关于STM32F103RET6 的ADC接口会输出200多mv的电压以及在工作中会输出低电平脉冲（频率是采样频率）的问题

``用单片机采集分压电阻过来的电压值，在调试期间，发现初始化完IO口后，ADC输入IO口的电压会上浮200mv左右，开始ADC采集时，会出现低电平脉冲，频率是ADC的采集频率，即35.7K。同时，采集到的电压值也不准确，不同电压值，ADC输出口上浮的电压不同。采集到的电压值和实际值偏差也不是固定，感觉有一个关系。

程序上是采用ADC+DMA的采集方式，数据是通过半传输完成这中断+传输完成中断里得到的，每次采集100个数据（数组）。一直连续采集500ms后停止，找出这一阶段中采集到的最大值。

程序如下

/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "adc.h"

/* USER CODE BEGIN 0 */
#include "tim.h"
uint16_t adc_data[100]= {0};
/* USER CODE END 0 */

ADC_HandleTypeDef hadc1;
DMA_HandleTypeDef hdma_adc1;

/* ADC1 init function */
void MX_ADC1_Init(void)
{

  /* USER CODE BEGIN ADC1_Init 0 */

  /* USER CODE END ADC1_Init 0 */

  ADC_ChannelConfTypeDef sConfig = {0};

  /* USER CODE BEGIN ADC1_Init 1 */

  /* USER CODE END ADC1_Init 1 */

  /** Common config
  */
  hadc1.Instance = ADC1;
  hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure Regular Channel
  */
  sConfig.Channel = ADC_CHANNEL_14;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_239CYCLES_5;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN ADC1_Init 2 */

    //HAL_ADCEx_Calibration_Start(&hadc1);
  /* USER CODE END ADC1_Init 2 */

}

void HAL_ADC_MspInit(ADC_HandleTypeDef* adcHandle)
{

  GPIO_InitTypeDef GPIO_InitStruct = {0};
  if(adcHandle->Instance==ADC1)
  {
  /* USER CODE BEGIN ADC1_MspInit 0 */
      GPIO_InitStruct.Pull = GPIO_NOPULL;
      GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  /* USER CODE END ADC1_MspInit 0 */
    /* ADC1 clock enable */
    __HAL_RCC_ADC1_CLK_ENABLE();

    __HAL_RCC_GPIOC_CLK_ENABLE();
    /**ADC1 GPIO Configuration
    PC4     ------> ADC1_IN14
    */
    GPIO_InitStruct.Pin = GPIO_PIN_4;
    GPIO_InitStruct.Mode = GPIO_MODE_ANALOG;
    HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

    /* ADC1 DMA Init */
    /* ADC1 Init */
    hdma_adc1.Instance = DMA1_Channel1;
    hdma_adc1.Init.Direction = DMA_PERIPH_TO_MEMORY;
    hdma_adc1.Init.PeriphInc = DMA_PINC_DISABLE;
    hdma_adc1.Init.MemInc = DMA_MINC_ENABLE;
    hdma_adc1.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD;
    hdma_adc1.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;
    hdma_adc1.Init.Mode = DMA_CIRCULAR;
    hdma_adc1.Init.Priority = DMA_PRIORITY_LOW;
    if (HAL_DMA_Init(&hdma_adc1) != HAL_OK)
    {
      Error_Handler();
    }

    __HAL_LINKDMA(adcHandle,DMA_Handle,hdma_adc1);

    /* ADC1 interrupt Init */
    HAL_NVIC_SetPriority(ADC1_2_IRQn, 2, 2);
    HAL_NVIC_EnableIRQ(ADC1_2_IRQn);
  /* USER CODE BEGIN ADC1_MspInit 1 */

