Timer - Xtreme Visual Basic Talk

08-26-2002, 04:05 PM

elettro

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Timer

I must interrogate the serial port once per second so I used
the TIMER CONTROL. (1000 msec.)

This control is not accurate, I don't know why.
How do I upgrade the time interval accuracy ?

Thank you.

08-26-2002, 04:11 PM

ChiefRedBull

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Use the QueryPerformanceCounter and QueryPerformanceFrequency APIs.

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08-26-2002, 04:21 PM

MarkVB6

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I think the lowest interval of an object timer (the general control) is about 55 milliseconds. What was the interval set at?

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08-26-2002, 06:04 PM

ChiefRedBull

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The lowest interval is 1ms, but that is only accurate to about 55ms, because of the way the Timer control works internally. The APIs i mentioned above are (AFAIK) as good as it gets. There have been many threads about this though, search for "performance" or "timer"

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08-26-2002, 06:14 PM

Volte

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If you are simply looking for a timer that has an accurate 1ms
resolution (QueryPerformance APIs are much more accurate
than that, but more complicated to use), then I believe timeGetTime
would be sufficient for your needs.

If you are making some sort of absolute graphing program or a
stopwatch or something, you would need QueryPerformaceCounter,
but for general timer stuff, it's not needed.

08-27-2002, 06:16 AM

elettro

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I have this code to do a thermometric curve length 2 hrs

Private Sub Timer1_Timer ()

MsComm1.Enabble = True
......
code
.....
End Sub

There is a time error of 20%. I suspect that the time interval is not real, but is the sum of the interval and an unknown time necessary to elaborate the code. I don't want this.
I ask you: How do i connect the code direct to the system watch ?

08-27-2002, 09:09 AM

Volte

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Use a Do While loop, in conjunction with one of the APIs above.

Code:

Do
  tempVar = timeGetTime
  '... code ...'
  Do Until timeGetTime > tempVar
    'do nothing
  Loop
Loop Until bEnd

Something like that.