1. What is Modbus RTU
Modbus RTU (Remote Terminal Unit) is a variant of the Modbus communication protocol used for serial communication. It is a common industrial control system communication protocol, usually used to collect sensor data, control actuators, and monitor device status. Modbus RTU uses binary encoding and uses serial communication protocols (such as RS-232 or RS-485) to transmit data between devices.
In Modbus RTU, data is transmitted in bytes with a simple request/response structure. The master device (such as a PLC or computer) sends a command frame to the slave device (such as a sensor or actuator), and the slave device responds with a frame containing the requested data. Each device has a unique address to distinguish different devices.
2.What are the characteristics of Modbus RTU?
The biggest feature of Modbus RTU is that it is simple, stable and reliable. It does not require complex network settings, and can achieve data exchange between devices through serial communication. It is like the “Mandarin” of the industrial world, and almost all industrial equipment can understand it.
3. Modbus RTU protocol format
Modbus RTU (Remote Terminal Unit) is a serial communication protocol commonly used in industrial automation systems. The protocol format is as follows:
Frame Header: The frame header consists of the address byte and function code byte, typically 11 bits.
Address Byte: Indicates the device or register to be accessed.
Function Code Byte: Determines the operation to be performed.
Data Field: Contains the transmitted data, with variable length.
CRC Check: Used to verify the accuracy of data transmission, typically a 16-bit cyclic redundancy check.
Frame Tail: Usually two stop bits used to indicate the end of the frame.
The protocol format of Modbus RTU is as follows:
| Address | Function Code | Data | CRC | Stop Bits |
4. What scenarios are suitable for using Modbus RTU?
If you work in the field of industrial automation, Modbus RTU is almost everywhere. For example, if you want to control a factory production line and need to read sensor data or send instructions to the controller, Modbus RTU can be very useful. It is suitable for any scenario that requires communication between devices, especially those with high requirements for real-time performance and stability.
5.C# implementation of Modbus RTU communication demo
Here is a simple C# code example:
using System;
using System.IO.Ports;
public class ModbusRTUDemo
{
public static void Main()
{
SerialPort serialPort = new SerialPort(“COM1”, 9600, Parity.None, 8, StopBits.One);
serialPort.Open();
// Send a command to read the device status
byte[] request = new byte[] { 0x01, 0x03, 0x00, 0x00, 0x00, 0x01, 0xE8, 0x03 };
serialPort.Write(request, 0, request.Length);
//Read response
byte[] response = new byte[7];
int bytesRead = serialPort.Read(response, 0, response.Length);
Console.WriteLine(“Received: {0}”, BitConverter.ToString(response, 0, bytesRead));
serialPort.Close();
}
}