#define CPU_FREQUENCY_MHZ 168
static __IO uint32_t TimingDelay;
/* Private function prototypes -----------------------------------------------*/
void delay_us(__IO uint32_t nTime)
{
int old_val,new_val,val;
if(nTime > 900)
{
for(old_val = 0; old_val < nTime/900; old_val++)
{
delay_us(900);
}
nTime = nTime%900;
}
old_val = SysTick->VAL;
new_val = old_val - CPU_FREQUENCY_MHZ*nTime;
if(new_val >= 0)
{
do
{
val = SysTick->VAL;
}
while((val < old_val)&&(val >= new_val));
}
else
{
new_val +=CPU_FREQUENCY_MHZ*1000;
do
{
val = SysTick->VAL;
}
while((val <= old_val)||(val > new_val));
}
}
这个是我常用的us延时，通过读取滴答定时器的计数值来延时，对滴答定时器的运行和中断没有影响。
|
楼主
