CAN Framing
Framing is the term used to describe the structure and format used to arrange data for transmission over the network for the context of the CAN (Controller Area Network) protocol. The CAN communication protocol, frequently used in automotive and industrial applications, enables many devices (or “nodes”) to talk to one another across a common bus.
A message is transmitted in the Controller Area Network (CAN) protocol using a particular format known as a frame. The frame has various fields that each convey details about the message.
CAN framing comprises the division of data into frames. Each CAN frame consists of several components which include –
- Start of Frame(SOF): This is the first part of the CAN frame which acts as a synchronization marker. It is composed of a particular bit pattern that marks the beginning of a new frame and aids in synchronizing receivers with the sender’s clock.
- Arbitration Field: When several nodes try to transmit at once, the arbitration field contains data that is used to establish the message’s precedence on the bus. Bus access will be granted to nodes with higher-priority messages.
- Identifier(ID): The priority and source or destination of a message are specified in the ID field. Depending on whether it’s a conventional or extended frame, the identifier can be either an 11-bit or a 29-bit number.
- Control Field: This field includes control bits that identify the frame type (such as data frame or remote frame) as well as additional control data.
- Data Field: The actual data that needs to be delivered is in the data field. This has a size range that commonly falls between 0 and 8 bytes in a typical CAN frame.
- CRC(Cyclic Redundancy Field): A checksum that is part of the CRC field aids in the identification of transmission mistakes. Receiving nodes can use it to check the frame’s integrity.
- Acknowledge Field: A node transmits an acknowledgment bit in this field after successfully receiving a frame to show that no errors were made in the transmission.
- End of Frame(EOF): The CAN frame comes to an end at the EOF. It consists of a certain bit pattern that indicates the frame’s end.
Data frames and remote frames are the two types of frames used by the CAN protocol. Whilst remote frames are used to request data from another node, data frames contain the actual data to be transferred.
All nodes in the network will get a message after it has been transmitted, but only the node that has the correct identifier will process it.
CAN Layered Architecture
CAN Layered Architecture :
The layered architecture of the CAN (Controller Area Network) protocol allows for modularity, flexibility, and simplicity of use. The layered architecture of the CAN protocol is composed of various layers, each with unique duties and tasks.
CAN Protocol consists of the following layers –
- Physical Layer: The physical transfer of bits via the communication media, for example, a cable or wireless link, is handled by this layer. Voltage levels, bit timing, as well as physical connectors, are included in this. For devices from many manufacturers to work together, a CAN physical layer is standardized.
- Presentation Layer: This layer is not clearly defined in the CAN protocol. The presentation and application layer tasks are frequently combined in CAN-based systems, streamlining the protocol stack.
- Data Link Layer: This layer is responsible for providing secure data transfer between nodes. It comprises two sublayers –
Logical Link Control (LLC): This sublayer is in charge of controlling access to the common CAN bus, as well as message arbitration, error handling, and error detection.
Media Access Control(MAC): The physical framing and management of data transmission on the bus is done by the MAC sublayer.
- Application Layer: This layer specifies the interfaces and services that are accessible for the application, which includes message sending and receiving and network status monitoring. The application layer is in charge of specifying the structure and content of messages, as well as the significance of data sent between nodes. Additionally, it manages higher-level protocols and actions particular to the program, like diagnostics and error management.
- Network Layer: Additionally, the CAN protocol lacks a conventional network layer. Since CAN networks are frequently small and the nodes interact directly on a shared bus, it operate at the data link layer and thus does not include network addressing or routing.
Applications
- Automotive Industry: CAN protocol was originally developed for the automotive industry. It serves a number of functions, including those related to climate control, transmission control, anti-lock brake systems (ABS), entertainment systems, airbag systems, gearbox control, etc.
- Industrial Automation: CAN enables real-time communication between sensors, actuators, and controllers, allowing for precise and effective control of production procedures, robotic systems, & factory automation.
- Medical Devices: Medical imaging gadgets, diagnostic tools, and patient monitoring systems are just a few examples of the equipment and devices that employ CAN. It makes it possible for trustworthy data interchange across various medical devices and systems.
- Telecommunications: For equipment monitoring and management within the network infrastructure, CAN is employed in some telecommunications applications.
- Renewable Energy Systems: In order to monitor and control power generation, maximize efficiency, and manage grid integration, CAN is utilized in wind turbines, solar power systems, and other renewable energy applications.
- Home Automation: CAN is used in home automation which may comprise ventilation, heating, control lights, security systems, air conditioning, etc.
- Military Applications: For intersystem communication in military vehicles and equipment, including weapons control, navigation, as well as surveillance systems, CAN is employed.
Conclusion
In a wide range of industries, the Controller Area Network (CAN) protocol has established itself as a reliable and essential communication standard. A popular choice across applications ranging from automotive, and industrial automation to aerospace and medical equipment, its design is geared towards real-time and reliable data sharing.
The layered architecture of CAN ensures deterministic behavior even in difficult and noisy situations while simplifying complex communication duties. It is ideally suited for important systems where accuracy and dependability are crucial thanks to its essential features, including message arbitration, error detection, and priority-based transmission.
Whether you’re controlling a piece of medical equipment, monitoring a manufacturing process, or operating a car, there’s a good possibility that CAN is discreetly ensuring that data flows consistently and seamlessly in the background. It is a communication protocol that is valuable to understand and appreciate because of its history and versatility in different applications.
In a world where efficient, real-time communication is essential, the CAN protocol stands as a testament to the power of simplicity, reliability, and versatility. As technology advances, we can expect CAN to remain a cornerstone in the networked systems that power our lives