Question

Public Class my_class

Dim WithEvents COMPort As New System.IO.Ports.SerialPort

Public Sub FindReader()

    Dim ports As String() = IO.Ports.SerialPort.GetPortNames()
    Dim port As String
    For Each port In ports
        MsgBox(port, MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation, "Serial port detecetd")
    Next port


  If COMPort.IsOpen Then
     COMPort.RtsEnable = False
     COMPort.DtrEnable = False
     COMPort.Close()
     System.Threading.Thread.Sleep(200)
  End If

    COMPort.PortName = "COM1"
    COMPort.BaudRate = 9600
    COMPort.DataBits = 8
    COMPort.Parity = IO.Ports.Parity.None
    COMPort.StopBits = IO.Ports.StopBits.One
    COMPort.Handshake = IO.Ports.Handshake.RequestToSend
    COMPort.ReadTimeout = 2000 
    COMPort.WriteTimeout = -1
    COMPort.NewLine = Chr(13)
    COMPort.ReadBufferSize = 12
    COMPort.ReceivedBytesThreshold = COMPort.ReadBufferSize

  Try
     COMPort.Open()
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try

  If COMPort.IsOpen Then
     COMPort.RtsEnable = True
     COMPort.DtrEnable = True

     'Kick start the serial port so it starts reading data.
     COMPort.BreakState = True
     System.Threading.Thread.Sleep(CInt(11000 / COMPort.BaudRate) + 2)   ' Min. 11 bit delay (startbit, 8 data bits, parity bit, stopbit
     COMPort.BreakState = False

     MsgBox(COMPort.PortName & " opened at " & COMPort.BaudRate.ToString & " baud", MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation, "FindReader()")

  End If
 End Sub

运行时，它显示一个COM端口“COM1”。我确信连接到它的设备是标准的8，n，1并使用9,600波特。

例外是“进入端口'COM1'被拒绝”。有什么想法吗？

Answer 1

拒绝访问可能意味着已经被其他应用程序打开了。

您是否可以使用其他已知良好的应用程序打开端口，例如Hyperterminal？

[因为如果你不是，那么问题不在你的代码上。]

或者，我认为Portmon可以用来确定哪个其他进程（如果有的话）已经打开了端口。

为什么这段代码不能打开串口？

1 个答案: