Individually read distinct inputs with STM32F0 ADC

Question

STM32F072CBU microcontroller.

I have multiple inputs to the ADC and would like to read them individually and separately. STMcubeMX produces boilerplate code which assumes I wish to read all of the inputs sequentially, and I have not been able to figure out how to correct this.

This blog post expresses the same problem I am having, but the solution given doesn't seem to work. Turning the ADC on and off for each conversion correlates with error in the returned value. Only when I configure a single ADC input in STMcubeMX and then poll without de-initializing the ADC are accurate readings returned.

cubeMX's adc_init function:

/* ADC init function */
static void MX_ADC_Init(void)
{

  ADC_ChannelConfTypeDef sConfig;

    /**Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion) 
    */
  hadc.Instance = ADC1;
  hadc.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
  hadc.Init.Resolution = ADC_RESOLUTION_12B;
  hadc.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc.Init.ScanConvMode = ADC_SCAN_DIRECTION_FORWARD;
  hadc.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc.Init.LowPowerAutoWait = DISABLE;
  hadc.Init.LowPowerAutoPowerOff = DISABLE;
  hadc.Init.ContinuousConvMode = DISABLE;
  hadc.Init.DiscontinuousConvMode = DISABLE;
  hadc.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc.Init.DMAContinuousRequests = DISABLE;
  hadc.Init.Overrun = ADC_OVR_DATA_PRESERVED;
  if (HAL_ADC_Init(&hadc) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel to be converted. 
    */
  sConfig.Channel = ADC_CHANNEL_0;
  sConfig.Rank = ADC_RANK_CHANNEL_NUMBER;
  sConfig.SamplingTime = ADC_SAMPLETIME_41CYCLES_5;
  if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel to be converted. 
    */
  sConfig.Channel = ADC_CHANNEL_1;
  if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel to be converted. 
    */
  sConfig.Channel = ADC_CHANNEL_2;
  if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel to be converted. 
    */
  sConfig.Channel = ADC_CHANNEL_3;
  if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel to be converted. 
    */
  sConfig.Channel = ADC_CHANNEL_4;
  if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel to be converted. 
    */
  sConfig.Channel = ADC_CHANNEL_TEMPSENSOR;
  if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel to be converted. 
    */
  sConfig.Channel = ADC_CHANNEL_VREFINT;
  if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

main.c

int main(void)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration----------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_ADC_Init();
  MX_USART1_UART_Init();

  /* USER CODE BEGIN 2 */
  //HAL_TIM_Base_Start_IT(&htim3);
  init_printf(NULL, putc_wrangler);
  HAL_ADCEx_Calibration_Start(&hadc);
  HAL_ADC_DeInit(&hadc); // ADC is initialized for every channel change
  schedule_initial_events();
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  event_loop();
  /* USER CODE END WHILE */

  /* USER CODE BEGIN 3 */

  /* USER CODE END 3 */

}

My process right now for turning the ADC off and reinitializing to change channels:

// Set up
  ADC_ChannelConfTypeDef channelConfig;

  channelConfig.SamplingTime = samplingT;
  channelConfig.Channel = sensorChannel;
  channelConfig.Rank = ADC_RANK_CHANNEL_NUMBER;

  if (HAL_ADC_Init(&hadc) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  if (HAL_ADC_ConfigChannel(&hadc, &channelConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

// Convert
  uint16_t retval;

  if (HAL_ADC_Start(&hadc) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  if (HAL_ADC_PollForConversion(&hadc, 1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  if (HAL_ADC_GetError(&hadc) != HAL_ADC_ERROR_NONE)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  retval = (uint16_t) HAL_ADC_GetValue(&hadc);

  if (HAL_ADC_Stop(&hadc) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

// Close
  HAL_ADC_DeInit(&hadc);

At this point I'm not really sure that there's a way to accomplish what I want, STM32 seems dead set on active ADC lines being in the regular group and being converted in order.

