How does CAN transfer 485 data correspond?

CAN (Controller Area Network) is a local area network technology used in automobile and industrial control systems. It has high reliability, real-time and flexibility. RS-485 is a serial communication protocol, commonly used for long-distance communication and multi-point communication. Converting CAN bus data to RS-485 data can easily realize data exchange between different communication protocols.

This article will introduce in detail the correspondence between CAN and RS-485 data, including the communication principles, data formats, conversion methods and application examples of CAN bus and RS-485.

1. CAN bus communication principle

1.1 CAN bus overview

CAN bus is a communication protocol based on time division. It uses a non-destructive arbitration mechanism to solve the conflict problem when multiple nodes send data at the same time. CAN bus has the following characteristics:

• High reliability: The CAN bus has error detection and error handling mechanisms to ensure the reliability of data transmission.

• Real-time: CAN bus adopts a time-slicing mechanism to ensure the real-time performance of data transmission.

• Flexibility: The CAN bus supports a variety of communication rates and distances, and can adapt to different application scenarios.

1.2 CAN bus data transmission process

The data transmission process of the CAN bus includes the following steps:

• Frame start: The sending node sends a frame start signal to indicate the start of data transmission.

• Arbitration Field: The sending node sends the arbitration field to determine the priority of data transmission.

• Control field: The sending node sends a control field, including the data length and the remote transmission request flag.

• Data field: The sending node sends the data field, which contains the actual transmitted data.

• CRC check: The sending node sends a CRC check code to detect errors during data transmission.

• Response field: The receiving node sends a response signal to indicate that the data has been successfully received.

• Frame end: The sending node sends a frame end signal to indicate the end of data transmission.

1. RS-485 communication principle

2.1 RS-485 Overview

RS-485 is a differential signal serial communication protocol with the following characteristics:

• Long distance communication: RS-485 can support a communication distance of up to 1200 meters.

• Multi-point communication: RS-485 supports multiple nodes communicating simultaneously, realizing multi-point communication.

• Anti-interference: RS-485 uses differential signals and has strong anti-interference capabilities.

2.2 RS-485 data transmission process

The RS-485 data transmission process includes the following steps:

• Start bit: The sending node sends a start bit to indicate the start of data transmission.

• Data bits: The sending node sends data bits, which contain the actual data transmitted.

• Parity bit: The sending node sends parity bit to detect errors during data transmission.

• Stop bit: The sending node sends a stop bit to indicate the end of data transmission.

1. CAN to 485 data format

3.1 CAN data format

The CAN data format consists of the following parts:

• Frame start: 1 bit

• Arbitration field: 11 bits (standard frame) or 29 bits (extended frame)

• Control field: 6 bits

• Data field: 0~64 bits

• CRC check: 15 bits

• Response field: 2 bits

• Frame end: 7 bits

3.2 RS-485 Data Format

The RS-485 data format consists of the following parts:

• Start bit: 1 bit

• Data bits: 8 bits

• Parity bit: 1 bit

• Stop bit: 1 or 2

1. CAN to 485 conversion method

4.1 Hardware Conversion

Hardware conversion refers to converting CAN bus data into RS-485 data through hardware devices. Common hardware conversion devices include CAN to RS-485 converters, CAN-RS-485 gateways, etc. The advantages of hardware conversion are simple implementation and high stability, but the cost is relatively high.

4.2 Software Conversion

Software conversion refers to converting CAN bus data into RS-485 data by writing a program. The advantages of software conversion are low cost and high flexibility, but the implementation is complex and the stability is relatively low.

4.3 Conversion Process

The conversion process of CAN to 485 is as follows:

• Receiving CAN bus data: First, you need to receive data on the CAN bus.

• Parse CAN data: Parse the received CAN data and extract information such as data field and control field.

• Convert data format: Convert the parsed CAN data into RS-485 data format, including start bit, data bit, parity bit and stop bit.

• Send RS-485 data: Send the converted RS-485 data through the RS-485 communication interface.

1. Application Examples

5.1 Industrial Automation

In the field of industrial automation, CAN bus and RS-485 communication protocols are widely used. Through the CAN to 485 converter, data exchange and collaborative work between industrial equipment can be achieved to improve production efficiency.

5.2 Automotive Electronics

In the field of automotive electronics, CAN bus is the main communication protocol. Through the CAN to 485 converter, the CAN bus data inside the car can be converted into RS-485 data to achieve communication with other electronic devices.