UInt32 CalibrateDelayLoop() {
UInt32 low = 1;
UInt32 high = 10000; // This should be high enough so that at least ONE
tick occurs during this many iterations of the loop
UInt32 x,y,s,t,d;
Char buffer[16];
while (high > low) {
x = ( high + low ) / 2;
y = x;
s = TimGetTicks();
do {
t = TimGetTicks();
} while (t == s);
// A tick *just* occurred. Now we count until the next.
while (x) {x--} // The delay loop
s = TimGetTicks();
if (s == t) {
low = y + 1; // Less than a tick occurred during delay, so try
again, but wait longer.
}
else {
high = y - 1;// A tick occurred, so we're over. Try again, but wait
less time.
}
}
return (y * SysTicksPerSecond()) / 1000;
}
I couldn't help myself. Here's a working version of my idea. It's still
untested, (as far a accuracy is concerned) but I think it's pretty accurate.
Regards,
Alan Ingleby
Systems Developer
ProfitLink Consulting Pty Ltd
309 Burwood Road
Hawthorn
Victoria 3122
Australia
"Alan Ingleby" <[EMAIL PROTECTED]> wrote in message
news:42276@palm-dev-forum...
>
> I have an idea for a different solution.. (I just came up with this on my
> afternoon break, so give me credit here 8-) ) I can't be bothered writing
> actual code, so this is just a rough idea of the actual code... It's
> basically a binary search for the loop value which causes a delay of one
> "Tick"
>
> /*BEGIN CODE*/
> low = 1;
> high = 1000000; // This should be high enough so that at least ONE tick
> occurs during this many iterations of the loop
>
> while (high > low) {
> x = ( high + low ) / 2;
>
> s = TimGetTicks();
>
> do {
> t = TimGetTicks();
> } while (t == s);
>
> // A tick *just* occurred. Now we count until the next.
>
> while (x) x--; // The delay loop
>
> if (t == TimGetTicks()) {
> low = x+1; // Less than a tick occurred during delay, so try
again,
> but wait longer.
> }
> else {
> high = x-1;// A tick occurred, so we're over. Try again, but wait
> less time.
> }
> }
>
> d = ( x * SysTicksPerSecond() ) / 1000;
> /*END CODE*/
>
> NOTE: This code is *guaranteed* to be bug-ridden, it's just intended to
> convey the rough idea I just had.
>
> The result *should* be a value for d which causes the delay loop to wait
one
> milisecond.
>
> Let me know what you think, or if I'm just a barfing idiot.. (Which is
more
> than likely).. 8-)
>
> Regards,
>
> Alan Ingleby
> Systems Developer
> ProfitLink Consulting Pty Ltd
> 309 Burwood Road
> Hawthorn
> Victoria 3122
> Australia
> "Bill Shaw" <[EMAIL PROTECTED]> wrote in message
news:42184@palm-dev-forum...
> >
> > Needing a millisecond delay routine for my smart card application, I
> > searched the archives and found others asking for a similar routine.
> > The reply was always negative; doesn't exist, can't do it. Not being
> > one to take no for an answer ;-) I thought about it for a few minutes
> > and came up with this solution. The timing is not perfect, and shorter
> > delays will be less accurate due to interrupts, but it's close enough
> > for my needs.
> >
> > Enjoy.
> >
> > bs
> >
> >
> >
>
/***************************************************************************
> **
> > *
> > * File Name: delay.c
> > * Millisecond delay routines.
> > *
> > * Author: Bill Shaw
> > * [EMAIL PROTECTED]
> > * Westbrook Systems:
> > * Windows, Mac OS, Palm, PIC, and smart card
development
> > *
> > * Date: 2/23/01
> > *
> >
>
****************************************************************************
> ***
> > *
> > * This code is emailware. If you find if useful, send me an email
> > * and tell me about your app!
> > *
> > * Also, please leave my headers intact. This is one form of
> advertising
> > * I like to take advantage of when I can!
> > *
> >
>
****************************************************************************
> ***
> > */
> > #include <PalmOS.h>
> >
> > UInt32 startTicks; // the time we started
> > UInt32 loopsPerMs; // # loops per millisecond
> > UInt32 endTicks; // the time we ended
> >
> >
>
/***************************************************************************
> ****
> > *
> > * calcDelay - Calculates the delay value (loopsPerMs) for this Palm.
> > * Call once during app initialization.
> > * returns - nothing
> > *
> >
>
****************************************************************************
> ***
> > */
> > void calcDelay(void)
> > {
> > UInt32 ticksPerSec;
> > UInt32 loopCount;
> >
> > ticksPerSec = SysTicksPerSecond(); // get # ticks per second
> > startTicks = TimGetTicks(); // get start time
> >
> > endTicks = startTicks + ticksPerSec; // calc end time
> >
> > // run the timing loop...
> > for (loopCount=0; TimGetTicks() < endTicks; loopCount++) {
> > ticksPerSec++;
> > }
> >
> > endTicks = TimGetTicks(); // get end time (for debug)
> > loopsPerMs = loopCount / 1000; // calc # loops/ms
> >
> > } // end of calcDelay()
> >
> >
>
/***************************************************************************
> ****
> > *
> > * msDelay - millisecond delay
> > * UInt32 ms = # milliseconds to delay
> > * returns - nothing
> > *
> >
>
****************************************************************************
> ***
> > */
> > void msDelay(UInt32 ms)
> > {
> > UInt32 loopCount, i;
> >
> > loopCount = loopsPerMs * ms; // calc # loops
> >
> > startTicks = TimGetTicks(); // get start time (for
debug)
> >
> > // run the delay loop...
> > for (i=0; i<loopCount; i++) {
> > endTicks = TimGetTicks();
> > }
> >
> > i = 0; // just to break on
> >
> > }
> >
> > // end of file delay.c
> >
> >
> >
> >
>
>
>
>
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