    __HAL_DMA_DISABLE_IT(&hdma_adc1,DMA_IT_TC | DMA_IT_HT);
  //  HAL_DMA_RegisterCallback(&hdma_adc1, HAL_DMA_XFER_CPLT_CB_ID, ADCDataCollect_DmaCplCb);
  //  HAL_DMA_RegisterCallback(&hdma_adc1, HAL_DMA_XFER_HALFCPLT_CB_ID, ADCDataCollect_DmaHalfCplCb);
  /* USER CODE END ADC1_MspInit 1 */
  }
}

void HAL_ADC_MspDeInit(ADC_HandleTypeDef* adcHandle)
{

  if(adcHandle->Instance==ADC1)
  {
  /* USER CODE BEGIN ADC1_MspDeInit 0 */

  /* USER CODE END ADC1_MspDeInit 0 */
    /* Peripheral clock disable */
    __HAL_RCC_ADC1_CLK_DISABLE();

    /**ADC1 GPIO Configuration
    PC4     ------> ADC1_IN14
    */
    HAL_GPIO_DeInit(GPIOC, GPIO_PIN_4);

    /* ADC1 DMA DeInit */
    HAL_DMA_DeInit(adcHandle->DMA_Handle);

    /* ADC1 interrupt Deinit */
    HAL_NVIC_DisableIRQ(ADC1_2_IRQn);
  /* USER CODE BEGIN ADC1_MspDeInit 1 */

  /* USER CODE END ADC1_MspDeInit 1 */
  }
}

/* USER CODE BEGIN 1 */
/**
  * @brief 鍚姩ADC+DMA浼犺緭
  * @retval None
  */
void ADC1Star(void)
{
    //HAL_ADCEx_Calibration_Start(&hadc1);
    //HAL_Delay(100);
    HAL_NVIC_EnableIRQ(DMA1_Channel1_IRQn);
    HAL_NVIC_EnableIRQ(ADC1_2_IRQn);
    __HAL_DMA_ENABLE_IT(&hdma_adc1, DMA_IT_TE | DMA_IT_TC);
    HAL_ADC_Start_DMA(&hadc1,(uint32_t*)adc_data,100);

}
/**
  * @brief 鍏抽棴ADC+DMA浼犺緭
  * @retval None
  */
void ADC1Stop(void)
{
    HAL_NVIC_DisableIRQ(DMA1_Channel1_IRQn);
    HAL_NVIC_DisableIRQ(ADC1_2_IRQn);
     __HAL_DMA_CLEAR_FLAG(&hdma_adc1, __HAL_DMA_GET_HT_FLAG_INDEX(&hdma_adc1));
     __HAL_DMA_CLEAR_FLAG(&hdma_adc1, __HAL_DMA_GET_TC_FLAG_INDEX(&hdma_adc1));
    __HAL_DMA_DISABLE_IT(&hdma_adc1, DMA_IT_TE | DMA_IT_TC);
    HAL_ADC_Stop_DMA(&hadc1);
    //HAL_ADC_MspDeInit(&hadc1);
}
/**
  * @brief DMA半传输完成中断
  * @retval None
  */
void HAL_ADC_ConvHalfCpltCallback(ADC_HandleTypeDef* hadc)
{
    uint8_t i;

    if(__HAL_TIM_GET_COUNTER(&htim1) < 4920)
    {
        for(i = 0;i<50;i++)
        {
            if(adc_data[i] > S_GLOBAL_VARIBLE.ultrasonic_ADC_DATA)
            {
                S_GLOBAL_VARIBLE.ultrasonic_ADC_DATA = adc_data[i];//找出最大值
            }
        }
    }

    //__HAL_DMA_ENABLE_IT(&hdma_adc1,DMA_IT_TC);    //启动全传输完成中断

}
/**
  * @brief DMA全传输完成中断
  * @retval None
  */
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
    uint8_t i;
    if(__HAL_TIM_GET_COUNTER(&htim1) < 4920)
    {
        for(i = 50;i<100;i++)
        {
            if(adc_data[i] > S_GLOBAL_VARIBLE.ultrasonic_ADC_DATA)
            {
                S_GLOBAL_VARIBLE.ultrasonic_ADC_DATA = adc_data[i];//找到最大值
            }
        }
    }

        //__HAL_DMA_ENABLE_IT(&hdma_adc1,DMA_IT_HT);//启动半传输完成中断
}
/* USER CODE END 1 */