frmwriteitem.frm

vb开发的一个opcclient源代码

VERSION 5.00
Begin VB.Form frmWriteItem 
   Caption         =   "OPC Write Item"
   ClientHeight    =   2985
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   6525
   ControlBox      =   0   'False
   LinkTopic       =   "Form1"
   ScaleHeight     =   2985
   ScaleWidth      =   6525
   ShowInTaskbar   =   0   'False
   StartUpPosition =   1  'CenterOwner
   Begin VB.CommandButton OkButton 
      Caption         =   "Ok"
      Height          =   375
      Left            =   5160
      TabIndex        =   1
      Top             =   2520
      Width           =   1215
   End
   Begin VB.CommandButton ApplyValue 
      Caption         =   "Apply Value"
      Height          =   375
      Left            =   3720
      TabIndex        =   0
      Top             =   2520
      Width           =   1335
   End
   Begin VB.Frame Frame1 
      Caption         =   "Value to Write"
      Height          =   2295
      Left            =   120
      TabIndex        =   2
      Top             =   120
      Width           =   6255
      Begin VB.TextBox DataType 
         Height          =   285
         Left            =   1080
         Locked          =   -1  'True
         TabIndex        =   11
         ToolTipText     =   "This box simply displays the selected Data Type for reference"
         Top             =   720
         Width           =   4935
      End
      Begin VB.OptionButton BooleanOff 
         Caption         =   "Off"
         Height          =   195
         Left            =   2040
         TabIndex        =   9
         Top             =   1800
         Width           =   615
      End
      Begin VB.OptionButton BooleanOn 
         Caption         =   "On"
         Height          =   195
         Left            =   1320
         TabIndex        =   8
         Top             =   1800
         Value           =   -1  'True
         Width           =   615
      End
      Begin VB.TextBox ItemID 
         Height          =   285
         Left            =   1080
         Locked          =   -1  'True
         TabIndex        =   6
         ToolTipText     =   "This box simply displays the selected ItemID for reference"
         Top             =   360
         Width           =   4935
      End
      Begin VB.TextBox WriteValue 
         Height          =   285
         Left            =   1080
         TabIndex        =   3
         Text            =   "0"
         ToolTipText     =   "Enter the value to be written here, for arrays separate each element by a comma"
         Top             =   1320
         Width           =   4935
      End
      Begin VB.Label Label4 
         Caption         =   "Data Type:"
         Height          =   255
         Left            =   195
         TabIndex        =   10
         Top             =   720
         Width           =   855
      End
      Begin VB.Label Label3 
         Caption         =   "Boolean Value:"
         Height          =   255
         Left            =   120
         TabIndex        =   7
         Top             =   1800
         Width           =   1095
      End
      Begin VB.Label Label1 
         Caption         =   "ItemID:"
         Height          =   255
         Left            =   480
         TabIndex        =   5
         Top             =   360
         Width           =   495
      End
      Begin VB.Label Label2 
         Caption         =   "Numeric and String Values"
         Height          =   495
         Left            =   120
         TabIndex        =   4
         Top             =   1200
         Width           =   1095
      End
   End
End
Attribute VB_Name = "frmWriteItem"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
' The OPC Write Item form is used to send new data
' to a specific OPC item. The form will automatically
' set itself to accept either numeric, string,
' or boolean input depending on the data type of the
' item selected.
'
' This write operation uses the AsyncWriteOPCItem function
' of the OPCGroupClass object The OPCGroupClass wraps the
' AsyncWrite function of the Automation interface.  The
' AsyncWrite function has the benefit of returning control
' immediately to your application.  There are other mehtods
' for doing writes to OPC items but using the Async method
' is the best way to insure that your application does not
' get blocked by the write operation of the OPC server.
' When you use the write function directly on an OPC item
' or the SyncWrite function on an OPC group the operation
' is blocked until the OPC server completes the write.
' This includes the round trip time to the physical device
' and back. Depending on your device this could be a long
' wait during which your VB application would appear to be
' locked up. Using the AsyncWrite as shown here insures
' that your VB application can continue to process other
' operations.  The results of the write operation is
' return to you later in the AsyncWriteComplete which is
' handled in the OPCGroupClass object.  This event will
' place the returned error in the specific Quality field
' of the OPC item.
'
' When the Write item form is displayed it will atempt the
' identify and dsiplay the data type of the item selected.
' If you check the VB help system for VarType Const you'll
' see that some 17 data types are listed. Many of these
' datatypes do not apply to data you will receive from an
' OPC server.  There is also the chance you will get back a
' datatype which doesn't fit one of these 17 datatypes.
' When this occurs you are most likely getting back an
' Unsigned Data type.  Most of the time the Automation
' Wrapper can handle these unsigned datatypes.  I have
' however seen a problem when attempting to write to an
' array of Unsigned short values.  This is why I force
' the user to select one of the data types when adding an
' OPC item.  I do allow the Native datatype selection which
' allows the OPC server to pick what it thinks is the
' default(canonical) datatype of the item.  This is where
' an items datatype can become unsigned.

Option Explicit
' The option Base is not set here since we need an
' array that can start with a lower bound of zero

Dim DataTypes(17) As String

' The ValueChange flag is used to determine if the
' value needs to be written when the OK button is
' pressed.  The Apply button allows you to write the
' value each time it is pressed without leaving the
' OPC Write Item form.  If you change the value without
' hitting the apply button and exit the dialog with Ok
' button the value will still be sent.  If the apply
' button is hit before the Ok button the value will not
' be written on the OK.
Dim ValueChange As Boolean


Private Sub Form_Load()
    ' Get the Item ID string for reference
    ItemID.Text = Module1.SelectedOPCItem.GetItemID
        
    ' This list of data types is derived from the VarType Constants
    ' Some of the data type in the VarType Constants don't apply to
    ' normal OPC data objects and are therefore marked as invalid
    
    DataTypes(0) = "Native - Data Type is not specific set by OPC Server"
    DataTypes(1) = "Invalid Data Type for this example"
    DataTypes(2) = "Integer - 16 bit Signed "
    DataTypes(3) = "Long - 32 bit Signed "
    DataTypes(4) = "Float - 32 bit Float "
    DataTypes(5) = "Double - 64 bit Real "
    DataTypes(6) = "Invalid Data Type for this example" ' Currency