STM32F0 adc时钟问题

BitFu 提问时间：2016-2-20 23:20 /

复制一个从标准库内的示例测试后ADC正常工作，但我想搞清楚ADC时钟，
示例中，ADC内部14M时钟是关闭的（RCC->CR2最低位），但ADC选择的是内部14M时钟（RCC->CFGR3中）；这种情况ADC为什么会工作呢？那工作的时钟究竟会是多少呢？

赞收藏评论2 发布时间：2016-2-20 23:20

2个回答

BitFu 回答时间：2016-2-22 11:09:49

最糟糕的是下面的代码出来的ADC时钟竟然是14mhZ,我本以为是48/4=12M呢
void AdcConfig(void)
{
  ADC_InitTypeDef    ADC_InitStructure;
  GPIO_InitTypeDef GPIO_InitStructure;

  /* ADC1 Periph clock enable */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);

  /* Configure ADC Channel11 as analog input */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3|GPIO_Pin_4;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  /* ADCs DeInit */
  ADC_DeInit(ADC1);

//¸´Î»ÄÚ²¿14MÊ±ÖÓ·¢ÉúÆ÷
//RCC->CR2 &= (uint32_t)0xFFFFFFFE;

//ADCÊ±ÖÓÎªPCLK/4  12MHz
RCC_ADCCLKConfig(RCC_ADCCLK_PCLK_Div4);

  //Initialize ADC structure
  ADC_StructInit(&ADC_InitStructure);

  /* Configure the ADC1 in continuous mode with a resolution equal to 12 bits  */
  ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
  ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
  ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_ScanDirection = ADC_ScanDirection_Upward;
  ADC_Init(ADC1, &ADC_InitStructure);

  /* Convert the ADC1 Channel with 239.5 Cycles as sampling time */
// ADC_ChannelConfig(ADC1, ADC_Channel_3 , ADC_SampleTime_7_5Cycles);
  ADC_ChannelConfig(ADC1, ADC_Channel_4 , ADC_SampleTime_239_5Cycles);

  /* ADC Calibration */
  ADC_GetCalibrationFactor(ADC1);

  /* Enable the ADC peripheral */
  ADC_Cmd(ADC1, ENABLE);

  /* Wait the ADRDY flag */
  while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_ADRDY));

  /* ADC1 regular Software Start Conv */
  ADC_StartOfConversion(ADC1);

}

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