水电之家讯：一直看到有些朋友在问ModBus主从站的通讯问题，今天抽空儿给大家发几篇。



事先申明，我是调用的主从站库，库本身并不是我编写的，我没有那么大的能耐。



另外，上位机是用VB编写，VB本身不是很熟，如果有什么错误，请大家海谅。



最后，这仅仅只是一个测试程序，如果各位想用到商业方面，还需要各位自己去完善。



说明：plc从站，PC作主站，用ModBus协议进行通讯。PC机读取PLCVW区的数据；PC机还读取PLC内部I或者O地址的状态。



///////////////////////////////////////



以下是PLC程序实现，方便贴出，已转换为STL



TITLE=程序注释



Network 1 // 网络标题



// 在第一个循环周期内初始化Modbus从站协议



LD SM0.1



CALL SBR3, 1, 12, 9600, 0, 0, 128, 32, 1000, &VB0, M10.1, MB11



Network 2



// 在每个循环周期内执行Modbus 从站协议



LD SM0.0



CALL SBR1, M10.2, MB12



Network 3



LD SM0.0



MOVW AIW0, VW100



/I +54, VW100



MOVW AIW2, VW102



/I +54, VW102



MOVW AIW4, VW104



/I +54, VW104



MOVW AIW6, VW106



/I +54, VW106



Network 4



LD SM0.0



= Q0.0



Network 5



LD I0.0



= Q0.1



Network 6



LD I0.1



= Q0.2



///////////////////////////////////



以下是VB源码



Option Explicit



Private Declare Function GetTickCount Lib "kernel32" () As Long



Dim x1



Dim p11, p12, p13, p14, p15, p16, p17, p18



Function CRC16(data() As Byte) As String



Dim CRC16Lo As Byte, CRC16Hi As Byte 'CRC寄存器



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



CRC16Lo = &HFF



CRC16Hi = &HFF



CL = &H1



CH = &HA0



For i = 0 To UBound(data)



CRC16Lo = CRC16Lo Xor data(i) '每一个数据与CRC寄存器进行异或



For Flag = 0 To 7



SaveHi = CRC16Hi



SaveLo = CRC16Lo



CRC16Hi = CRC16Hi \ 2 '高位右移一位



CRC16Lo = CRC16Lo \ 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



CRC16Lo = CRC16Lo 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



CRC16Hi = CRC16Hi Xor CH



CRC16Lo = CRC16Lo Xor CL



End If



Next Flag



Next i



Dim ReturnData(1) As Byte



ReturnData(0) = CRC16Hi 'CRC高位



ReturnData(1) = CRC16Lo 'CRC低位



CRC16 = ReturnData



End Function



Private Sub about_Click()



frmabout.Show



End Sub



Private Sub Form_Load() '初始化



Timer1.EnabLED = False '定时器1无效



Timer1.Interval = 1000 '定时器1时间为1S



Timer2.Enabled = True '定时器2有效



Timer2.Interval = 1000 '定时器2时间为1S



Text1.Text = ""



Text2.Text = ""



Text3.Text = ""



Text4.Text = ""



Text5.Text = ""



Text6.Text = ""



Text8.Text = ""



Text10.Text = ""



MSComm1.CommPort = 1 '设定端口号



MSComm1.Settings = "9600,n,8,1" '设定通讯波特率



MSComm1.InBufferSize = 1024 '接收缓冲器大小



MSComm1.OutBufferSize = 1024 '输出缓冲器大小



MSComm1.InputMode = comInputModeBinary '以二进制传输



MSComm1.RThreshold = 1 '



MSComm1.SThreshold = 0



MSComm1.InputLen = 0 '读取接收缓冲器所有字符



MSComm1.OutBufferCount = 0 '清空发送缓冲区



MSComm1.InBufferCount = 0 '清空接收缓冲区



If MSComm1.PortOpen = False Then



Command3.Caption = "打开串口"



Else



Command3.Caption = "关闭串口"



End If



End Sub



Private Sub Command1_Click()



