C# serial communication example tutorial

Because I participated in a small project and needed to control the relay through the serial port, I learned basic serial port programming in the past two days. A colleague has a JAVA serial communication package, but it was downloaded from the Internet. It is quite messy and it is difficult to accurately grasp the process and content of serial communication. Therefore, I personally implemented basic serial communication programming using C# by learning the methods of online experts. The following is a summary of the learning results, I hope it will be helpful to everyone.

1. Introduction to serial communication

The serial interface (serial port) is a type that can convert parallel data characters received from the CPU into continuous serial The data stream is sent out, and the received serial data stream can be converted into parallel data characters and supplied to the CPU device. Generally, the circuit that completes this function is called a serial interface circuit.

The concept of serial communications (Serial Communications) is very simple. The serial port sends and receives bytes bit by bit. Although slower than byte-by-byte parallel communication, a serial port can send data on one wire while receiving data on another wire. The most important parameters of serial communication are baud rate, data bits, stop bits and parity. For two ports to communicate, these parameters must match.

1. Baud rate: This is a parameter that measures the symbol transmission rate. It refers to the change in unit time after the signal is modulated, that is, the number of carrier parameter changes per unit time. For example, 960 characters are transmitted per second, and each character format contains 10 bits (1 start bit, 1 Stop bit, 8 data bits), the baud rate at this time is 960Bd, and the bit rate is 10 bits * 960 bits/second = 9600bps.

2. Data bits: This is a parameter that measures the actual data bits in communication. When a computer sends a packet of information, the actual data is often not 8 bits; standard values ​​are 6, 7, and 8 bits. The standard ASCII code is 0~127 (7 bits), and the extended ASCII code is 0~255 (8 bits).

3. Stop bit: used to represent the last few bits of a single packet. Typical values ​​are 1, 1.5 and 2 bits. Since the data is timed on the transmission line, and each device has its own clock, it is possible for a small desynchronization between the two devices to occur during the communication. The stop bit therefore not only indicates the end of the transfer, but also provides the computer with an opportunity to correct clock synchronization.

4. Check digit: A simple error detection method in serial communication. There are four error detection modes: even, odd, high and low. Of course, it is also possible to have no check digit.

2. C# serial port programming class

Starting from .NET Framework 2.0, C# provides the SerialPort class for serial port control. Namespace:System.IO.Ports. For detailed member introduction, please refer to the MSDN documentation. The following introduces its commonly used fields, methods and events.

1. Commonly used fields:

Name	Description
PortName	Get or set the communication port
BaudRate	Get or set the serial baud rate
DataBits	Get Or set the standard data bit length per byte
Parity	Get or set the parity check protocol
StopBits	Gets or sets the standard number of stop bits per byte

2. Commonly used methods:

##ReadSerialPortWrite

Name	Description
Close	Close the port connection, set the IsOpen property to false, and release the internal Stream object
GetPortNames	Get the serial port name array of the current computer
Open	## Open a new serial port connection
## from the	input buffer Read
Write data to the serial port output buffer

3. Common events:

NameDataReceivedSerialPort

Description
Indicates the method that will handle the data receiving event of the	object

3. Basic Usage

The following is a combination of an existing relay to give serial communication Basic usage for reference.

