' Eine Instance von SerialPort erstellen
        ' Im Normalfall ist das COM1:
        Me.myComPort = New IO.Ports.SerialPort("COM9")
 
        ' Die folgenden vier Einstellungen müssen denen der 
        ' Gegenstelle entsprechen
        Me.myComPort.BaudRate = 9600
        Me.myComPort.DataBits = 8
        Me.myComPort.StopBits = IO.Ports.StopBits.Two
        Me.myComPort.Parity = IO.Ports.Parity.None
        Me.myComPort.RtsEnable = False
        Me.myComPort.DtrEnable = False

    Private Sub Send(ByVal command As String)
        Me.myComPort.Write(command))
     End Sub

Dim ba As New BitArray(7)
Dim startbit, stoppbit As Boolean
ba(0) = startbit '?
ba(1) = startbit
'Kommando_Teil (Hexadecimalwert) in Bitmuster wandeln und
'dieses Muster auf Position 2-6 des Array zuweisen
ba(7) = stoppbit '?

Me.myComPort.Write(chr(43) & chr(97) & chr(00) & chr(00) & chr(01))

'Test ohne Gerät! Nur durch die Verbindung von RD+TD (9polig = Pin2 mit Pin3)
Imports System.IO.Ports
 
Public Class Form1
    Dim Tb1 As New TextBox With {.Text = "4387000001", .Dock = DockStyle.Top, _
      .Parent = Me}
    Dim Tb2 As New TextBox With {.Dock = DockStyle.Bottom, .Parent = Me}
    Dim WithEvents Btn As New Button With {.Text = "Senden", .Dock = _
      DockStyle.Bottom, .Parent = Me}
    'PortName einsetzen und Abweichung von der Standardeinstellung angeben
    Dim WithEvents myComPort As New SerialPort("COM9") With {.StopBits = _
      StopBits.Two}
 
    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) _
      Handles MyBase.Load
        myComPort.Open()
    End Sub
 
    Private Sub Btn_Click(sender As Object, e As EventArgs) Handles Btn.Click
        If Tb1.Text.Count = 10 Then ' 5 Hex-Zeichen-Befehle!
            WriteHexString(Tb1.Text)
        End If
    End Sub
 
    Private Sub WriteHexString(txt As String)
        Dim b(4) As Byte
        Dim nr As Int32
        For i As Int32 = 0 To txt.Length - 1 Step 2
            b(nr) = Convert.ToByte(txt.Substring(i, 2), 16)
            nr += 1
        Next
        myComPort.Write(b, 0, b.Count)
    End Sub
 
    Private Sub myComPort_DataReceived(sender As Object, e As _
      SerialDataReceivedEventArgs) Handles myComPort.DataReceived
        Me.Invoke(Sub()
                      Dim txt As String = ""
                      Do While myComPort.BytesToRead > 0
                          txt &= "  " & myComPort.ReadByte
                      Loop
                      Tb2.Text = txt ' Bytes in Tb2 ausgeben
                  End Sub)
    End Sub
End Class

Me.myComPort.Encoding = System.Text.Encoding.Default  'Wichtig, da Standard nur 
' Ascii 
Me.myComPort.Write(chr(67) & chr(151) & chr(00) & chr(00) & chr(01))
'Me.myComPort.Write(chr(&h43) & chr(&H97) & chr(00) & chr(00) & chr(01))

Dim data() As Byte = {67, 151, 0, 0, 01}
Me.myComPort.Write(data, 0, 5)
'Kein Encoding erforderlich

    Function YaesuToDec(ByVal PortReceived As Integer) As String
 
        Dim Bit1 As Integer
        Dim Bit2 As Integer
 
        Bit1 = Int(PortReceived / 16)
        Bit2 = PortReceived - (Bit1 * 16)
 
            YaesuToDec = Bit1 & Bit2
 
    End Function