different sectors. These examples show how the CAN bus facilitates reliable and secure communication, a crucial aspect for modern technologies. While we have seen its impact in automobiles, industry, aviation and soft electric mobility, the next chapter will focus on “Innovations and Perspectives” of the CAN bus. There we will discover the latest technological advances in this field and how they are shaping the future of the CAN bus.

IV. Bus Innovations and Perspectives

The CAN bus, already well established in several sectors, continues to evolve. It adapts to new technological requirements and paves the way for future innovations. This section looks at recent developments and trends shaping the future of CAN bus.

a) Introduction of CAN FD (Flexible Data-Rate): Evolution and Applications

The most significant innovation in the evolution of the CAN bus is undoubtedly the development of CAN FD (Flexible Data-Rate). This improved version of the classic CAN protocol offers significant advantages, essential to meet the growing needs for bandwidth and speed of data transmissions.

Expanded Capabilities

CAN FD can handle up to 64 bytes of data per frame, eight times more than traditional CAN. This extension reduces the protocol overhead and improves the general efficiency of the system​.

Increased Transmission Speeds

With CAN FD, data transmission speeds can be up to 5 Mbit/s. They can even be higher, depending on the network topology. This increase in speed is vital for applications like autonomous vehicles, which require fast and reliable transmission of sensor data.

Applications in Autonomous Vehicles

An advanced driver assistance system (ADAS) in a modern vehicle, for example, relies on real-time data from various sensors such as cameras, lidar and radar. CAN FD plays a crucial role here, enabling the rapid and efficient transmission of large amounts of data, essential to vehicle safety and performance​.

Management of Battery Systems in Electric Vehicles

In electric vehicles, CAN FD facilitates communication between the vehicle and its battery management system. This allows continuous monitoring of essential parameters such as temperature, voltage and current. The expanded CAN FD frame format allows this information to be transmitted in larger quantities, improving communication efficiency and decision-making​.

CAN FD represents a significant advancement in the field of vehicle communications networks. It meets the growing data and performance needs of modern systems.

b) Technology Trends in the CAN Bus

While CAN FD represents a major advance, other technological trends are also emerging in the CAN bus world, revealing its scalable potential and its ability to adapt to technological challenges:

  1. Security and Cryptography : With increasing cybersecurity concerns, the CAN bus incorporates advanced cryptography and security features. These innovations are crucial for protecting data against intrusion and manipulation in critical embedded systems.
  2. Coexistence of CAN and Ethernet : Although Ethernet offers higher transmission speeds, CAN is specifically designed for distributed embedded control systems, where data consistency and message collision resolution are essential. In the future, it is possible for CAN and Ethernet to coexist on the same physical layer, allowing greater flexibility in communication systems​.
  3. IoT Integration and Improved Connectivity : The Internet of Things (IoT) is gaining ground, and the CAN bus is adapting to provide improved connectivity and interoperability. This integration enables smarter, more connected applications, particularly in building management systems and industrial networks.
  4. Towards Greater Payload Capacities : Future CAN bus developments could see a notable increase in frame payload capacity. This would enable more complex communications and the transfer of large data for certain applications.
  5. Emerging Applications : The CAN bus is being deployed in new areas such as energy management, electric vehicles and portable technologies. Its reliability and flexibility are particularly appreciated.

These trends show that the CAN bus continues to adapt and renew itself, proving its continued relevance in today's dynamic technology landscape.

Conclusion

Our exploration of the CAN bus has covered its foundations, its various applications and its constant innovations. This highlights its growing importance in an increasingly connected world. The CAN bus is more than just a communication system. It is essential for connecting and enhancing the security and efficiency of complex systems.

The CAN bus has proven to be much more than an automotive innovation. It now plays a key role in various sectors, from heavy industry to aviation to electric bicycles. It adapts to the specific requirements of each area. The arrival of CAN FD marks a further development, meeting growing needs in terms of speed and data volume.

As readers who are passionate about technology, we have every interest in following the evolution of the CAN bus. Its continued development is an eloquent testament to how technology solutions can adapt, evolve and remain relevant in the face of changing challenges. The CAN bus doesn't just keep up; he defines it.

Keep an eye on this technology. It has shaped the past, plays a crucial role in the present and is undeniably focused on the future.

Additional Resources

  1. Embedded Computing (EN) : This article explores the continuing role of the CAN bus in control systems, highlighting its importance for today and the future.
  2. CSS Electronics (EN) : An in-depth resource on CAN FD, providing an introduction to Flexible Data-Rate and its applications.
  3. DEV Community (EN) : An article that focuses on the use of CAN FD in the automotive industry. It highlights its advantages in terms of speed and reliability.
  4. Kadionik on Developpez.com (FR) : This document presents the essential characteristics of the CAN bus, its communication protocol as well as its physical and electrical characteristics​.
  5. Engineering Techniques (FR) : A complete file on the CAN bus, addressing its operation, its communication protocol, and its advantages, including the CAN-FD version​.
  6. Mechanical News (FR) : This article explores the CAN bus communication technology widely used in the automotive industry and explains how it facilitates the transmission of data between components of a vehicle​.
  7. Velco.tech : This article describes the implementation of the CAN protocol in the automotive industry to reduce wiring and interconnect sensors and actuators. It also discusses the use of the CAN bus in electric bicycles, highlighting its reliability and safety. The article thus highlights the advantages of the CAN bus in different contexts of use.
  8. Tritekbattery.com : This blog examines the CAN communication protocol in high-end electric drive systems. He highlights its growing adoption in electric bikes and its advantages over other protocols. He also mentions the Smart BMS (Intelligent Battery Management System), which communicates directly with CAN bus systems for better control of the bike's performance and safety features.

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