Systick定时器几个简单的函数简介_systick函数

void SysTick_CLKSourceConfig(uint32_t SysTick_CLKSource)  
{  
  /* Check the parameters */  
  assert_param(IS_SYSTICK_CLK_SOURCE(SysTick_CLKSource));  
  if (SysTick_CLKSource == SysTick_CLKSource_HCLK)  
  {  
    SysTick->CTRL |= SysTick_CLKSource_HCLK;  
  }  
  else  
  {  
    SysTick->CTRL &= SysTick_CLKSource_HCLK_Div8;  
  }  
}  

static __INLINE uint32_t SysTick_Config(uint32_t ticks)  
{   
  if (ticks > SysTick_LOAD_RELOAD_Msk)  return (1);            /* Reload value impossible */  
                                                                 
  SysTick->LOAD  = (ticks & SysTick_LOAD_RELOAD_Msk) - 1;      /* set reload register */  
  NVIC_SetPriority (SysTick_IRQn, (1<<__NVIC_PRIO_BITS) - 1);  /* set Priority for Cortex-M0 System Interrupts */  
  SysTick->VAL   = 0;                                          /* Load the SysTick Counter Value */  
  SysTick->CTRL  = SysTick_CTRL_CLKSOURCE_Msk |   
                   SysTick_CTRL_TICKINT_Msk   |   
                   SysTick_CTRL_ENABLE_Msk;                    /* Enable SysTick IRQ and SysTick Timer */  
  return (0);                                                  /* Function successful */  
}  

static __INLINE uint32_t SysTick_Config(uint32_t ticks)  
{   
  if (ticks > SysTick_LOAD_RELOAD_Msk)  return (1);            /* 判断计数值是否超过MAX */  
                                                                 
  SysTick->LOAD  = (ticks & SysTick_LOAD_RELOAD_Msk) - 1;      /* 设置预定的计数值，以便从该数值开始倒数至0 */  
  NVIC_SetPriority (SysTick_IRQn, (1<<__NVIC_PRIO_BITS) - 1);  /* 配置中断优先级 */  
  SysTick->VAL   = 0;                                          /* 初始值设置为零 */  
  SysTick->CTRL  = SysTick_CTRL_CLKSOURCE_Msk |   
                   SysTick_CTRL_TICKINT_Msk   |   
                   SysTick_CTRL_ENABLE_Msk;                    /* 使能中断请求(IRQ)和定时器timer */  
  return (0);                                                  /* 函数调用成功 */  
} 

#define SysTick_CTRL_COUNTFLAG_Pos         16                                             /*!< SysTick CTRL: COUNTFLAG Position */  
#define SysTick_CTRL_COUNTFLAG_Msk         (1ul << SysTick_CTRL_COUNTFLAG_Pos)            /*!< SysTick CTRL: COUNTFLAG Mask */  
  
#define SysTick_CTRL_CLKSOURCE_Pos          2                                             /*!< SysTick CTRL: CLKSOURCE Position */  
#define SysTick_CTRL_CLKSOURCE_Msk         (1ul << SysTick_CTRL_CLKSOURCE_Pos)            /*!< SysTick CTRL: CLKSOURCE Mask */  
  
#define SysTick_CTRL_TICKINT_Pos            1                                             /*!< SysTick CTRL: TICKINT Position */  
#define SysTick_CTRL_TICKINT_Msk           (1ul << SysTick_CTRL_TICKINT_Pos)              /*!< SysTick CTRL: TICKINT Mask */  
  
#define SysTick_CTRL_ENABLE_Pos             0                                             /*!< SysTick CTRL: ENABLE Position */  
#define SysTick_CTRL_ENABLE_Msk            (1ul << SysTick_CTRL_ENABLE_Pos)               /*!< SysTick CTRL: ENABLE Mask */  

void delay_init() // 去除了OS的相关内容  
{  
    SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8);   //选择外部时钟  HCLK/8  
    fac_us=SystemCoreClock/8000000;             //为系统时钟的1/8    
    fac_ms=(u16)fac_us*1000;                    //非OS下,代表每个ms需要的systick时钟数     
} 

​​​​​​​            

#ifdef SYSCLK_FREQ_HSE  
  uint32_t SystemCoreClock         = SYSCLK_FREQ_HSE;        /*!< System Clock Frequency (Core Clock) */  
#elif defined SYSCLK_FREQ_24MHz  
  uint32_t SystemCoreClock         = SYSCLK_FREQ_24MHz;        /*!< System Clock Frequency (Core Clock) */  
#elif defined SYSCLK_FREQ_36MHz  
  uint32_t SystemCoreClock         = SYSCLK_FREQ_36MHz;        /*!< System Clock Frequency (Core Clock) */  
#elif defined SYSCLK_FREQ_48MHz  
  uint32_t SystemCoreClock         = SYSCLK_FREQ_48MHz;        /*!< System Clock Frequency (Core Clock) */  
#elif defined SYSCLK_FREQ_56MHz  
  uint32_t SystemCoreClock         = SYSCLK_FREQ_56MHz;        /*!< System Clock Frequency (Core Clock) */  
#elif defined SYSCLK_FREQ_72MHz  
  uint32_t SystemCoreClock         = SYSCLK_FREQ_72MHz;        /*!< System Clock Frequency (Core Clock) */  
#else /*!< HSI Selected as System Clock source */  
  uint32_t SystemCoreClock         = HSI_VALUE;        /*!< System Clock Frequency (Core Clock) */  
#endif  

void delay_us(u32 nus) // 非OS的delay函数的调用  
{         
    u32 temp;              
    SysTick->LOAD=nus*fac_us;                    //时间加载             
    SysTick->VAL=0x00;                           //清空计数器  
    SysTick->CTRL|=SysTick_CTRL_ENABLE_Msk ; //使能systcik滴答定时器        
    do  
    {  
        temp=SysTick->CTRL;  
    }while((temp&0x01)&&!(temp&(1<<16)));     //等待直达条件不成立     
    SysTick->CTRL&=~SysTick_CTRL_ENABLE_Msk; //关闭计数器  
    SysTick->VAL =0X00;                           //清空计数器       
}  
// systick滴答定时器退出循环的标志：systick滴答定时器被使能+计数器自减至0