OPC Client - VB.NET Sample

It introduces the easy sample program using the OPC Server. The code of this sample uses OPC
If you access to OPC Server from .NET, the wrapper which exchanges COM and .NET is needed.
Automation Wrapper (OPCDAAUTO.DLL), so it is almost equal to VB6.0.




Declaration
Option Explicit Public OpcServer As IOPCServerDisp Public OpcItemMgt As IOPCItemMgtDisp Public OpcItem As IOPCItemDisp Private Const ItemMax = 8 Private Const OPC_DS_CACHE = 1 Private Const OPC_DS_DEVICE = 2 Dim ClientHandles(ItemMax) As Long Dim ServerHandles As Variant Dim bConnect As Boolean

Connect to OPC Server, Create OPCGroup and Add Tags
Private Sub CONNECT_Click() On Error GoTo err_hd Dim i% If bConnect Then CONNECT.Caption = "Connect" Set OpcServer = Nothing Set OpcItemMgt = Nothing Set OpcItem = Nothing bConnect = False READ_Button.Enabled = False WRITE_Button.Enabled = False For i% = ItemName.lbound To ItemName.ubound ItemName(i%).Enabled = True Next i% Exit Sub End If '*** Connect to OPC Server *** Set OpcServer = CreateObject(Form1.ServerName.Text) If TypeName(OpcServer) = TypeName(Nothing) Then Return '*** Add OPCGroup *** Dim UpdateRate As Long Dim ServerHdl As Long UpdateRate = UpdateRateSet.Text Set OpcItemMgt = OpcServer.AddGroup("Group One", True, UpdateRate, 22, 1, 0, ServerHdl, UpdateRate) If TypeName(OpcItemMgt) = TypeName(Nothing) Then Return '*** Add OPCItems *** Dim ItemIDs(ItemMax) As String Dim AccessPaths(ItemMax) As String Dim Active(ItemMax) As Boolean Dim Errors As Variant Dim ItemObjects As Variant Dim DataType(ItemMax) As Variant For i% = 0 To ItemMax - 1 Active(i%) = True ClientHandles(i%) = 22 + i% AccessPaths(i%) = "" ItemIDs(i%) = Form1.ItemName(i%).Text DataType(i%) = 2 Next i% OpcItemMgt.AddItems ItemMax, ItemIDs, Active,ClientHandles, ServerHandles, Errors, ItemObjects, AccessPaths, DataType Set OpcItem = ItemObjects(0) bConnect = True CONNECT.Caption = "DisConnect" READ_Button.Enabled = True WRITE_Button.Enabled = True For i% = ItemName.lbound To ItemName.ubound ItemName(i%).Enabled = False Next i% Exit Sub err_hd: MsgBox "Error connecting" For i% = 0 To ItemMax - 1 Form1.Value(i%) = "Error" Next i% End Sub

Cache Read
Private Sub READ_Button_Click() Dim ReadValue As Variant Dim pQuality As Variant Dim pTimestamp As Variant Dim Errors As Variant Dim i% Dim io As IOPCSyncIODisp Set io = OpcItemMgt '*** Cache Read *** io.OPCRead OPC_DS_CACHE, ItemMax, ServerHandles, ReadValue, pQuality, pTimestamp, Errors For i% = 0 To ItemMax - 1 Form1.Value(i%) = ReadValue(i%) pTimestamp(i%) = DateAdd("h", 9, pTimestamp(i%)) Form1.Time(i%) = pTimestamp(i%) Form1.Quality(i%) = pQuality(i%) Next i% End Sub

SyncWrite
Private Sub WRITE_Button_Click() Dim WriteValue(ItemMax) As Variant Dim io As IOPCSyncIODisp Dim Errors As Variant Dim i% Set io = OpcItemMgt For i% = 0 To ItemMax - 1 WriteValue(i%) = Form1.Value(i%) Next i% '*** SyncWrite *** io.OPCWrite ItemMax, ServerHandles, WriteValue, Errors End Sub

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