Enabled Scan doesn't Work

[Rodrigue]

Hello, sorry for my bad english .... :D

I need help because scan not working for me.

No error message, no Exception .... Just not working in call "

oTWDatasource.Enable(NTwain.SourceEnableMode.NoUI, False, IntPtr.Zero)

I d'ont understand, i'm so tired to looking for resolve my problem.

Here my code, please help me lol

  Private _oTwain As NTwain.TwainSession


    Public Function ScanImage(p_oForm As Form) As Image

        Dim oTwIdentity As NTwain.Data.TWIdentity = NTwain.Data.TWIdentity.CreateFromAssembly(NTwain.Data.DataGroups.Image, Reflection.Assembly.GetEntryAssembly())


        _oTwain = New NTwain.TwainSession(oTwIdentity)

        _oTwain.SynchronizationContext = WindowsFormsSynchronizationContext.Current

        ' ajout des événements
        AddHandler _oTwain.TransferReady, AddressOf TW_TransfertReady
        AddHandler _oTwain.DataTransferred, AddressOf Tw_DataTransfert

        _oTwain.Open()



        If _oTwain IsNot Nothing AndAlso _oTwain.Count > 0 Then

            For Each oTWDatasource As NTwain.DataSource In _oTwain

                If oTWDatasource.Name = "EPSON GT-1500" Then

                    oTWDatasource.Open()

                    oTWDatasource.Enable(NTwain.SourceEnableMode.NoUI, False, IntPtr.Zero)

                    oTWDatasource.Close()
                    Exit For
                End If

            Next

            _oTwain.Close()

        End If


        ' zone de paramètreage
        For Each enc As System.Drawing.Imaging.ImageCodecInfo In System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()
            If enc.MimeType = "image/tiff" Then
                _oTiffCodec = enc
                Exit For
            End If
        Next

    End Function

    Private Sub Tw_DataTransfert(sender As Object, e As NTwain.DataTransferredEventArgs)

        e.ToString()

    End Sub

    Private Sub TW_TransfertReady(sender As Object, e As NTwain.TransferReadyEventArgs)

        e.ToString()

    End Sub

    Private Sub TW_DataSourceDisable(sender As Object, e As EventArgs)
        e.ToString()
    End Sub

[Eugene Wang]

It may help by checking the return code of each call for success before moving onto the next one (and get detailed status if not success).

// I only know c# but should be similar to vb
ReturnCode rc = oTWDatasource.Open();
if (rc == ReturnCode.Success) {
    rc = oTWDatasource.Enable(...);
    if (rc == ReturnCode.Success)
    {
        return;
    }
}

TWStatus status = oTwain.GetStatus();
// log status and rc values here

// close source if didn't enable successfully
if (oTwain.State == 4) { oTWDatasource.Close(); }

Also you're trying to close the source right after Enable(), which wouldn't work because Enable does not block. You should only close when source is in state 4 (opened state). The scanner is in this state in both the SourceDisabled event handler and before you successfully enable a source.

[Rodrigue]

Thank for your rapid answer.

i have updated my source to obtain that

 If oTWDatasource.Name = "EPSON GT-1500" Then

                        oRC = oTWDatasource.Open()

                        If oRC = NTwain.Data.ReturnCode.Success Then

                            oRC = oTWDatasource.Enable(NTwain.SourceEnableMode.NoUI, False, IntPtr.Zero) 'Succes But my scan doesn't work and don't make a mecanic scan

                            If oRC = NTwain.Data.ReturnCode.Success Then

                                oTWDatasource.Close()

                            Else

                                oTWStatus = _oTwain.GetStatus()

                            End If

                            Exit For
                            End If
                        End If

But, alls operations give me a Sucess result. For the close, in fact, doesn't work but it is normal.

I dont understand ... I'm so disapointed by this problem

[Petr Valenta]

Hello

I'm facing the same trouble.

Before the Enable I'm in state 4, after it I remain in 5 ...

Is there any solution?

Petr Valenta

Possible explanation:

Just wait a few seconds in the code just somewhere near Enable by means of Yield() and Sleep(...);. The scanner seems to need some time to awake the appropriate structures. If the code immediately leaves, the scanner is not contacted.

[Bogdan Anghel]

Hi guys. I had the same issue and after many hours of testing I've managed to get it to work with a Thread.Sleep(1000) call just before the Enable call. Now it's all good. Hope this helps.