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Update board.c 

优化void rt_hw_us_delay(rt_uint32_t us)
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杨连钊 2019-01-16 16:38:16 +08:00 committed by GitHub
parent 4006129dce
commit a5a4c6a503
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1 changed files with 8 additions and 11 deletions
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19
bsp/stm32f10x-HAL/drivers/board.c
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@ -186,15 +186,12 @@ void rt_hw_board_init(void)
*/
void rt_hw_us_delay(rt_uint32_t us)
{
rt_uint32_t delta;
us = us * (SysTick->LOAD / (1000000 / RT_TICK_PER_SECOND));
delta = SysTick->VAL;
if (delta < us)
{
/* wait current OSTick left time gone */
while (SysTick->VAL < us);
us -= delta;
delta = SysTick->LOAD;
}
while (delta - SysTick->VAL < us);
unsigned int start, now, delta, reload, us_tick;
start = SysTick->VAL;
reload = SysTick->LOAD;
us_tick = SystemCoreClock / 1000000UL;
do{
now = SysTick->VAL;
delta = start > now ? start - now : reload + start - now;
} while(delta < us_tick * us);
}