STM32F407 Systick 笔记整理

Systick 部分简单解析

总结：其官方资料在Cortex-M4中： 

Systick是一个24位计数器，vlue自减等于0时触发中断，并重新加载load值，如此循环。

SystemCoreClock是时钟频率=168000000，执行SystemCoreClock次tick的时间是1秒。

其官方资料:

int main(void)

{

  /* Initialize Leds mounted on STM32F4-Discovery board */
  STM_EVAL_LEDInit(LED4);
  STM_EVAL_LEDInit(LED3);
  STM_EVAL_LEDInit(LED5);
  STM_EVAL_LEDInit(LED6);
  /* Turn on LED4 and LED5 */
  STM_EVAL_LEDOn(LED4);
  STM_EVAL_LEDOn(LED5);
  /* Setup SysTick Timer for 1 msec interrupts.
     ------------------------------------------
    1. The SysTick_Config() function is a CMSIS function which configure:
       - The SysTick Reload register with value passed as function parameter.
       - Configure the SysTick IRQ priority to the lowest value (0x0F).
       - Reset the SysTick Counter register.
       - Configure the SysTick Counter clock source to be Core Clock Source (HCLK).
       - Enable the SysTick Interrupt.
       - Start the SysTick Counter.


    2. You can change the SysTick Clock source to be HCLK_Div8 by calling the
       SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8) just after the
       SysTick_Config() function call. The SysTick_CLKSourceConfig() is defined
       inside the misc.c file.
    3. You can change the SysTick IRQ priority by calling the
       NVIC_SetPriority(SysTick_IRQn,...) just after the SysTick_Config() function
       call. The NVIC_SetPriority() is defined inside the core_cm4.h file.
    4. To adjust the SysTick time base, use the following formula:
        Reload Value = SysTick Counter Clock (Hz) x  Desired Time base (s)
       - Reload Value is the parameter to be passed for SysTick_Config() function
       - Reload Value should not exceed 0xFFFFFF
   */
  if (SysTick_Config(SystemCoreClock /1000  ))
  {
    /* Capture error */
    while (1);
  }

  while (1000)
  {
    /* Toggle LED3 and LED6 */
    STM_EVAL_LEDToggle(LED3);
    STM_EVAL_LEDToggle(LED6);

    /* Insert 50 ms delay */
    Delay(1000 );
    /* Toggle LED4 and LED5 */
    STM_EVAL_LEDToggle(LED4);
    STM_EVAL_LEDToggle(LED5);
    /* Insert 100 ms delay */
    Delay(1000  );
  }
}

/**
  * @brief  Inserts a delay time.
  * @param  nTime: specifies the delay time length, in milliseconds.
  * @retval None
  */
void Delay(__IO uint32_t nTime)
{
  TimingDelay = nTime;
  while(TimingDelay != 0);
}

/**
  * @brief  Decrements the TimingDelay variable.
  * @param  None
  * @retval None
  */
void TimingDelay_Decrement(void)
{
  if (TimingDelay != 0x00)
  {
    TimingDelay--;
  }

}