Read/Write of OPC Data with OPC Data Control using VB Code
Writing the Code - sample code without comments

Now it's time to write the Visual Basic code for this example. Double click the Exit button on your form. This will bring up the code section for our form.  Important: In the code shown below, you only need to insert the code NOT shown in blue text.  We also have this code available with comments.

Feel free to "cut and paste" the code from here. You may also download our code exactly as it's written for this document and modify it to suit your needs.

Insert the following code for Exit button click event.

Private Sub cmdExit_Click()
   Dim result As Long

   result = OPCData1.Disconnect

   'end program
   End
End Sub

Insert the following code for Multiple Write button click event.

Private Sub cmdMultipleWrite_Click()

   Dim result As Long
   Dim States As Variant
   Dim VarNames(0 To 1) As String
   Dim VarValues(0 To 1) As Variant

   Label1 = ""
   Label2 = ""

   VarNames(0) = "Device1.Group1.Tag1"
   VarNames(1) = "Device1.Group1.Tag2"

   VarValues(0) = txtMultipleWriteValue1.Text
   VarValues(1) = txtMultipleWriteValue2.Text

   result = OPCData1.WriteMultiVariables(VarNames, VarValues, States)

   If result = 0 Then
       Label1 = "Multiple Write Success"
   Else
       Label1 = "Multiple Write Failure"
   End If

End Sub

Type the following code for Multiple Read button click event.

Private Sub cmdMultipleRead_Click()

   Dim result As Long
   Dim States As Variant
   Dim VarValues As Variant
   Dim VarNames(0 To 1) As String

   Label2 = ""

   VarNames(0) = "Device1.Group1.Tag1"
   VarNames(1) = "Device1.Group1.Tag2"

   result = OPCData1.ReadMultiVariables(VarNames, VarValues, States)

   If result = 0 Then
       Label2 = "Multiple Read Success Value 1 = " & VarValues(0) & "               Value 2 = " & 
       VarValues(1)
   Else
       Label2 = "Multiple Read Failure"
   End If

End Sub

Type the following code for Single Read button click event.

Private Sub cmdSingleRead_Click()

   Dim result As Long
   Dim State As Long
   Dim Value As Variant

   Label4 = ""

   result = OPCData1.ReadVariable("Device1.Group1.Tag1", Value, State, 3000)

   If result = 0 Then
       Label4 = "Single Read Success Value = " & Value
   Else
       Label4 = "Single Read Failure"
   End If

End Sub

Type the following code for Single Write button click event.

Private Sub cmdSingleWrite_Click()

   Dim result As Long
   Dim Value As Variant

   Label3 = ""
   Label4 = ""

   Value = txtSingleWriteValue

   result = OPCData1.WriteVariable("Device1.Group1.Tag1", Value, 3000)

   'display write result
   If result = 0 Then
       Label3 = "Single Write Success"
   Else
       Label3 = "Single Write Failure"
   End If

End Sub

You should now be able to run your project and access data from your plc.

Copyright Software Toolbox, Inc., 1996-2002, All Rights Reserved Worldwide.
148A East Charles Street, Matthews, North Carolina, USA 28105
Phone: 704-849-2773 or 1-888-665-3678 (US), Fax: 704-849-6388
Business hours - Monday to Friday, 8 AM to 5 PM EST (GMT-5)