VB.NET串口通信例子--我的回忆录
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这是我3年前的一个例子，最近翻出来回忆一下。 串口是计算机上一种非常通用设备通信的协议。大多数计算机包含两个基于RS232的串口，现在配电脑好像只有一个。串口同时也是仪器仪表设备通用的通信协议；很多GPIB兼容的设备也带有RS-232口。同时，串口通信协议也可以用于获取远程采集设备的数据。串口通信在工控领域用途很广。 典型地，串口用于ASCII码字符的传输。通信使用3根线完成：（1）地线，（2）发送，（3）接收。由于串口通信是异步的，端口能够在一根线上发送数据同时在另一根线上接收数据。其他线用于握手，但是不是必须的。串口通信最重要的参数是波特率、数据位、停止位和奇偶校验。对于两个进行通行的端口，这些参数必须匹配： 串口通信还有一个参数是单工、半双工和双工。 如果在通信过程的任意时刻，信息只能由一方A传到另一方B，则称为单工。 如果在任意时刻，信息既可由A传到B，又能由B传A，但只能由一个方向上的传输存在，称为半双工传输。 如果在任意时刻，线路上存在A到B和B到A的双向信号传输，则称为全双工。 电话线就是二线全双工信道。 由于采用了回波抵消技术，双向的传输信号不致混淆不清。双工信道有时也将收、发信道分开，采用分离的线路或频带传输相反方向的信号，如回线传输。 在调试时可以用串口助手和windows的超级终端，不要带电插拔串口，容易烧毁。 在VB.NET中提供了IO.Ports类，是我们的编程变得很简单，下面是我的例子： Form1.vb ?Imports System.IO.Ports
Public Class Form1
Dim WithEvents RS232 As SerialPort
Delegate Sub SetTextCallback(ByVal InputString As String) '声明一个代理
Private Sub Form1_Load(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles MyBase.Load
For Each sp As String In SerialPort.GetPortNames()
cmbCom.Items.Add(sp)
Next
cmbCom.Sorted = True
cmbCom.SelectedIndex = 0
End Sub
Private Sub btnStart_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles btnStart.Click
Dim mBaudRate As Integer
Dim mParity As IO.Ports.Parity
Dim mDataBit As Integer
Dim mStopBit As IO.Ports.StopBits
Dim mPortName As String
mPortName = cmbCom.SelectedItem.ToString
mBaudRate = 9600
mParity = Parity.None
mDataBit = 8
mStopBit = StopBits.One
RS232 = New IO.Ports.SerialPort(mPortName,mBaudRate,mParity,mDataBit,mStopBit)
If Not RS232.IsOpen Then
RS232.Open()
btnSend.Enabled = True
RS232.ReceivedBytesThreshold = 1 '设置引发事件的门限值
Else
MsgBox("通讯端口打开错误！",MsgBoxStyle.Critical)
End If
End Sub
Private Sub RS232_DataReceived(ByVal sender As Object,ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles RS232.DataReceived
Dim InByte() As Byte,ReadCount As Integer,strRead As String
If RS232.BytesToRead <= 0 Then Exit Sub
ReDim InByte(RS232.BytesToRead - 1)
ReadCount = RS232.Read(InByte,RS232.BytesToRead)
strRead = ""
If ReadCount = 0 Then
Exit Sub
Else
For Each bData As Byte In InByte
strRead += bData.ToString & vbCrLf '若有数据则加到接收文本框
DisplayText(strRead)
Next
End If
End Sub
'*************************************************
'代理子程序
'处理上述通信端口的接收事件
'由于欲将数据显示到接收文本框中，因此必须检查
'是否由另外得Thread所调用的，若是，则必须先
'建立代理对象
'Invoke用于在拥有控件基础窗口控制代码的线程上
'运行代理
'*************************************************
Private Sub DisplayText(ByVal comData As String)
'如果调用txtReceive的另外的线程，返回true
If Me.txtReceive.InvokeRequired Then
'利用代理类型建立对象，并指定代理的函数
Dim d As New SetTextCallback(AddressOf DisplayText)
Me.Invoke(d,New Object() {comData}) '以指定的自变量列表调用函数
Else '相同的线程
'showstring(comData) '将收到的数据填入接收文本框中
Me.txtReceive.Text += comData
End If
End Sub
Private Sub btnClose_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles btnClose.Click
If RS232 Is Nothing OrElse Not RS232.IsOpen Then '尚未打开
MsgBox("通讯端口尚未打开",MsgBoxStyle.Critical Or MsgBoxStyle.OkCancel)
Else
RS232.Close()
btnStart.Enabled = False
btnClose.Enabled = False
