'加载本机所有的com

    Sub GetSerialPortNames()
        For Each sp As String In My.Computer.Ports.SerialPortNames
            ComboBox1.Items.Add(sp)
        Next
        If ComboBox1.Items.Count > 0 Then
            ComboBox1.SelectedIndex = 0
        End If
    End Sub

'打开串口

       If SerialPort1.IsOpen Then
            SerialPort1.Close()
        End If

        Try
            With SerialPort1
                .PortName = ComboBox1.Text
                .BaudRate = 9600

                .Parity = IO.Ports.Parity.None '奇偶校验
                .DataBits = 8 '数据位
                .StopBits = IO.Ports.StopBits.One '停止位
            End With
            '打开
            SerialPort1.Open()

            Label1.Text = "Connected"
            Button1.Enabled = False
            Button2.Enabled = True
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try

'关闭串口

SerialPort1.close()

'发送数据

一般的数据

dim data as string=textbox1.text

SerialPort1.write(data)

十六进制字符串

发送十六进制字符串时，我们用数组保存要发送的信息

比如发送数据为：FF 01 00 00 01 00 00 FE

        Try
            Dim data(8) As Byte
            data(0) = &HFF
            data(1) = &H1
            data(2) = &H0
            data(3) = &H0
            data(4) = &H1
            data(5) = &H0
            data(6) = &H0
            data(7) = &HFE
            SerialPort1.DiscardOutBuffer()
            SerialPort1.Write(data, 0, 8)
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try

接收数据

SerialPort有个DataReceived事件，我们可以在里面写接受数据代码

接受字符串：SerialPort.ReadExisting

接受流数据：

dim byteToRead as int16=SerialPort.bytestoread(读取缓冲区的字节长度)

dim ch(byteToRead) as byte

dim bytesRead as int16=0

bytesRead=SerialPort.read(ch,0,bytetoread)

for i as int16=0 to bytesRead-1

  indata=indata & DecToHex(ch(i))

next

indata 就是读取到的数据

自定义函数：DecToHex （返回十六进制字符）

    Public Function DecToHex(ByVal DecNumber As Byte) As String '转换成十六进制字符串
        If DecNumber <= 15 Then
            DecToHex = "  0" & Hex(DecNumber)
        Else : DecToHex = "  " & Hex(DecNumber)
        End If
    End Function