Timer Gurus - How to make a stable 30 second timer?

Here's my problem: I need to generate an event every 30 seconds, but I need the event to occur at the same time consistently (+- 1 second) - with respect to the system clock.

I've written a simple app that starts a 30 second timer at 15 seconds into a minute interval. Unfortunately, I have observed that it does not stay synchronized to this start time ... so how can I reliably generate an event every 15 seconds and 45 seconds into each minute ... for an entire day?

All suggestions are welcome!

Dave

without getting too complicate, i would generate a regular timer event every second and i would only execute what i need to if the "seconds" part of the current system time is 15 or 45. you may still be missing 'heartbeats' (like, because of the drift of the timer control, it would miss a 'tick' on second 15 or 45). depending on how critical it is for your app, you may want to ignore this mishap, or you may want to provide the logic to make sure that the code i need gets executed at least once in the 15-44 interval, and at least once in the 45-59 and 0-14 interval.

if there is something that would prevent the timer to tick properely, it would be your application itself. in other words, a slow-executing sub or function in your own app may delay the timer event; same loop executing in another app will not affect your timer.

Have a play with this:

VB Code:

Option Explicit
 
Private Declare Function GetTickCount Lib "kernel32" () As Long
 
Private Sub Form1_Load()
    My_Timer
    MsgBox "Times up"
End Sub
 
Private Sub My_Timer()
    Dim tStart As Long
 
    tStart = GetTickCount() \ 1000
 
    Do
        DoEvents
    Loop Until GetTickCount() \ 1000 >= tStart + 5
 
End Sub

It'll display a MessageBox 5 seconds after Form1 load.

Here is some code for a timer control with its interval set to 1000.

VB Code:

Private Sub Timer1_Timer()
'The next second we gotta "tick" on
Static NextSecond As Long
'The second we're at now
Dim ThisSecond As Long
'This will get set to true on the 15th
'and 45th seconds
Dim IsTime As Boolean
 
'Get the current second
ThisSecond = Second(Now)
 
'Initialize NextSecond if it is zero
If NextSecond = 0 Then
    If ThisSecond <= 15 Or ThisSecond > 45 Then
        NextSecond = 15
    Else
        NextSecond = 45
    End If
End If
 
'Determine whether it is time to "tick"
If NextSecond = 45 Then
    If ThisSecond >= 45 Then
        IsTime = True
        NextSecond = 15
    End If
Else 'NextSecond = 15
    If ThisSecond < 45 And ThisSecond >= 15 Then
        IsTime = True
        NextSecond = 45
    End If
End If
 
'If it's time, run your code
If IsTime Then
    'put your code here that is to execute
    'on the 15th and 45th seconds
End If
End Sub

Thanks for the suggestions ... I'll play around with these ideas to see if I get satisfactory results.

Thanks,

Dave

slap a timer on a form, with an interval low enough to make sure it fires at least once each second, and use code like this:

VB Code:

Private Sub Timer1_Timer()
    Dim strSecond As String
    Dim strLastTick As String
 
    strSecond = Mid(Time$, 7, 2)
    If strSecond = "15" Or strSecond = "45" And strLastTick <> strSecond Then
        'your code here
        
        strLastTick = strSecond
    End If
End Sub

it's simple and it works :)

hope it helps,

Quote:

---

Originally posted by glyptar
slap a timer on a form, with an interval low enough to make sure it fires at least once each second, and use code like this:

[some code here]

it's simple and it works :)

hope it helps,

---

... unless... if somewhere else in another part of the app i have a loop like this

VB Code:

For i = 0 to BiggestValueEver
Next i

and if the execution of this loop (and actually of all the call stack associated with it) takes more than 30 seconds, you will be definitely missing a beat. the code that tygur provided kinda makes sure that, even if the timer doesnt fire in the right second, at least it will pop up and execute sometime later, and will only execute once. supposedly, this is the desired effect

Your best bet is using the GETTICKCOUNT() api. It gets the number of miliseconds the system has been up. THis is preferable because the sytem timer has the highest priority in windows. so you're positive that it'll never be inaccurate. Well, don't kill the VB code either, kuz VB isn't lightening either!

Quote:

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Originally posted by INF3RN0666
Your best bet is using the GETTICKCOUNT() api.

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Hmmmm, I thought that was what I posted earlier :)

I believe that you can prevent your own program from stopping your own timer by using the doevents command in loops. This stops stack build-up.