Modbus RTU与PLC通讯问题

[qq_41601650]

c#做了个简单的上位机与PLC通讯，直接与PLC通讯时写线圈、保持型寄存器等功能正常，但是读PLC数据只返回一个255。我用别的上位机软件与PLC通讯正常，这时再用我的程序读数据也正常了，把串口线拔掉再插上就又不行了。

[qq_41601650]

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;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            System.Windows.Forms.Control.CheckForIllegalCrossThreadCalls = false; 
        }
        SerialPort sp = new SerialPort();
        delegate void UpdateTextEventHandler(byte[] text);
        private void Form1_Load(object sender, EventArgs e)
        {
            sp.PortName = "COM9";
            sp.BaudRate = 9600;
            sp.Parity = Parity.Even;
            sp.DataBits = 8;
            sp.StopBits = StopBits.One;
            sp.ReadTimeout = 200;
            sp.WriteTimeout = 200;
            sp.ReceivedBytesThreshold = 1;
            sp.DataReceived += new SerialDataReceivedEventHandler(SPort_DataReceived);       
            sp.Open();


        }
        void SPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            byte[] ReDatas = new byte[sp.BytesToRead]; 
            sp.Read(ReDatas, 0, ReDatas.Length);
            UpdateTextEventHandler Text = new UpdateTextEventHandler(UpdateTextBox);
            Text(ReDatas);
        }
        private void UpdateTextBox(byte[] text)  //显示接收数据
        {
            
            for (int i = 0; i < text.Length; i++)
            {
                textBox1.Text += text[i];
                textBox1.Text += ',';
                if (i == text.Length - 1)
                {
                    textBox1.Text += System.Environment.NewLine;  //换行
                }
            }

        }

        private void button1_Click(object sender, EventArgs e)
        {
            byte[] message = new byte[8];
            message[0] = (byte)0x01;
            message[1] = (byte)0x03;  
            message[2] = (byte)0x00;  
            message[3] = (byte)0x00; 
            message[4] = (byte)0x00;  
            message[5] = (byte)0x01;     
            message[6] = (byte)0x84;
            message[7] = (byte)0x0A;
            sp.Write(message, 0, message.Length);
        }


    }
}

[无情时尚]

革命尚未成功，同志任需努力！

[xian_wwq]

DataReceived 事件在接收到了ReceivedBytesThreshold设置的字符个数或接收到了文件结束字符 并将其放入了输入缓冲区时被触发。 sp.ReceivedBytesThreshold = 1; //设置 DataReceived 事件发生前内部输入缓冲区中的字节数 每次只收到一个字节是因为设定如此

[巴顿的烦恼]

你在formload 里执行了串口接收事件的重构和串口打开的操作

[zmyouren1983]

你确认PLC端强制拔串口没有问题？ 是不是PLC端数据发不出来了。