Modbus通信VB源程序.doc

用Visual Basic编写的Modbus 通信源程序以下是PC机与PLC进行Modbus通信的VB源程序，提供给大家做个参考。1） 模块文件：modCRC，其中包含了CRC校验的函数。data 待校验的数组名称no 数组中元素个数btLoCRC 算出的CRC高字节btHiCRC 算出的CRC低字节Public Function CalCRC16Fast(data() As Byte, no As Integer, btLoCRC As Byte, btHiCRC As Byte) As String Dim CL As Byte, CH As Byte 多项式码&HA001 Dim SaveHi As Byte, SaveLo As Byte Dim i As Integer Dim Flag As Integer btHiCRC = &HFF btLoCRC = &HFF CL = &H1 CH = &HA0 For i = 0 To (no - 1) btHiCRC = btHiCRC Xor data(i) 每一个数据与CRC寄存器进行异或 For Flag = 0 To 7 SaveHi = btLoCRC SaveLo = btHiCRC btLoCRC = btLoCRC 2 高位右移一位 btHiCRC = btHiCRC 2 低位右移一位 If (SaveHi And &H1) = &H1) Then 如果高位字节最后一位为1 btHiCRC = btHiCRC Or &H80 则低位字节右移后前面补1 End If 否则自动补0 If (SaveLo And &H1) = &H1) Then 如果LSB为1，则与多项式码进行异或 btLoCRC = btLoCRC Xor CH btHiCRC = btHiCRC Xor CL End If Next Flag Next i Dim ReturnData(1) As Byte ReturnData(0) = btHiCRC CRC高位 ReturnData(1) = btLoCRC CRC低位 CalCRC16Fast = ReturnData End FunctionPublic Function CalCRC16Tbl(data() As Byte, no As Integer, btLoCRC As Byte, btHiCRC As Byte) As String Dim btLoCRC As Byte Dim btHiCRC As Byte btLoCRC = &HFF btHiCRC = &HFF Dim i As Integer Dim iIndex As Long For i = 0 To (no - 1) iIndex = btHiCRC Xor data(i) btHiCRC = btLoCRC Xor GetCRCLo(iIndex) 低位处理 btLoCRC = GetCRCHi(iIndex) 高位处理 Next i Dim ReturnData(1) As Byte ReturnData(0) = btHiCRC CRC高位 ReturnData(1) = btLoCRC CRC低位 CalCRC16Tbl = ReturnDataEnd FunctionCRC低位字节值表Function GetCRCLo(Ind As Long) As Byte GetCRCLo = Choose(Ind + 1, _ &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _ &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, _ &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, _ &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, _ &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, _ &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, _ &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, _ &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, _ &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _ &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, _ &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, _ &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, _ &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _ &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, _ &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, _ &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, _ &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _ &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, _ &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, _ &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, _ &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, _ &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, _ &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, _ &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40)End FunctionCRC高位字节值表Function GetCRCHi(Ind As Long) As Byte GetCRCHi = Choose(Ind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nd Function2）窗体：FORM1，上面放置的控件如下：Begin VB.Form frmCom Caption = Form1 ClientHeight = 8235 ClientLeft = 3885 ClientTop = 2250 ClientWidth = 6810 LinkTopic = Form1 ScaleHeight = 8235 ScaleWidth = 6810 Begin VB.TextBox txtReceive 注：放置接收上来的IB0数据 Height = 495 Left = 1200 TabIndex = 2 Top = 2280 Width = 1335 End Begin VB.CommandButton Command1 Caption = 读取IB0 Height = 495 Left = 2760 TabIndex = 1 Top = 2280 Width = 1695 End Begin VB.CommandButton cmdSDO Caption = 置位Q1.1 Height = 495 Left = 2160 TabIndex = 0 Top = 3720 Width = 1575 End Begin MSCommLib.MSComm ComK3 Left = 480 Top = 1080 _ExtentX = 1005 _ExtentY = 1005 _Version = 393216 DTREnable = -1 True EndEnd Form_Load事件，在此主要是实现了打开并初始化串口Private Sub Form_Load() With ComK3 .CommPort = 1 .Settings = 19200,N,8,1 .InputMode = comInputModeBinary 二进制收发 .InBufferSize = 512 .OutBufferSize = 512 If (Not .PortOpen) Then .PortOpen = True End WithEnd Sub Form_UnLoad事件，在此主要是关闭串口Private Sub Form_Unload(Cancel As Integer) If (ComK3.PortOpen) Then ComK3.PortOpen = False End If End Sub “置位Q1.1”按钮单击事件设置Q1.1为1 Private Sub cmdSDO_Click() Dim btSend(8) As Byte btSend(0) = &H1 目标站号 btSend(1) = &H5 功能码 btSend(2) = &H0 Q1.1地址（0009）高字节 btSend(3) = &H9 Q1.1地址（0009）低字节 btSend(4) = &HFF 强制值高字节 btSend(5) = &H0 强制值低字节 Dim crc Dim btCRCHi As Byte, btCRCLo As Byte crc = CalCRC16Fast(btSend, 6, btCRCLo, btCRCHi) btSend(6) = btCRCHi btSend(7) = btCRCLo ComK3.Output = CVar(btSend) End Sub “读取IB0”按钮单击事