Delay Function Without SysTick_Handler Interrupt

[leventeyigel52]

Posted on May 27, 2013 at 15:58

Hello ,

I want to try use a function that is without  SysTick_Handler Interrupt : I wrote this function  : void DelayUs(int us) { unsigned int cnt; while(us-- >0) {    cnt = SysTick_GetCounter(); // get systick counter, ticking each 500nS    while( (SysTick_GetCounter()-cnt) < 2); // repeat till 2 ticks } } but cnt value is zero , i can't see any value from SysTick_GetCounter() ; How can i solve this problem ? Does anyone have any advice  ?

[emalund]

Posted on May 27, 2013 at 16:41

show how you initialize the systick

[zzdz2]

Posted on May 27, 2013 at 17:04

I use this:

#define TICKSGN ((SysTick_VAL_CURRENT_Msk+1)>>1)
#define WAITMAX (SysTick_VAL_CURRENT_Msk >> 1)
static inline void waittick(uint32_t step)
{
static uint32_t tick0;
if (!step)
{
tick0 = SysTick->VAL;
return;
}
tick0 -= step;
while ((tick0 - SysTick->VAL) & TICKSGN)
{
__NOP();
__NOP();
}
}
static inline void sleep(uint32_t delay)
{
waittick(0);
delay++;
while (delay > WAITMAX)
{
waittick(WAITMAX);
delay -= WAITMAX;
}
waittick(delay);
}

[leventeyigel52]

Posted on May 27, 2013 at 17:04

SysTick_Config(SystemFrequency / 1000);

I only use this initializition function.

[zzdz2]

Posted on May 27, 2013 at 17:26

Try my code above and initialize SysTick like this:

SysTick->LOAD = 0xffffff;
SysTick->CTRL = SysTick_CTRL_ENABLE_Msk;

Edit: Thismay be better:

SysTick->LOAD = SysTick_VAL_CURRENT_Msk;
SysTick->CTRL = SysTick_CTRL_ENABLE_Msk;

[leventeyigel52]

Posted on May 28, 2013 at 11:01

SysTick_VAL_CURRENT_Msk;
SysTick_CTRL_ENABLE_Msk;

I couldn't find these variables on my project. which library does include these variables?

[zzdz2]

Posted on May 28, 2013 at 13:47

It's defined in core_cm3.h