请教独立看门狗定时器校准

悠然提问时间：2018-12-19 15:56 /

问答
是否解决:

void TIM5_IRQHandler(void)
{
  if (TIM_GetITStatus(TIM5, TIM_IT_CC4) != RESET)
  {
if(CaptureNumber == 0)
{
   /* Get the Input Capture value */
   IC1ReadValue1 = TIM_GetCapture4(TIM5);
}
else if(CaptureNumber == 1)
{
   /* Get the Input Capture value */
   IC1ReadValue2 = TIM_GetCapture4(TIM5);

   /* Capture computation */
   if (IC1ReadValue2 > IC1ReadValue1)
   {
      Capture = (IC1ReadValue2 - IC1ReadValue1);
   }
   else
   {
      Capture = ((0xFFFF - IC1ReadValue1) + IC1ReadValue2);
   }
   /* Frequency computation */
   LsiFreq = (uint32_t) SystemCoreClock / Capture;
   LsiFreq *= 8;
}

CaptureNumber++;

/* Clear TIM5 Capture compare interrupt pending bit */
TIM_ClearITPendingBit(TIM5, TIM_IT_CC4);
  }
}
ST官方的例程，用于检测内部LSI时钟频率，为什么计算出来的频率要乘以8
LsiFreq *= 8;

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6个回答

七哥回答时间：2018-12-19 16:39:21

本帖最后由 toofree 于 2018-12-19 17:49 编辑

请提完整工程，只凭你给出的信息，无法判断。

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悠然回答时间：2018-12-19 17:17:24

/* IWDG timeout equal to 250 ms (the timeout may varies due to LSI frequency
   dispersion) */
  /* Enable write access to IWDG_PR and IWDG_RLR registers */
  IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable);

  /* IWDG counter clock: LSI/32 */
  IWDG_SetPrescaler(IWDG_Prescaler_32);

  /* Set counter reload value to obtain 250ms IWDG TimeOut.
   Counter Reload Value = 250ms/IWDG counter clock period
                        = 250ms / (LSI/32)
                        = 0.25s / (LsiFreq/32)
                        = LsiFreq/(32 * 4)
                        = LsiFreq/128
*/
  IWDG_SetReload(LsiFreq/128);

  /* Reload IWDG counter */
  IWDG_ReloadCounter();

  /* Enable IWDG (the LSI oscillator will be enabled by hardware) */
  IWDG_Enable();

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