上位机和单片机通信用16进制比较多，下面是16进制通信的例子，数据发送用Write，数据接收用ReadByte。

Imports System.IO.Ports '使用SerialPort所引用的命名空间
Public Class Form1
Dim fx() As Byte '待发送数据数组
Dim Rc() As Byte '接收数据数组
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
If Button1.Text = "打开串口" Then
SerialPort1.PortName = "COM1"
SerialPort1.Open() '串口打开与关闭 Button1.Text = "关闭串口"
Button2.Enabled = True
Timer1.Enabled = True
Else
If SerialPort1.IsOpen Then SerialPort1.Close()
Button1.Text = "打开串口"
Timer1.Enabled = False
Button2.Enabled = False
End If
End Sub
'待发送数据处理与发送
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim i As Integer
Dim n As Integer
Dim Cmd As String = TextBox1.Text
n = Len(Cmd) \ 2
ReDim fx(n)
For i = 1 To n
fx(i) = CByte("&H" & Mid(Cmd, 2 * i - 1, 2))
Next
SerialPort1.Write(fx, 1, n) '发送数组fx第1到n数据
End Sub
'数据定时接收与显示
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
Dim StrRc As String
Dim i As Integer
Dim n As Integer
n = SerialPort1.BytesToRead '读缓冲区数据量，有数据则接收 If n > 0 Then
ReDim Rc(n)
StrRc = ""
For i = 1 To n
Rc(i) = SerialPort1.ReadByte
StrRc += CStr(Hex(Rc(i))) & " " '数据转为16进制显示 Next
TextBox2.Text = StrRc
End If
End Sub
End Class。