Option Explicit

'**********************************************************************

'* S2L6.bas - (Section 2, Lesson 6) RECEIVING DATA FROM MULTIPLE

'*            CHANNELS

'*            This is the RTDX Host Client for Section 2, Lesson 6

'*

'* This example receives integer values:

'* 3 from channel ochan1

'* 2 from channel ochan2

'* 1 from channel ochan3

'**********************************************************************



Const Success = &H0                     ' Method call is valid

Const Failure = &H80004005              ' Method call failed

Const ENoDataAvailable = &H8003001E     ' No data was available.

                                        ' However, more data may be

                                        ' available in the future.

Const EEndOfLogFile = &H80030002        ' No data was available

                                        ' The end of the log file has

                                        ' been reached.





'**********************************************************************

' Insert code from Step #3 here - to create a structure to hold the

'                                 attributes

'**********************************************************************

Public Type RTDX_Channel

    obj As Object

    name As String

    type As String

    opened As Boolean

End Type





Sub main()

    '******************************************************************

    ' Insert code here to create an array instance of the type

    ' RTDX_Channel

    '******************************************************************

    Dim rtdx(1 To 3) As RTDX_Channel

    

    Dim data As Long

    Dim status As Long

    Dim i As Long



    On Error GoTo Error_Handler

    '******************************************************************

    ' Insert code from Step #4 here - to initialize the channel name

    '******************************************************************

    rtdx(1).name = "ochan1"

    rtdx(2).name = "ochan2"

    rtdx(3).name = "ochan3"



 

    '******************************************************************

    ' Insert code from Step #5 here - to create an instance of the RTDX

    '                                 COM Object and open the channels

    '******************************************************************

    For i = LBound(rtdx) To UBound(rtdx)

        rtdx(i).type = "R"

        rtdx(i).opened = False

        Set rtdx(i).obj = CreateObject("RTDX")

        status = rtdx(i).obj.Open(rtdx(i).name, _

            rtdx(i).type)

        If status <> Success Then

            Debug.Print "Opening of channel " & _

                        rtdx(i).name & _

                        " failed"

        Else

            rtdx(i).opened = True

        End If

    Next i





    For i = LBound(rtdx) To UBound(rtdx)

        If rtdx(i).opened Then



            '**********************************************************

            ' Insert code from Step #6 here - to read a 32-bit integer

            '                                 from the target

            '**********************************************************

            status = rtdx(i).obj.ReadI4(data)

            

            Select Case (status)

            

                Case Success

                    Debug.Print "Value " & _

                                data & _

                                " was received from target via channel " & _

                                rtdx(i).name

                Case ENoDataAvailable

                    Debug.Print "No data is currently available"

                Case EEndOfLogFile

                    Debug.Print "End of log file has been detected"

                    rtdx(i).opened = False

                Case Failure

                    Debug.Print "ReadI4 returned failure"

                    rtdx(i).opened = False

                Case Else

                    Debug.Print "Unknown return code"

                    Exit For

            End Select

        End If

    Next i

    

    '******************************************************************

    ' Insert code from Step #7 here - to close the channel and release

    '                                 the reference to the RTDX COM

    '                                 object

    '******************************************************************

    For i = LBound(rtdx) To UBound(rtdx)

        status = rtdx(i).obj.Close()

        Set rtdx(i).obj = Nothing

    Next i

    

    Exit Sub



Error_Handler:

Debug.Print "Error in COM method call"



' Release the reference to the RTDX COM object

For i = LBound(rtdx) To UBound(rtdx)

    Set rtdx(i).obj = Nothing

Next i



End Sub