Timing loops

[RED SNIPE]

This is a quick question that I need advice on. I am loading a counter with a different value at a specific frequency. Presently I am using a basic while loop with a delay of the time step to get the frequency. Is this an effective method to perform this task or should I be doing something else? I need this task to be as precise as possible as the frequency will be quite high. I am open to any suggestions (code is simplified)

while (iStop != 1 && iStep <= 5000)
{
LoadValue = iLoadValues[iStep]; /* Load Counter */
iStep++;
ProcessSystemEvents();
Delay(dTimeStep);
}

Thank you for any assistance you provide.

RED

[hendra@ngms]

My opinion, and I'm not an expert here.

The moment you said "as precise as possible" you lost it. It won't be, particulary since you are calling ProcessSystemEvents(), which will take a widely variable period of time.

The best you can do in LabWindows is to run a function like this in a separate thread, with no call to ProcessSystemEvents.

Some code like:
timerFlag = 1;
CmtScheduleThreadPoolFunction (DEFAULT_THREAD_POOL_HANDLE, TimerThread, NULL, NULL);


int CVICALLBACK TimerThread(void *ctrlID)
{
while(timerFlag)
{
Your code, without ProcessSystemEvents()
}
}

[RED SNIPE]

Thanks hendra,

Exactly what I thought. I've been trying to read up on multitreading as I have never done it before and it appeared to be a possible solution. Thanks for your suggestion (expert or not). My main concern is the timing so I'll give it a go. If others have opinions I take all the help I can get.

Cheers,

RED

[cdk52]

Hi RED,

Try using asynchronous timers (see asynctmr.fp and associated example programs). The callbacks execute in a separate, high-priority thread.

However, don't expect reliable timing if dTimeStep is under about 10 milliseconds.

Colin.

[RED SNIPE]

Thanks Colin,

I'll try it soon. I've heard mention of the 10 millisecond rule before, thanks for the heads up.

Cheers,

RED