user_11615019 · Answer

I had the similar problem. I was using STM32F091RC. On ADC_V_PIN I had external multiplexer. On ADC_T_PIN I had NTC reading. I was controlling external multiplexer with GPIOs (this is not seen in the code below). What I needed was multiple successive readings of ADC_V_PIN, after that single ADC_T_PIN reading. With default sequential reading of ADC I would get between each external multiplexed reading of ADC_V_PIN also ADC_T_PIN reading. Using HAL_ADC_ConfigChannel multiple times seemed to OR with each other, and I had problems with reading. So I didn't use HAL_ADC_ConfigChannel at all. Instead, I reconfigured CHSELR register before each software triggered AD conversion. This was the way to make internal and external multiplexer work together.

Here is initialization code:

    GPIO_InitStruct.Pin = ADC_V_PIN;
    GPIO_InitStruct.Mode  = GPIO_MODE_ANALOG;
    GPIO_InitStruct.Pull  = GPIO_NOPULL;
    HAL_GPIO_Init(ADC_V_PORT, &GPIO_InitStruct);

    GPIO_InitStruct.Pin = ADC_T_PIN;
    GPIO_InitStruct.Mode  = GPIO_MODE_ANALOG;
    GPIO_InitStruct.Pull  = GPIO_NOPULL;
    HAL_GPIO_Init(ADC_T_PORT, &GPIO_InitStruct);

    g_AdcHandle.Instance = ADC1;

    if (HAL_ADC_DeInit(&g_AdcHandle) != HAL_OK)
    {
        /* ADC initialization error */
        Error_Handler();
    }

    g_AdcHandle.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
    g_AdcHandle.Init.Resolution = ADC_RESOLUTION_12B;
    g_AdcHandle.Init.DataAlign = ADC_DATAALIGN_RIGHT;
    g_AdcHandle.Init.ScanConvMode = ADC_SCAN_DIRECTION_FORWARD;;
    g_AdcHandle.Init.ContinuousConvMode = DISABLE;
    g_AdcHandle.Init.DiscontinuousConvMode = ENABLE;
    g_AdcHandle.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
    g_AdcHandle.Init.LowPowerAutoWait      = DISABLE;
    g_AdcHandle.Init.LowPowerAutoPowerOff  = DISABLE;

    g_AdcHandle.Init.ExternalTrigConv      = ADC_SOFTWARE_START;
    g_AdcHandle.Init.ExternalTrigConvEdge  = ADC_EXTERNALTRIGCONVEDGE_NONE;


    g_AdcHandle.Init.DMAContinuousRequests = DISABLE;
    g_AdcHandle.Init.Overrun               = ADC_OVR_DATA_OVERWRITTEN;
    g_AdcHandle.Init.SamplingTimeCommon    = ADC_SAMPLETIME_239CYCLES_5;

    if (HAL_ADC_Init(&g_AdcHandle) != HAL_OK)
    {
      /* ADC initialization error */
      Error_Handler();
    }

    if (HAL_ADCEx_Calibration_Start(&g_AdcHandle) != HAL_OK)
    {
      /* Calibration Error */
      Error_Handler();
    }

while(1){

        ADC1->CHSELR = ADC_CHSELR_CHSEL0;
        HAL_ADC_Start(&g_AdcHandle);
        HAL_ADC_PollForConversion(&g_AdcHandle, 10);
        V = HAL_ADC_GetValue(&g_AdcHandle);
        HAL_ADC_Stop(&g_AdcHandle);

        ADC1->CHSELR = ADC_CHSELR_CHSEL10;
        HAL_ADC_Start(&g_AdcHandle);
        HAL_ADC_PollForConversion(&g_AdcHandle, 10);
        T = HAL_ADC_GetValue(&g_AdcHandle);
        HAL_ADC_Stop(&g_AdcHandle);
    }

Individually read distinct inputs with STM32F0 ADC

2 Answers