Delay in For Loop - Causes Overflow

[mi-ena]

Hi,

I am new to VB6 programming and have some difficulties...

Here is my question:

I have a For Loop running, wherein there should be some communicating with a serial port to get new data (will be implemented later), updating a data array and the corresponding graph.
This works all fine...

But then: When I apply a delay within the For Loop to wait some time (about 1 second) for the next loop iteration to start I get a 'Runtime error: Overflow' message.

How can I avoid this?

Thanks in advance!

My code:

Private Declare Function GetTickCount Lib "kernel32" () As Integer
Private Declare Sub Sleep Lib "kernel32" (ByVal ms As Integer)

Public Sub Delay(ByVal delayms As Integer)
    Dim delayTime As Long
    delayTime = GetTickCount + delayms
    
    Do Until GetTickCount >= delayTime
        Sleep 10
        DoEvents
    Loop
End Sub

Public Sub GetData()
    Dim i As Integer
    Dim Start, Finish, Duration As Integer
    
    For i = 1 To End
        Start = GetTickCount
        
	' Get new Data         
	...
	' Refresh DataArray
        ...
        ' Refresh Graph
        ...
        
        Finish = GetTickCount
        Duration = Start - Finish
        'Delay: Loop repetition after 1s
        Delay (1000 - Duration)
    Next i
End Sub

[jccaldz]

For i = 1 To End >>> what is END?
check this limit.

[mi-ena]

the limit is formerly defined (not shown in the excerpt of my code) as a value taken from another array.

Again: The program works fine without the delay...

[vb5prgrmr]

You could possibly be passing a negative value if your process takes longer than a second (Delay 1000 - Duration). Second, "End" is an execution command so perhaps you should change the declaration MyEnd or something else.

Good Luck

[mi-ena]

the process takes definitely less than one second and I just placed End here as the variable for short - in my code it's called EndSetRows... (sorry for confusion)

[jccaldz]

Private Declare Function GetTickCount Lib "kernel32" () As Integer
Private Declare Sub Sleep Lib "kernel32" (ByVal ms As Integer)

Public Sub Delay(ByVal delayms As Integer)
    Dim delayTime As Long
    delayTime = GetTickCount + delayms

    Do Until GetTickCount >= delayTime
        Sleep 10
        DoEvents
    Loop
End Sub

Public Sub GetData()
    Dim i As Integer
    Dim Start, Finish, Duration As Integer

    For i = 1 To End
        Start = GetTickCount

    ' Get new Data         
    ...
    ' Refresh DataArray
        ...
        ' Refresh Graph
        ...

        Finish = GetTickCount
        Duration = Start - Finish
        'Delay: Loop repetition after 1s
        Delay (1000 - Duration)
    Next i
End Sub

[mi-ena]

@ jccaldz: ?

[cguan_77]

hi just try this: don't know if it will help never test
try to add an if then else statement...

if Finish = GetickCount then
  Delay (1000 - Duration)
else 
end if

[mi-ena]

The problem seems to solved...

First I redefined my Delay function using a Timer:

Private Declare Function GetTickCount Lib "kernel32" () As Integer
Private Declare Sub Sleep Lib "kernel32" (ByVal ms As Integer)

Private Sub Timer1_Timer()
    Timer1.Enabled = False
End Sub

Public Sub Delay(ByVal tDelay As Double)
    Timer1.Interval = tDelay
    Timer1.Enabled = True
    Do While Timer1.Enabled
        Sleep 10
        DoEvents
    Loop
End Sub

But that still causes an error message when starting a long-time measurement... :icon_sad:

Then I have put the "Duration" as an absolute value:

...
Duration = Abs(Start - Finish)
Delay (1000 - Duration)
...

Now it works fine even for a long-time running programm. :icon_biggrin:

To stay on the safe side I inserted a condition if the loop process should take longer than one second:

If Duration >= 1000 Then
    Duration = 990
End If

Well everything seems to be okay now - BUT:
I just want to understand...

It seems as if the problem is occuring when the "Duration" gets a negative value (and the Delay function has a value of more than one second).
Why on earth does the delay function have this problem - as the timer interval is set within the program to any value (1000-Duration) ??? :icon_confused:
It shouldn't have problems with timer intervals over 1000ms ?

Thanks for your ideas anyway!!!