LPC1768菜鸟学习之路systick

LPC1768在代码里用到使用systick时，是以如下形式出现

  if (SysTick_Config(SystemCoreClock /1000))/1ms进入一次中断/

 {

    while (1);                                  /* 错误情况下就停在这里

  }

这个函数的原型是

__STATIC_INLINEuint32_t SysTick_Config(uint32_t ticks)

{

  if ((ticks - 1) > SysTick_LOAD_RELOAD_Msk) 

return(1);      /* Reload value impossible */

  SysTick->LOAD  = ticks - 1;                                  /* set reloadregister */

  NVIC_SetPriority (SysTick_IRQn,(1<<__NVIC_PRIO_BITS) - 1);  /* setPriority for Systick Interrupt */

  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 andSysTick Timer */

  return (0);                                                 /* Function successful */

}

节拍函数的初始化，需要提一下的是这个函数的形参SystemCoreClock/1000,SystemCoreClock 是CPU频率，假设是100M的情况下，100M/1000= 100K，节拍定时器在100M的时钟下计数100K次，1S可以溢出1000次，就是说1ms溢出一次，所以就是定时1ms。如果想定时10ms,就把除数改成100。

延迟函数可以这样写：

staticvoid Delay (uint32_t dlyTicks) {
  uint32_t curTicks;

  curTicks = msTicks;
  while ((msTicks - curTicks) <dlyTicks);
}

voidSysTick_Handler(void) {
  msTicks++;                        /* increment counternecessary in Delay() *

}