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STM32u5 ADC not reading 4 channels properly using polling mode/ADC scan mode)

aristot
Associate

Hello,

I am working on simple program to read ADC using the STM32u585QII microcontroller.

I am using polling method in Scan mode on 4 channels. All set as 14 bit but understood the readin will be in 12 bit.

The problem is the values I am getting are not reflecting the real value at the input. I am receiving something like 

1586 cnts on 1st and 3rd channel and 2395 cnts on 2nd and 4th channel. Values make no sense assuming I have stable (verified with oscilloscope) voltage 1.61V. Vref is 2.5V external.

Also when I am trying change voltage at the inputs the reading doesn't change.

Can someone point me the possible issue with the configuration.

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2025 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* 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;

DCACHE_HandleTypeDef hdcache1;

/* 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_DCACHE1_Init(void);
static void MX_ICACHE_Init(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
	int isADCfinished = 1;
	uint32_t ADC_Data[4];
	uint32_t Singl_Read;
	uint32_t timestamp;
	int i = 0;

	int _write(int32_t file, uint8_t *ptr, int32_t len)
	{
	    for (int i = 0; i < len; i++)
	    {
	        ITM_SendChar(*ptr++);
	    }
	    return len;
	}


/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
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_ADC1_Init();
  MX_DCACHE1_Init();
  MX_ICACHE_Init();
  /* USER CODE BEGIN 2 */
//  HAL_ADC_Start(&hadc1)

  HAL_PWREx_EnableVddA();
  HAL_PWREx_EnableVddIO2();
  HAL_PWREx_EnablePullUpPullDownConfig();
  HAL_ADCEx_Calibration_Start(&hadc1, ADC_CALIB_OFFSET, ADC_SINGLE_ENDED);
  printf("Hello World!!\n");
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
	  for(i=0; i<4; i++)
	  	  {
	  		  HAL_ADC_Start(&hadc1);
	  		  HAL_Delay(10);
	  		  HAL_ADC_PollForConversion(&hadc1, 1);
	  //		  HAL_Delay(10);
	  		  Singl_Read = HAL_ADC_GetValue(&hadc1);
	  		  switch(i)
	  		  {
	  		  	  case 0:
	  		  		ADC_Data[0] = Singl_Read;
	  		  		  break;
	  		  	  case 1:
	  		  		ADC_Data[1] = Singl_Read;
	  		  		  break;
	  		  	  case 2:
	  		  		ADC_Data[2] = Singl_Read;
	  		  		  break;
	  		  	  case 3:
	  		  		ADC_Data[3] = Singl_Read;
	  		  		  break;

	  		  }
	  	  }

	  HAL_Delay(5);
	  	  printf("SIN_A = %lu COS_A = %lu SIN_B = %lu COS_B = %lu\n", ADC_Data[0],ADC_Data[1],ADC_Data[2],ADC_Data[3]);
	  	  for(i=0; i<4; i++)
	  	  {
	  		  ADC_Data[i]=0;
	  	  }
	  	  HAL_Delay(5);
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
  /* 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
  */
  if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMBOOST = RCC_PLLMBOOST_DIV1;
  RCC_OscInitStruct.PLL.PLLM = 1;
  RCC_OscInitStruct.PLL.PLLN = 20;
  RCC_OscInitStruct.PLL.PLLP = 2;
  RCC_OscInitStruct.PLL.PLLQ = 2;
  RCC_OscInitStruct.PLL.PLLR = 1;
  RCC_OscInitStruct.PLL.PLLRGE = RCC_PLLVCIRANGE_1;
  RCC_OscInitStruct.PLL.PLLFRACN = 0;
  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_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB3CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief ADC1 Initialization Function
  *  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_14B;
  hadc1.Init.GainCompensation = 0;
  hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc1.Init.LowPowerAutoWait = DISABLE;
  hadc1.Init.ContinuousConvMode = DISABLE;
  hadc1.Init.NbrOfConversion = 4;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.TriggerFrequencyMode = ADC_TRIGGER_FREQ_HIGH;
  hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;
  hadc1.Init.LeftBitShift = ADC_LEFTBITSHIFT_NONE;
  hadc1.Init.ConversionDataManagement = ADC_CONVERSIONDATA_DR;
  hadc1.Init.OversamplingMode = DISABLE;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure Regular Channel
  */
  sConfig.Channel = ADC_CHANNEL_7;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_5CYCLE;
  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_8;
  sConfig.Rank = ADC_REGULAR_RANK_2;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure Regular Channel
  */
  sConfig.Channel = ADC_CHANNEL_10;
  sConfig.Rank = ADC_REGULAR_RANK_3;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure Regular Channel
  */
  sConfig.Channel = ADC_CHANNEL_11;
  sConfig.Rank = ADC_REGULAR_RANK_4;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN ADC1_Init 2 */

