'在窗體的Load事件中加入下列代碼對(duì)串口進(jìn)行初始化:
Private Sub Form_Load()
  MSComm1.CommPort = 1                  ' 設(shè)置通信端口號(hào)為COM1
  MSComm1.InputMode = 1                 ' 接收二進(jìn)制型數(shù)據(jù)
  MSComm1.RThreshold = 1                ' 設(shè)置并返回要接收的字符數(shù)
  MSComm1.SThreshold = 1                ' 設(shè)置并返回發(fā)送緩沖區(qū)中允許的最小字符數(shù)
  MSComm1.Settings = "9600,E,7,1"       ' 設(shè)置串口1通信參數(shù)
  MSComm1.PortOpen = True               ' 打開(kāi)通信端口1
  Timer1.Enabled = False
End Sub
'向PLC發(fā)送指令：02 30 31 30 30 30 32 30 03 35 36，功能是從D0開(kāi)始讀取32個(gè)字節(jié)數(shù)據(jù)
Private Sub Cmdsend_Click()
  MSComm1.Output = Chr(&H2) & Chr(&H30) & Chr(&H31) & Chr(&H30) & Chr(&H30) & Chr(&H30) & Chr(&H32) & Chr(&H30) & Chr(&H3) & Chr(&H35) & Chr(&H38)
  Timer1.Enabled = True
End Sub
'獲得各輸入端口狀態(tài)
Private Sub Timer1_Timer()
  Dim Inbyte() As Byte
  Dim buffer As String
  ReDim Inbyte(100)
  Inbyte = MSComm1.Input                         '返回的數(shù)據(jù)串
  For i = LBound(Inbyte) To UBound(Inbyte)
     buffer = buffer + Hex(Inbyte(i)) + Chr(32)
  Next i
  'Text1.Text = buffer                            '顯示返回的數(shù)據(jù)串，需自己添加TextBox
  If Hex(Inbyte(2)) = "31" Then                  '31表示觸點(diǎn)閉合
    Shape1(0).FillColor = QBColor(12)
  Else                                           '30表示觸點(diǎn)斷開(kāi)
    Shape1(0).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(6)) = "31" Then
    Shape1(1).FillColor = QBColor(12)
  Else
    Shape1(1).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(10)) = "31" Then
    Shape1(2).FillColor = QBColor(12)
  Else
    Shape1(2).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(14)) = "31" Then
    Shape1(3).FillColor = QBColor(12)
  Else
    Shape1(3).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(18)) = "31" Then
    Shape1(4).FillColor = QBColor(12)
  Else
    Shape1(4).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(22)) = "31" Then
    Shape1(5).FillColor = QBColor(12)
  Else
    Shape1(5).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(26)) = "31" Then
    Shape1(6).FillColor = QBColor(12)
  Else
    Shape1(6).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(30)) = "31" Then
    Shape1(7).FillColor = QBColor(12)
  Else
    Shape1(7).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(34)) = "31" Then
    Shape1(8).FillColor = QBColor(12)
  Else
    Shape1(8).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(38)) = "31" Then
    Shape1(9).FillColor = QBColor(12)
  Else
    Shape1(9).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(42)) = "31" Then
    Shape1(10).FillColor = QBColor(12)
  Else
    Shape1(10).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(46)) = "31" Then
    Shape1(11).FillColor = QBColor(12)
  Else
    Shape1(11).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(50)) = "31" Then
    Shape1(12).FillColor = QBColor(12)
  Else
    Shape1(12).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(54)) = "31" Then
    Shape1(13).FillColor = QBColor(12)
  Else
    Shape1(13).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(58)) = "31" Then
    Shape1(14).FillColor = QBColor(12)
  Else
    Shape1(14).FillColor = QBColor(10)
  End If
  If Hex(Inbyte(62)) = "31" Then
    Shape1(15).FillColor = QBColor(12)
  Else
    Shape1(15).FillColor = QBColor(10)
  End If
  Timer1.Enabled = False
End Sub
'當(dāng)退出程序時(shí)，關(guān)閉串行口
Private Sub Cmdquit_Click()
  MSComm1.PortOpen = False           '關(guān)閉串口
  Unload Me
End Sub
// 讀不到PLC 輸入點(diǎn)，下標(biāo)越界，望高手指點(diǎn)修改

為什么不用專用協(xié)議做呢？格式一或格式四都可。