STM32 ADC Continuous Conv Mode does not automatically start conversion

Question

I am trying to configure ADC over a STM32F411RE in simple Continuous Conv Mode. I used CubeMX to generate the code based on HAL drivers and this is some parts of the generated code which intialize ADC:

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

    /**Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion) 
    */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV8;
  hadc1.Init.Resolution = ADC_RESOLUTION_8B;
  hadc1.Init.ScanConvMode = DISABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

}

and here is the main function:

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();

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

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_ADC1_Init();
  MX_USART2_UART_Init();

  /* USER CODE BEGIN 2 */
  uint8_t analogVal;
  uint8_t string[] = "Poll failed\n";

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  HAL_Delay(1000);
  if( HAL_ADC_Start(&hadc1) == HAL_OK) HAL_UART_Transmit(&huart2,(uint8_t*)"STRT OK\n",8,100);
  else HAL_UART_Transmit(&huart2,(uint8_t *)HAL_ADC_Start(&hadc1),1,100);
  while (1)
  {
  /* USER CODE END WHILE */

  /* USER CODE BEGIN 3 */
    if(HAL_ADC_PollForConversion(&hadc1,1) == HAL_OK){
      analogVal = HAL_ADC_GetValue(&hadc1);
      HAL_UART_Transmit(&huart2,&analogVal,sizeof(analogVal),100);
    }
    else{
      HAL_UART_Transmit(&huart2,string,sizeof(string)-1,100);
    }
    HAL_Delay(100);
  }
  /* USER CODE END 3 */

}

If I compile and upload this code into the microcontroller, no more than once analogVal would be transmitted over UART. But if I place HAL_ADC_Start function inside the while loop, HAL_ADC_PollForConversion returned value will be HAL_OK in every cycle of while and there will be a analogVal to report.

My question is, why should I everytime ask the ADC to start if I have enabled ContinuousConvMode?

Solution

I am sure that the EOC flag setting is the problem. hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV; should be changed to hadc1.Init.EOCSelection = EOC_SEQ_CONV;.

Your current option ADC_EOC_SINGLE_CONV acts like an enable of single conversion, but you need EOC_SEQ_CONV aka sequential conversions.

It is pretty much the same problem that has been discussed here.