VB程序员博客
各位好，现在正在做一程序，vb和西门子plc，s7-300通讯的项目。上位机接受数据成功了 ，然后不知道发送数据应该如何写。协议是：上位机接受40字节。发送25字节。第一位起始位255，
具体代码如下
Private Sub MSComPLC_OnComm()
Dim buffer As Variant
Dim InString(0 To PLCRxCount - 1) As Byte
Dim i As Integer
Dim SupplyNum As Integer
Dim CheckInt As Integer
Dim CheckByte As Byte
Dim errTemp As Integer
' On Error GoTo Err
Select Case MSComPLC.CommEvent
'==================================================================
' 接收数据
'==================================================================
Case comEvReceive
MSComPLC.InputLen = 0
buffer = MSComPLC.Input
For i = 0 To PLCRxCount - 1
InString(i) = buffer(i)
Next i
'==================================================================
' 检查数据完整性/ 计算校验和
'==================================================================
CheckInt = 0
For i = 0 To PLCRxCount - 2
CheckInt = CheckInt + InString(i)
Next i
CheckByte = CheckInt Mod 256
'==================================================================
' 更新上纸台信息，并设置Refresh标志以便更新显示
'==================================================================
If (InString(0) = 255) And (CheckByte = InString(PLCRxCount - 1)) Then
'上纸台可以接受命令
If InString(1) And 1 Then
Supply(1).RightReady = True
Else
Supply(1).RightReady = False
End If
End Select
Exit Sub
Err:
LblError.Caption = "MsComPLC:" & Err.Description
Resume Next
End Sub
Private Sub TmPLC_Timer()
Dim OutString(0 To PLCTxCount - 1) As Byte
Dim CheckInt As Integer
Dim j As Integer
Dim i As Integer
Dim AndBit As Integer
' 特征字节
OutString(0) = 255
'自动发纸命令
AndBit = 1
For i = 1 To 3
If Supply(i).RightTransmit Then
OutString(1) = OutString(1) + AndBit
ElseIf Supply(i).LeftTransmit Then
OutString(1) = OutString(1) + AndBit * 2
End If
AndBit = AndBit * 4
Next i
AndBit = 1
For i = 4 To SUPPLY_NUMBER
If Supply(i).RightTransmit Then
OutString(2) = OutString(2) + AndBit
ElseIf Supply(i).LeftTransmit Then
OutString(2) = OutString(2) + AndBit * 2
End If
AndBit = AndBit * 4
Next i
' 急停与复位
AndBit = 1
For i = 1 To SUPPLY_NUMBER
If Supply(i).Stop Then OutString(3) = OutString(3) + AndBit
AndBit = AndBit * 2
Next i
'手动命令
For i = 1 To SUPPLY_NUMBER
If Supply(i).mode = MANUAL_MODE Then
OutString(3 + i) = Supply(i).Order
Else
OutString(3 + i) = 0
End If
Next i
'自动模式
AndBit = 1
For i = 1 To SUPPLY_NUMBER
If Supply(i).mode = AUTO Then OutString(10) = OutString(10) + AndBit
AndBit = AndBit * 2
Next i
'手动模式
AndBit = 1
For i = 1 To SUPPLY_NUMBER
If Supply(i).mode = MANUAL_MODE Then OutString(11) = OutString(11) + AndBit
AndBit = AndBit * 2
Next i
'故障模式
AndBit = 1
For i = 1 To SUPPLY_NUMBER
If Supply(i).mode = ERROR_MODE Then OutString(12) = OutString(12) + AndBit
AndBit = AndBit * 2
Next i
'故障恢复信号
AndBit = 1
For i = 1 To SUPPLY_NUMBER
If Supply(i).Reset Then OutString(13) = OutString(13) + AndBit
AndBit = AndBit * 2
Next i
' 校验字节，由计算确定
CheckInt = 0
For j = 0 To PLCTxCount - 2
CheckInt = CheckInt + OutString(j)
Next j
OutString(PLCTxCount - 1) = CheckInt Mod 256
Labout.Caption = ""
For i = 0 To PLCTxCount - 1
Labout.Caption = Labout.Caption + " " + CStr(OutString(i))
Next i
'==========================================================================
' 发送通讯字节内容
'==========================================================================
MSComPLC.InBufferCount = 0
MSComPLC.Output = OutString
End Sub
但是发送就是不通，是不是在timer里面写发送的代码啊？还请各位指教一下
谢谢,忘记timer设置了，总感觉哪里少点东西就是不知道如何写，多谢提醒。