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Timer smaller than 1 milisecond(ms)? I need microseconds(us)!

Posted on 2002-05-17
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Last Modified: 2008-02-01
Dear friends,
I am buidind a small data aquisition program for a custom designed interface, through the LPT.
The A/D converter needs a start signal to convert a value. But before reading it, I must wait about 50-60 MICROSECONDS (about 0.05 miliseconds).
How can I do that in Visual Basic?
Thanks.
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Question by:robertut
8 Comments
 
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RichW earned 70 total points
ID: 7016176
Public Declare Sub Sleep Lib "kernel32" Alias "Sleep" (ByVal dwMilliseconds As Long)



Sleep 0.05
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by:EDDYKT
ID: 7016203
?->
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Expert Comment

by:HobbitHouse
ID: 7016327
due to a hangover from the earliest days of PCs, the timer available to programmers has a resolution of 55 ms, so I think you're out of luck
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by:RichW
ID: 7016408
If you run the SLEEP you've got te 0.05 milliseconds pause without the need of a timer.
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by:hiranmaya
ID: 7016627
Sleep may not be the good suggestion.
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by:robertut
ID: 7016770
I am planning to use sleep.
"Sleep may not be the good suggestion." - why is that?
Robert
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by:RichW
ID: 7016886
Robertut, the Sleep api is a good suggestion for a pause without using a timer object.  

It's really not much different from something like:

Dim x as Long

Do Until x = 500
   x = x + 1
Loop

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Expert Comment

by:bal3x
ID: 23586140
I had the same problem a week ago, i needed to capture data from LPT in order of microseconds.

Try this way

If you don't need accurate timing (i dont think that SLEEP can help you, it is not very accurate)
better solution is to set your application in REALTIME level of process priority
next thing to do is to capture data from LPT with exact number of samples

Example: For i=1 to (number of samples)
                 {read from LPT]
                 {store value in array with same lenght as the number of samples]
               Next

When finished with reading return to normal level of priority.

Here is my source code

Private Sub SetProcessPriority(ByVal processname As String, ByVal priority As ProcessPriorityClass)
        Dim pl() As Process = Process.GetProcessesByName(processname)
        For Each p As Process In pl
            p.PriorityClass = priority
        Next
End Sub


Private Sub cmbRead_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbRead.Click
     
    SetProcessPriority("app name", ProcessPriorityClass.RealTime)
     
    For a = 1 To NoSamples
            pole(a) = "read from LPT"    'write command to read from lpt, i used external module to read'
    Next
   
    SetProcessPriority("app name"t, ProcessPriorityClass.Normal)

End Sub

HAVE FUN
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