  1 using System;  2 using System.Windows.Forms;  3 using System.IO.Ports;  4 using System.Text;  5   6 namespace Traveller_SerialPortControl  7 {  8     public partial class Form1 : Form  9     { 10         //定义端口类 11         private SerialPort ComDevice = new SerialPort(); 12         public Form1() 13         { 14             InitializeComponent(); 15             InitralConfig(); 16         } 17         /// <summary> 18         /// 配置初始化 19         /// </summary> 20         private void InitralConfig() 21         { 22             //查询主机上存在的串口 23             comboBox_Port.Items.AddRange(SerialPort.GetPortNames()); 24  25             if (comboBox_Port.Items.Count > 0) 26             { 27                 comboBox_Port.SelectedIndex = 0; 28             } 29             else 30             { 31                 comboBox_Port.Text = "未检测到串口"; 32             } 33             comboBox_BaudRate.SelectedIndex = 5; 34             comboBox_DataBits.SelectedIndex = 0; 35             comboBox_StopBits.SelectedIndex = 0; 36             comboBox_CheckBits.SelectedIndex = 0; 37             pictureBox_Status.BackgroundImage = Properties.Resources.red; 38  39             //向ComDevice.DataReceived（是一个事件）注册一个方法Com_DataReceived，当端口类接收到信息时时会自动调用Com_DataReceived方法 40             ComDevice.DataReceived += new SerialDataReceivedEventHandler(Com_DataReceived); 41         } 42  43         /// <summary> 44         /// 一旦ComDevice.DataReceived事件发生，就将从串口接收到的数据显示到接收端对话框 45         /// </summary> 46         /// <param name="sender"></param> 47         /// <param name="e"></param> 48         private void Com_DataReceived(object sender, SerialDataReceivedEventArgs e) 49         { 50             //开辟接收缓冲区 51             byte[] ReDatas = new byte[ComDevice.BytesToRead]; 52             //从串口读取数据 53             ComDevice.Read(ReDatas, 0, ReDatas.Length); 54             //实现数据的解码与显示 55             AddData(ReDatas); 56         } 57  58         /// <summary> 59         /// 解码过程 60         /// </summary> 61         /// <param name="data">串口通信的数据编码方式因串口而异，需要查询串口相关信息以获取</param> 62         public void AddData(byte[] data) 63         { 64             if (radioButton_Hex.Checked) 65             { 66                 StringBuilder sb = new StringBuilder(); 67                 for (int i = 0; i < data.Length; i++) 68                 { 69                     sb.AppendFormat("{0:x2}" + " ", data[i]); 70                 } 71                 AddContent(sb.ToString().ToUpper()); 72             } 73             else if (radioButton_ASCII.Checked) 74             { 75                 AddContent(new ASCIIEncoding().GetString(data)); 76             } 77             else if (radioButton_UTF8.Checked) 78             { 79                 AddContent(new UTF8Encoding().GetString(data)); 80             } 81             else if (radioButton_Unicode.Checked) 82             { 83                 AddContent(new UnicodeEncoding().GetString(data)); 84             } 85             else 86             { 87                 StringBuilder sb = new StringBuilder(); 88                 for (int i = 0; i < data.Length; i++) 89                 { 90                     sb.AppendFormat("{0:x2}" + " ", data[i]); 91                 } 92                 AddContent(sb.ToString().ToUpper()); 93             } 94         } 95  96         /// <summary> 97         /// 接收端对话框显示消息 98         /// </summary> 99         /// <param name="content"></param>100         private void AddContent(string content)101         {102             BeginInvoke(new MethodInvoker(delegate103             {              
104                     textBox_Receive.AppendText(content);              
105             }));106         }107 108         /// <summary>109         /// 串口开关110         /// </summary>111         /// <param name="sender"></param>112         /// <param name="e"></param>113         private void button_Switch_Click(object sender, EventArgs e)114         {115             if (comboBox_Port.Items.Count <= 0)116             {117                 MessageBox.Show("未发现可用串口，请检查硬件设备");118                 return;119             }120 121             if (ComDevice.IsOpen == false)122             {123                 //设置串口相关属性124                 ComDevice.PortName = comboBox_Port.SelectedItem.ToString();125                 ComDevice.BaudRate = Convert.ToInt32(comboBox_BaudRate.SelectedItem.ToString());126                 ComDevice.Parity = (Parity)Convert.ToInt32(comboBox_CheckBits.SelectedIndex.ToString());127                 ComDevice.DataBits = Convert.ToInt32(comboBox_DataBits.SelectedItem.ToString());128                 ComDevice.StopBits = (StopBits)Convert.ToInt32(comboBox_StopBits.SelectedItem.ToString());129                 try130                 {131                     //开启串口132                     ComDevice.Open();133                     button_Send.Enabled = true;134                 }135                 catch (Exception ex)136                 {137                     MessageBox.Show(ex.Message, "未能成功开启串口", MessageBoxButtons.OK, MessageBoxIcon.Error);138                     return;139                 }140                 button_Switch.Text = "关闭";141                 pictureBox_Status.BackgroundImage = Properties.Resources.green;142             }143             else144             {145                 try146                 {147                     //关闭串口148                     ComDevice.Close();149                     button_Send.Enabled = false;150                 }151                 catch (Exception ex)152                 {153                     MessageBox.Show(ex.Message, "串口关闭错误", MessageBoxButtons.OK, MessageBoxIcon.Error);154                 }155                 button_Switch.Text = "开启";156                 pictureBox_Status.BackgroundImage = Properties.Resources.red;157             }158 159             comboBox_Port.Enabled = !ComDevice.IsOpen;160             comboBox_BaudRate.Enabled = !ComDevice.IsOpen;161             comboBox_DataBits.Enabled = !ComDevice.IsOpen;162             comboBox_StopBits.Enabled = !ComDevice.IsOpen;163             comboBox_CheckBits.Enabled = !ComDevice.IsOpen;164         }165 166       167         /// <summary>168         /// 将消息编码并发送169         /// </summary>170         /// <param name="sender"></param>171         /// <param name="e"></param>172         private void button_Send_Click(object sender, EventArgs e)173         {174             if (textBox_Receive.Text.Length > 0)175             {176                 textBox_Receive.AppendText("\n");177             }178 179             byte[] sendData = null;180 181             if (radioButton_Hex.Checked)182             {183                 sendData = strToHexByte(textBox_Send.Text.Trim());184             }185             else if (radioButton_ASCII.Checked)186             {187                 sendData = Encoding.ASCII.GetBytes(textBox_Send.Text.Trim());188             }189             else if (radioButton_UTF8.Checked)190             {191                 sendData = Encoding.UTF8.GetBytes(textBox_Send.Text.Trim());192             }193             else if (radioButton_Unicode.Checked)194             {195                 sendData = Encoding.Unicode.GetBytes(textBox_Send.Text.Trim());196             }197             else198             {199                 sendData = strToHexByte(textBox_Send.Text.Trim());200             }201 202             SendData(sendData);203         }204 205         /// <summary>206         /// 此函数将编码后的消息传递给串口207         /// </summary>208         /// <param name="data"></param>209         /// <returns></returns>210         public bool SendData(byte[] data)211         {212             if (ComDevice.IsOpen)213             {214                 try215                 {216                     //将消息传递给串口217                     ComDevice.Write(data, 0, data.Length);218                     return true;219                 }220                 catch (Exception ex)221                 {222                     MessageBox.Show(ex.Message, "发送失败", MessageBoxButtons.OK, MessageBoxIcon.Error);223                 }224             }225             else226             {227                 MessageBox.Show("串口未开启", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error);228             }229             return false;230         }231 232         /// <summary>233         /// 16进制编码234         /// </summary>235         /// <param name="hexString"></param>236         /// <returns></returns>237         private byte[] strToHexByte(string hexString)238         {239             hexString = hexString.Replace(" ", "");240             if ((hexString.Length % 2) != 0) hexString += " ";241             byte[] returnBytes = new byte[hexString.Length / 2];242             for (int i = 0; i < returnBytes.Length; i++)243                 returnBytes[i] = Convert.ToByte(hexString.Substring(i * 2, 2).Replace(" ", ""), 16);244             return returnBytes;245         }246 247         //以下两个指令是结合一款继电器而设计的248         private void button_On_Click(object sender, EventArgs e)249         {250             textBox_Send.Text = "005A540001010000B0";251         }252 253         private void button_Off_Click(object sender, EventArgs e)254         {255             textBox_Send.Text = "005A540002010000B1";256         }257     }258 }

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