Tech Chat | What is CAN protocol?
In today's rapidly evolving world of agriculture, where precision and efficiency are paramount, GNSS technology plays a pivotal role in maximizing yields while minimizing resource consumption, such as our SAgro100 GNSS Autosteer System.
To keep ±2.5cm auto-steering accuracy of your tractor, in addition to high-precision GNSS positioning, real-time communication and high-speed data transmission are also important. Today we will introduce the Controller Area Network (CAN) protocol, the data transfer protocol used in our SAgro-series, enabling farmers to achieve greater productivity and cost-efficiency.
What is CAN Protocol?
Controller Area Network, or CAN, is a serial communication protocol designed for real-time applications. Initially developed to streamline communication between different components in automobiles, CAN has proven its robustness and versatility in various automation and industrial settings. It relies on twisted-pair wires for signal transmission, replacing costly and cumbersome distribution harnesses.
Key Features of CAN Protocol
- Complete Serial Data Communication: CAN offers efficient, bidirectional communication between devices.
- Real-time Support: It enables time-critical operations, crucial for applications like our autosteer and guidance systems.
- High Transmission Rates: With speeds of up to 1Mb/s, CAN ensures swift data transfer.
- 11-bit Addressing: CAN uses a unique identifier for each message, facilitating seamless communication in distributed control systems.
Evolution of CAN Protocol
The CAN protocol has come a long way since its inception. In 1991, the CAN bus technical specification (Version 2.0) was introduced, comprising two parts: 2.0A and 2.0B, which established standard and extended formats for CAN messages. Subsequently, in 2000, the Society of Automotive Engineers (SAE) proposed the protocol, and it has since become the common standard for controller area networks in trucks and buses.
How CAN Protocol Works
CAN operates on a broadcast principle, meaning when one node on the network sends data, it is received by all nodes. Each packet starts with an 11-bit identifier that defines its priority, ensuring seamless communication even when multiple nodes compete for access to the bus. This content-oriented addressing scheme prevents collisions and guarantees efficient data exchange.
The CAN Communication Diagram
CAN Communication Diagram
CAN uses two voltage levels, "CAN_HIGH" and "CAN_LOW," to represent logic signals. When CAN_HIGH-CAN_LOW < 0.5V, it signifies an "implicit" logic 1 (high level), and when CAN_HIGH-CAN_LOW > 0.9V, it indicates a "dominant" logic 0 (low level). The inclusion of a 120-ohm terminal resistor at both ends of the CAN bus ensures impedance matching, reducing echo reflection and maintaining signal stability. CAN's use of differential signals enhances reliability, as changes in voltage affect both CAN_HIGH and CAN_LOW equally.
CAN employs a sophisticated arbitration mechanism to manage data collisions. When multiple nodes attempt to send data simultaneously, the bus compares the identifier (ID) of each message bit by bit. The message with the most zeros in its ID gains priority. This prioritization ensures orderly data transmission on the network.
Key Characteristics of CAN Protocol
1. Multi-Master Control: Multiple nodes can actively communicate without a central controller.
2. Ease of Node Addition: Expanding the network is straightforward, making it adaptable to evolving requirements.
3. Fast Communication: CAN offers rapid data transfer over long distances.
4. Error Detection and Recovery: It boasts robust error-handling capabilities, critical for mission-critical applications.
5. Fault Isolation: CAN can isolate faulty nodes while maintaining network integrity.
6. Scalability: It supports a high number of connected nodes, making it ideal for complex systems.
Powering Our Precision Agriculture
In conclusion, the CAN protocol is a critical component of our autosteer and guidance systems, facilitating reliable data transmission. Our commitment to innovation in precision agriculture is unwavering, and we're dedicated to driving the future of farming.
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