ADC problems

[tompa]

Hi, 

I am having a strange ADC problem on my STM32L431 device. I am sampling 6 channels without DMA using polling method with the following code:

 while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
	  ADC_Select_CH0();
		HAL_ADC_Start(&hadc1);
		HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
		adc_values[0] = HAL_ADC_GetValue(&hadc1);
		HAL_ADC_Stop(&hadc1);

		HAL_Delay(100);

		ADC_Select_CH1();
		HAL_ADC_Start(&hadc1);
		HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
		adc_values[1] = HAL_ADC_GetValue(&hadc1);
		HAL_ADC_Stop(&hadc1);

		HAL_Delay(100);

		ADC_Select_CH2();
		HAL_ADC_Start(&hadc1);
		HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
		adc_values[2] = HAL_ADC_GetValue(&hadc1);
		HAL_ADC_Stop(&hadc1);

		HAL_Delay(100);

		ADC_Select_CH3();
		HAL_ADC_Start(&hadc1);
		HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
		adc_values[3] = HAL_ADC_GetValue(&hadc1);
		HAL_ADC_Stop(&hadc1);

		HAL_Delay(100);

		ADC_Select_CH4();
		HAL_ADC_Start(&hadc1);
		HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
		adc_values[4] = HAL_ADC_GetValue(&hadc1);
		HAL_ADC_Stop(&hadc1);

		HAL_Delay(100);

		ADC_Select_CH5();
		HAL_ADC_Start(&hadc1);
		HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
		adc_values[5] = HAL_ADC_GetValue(&hadc1);
		HAL_ADC_Stop(&hadc1);

		HAL_Delay(100);

		printf("IN 4  = H1:21 = %d\n\r",adc_values[0]);
		printf("IN 9  = H2:7  = %d\n\r",adc_values[1]);
		printf("IN 13 = H2:15 = %d\n\r",adc_values[2]);
		printf("IN 14 = H2:17 = %d\n\r",adc_values[3]);
		printf("IN 15 = H2:19 = %d\n\r",adc_values[4]);
		printf("IN 16 = H2:21 = %d\n\r",adc_values[5]);

		printf("\nFinished ADC Conversion for all channels\r\n");
		HAL_Delay(2000);
  }

only IN 16 shows 0 and 4095 when connected to GND and Vdd. All other channels showing unexpected values - around 3500 for Vdd and around 1500 for GND. What could be a problem ? ADC_Select functions are these - always rank 1:

void ADC_Select_CH0 (void)
{
	ADC_ChannelConfTypeDef sConfig = {0};
	  /** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
	  */
	  sConfig.Channel = ADC_CHANNEL_4;
	  sConfig.Rank = 1;
	  sConfig.SamplingTime = ADC_SAMPLETIME_47CYCLES_5;
	  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	  {
		  printf("govance");
		  Error_Handler();
	  }
}

void ADC_Select_CH1 (void)
{
	ADC_ChannelConfTypeDef sConfig = {0};
	  /** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
	  */
	  sConfig.Channel = ADC_CHANNEL_9;
	  sConfig.Rank = 1;
	  sConfig.SamplingTime = ADC_SAMPLETIME_47CYCLES_5;
	  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	  {
	    Error_Handler();
	  }
}

void ADC_Select_CH2 (void)
{
	ADC_ChannelConfTypeDef sConfig = {0};
	  /** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
	  */
	  sConfig.Channel = ADC_CHANNEL_13;
	  sConfig.Rank = 1;
	  sConfig.SamplingTime = ADC_SAMPLETIME_47CYCLES_5;
	  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	  {
	    Error_Handler();
	  }
}

void ADC_Select_CH3 (void)
{
	ADC_ChannelConfTypeDef sConfig = {0};
	  /** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
	  */
	  sConfig.Channel = ADC_CHANNEL_14;
	  sConfig.Rank = 1;
	  sConfig.SamplingTime = ADC_SAMPLETIME_47CYCLES_5;
	  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	  {
	    Error_Handler();
	  }
}

void ADC_Select_CH4 (void)
{
	ADC_ChannelConfTypeDef sConfig = {0};
	  /** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
	  */
	  sConfig.Channel = ADC_CHANNEL_15;
	  sConfig.Rank = 1;
	  sConfig.SamplingTime = ADC_SAMPLETIME_47CYCLES_5;
	  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	  {
	    Error_Handler();
	  }
}

void ADC_Select_CH5 (void)
{
	ADC_ChannelConfTypeDef sConfig = {0};
	  /** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
	  */
	  sConfig.Channel = ADC_CHANNEL_16;
	  sConfig.Rank = 1;
	  sConfig.SamplingTime = ADC_SAMPLETIME_47CYCLES_5;
	  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	  {
	    Error_Handler();
	  }
}