RS232 = Nothing
End If
End Sub
Private Sub btnEnd_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles btnEnd.Click
If Not RS232 Is Nothing Then
If RS232.IsOpen Then RS232.Close()
End If
End
End Sub
Private Sub btnSend_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles btnSend.Click
Dim bDataOut(0) As Byte
Try
bDataOut(0) = CType(Me.txtSend.Text,Byte) '将类型转换为字节
RS232.Write(bDataOut,1)
Catch ex As Exception
MessageBox.Show("输入数值错误：" + ex.ToString,"错误通知：",MessageBoxButtons.OK,MessageBoxIcon.Exclamation)
End Try
End Sub
Private Sub cmbCom_KeyPress(ByVal sender As Object,ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles cmbCom.KeyPress
e.KeyChar = ChrW(0) '禁止用户在其中输入任何文字
End Sub
Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click
Me.Hide()
Form2.Show()
End Sub
End ClassForm2.vb
?'**************************************************************
'时间：2008-11-08
'作者：lincyang
'实际应用中，串行通信的数据可能一次发送大量的数据，
'发送之前就必须将数据先编码，
'将其编成我们需要的字节数组数据，
'才能将这些数据以字节的方式发送出去
'目前操作系统使用的字符数据是Unicode：所有的字符均使用
'两个字节来表示一个字符
'**************************************************************
Imports System.IO.Ports
Imports System.Text
Public Class Form2
Dim RS232 As SerialPort
Private Sub Form2_Load(ByVal sender As System.Object,mStopBit)
If Not RS232.IsOpen Then
RS232.Open()
btnSend.Enabled = True
Timer1.Interval = 100
Timer1.Enabled = True
Else
MsgBox("通讯端口打开错误！",MsgBoxStyle.Critical)
End If
End Sub
Private Sub Timer1_Tick(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Timer1.Tick
Dim InByte() As Byte,ReadCount As Integer
If RS232.BytesToRead <= 0 Then Exit Sub
ReDim InByte(RS232.BytesToRead - 1)
ReadCount = RS232.Read(InByte,RS232.BytesToRead)
If ReadCount = 0 Then
Exit Sub
Else
For Each bData As Byte In InByte
Me.txtReceive.Text += bData.ToString & vbCrLf '若有数据则加到接收文本框
Next
End If
End Sub
Private Sub btnClose_Click(ByVal sender As System.Object,MsgBoxStyle.Critical Or MsgBoxStyle.OkCancel)
Else
RS232.Close()
btnStart.Enabled = False
btnClose.Enabled = False
Timer1.Enabled = False
RS232 = Nothing
End If
End Sub
Private Sub btnSend_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles btnSend.Click
Dim bDataOut() As Byte,Buf As String
Dim iSentCount As Integer
Dim Encode1 As Encoding = Encoding.ASCII '声明编码对象，使用ASCII
Try
Buf = txtSend.Text.Trim()
bDataOut = Encode1.GetBytes(Buf) '将字符串转换为字节数组
iSentCount = bDataOut.GetLength(0) '发送总字节数
'显示出总字节数
lblSentCount.Text = "总传输量：" & iSentCount.ToString & "字节"
RS232.Write(bDataOut,iSentCount)
Catch ex As Exception
MessageBox.Show("输入数值错误：" + ex.ToString,"错误通知",MessageBoxIcon.Exclamation)
End Try
End Sub
Private Sub btnEnd_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles btnEnd.Click
If Not RS232 Is Nothing Then
If RS232.IsOpen Then RS232.Close()
End If
End
End Sub
Private Sub cmbCom_KeyPress(ByVal sender As Object,ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles cmbCom.KeyPress
e.KeyChar = ChrW(0) '禁止用户在其中输入任何文字
End Sub
End Class
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