背景知识：modbus协议介绍

相关工具

• mbslave:充当从站。
• 虚拟串口工具:虚拟出一对串口。
• VS2022。

实现过程以及Demo

1. 打开虚拟串口工具:
   
2. 打开mbslave:
   
   
   此处从站连接COM1口。

Demo实现

1. 创建DLL库，创建ModbusRTU类,进行实现：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.IO.Ports;
using System.Threading;namespace modBusDLL
{public class ModBusRTU{private SerialPort serialPort = null;public ModBusRTU(){serialPort = new SerialPort();}//连接方法//端口号，波特率，数据位，校验位，停止位public void Connect(string portName,int baudRate=9600,int dataBits=8,Parity parity=Parity.None,StopBits stopBits=StopBits.One){ if (serialPort.IsOpen) {serialPort.Close();}serialPort.BaudRate = baudRate;serialPort.PortName = portName;serialPort.Parity = parity;serialPort.StopBits = stopBits;serialPort.DataBits = dataBits;serialPort.Open();}//断开连接方法public void Disconnect(){if (serialPort.IsOpen){serialPort.Close();}}//读消息方法public byte[] ReadKeepRegisters(byte devAdd,ushort start,ushort length){ //拼接报文，发送报文，接受报文，校验报文，解析报文//创建一个字节集合List<byte> ret = new List<byte>();//协议格式：站地址+功能码+起始寄存器地址+寄存器数量+CRC//站地址ret.Add(devAdd);//功能码ret.Add(0x03);//起始寄存器地址//高位地址ret.Add((byte)(start / 256));//低位地址ret.Add((byte)(start % 256));//寄存器数量//高位地址ret.Add((byte)(length / 256));//低位地址ret.Add((byte)(length % 256));byte[] crc= CRCCalc(ret.ToArray());ret.AddRange(crc);//发送报文serialPort.Write(ret.ToArray(), 0, ret.Count);Thread.Sleep(50);//接受长度int byteCount = serialPort.BytesToRead;byte[] data = new byte[byteCount];//读入dataserialPort.Read(data, 0, data.Length);byte[] result = new byte[length*2]; Array.Copy(data,3,result, 0,length*2);return result;}#region 16位CRC校验/// <summary>/// CRC校验，参数data为byte数组/// </summary>/// <param name="data">校验数据，字节数组</param>/// <returns>字节0是高8位，字节1是低8位</returns>public static byte[] CRCCalc(byte[] data){//crc计算赋初始值int crc = 0xffff;for (int i = 0; i < data.Length; i++){crc = crc ^ data[i];for (int j = 0; j < 8; j++){int temp;temp = crc & 1;crc = crc >> 1;crc = crc & 0x7fff;if (temp == 1){crc = crc ^ 0xa001;}crc = crc & 0xffff;}}//CRC寄存器的高低位进行互换byte[] crc16 = new byte[2];//CRC寄存器的高8位变成低8位，crc16[1] = (byte)((crc >> 8) & 0xff);//CRC寄存器的低8位变成高8位crc16[0] = (byte)(crc & 0xff);return crc16;}/// <summary>/// CRC校验，参数为空格或逗号间隔的字符串/// </summary>/// <param name="data">校验数据，逗号或空格间隔的16进制字符串(带有0x或0X也可以),逗号与空格不能混用</param>/// <returns>字节0是高8位，字节1是低8位</returns>public static byte[] CRCCalc(string data){//分隔符是空格还是逗号进行分类，并去除输入字符串中的多余空格IEnumerable<string> datac = data.Contains(",") ? data.Replace(" ", "").Replace("0x", "").Replace("0X", "").Trim().Split(',') : data.Replace("0x", "").Replace("0X", "").Split(' ').ToList().Where(u => u != "");List<byte> bytedata = new List<byte>();foreach (string str in datac){bytedata.Add(byte.Parse(str, System.Globalization.NumberStyles.AllowHexSpecifier));}byte[] crcbuf = bytedata.ToArray();//crc计算赋初始值return CRCCalc(crcbuf);}/// <summary>///  CRC校验，截取data中的一段进行CRC16校验/// </summary>/// <param name="data">校验数据，字节数组</param>/// <param name="offset">从头开始偏移几个byte</param>/// <param name="length">偏移后取几个字节byte</param>/// <returns>字节0是高8位，字节1是低8位</returns>public static byte[] CRCCalc(byte[] data, int offset, int length){byte[] Tdata = data.Skip(offset).Take(length).ToArray();return CRCCalc(Tdata);}#endregion}
}

2. 在窗体代码中进行调用：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO.Ports;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using modBusDLL;namespace easyProjectPractice
{public partial class Form1 : Form{public Form1(){InitializeComponent();this.comboBox1.DataSource=SerialPort.GetPortNames();}private ModBusRTU modBusRTU = new ModBusRTU();private void label1_Click(object sender, EventArgs e){}private void Form1_Load(object sender, EventArgs e){}private void button1_Click(object sender, EventArgs e){modBusRTU.Connect(this.comboBox1.Text);MessageBox.Show("连接成功");}private void button2_Click(object sender, EventArgs e){modBusRTU.Disconnect();MessageBox.Show("断开连接");}private void button3_Click(object sender, EventArgs e){byte[] data = modBusRTU.ReadKeepRegisters(1, 2, 1);textBox1.Text = (data[0] * 256 + data[1]).ToString();}private void textBox1_TextChanged(object sender, EventArgs e){}}
}

3. 最终可实现通过mdbusRTU协议进行主从站通信：
   
   

总结

简单的modbusRTU主从通信自定义。

接触过的所有通信协议Demo代码