The following is an introduction to common communication protocols based on the UART bus:
1. Modbus Protocol (RTU Mode)
•Introduction:Modbus is a widely used master-slave communication protocol in industrial control, divided into RTU (Remote Terminal Unit) and ASCII modes, with RTU mode being the most commonly used version of UART.
•Features:
◦Binary Transmission：Data is packed in binary form, providing high transmission efficiency (compared to ASCII mode).
◦Frame Structure：Includes slave address, function code, data area, and CRC checksum.
◦Checksum Method：Uses CRC-16 checksum to ensure data integrity.
•Application Scenarios：Communication between industrial devices (such as PLC, sensors, and frequency converters).
•Example：
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Frame Format:[Slave Address][Function Code][Data Area][CRC Checksum] For example:01 03 00 00 00 02 C4 0B (Read data from slave 1 for registers 0-1) |
2. Modbus Protocol (ASCII Mode)
•Introduction:Another mode of Modbus, where data is transmitted in ASCII character form.
•Features:
◦Text Transmission：High readability, but lower transmission efficiency (each byte needs to be converted to two ASCII characters).
◦Checksum Method：Uses LRC (Longitudinal Redundancy Check).
•Application Scenarios：Early Modbus devices or scenarios requiring direct data visibility.
•Example：
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Frame Format:[:][Slave Address][Function Code][Data Area][LRC Checksum][CR][LF] For example::010300000002840A |
3. UART Custom Protocol
•Introduction：A dedicated protocol designed by developers based on requirements, commonly found in embedded systems or IoT devices.
•Features:
◦High Flexibility：Customizable frame header, data length, and checksum method.
◦Typical Structure:
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[Frame Header][Device Address][Data Length][Data Area][Checksum][Frame Tail] |
◦Checksum Method：Checksum by sum, CRC checksum, or XOR checksum.
•Application Scenarios：Smart home devices, sensor modules, private communication systems.
•Example：
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Frame Format:0xFF 0x01 0x02 0xAB 0xCD 0x12 0xFF (Custom protocol example) |
4. IRDA (Infrared Data Association Protocol)
•Introduction：A short-range communication protocol based on infrared transmission, commonly using UART interfaces at the physical layer.
•Features:
◦Half-Duplex：Short communication distance (usually <1 meter), requires direct alignment.
◦Rate：Supports 9600bps to 4Mbps.
•Application Scenarios：Early mobile phones, remote controls, data synchronization devices.
5. Bluetooth SPP (Serial Port Profile)
•Introduction：Bluetooth’s serial communication protocol, simulating serial communication through UART.
•Features:
◦Wireless：Realizes wireless extension of UART, with a communication distance of about 10 meters.
◦Transparent Transmission：User layer can be seen as a normal serial port, without concern for Bluetooth protocol details.
•Application Scenarios：Communication between Bluetooth modules and mobile phones, PCs.
6. Other Common Protocols
•ZigBee：Low-power wireless communication protocol, with some modules supporting UART transparent transmission.
•LoRa：Long-range low-power communication, with some terminal devices interacting with gateways via UART.
•Custom Protocols：Such as Huawei’s HiLink, Tuya Smart, and other IoT platform proprietary protocols.
Considerations for Protocol Selection
1.Data Volume and Rate：Modbus RTU is suitable for industrial low-speed scenarios, while custom protocols can optimize high-speed transmission.
2.Compatibility：Modbus is an industry standard, suitable for cross-device communication.
3.Security：Proprietary protocols can add encryption mechanisms (such as AES), enhancing security.
4.Development Cost：Using mature protocols can reduce development cycles, while custom protocols require more debugging resources.
Choose the appropriate protocol based on specific needs, or design a dedicated protocol based on UART to balance functionality and efficiency.