Timer1.Enabled = True



End Sub



Private Sub Command2_Click() '退出程序，定时器1无效



Timer1.Enabled = False



Cls



Unload Me



End Sub



Private Sub Command3_Click()



On Error Resume Next



If MSComm1.PortOpen = False Then



MSComm1.PortOpen = True



Else



MSComm1.PortOpen = False



End If



If MSComm1.PortOpen Then '打开关闭按钮显示文字



Command3.Caption = "关闭串口"



Else



Command3.Caption = "打开串口"



End If



If Err Then '打开串口失败，则显示出错信息



MsgBox Error$, 48, "错误信息"



Exit Sub



End If



End Sub



Private Sub Timer1_Timer() '读V存储区数据



Dim CRC() As Byte



Dim FGetData As String



Dim aa() As Byte



Dim s As String

Dim str As String



Dim i As Integer



Dim bb, cc As String



ReDim aa(5) As Byte '定义动态数组



aa(0) = &HC



aa(1) = &H3



aa(2) = &H0



aa(3) = &H32



aa(4) = &H0



aa(5) = &H4



CRC = CRC16(aa)



str = CRC



s = ""



For i = 1 To LenB(str)



s = s + Hex(AscB(MidB(str, i, 1)))



Next i



bb = Right(s, 2)



cc = Mid(s, 1, 2)



If Len(s) < 4 Then



cc = Mid(s, 1, 1)



End If



ReDim Preserve aa(0 To 7) As Byte



aa(6) = Val("&H" & bb)



aa(7) = Val("&H" & cc)



MSComm1.OutBufferCount = 0 '清空输出寄存器



MSComm1.Output = aa



FGetData = ReceiveData



Text5.Text = FGetData



p11 = Val("&H" & Mid(FGetData, 7, 4))



p12 = Val("&H" & Mid(FGetData, 11, 4))



p13 = Val("&H" & Mid(FGetData, 15, 4))



p14 = Val("&H" & Mid(FGetData, 19, 4))



End Sub



Private Sub Command4_Click() 'I状态



Dim CRC() As Byte



Dim FGetData As String



Dim aa() As Byte



Dim s As String



Dim str As String



Dim i As Integer



Dim bb, cc As String



ReDim aa(5) As Byte '定义动态数组



aa(0) = &HC



aa(1) = &H2



aa(2) = &H0



aa(3) = &H0



aa(4) = &H0



aa(5) = &H1



CRC = CRC16(aa)



str = CRC



s = ""



For i = 1 To LenB(str)



s = s + Hex(AscB(MidB(str, i, 1)))



Next i



bb = Right(s, 2)



cc = Mid(s, 1, 2)



If Len(s) < 4 Then



cc = Mid(s, 1, 1)



End If



ReDim Preserve aa(0 To 7) As Byte



aa(6) = Val("&H" & bb)



aa(7) = Val("&H" & cc)



MSComm1.OutBufferCount = 0 '清空输出寄存器



MSComm1.Output = aa



FGetData = IReceiveData



p17 = Val("&H" & Mid(FGetData, 7, 2))



p18 = Val("&H" & Mid(FGetData, 9, 2))



End Sub



Private Sub Command5_Click() 'Q状态



Dim CRC() As Byte



Dim FGetData As String



Dim aa() As Byte



Dim s As String



Dim str As String



Dim i As Integer



Dim bb, cc As String



ReDim aa(5) As Byte '定义动态数组



aa(0) = &HC



aa(1) = &H1



aa(2) = &H0



aa(3) = &H0



aa(4) = &H0



aa(5) = &H1



CRC = CRC16(aa)



str = CRC



s = ""



For i = 1 To LenB(str)



s = s + Hex(AscB(MidB(str, i, 1)))



Next i



bb = Right(s, 2)



cc = Mid(s, 1, 2)



If Len(s) < 4 Then



cc = Mid(s, 1, 1)



End If



ReDim Preserve aa(0 To 7) As Byte



aa(6) = Val("&H" & bb)



aa(7) = Val("&H" & cc)