 My ADC Init function is here:

static 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.ClockPrescaler = ADC_CLOCK_ASYNC_DIV16;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SEQ_CONV;
  hadc1.Init.LowPowerAutoWait = DISABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.NbrOfConversion = 6;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;
  hadc1.Init.OversamplingMode = DISABLE;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure Regular Channel
  */
//  sConfig.Channel = ADC_CHANNEL_4;
//  sConfig.Rank = ADC_REGULAR_RANK_1;
//  sConfig.SamplingTime = ADC_SAMPLETIME_247CYCLES_5;
//  sConfig.SingleDiff = ADC_SINGLE_ENDED;
//  sConfig.OffsetNumber = ADC_OFFSET_NONE;
//  sConfig.Offset = 0;
//  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
//  {
//    Error_Handler();
//  }
//
//  /** Configure Regular Channel
//  */
//  sConfig.Channel = ADC_CHANNEL_9;
//  sConfig.Rank = ADC_REGULAR_RANK_2;
//  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
//  {
//    Error_Handler();
//  }
//
//  /** Configure Regular Channel
//  */
//  sConfig.Channel = ADC_CHANNEL_13;
//  sConfig.Rank = ADC_REGULAR_RANK_3;
//  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
//  {
//    Error_Handler();
//  }
//
//  /** Configure Regular Channel
//  */
//  sConfig.Channel = ADC_CHANNEL_14;
//  sConfig.Rank = ADC_REGULAR_RANK_4;
//  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
//  {
//    Error_Handler();
//  }
//
//  /** Configure Regular Channel
//  */
//  sConfig.Channel = ADC_CHANNEL_15;
//  sConfig.Rank = ADC_REGULAR_RANK_5;
//  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
//  {
//    Error_Handler();
//  }
//
//  /** Configure Regular Channel
//  */
//  sConfig.Channel = ADC_CHANNEL_16;
//  sConfig.Rank = ADC_REGULAR_RANK_6;
//  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
//  {
//    Error_Handler();
//  }
  /* USER CODE BEGIN ADC1_Init 2 */

  /* USER CODE END ADC1_Init 2 */

}

 Any advice is really appreciated, thank you very much!

[Karl Yamashita]

You don't check the HAL status when you call HAL_ADC_PollForConversion. So how do you know if it return HAL_OK, HAL_ERROR or HAL_TIMEOUT?

[waclawek.jan]

What hardware is this, your own or a "known good" board like Nucleo or Disco?

How exactly are you "connecting the pins to GND or VCC", via a resistor or directly?

Read out and check/compare-to-working/post ADC and relevant GPIO registers content.

JW

[tompa · Accepted solution]

Thank you very much for your replay,

Yes, I changed my code to this:

void ADC_Select_Channel(uint32_t channel, uint16_t *result)
{
    ADC_ChannelConfTypeDef sConfig = {0};

    sConfig.Channel = channel;
    sConfig.Rank = ADC_REGULAR_RANK_1;
    sConfig.SamplingTime = ADC_SAMPLETIME_12CYCLES_5;
    sConfig.SingleDiff = ADC_SINGLE_ENDED;
    sConfig.OffsetNumber = ADC_OFFSET_NONE;
    sConfig.Offset = 0;

    if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
    {
        Error_Handler();
    }

    uint32_t sum = 0;
    for (int i = 0; i < 3; i++)
    {
        HAL_ADC_Start(&hadc1);

        if (HAL_ADC_PollForConversion(&hadc1, 100) == HAL_OK)
        {
            sum += HAL_ADC_GetValue(&hadc1);
        }
        else
        {
            printf("ADC Polling Error on channel %lu\r\n", channel);
            Error_Handler();
        }

        HAL_ADC_Stop(&hadc1);
        //HAL_Delay(10); // Pauza između mjerenja
    }

    *result = sum / 3; // Spremi srednju vrijednost
}

void Measure_All_Channels(void)
{
    uint16_t result_CH0, result_CH1, result_CH2, result_CH3, result_CH4, result_CH5, result_CH6;

    ADC_Select_Channel(ADC_CHANNEL_4, &result_CH0);
    printf("Channel 0 Average Value: %u\r\n", result_CH0);

    ADC_Select_Channel(ADC_CHANNEL_9, &result_CH1);
    printf("Channel 1 Average Value: %u\r\n", result_CH1);

    ADC_Select_Channel(ADC_CHANNEL_13, &result_CH2);
    printf("Channel 2 Average Value: %u\r\n", result_CH2);

    ADC_Select_Channel(ADC_CHANNEL_14, &result_CH3);
    printf("Channel 3 Average Value: %u\r\n", result_CH3);

    ADC_Select_Channel(ADC_CHANNEL_15, &result_CH4);
    printf("Channel 4 Average Value: %u\r\n", result_CH4);

    ADC_Select_Channel(ADC_CHANNEL_16, &result_CH5);
    printf("Channel 5 Average Value: %u\r\n", result_CH5);

    printf("------------------------\n");
}

and it works OK in this most simplistic way. I tried also a Scan Conversion Mode but I didn't succeed.
And with DMA usage my main loop stops to iterate... 

[tompa]

Thank you very much for your reply!

I finally made it with the code I posted in earlier reply.

I use my own board and connecting pins to GND and VCC directly - but it works ok now except Scan Conversion Mode. I obviously don't know how to do it... More studying to come. 

[Saket_Om]

Hello @tompa 

For the scan mode you can refer to this LL example on STM32F411-Nucleo board.