[ADVANCED-DOTNET] Timers and Process Monitoring

Grant Fri, 26 Dec 2003 12:50:16 -0800

I have 3 objects in my VB .NET project:

1. DeltaTau
   wrapped COM object (talking to a PMAC controller over USB)
   Updates GUI textbox controls with current process status info


2. Vision
   native .NET object (controlling a vision process over Matrox Mil 7.5)
   displays a continuous live camera image

3. MainForm
   .NET form with several wrapped COM objects talking to a DDE Server.
   Contains a tab control with separate tabs for Vision and DeltaTau

The DeltaTau object controls an insertion process that needs monitoring.
When complete or on error various bits are set that indicate status.
Concurrent with this monitoring the Vision system is acquiring images from
a camera system and displaying them on the screen.

I started using a System.Timers.Timer for best resolution in my process
monitoring in the DeltaTau object.  However when I have the
System.Timers.Timer enabled my vision object locks up the UI Form.  I
asked some of the .NET folks around here and was told I need to use
BeginInvoke on any function that needs to update the GUI since
System.Timers.Timer operates in it's own thread space.

    Private Sub myDatatimer_Elapsed(ByVal sender As System.Object, ByVal e
As System.Timers.ElapsedEventArgs)
        Dim ActualPosition, CurrentForce, EndingForce, EndingPosition,
PeakForce As Single

        Try
            ' Live Data
            ActualPosition = PTalkDT2.DPRGetFloat(GCACTUAL_POSITION_OFFSET)
            CurrentForce = PTalkDT2.DPRGetFloat(GCFEEDBACK_FORCE_OFFSET)
            EndingForce = PTalkDT2.DPRGetFloat
(GCFORCE_INSERTION_COMPLETE_OFFSET)
            EndingPosition = PTalkDT2.DPRGetFloat
(GCPOSITION_INSERTION_COMPLETE_OFFSET)
            PeakForce = PTalkDT2.DPRGetFloat(GCPEAK_FORCE_OFFSET)

            RaiseEvent LiveData(ActualPosition, CurrentForce, EndingForce,
EndingPosition, PeakForce)
        Catch ex As Exception
            RaiseEvent PMACDPRamReadFailed()
            Exit Sub
        End Try
    End Sub

' Live Data
    Private Sub DeltaTau2_LiveData(ByVal ActualPosition As Single, ByVal
CurrentForce As Single, ByVal EndingForce As Single, ByVal EndingPosition
As Single, ByVal PeakForce As Single) Handles DeltaTau2.LiveData
        BeginInvoke(New DeltaTau1.__Delegate_LiveData(AddressOf LiveData),
New Object() {ActualPosition, CurrentForce, EndingForce, EndingPosition,
PeakForce})
    End Sub

Private Sub LiveData(ByVal ActualPosition As Single, ByVal CurrentForce As
Single, ByVal EndingForce As Single, ByVal EndingPosition As Single, ByVal
PeakForce As Single)
        ' ensure exclusive access to data
        SyncLock txtActualPosition.Text
            txtActualPosition.Text = ActualPosition
            txtCurrentForce.Text = CurrentForce
            txtEndForce.Text = EndingForce
            txtEndPosition.Text = EndingPosition
            txtPeakForce.Text = PeakForce
        End SyncLock
    End Sub

However this does not seem to clear up the GUI lock up problem.  Any ideas?

Thank you,

Grant

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[ADVANCED-DOTNET] Timers and Process Monitoring

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