MSComm1.OutBufferCount = 0 '清空输出寄存器



MSComm1.Output = aa



FGetData = QReceiveData



p15 = Val("&H" & Mid(FGetData, 7, 2))



p16 = Val("&H" & Mid(FGetData, 9, 2))



End Sub



Private Function ReceiveData() As String '返回V存储器区数据



Dim FGetData As String



Dim t1 As Long



Dim av As Variant



Dim i As Integer



Dim ReDataLen As Integer



FGetData = ""



t1 = GetTickCount() '取时间，做延时用



Do '循环等待接收数据



DoEvents



If MSComm1.InBufferCount > 0 Then '串口有数据了



ReDataLen = MSComm1.InBufferCount '取数据长度



av = MSComm1.Input '将串口数据取出来



For i = 0 To ReDataLen - 1



FGetData = FGetData & Right("00" & Hex(av(i)), 2)



Next i



End If



If Len(FGetData) >= 6 Then



If Len(FGetData) > Val("&H" & Mid(FGetData, 5, 2)) * 2 + 8 Then



ReceiveData = FGetData



Exit Function



End If



End If



If GetTickCount - t1 > 2000 Then '2秒没收完就不收了



ReceiveData = ""



Exit Function



End If



Loop



End Function



Private Function IReceiveData() As String '反回I状态



Dim FGetData As String



Dim t1 As Long



Dim av As Variant



Dim i As Integer



Dim ReDataLen As Integer



FGetData = ""



t1 = GetTickCount() '取时间，做延时用



Do '循环等待接收数据



DoEvents



If MSComm1.InBufferCount > 0 Then '串口有数据了



ReDataLen = MSComm1.InBufferCount '取数据长度

av = MSComm1.Input '将串口数据取出来



For i = 0 To ReDataLen - 1



FGetData = FGetData & Right("00" & Hex(av(i)), 2)



Next i



End If



If Len(FGetData) >= 6 Then



If Len(FGetData) > Val("&H" & Mid(FGetData, 5, 2)) * 2 + 8 Then



IReceiveData = FGetData



Exit Function



End If



End If



If GetTickCount - t1 > 2000 Then '2秒没收完就不收了



IReceiveData = ""



Exit Function



End If



Loop



End Function



Private Function QReceiveData() As String '反回Q状态



Dim FGetData As String



Dim t1 As Long



Dim av As Variant



Dim i As Integer



Dim ReDataLen As Integer



FGetData = ""



t1 = GetTickCount() '取时间，做延时用



Do '循环等待接收数据



DoEvents



If MSComm1.InBufferCount > 0 Then '串口有数据了



ReDataLen = MSComm1.InBufferCount '取数据长度



av = MSComm1.Input '将串口数据取出来



For i = 0 To ReDataLen - 1



FGetData = FGetData & Right("00" & Hex(av(i)), 2)



Next i



End If



If Len(FGetData) >= 6 Then



If Len(FGetData) > Val("&H" & Mid(FGetData, 5, 2)) * 2 + 8 Then



QReceiveData = FGetData



Exit Function



End If



End If



If GetTickCount - t1 > 2000 Then '2秒没收完就不收了



QReceiveData = ""



Exit Function



End If



Loop



End Function



Private Sub Timer2_Timer()



x1 = x1 + 1



Text10.Text = str(x1)



Text1.Text = str(p11)



Text2.Text = str(p12)



Text3.Text = str(p13)



Text4.Text = str(p14)



Text7.Text = str(p15)



If Text7.Text = 1 Then Text7.BackColor = RGB(255, 0, 255)



If Text7.Text = 0 Then Text7.BackColor = RGB(0, 255, 255)



'Text6.Text = str(p16)



Text9.Text = str(p17)



If Text9.Text = 1 Then Text9.BackColor = RGB(255, 0, 255)



If Text9.Text = 0 Then Text9.BackColor = RGB(0, 255, 255)



'Text8.Text = str(p18)



End Sub



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