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ADC value Oscillates form 0 to 151 even when the ADC pin is grounded

pagurudeen
Associate II


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


/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <string.h>
#include <stdio.h>
/* USER CODE END Includes */


/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */


/* USER CODE END PTD */


/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */


/* USER CODE END PD */


/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */


/* USER CODE END PM */


/* Private variables ---------------------------------------------------------*/
ADC_HandleTypeDef hadc1;


UART_HandleTypeDef huart7;


/* USER CODE BEGIN PV */


/* USER CODE END PV */


/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_ADC1_Init(void);
static void MX_UART7_Init(void);
/* USER CODE BEGIN PFP */


/* USER CODE END PFP */


/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
uint32_t adc_val;


/* USER CODE END 0 */


/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{
  /* USER CODE BEGIN 1 */
uint16_t raw;
  char msg[10];
  /* 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_ADC1_Init();
  MX_UART7_Init();
  /* USER CODE BEGIN 2 */
//  HAL_ADC_Start(&hadc1, &buffer, 1);


  /* USER CODE END 2 */


  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */


    /* USER CODE BEGIN 3 */


    // Test: Set GPIO pin high
    HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0, GPIO_PIN_SET);


    // Get ADC value
    HAL_ADC_Start(&hadc1);
    HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
    raw = HAL_ADC_GetValue(&hadc1);


    // Test: Set GPIO pin low
    HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0, GPIO_PIN_RESET);


    // Convert to string and print
    sprintf(msg, "%hu\r\n", raw);
    HAL_UART_Transmit(&huart7, (uint8_t*)msg, strlen(msg), HAL_MAX_DELAY);


    // Pretend we have to do something else for a while
    HAL_Delay(100);
  }
  /* USER CODE END 3 */
}


/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};


  /** Configure the main internal regulator output voltage
  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE3);


  while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}


  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSIDiv = RCC_HSI_DIV2;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }


  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2
                              |RCC_CLOCKTYPE_PCLK3;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB3CLKDivider = RCC_HCLK_DIV1;


  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
  {
    Error_Handler();
  }
}


/**
  * @brief ADC1 Initialization Function
  * @PAram None
  * @retval None
  */
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_DIV1;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc1.Init.LowPowerAutoWait = DISABLE;
  hadc1.Init.ContinuousConvMode = DISABLE;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.SamplingMode = ADC_SAMPLING_MODE_NORMAL;
  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_0;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_2CYCLES_5;
  sConfig.SingleDiff = ADC_SINGLE_ENDED;
  sConfig.OffsetNumber = ADC_OFFSET_NONE;
  sConfig.Offset = 0;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN ADC1_Init 2 */


  /* USER CODE END ADC1_Init 2 */

 

I'm using STM32H563ZIT6 (Nucleo Board) and configured a single ADC input pin PA0, with a frequency of 32MHz and the following configuration as in image. However, when the ADC pin is connected to ground, the ADC value oscillates between 0 and 152 ADC counts. Please help me to solve this issue.

4 REPLIES 4
AScha.3
Chief

Hi,

you have to run calibration on ADC first ! (read in rm! )

HAL_ADCEx_Calibration_Start(..);

If you feel a post has answered your question, please click "Accept as Solution".

Thanks for the reply,  I have calibrated the ADC as you mentioned and the results are better but still I'm getting the ADC value up to  96.

if (HAL_ADCEx_Calibration_Start(&hadc1, ADC_SINGLE_ENDED) == HAL_OK)
{
HAL_UART_Transmit(&huart7, (uint8_t*)"Successfull", 12, HAL_MAX_DELAY);
}

I'm working in a project where I need to configure 14 ADC pins, so I have actually configured 14 ADC pins using DMA, but in 11 ADC pins I'm facing the same issue (Getting oscillating ADC value up to 200 ADC counts). So I have created a new project and configured only a single ADC pin (without DMA) and posted earlier. 

 

As for the remaining 3 ADC pins,

1. In two ADC pins (PC4 & PC5) - The voltage of sensor output pin is reduced when connected to the ADC pin of the STM32H563 controller.

2. In last ADC pin (PA2) - The voltage of sensor output pin is Increased when connected to the ADC pin of the STM32H563 controller.

But when i give 3.3v to the ADC pins, i got 4095 (12 bit max value) from all 14 ADC pins.

Ok, so next "problem" : you set very short sampling time, this works only on low impedance input.

-> read in ds...

AScha3_0-1709991294253.png

and set longer sampling time or (if slow signal or DC ) a big cer.cap (100nF or so) on short connection adc-input to gnd.

If still "Getting oscillating ADC value" look with a scope on adc-input pin - maybe adc is right. 🙂

If you feel a post has answered your question, please click "Accept as Solution".

Sorry for the delay, I have increased the sampling time every steps up to 640.5 cycles but the still the ADC value is oscillating as earlier. 

I have checked the Vref+ and VDDA pin voltage on scope and the voltage varies from 3.28V to 3.3V and On ground pin the voltage is zero but there is a noise with voltage of 80mV which is around 100 ADC count. 

In Errata sheet of this controller, I can't find any issue on the GND pin.