  /* USER CODE END ADC1_Init 2 */

}

/**
  * @brief DCACHE1 Initialization Function
  *  None
  * @retval None
  */
static void MX_DCACHE1_Init(void)
{

  /* USER CODE BEGIN DCACHE1_Init 0 */

  /* USER CODE END DCACHE1_Init 0 */

  /* USER CODE BEGIN DCACHE1_Init 1 */

  /* USER CODE END DCACHE1_Init 1 */
  hdcache1.Instance = DCACHE1;
  hdcache1.Init.ReadBurstType = DCACHE_READ_BURST_WRAP;
  if (HAL_DCACHE_Init(&hdcache1) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN DCACHE1_Init 2 */

  /* USER CODE END DCACHE1_Init 2 */

}

/**
  * @brief ICACHE Initialization Function
  *  None
  * @retval None
  */
static void MX_ICACHE_Init(void)
{

  /* USER CODE BEGIN ICACHE_Init 0 */

  /* USER CODE END ICACHE_Init 0 */

  /* USER CODE BEGIN ICACHE_Init 1 */

  /* USER CODE END ICACHE_Init 1 */
  /* USER CODE BEGIN ICACHE_Init 2 */

  /* USER CODE END ICACHE_Init 2 */

}

/**
  * @brief GPIO Initialization Function
  *  None
  * @retval None
  */
static void MX_GPIO_Init(void)
{
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 */

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOH_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();

/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  *   file: pointer to the source file name
  *   line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

 

1 ACCEPTED SOLUTION

Accepted Solutions

Hello,

You need to use DMA for that. You can't read sequentially the data from the ADC like that:

	  for(i=0; i<4; i++)
	  	  {
	  		  HAL_ADC_Start(&hadc1);
	  		  HAL_Delay(10);
	  		  HAL_ADC_PollForConversion(&hadc1, 1);
	  //		  HAL_Delay(10);
	  		  Singl_Read = HAL_ADC_GetValue(&hadc1);
	  		  switch(i)
	  		  {
	  		  	  case 0:
	  		  		ADC_Data[0] = Singl_Read;
	  		  		  break;
	  		  	  case 1:
	  		  		ADC_Data[1] = Singl_Read;
	  		  		  break;
	  		  	  case 2:
	  		  		ADC_Data[2] = Singl_Read;
	  		  		  break;
	  		  	  case 3:
	  		  		ADC_Data[3] = Singl_Read;
	  		  		  break;

	  		  }
	  	  }

There is only one register to read the ADC value from and you are reading 4 channels that are stored in the same ADC register and you don't have a good synchronization (moreover using HAL_Delay()) in your implementation. This will completely introduce errors in the reading. Using DMA will manage that sequence automatically and it will fill your ADC_Data[] table with the correct values in their respective order.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

View solution in original post

8 REPLIES 8
Andrew Neil
Super User

Welcome to the forum.

Please see How to write your question to maximize your chances to find a solution for best results.

In particular, please give full details of your hardware setup.

 


@aristot wrote:

assuming I have stable (verified with oscilloscope) voltage 1.61V. 


Sure, we can assume that - but have you verified that it is actually true?

Have you measured directly at the MCU pins?

 

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Sorry for being not clear.

Yes I veriffied it using the oscilloscope directly on MCU pins.

I also verify that VREF is stable.

You still haven't given any details of your hardware setup:

  • schematics, etc;
  • details of whatever is sourcing the signals to the ADCs
  • some good, clear photos may help...

 

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Appologize but can't share a photo.

The sourcing is as on attached screen.

aristot_0-1757508355121.png

So I am driving it through 100ohm resistor using the OPA2325 opamp.

STM32 schematic ?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Hello,

You need to use DMA for that. You can't read sequentially the data from the ADC like that:

	  for(i=0; i<4; i++)
	  	  {
	  		  HAL_ADC_Start(&hadc1);
	  		  HAL_Delay(10);
	  		  HAL_ADC_PollForConversion(&hadc1, 1);
	  //		  HAL_Delay(10);
	  		  Singl_Read = HAL_ADC_GetValue(&hadc1);
	  		  switch(i)
	  		  {
	  		  	  case 0:
	  		  		ADC_Data[0] = Singl_Read;
	  		  		  break;
	  		  	  case 1:
	  		  		ADC_Data[1] = Singl_Read;
	  		  		  break;
	  		  	  case 2:
	  		  		ADC_Data[2] = Singl_Read;
	  		  		  break;
	  		  	  case 3:
	  		  		ADC_Data[3] = Singl_Read;
	  		  		  break;

	  		  }
	  	  }

There is only one register to read the ADC value from and you are reading 4 channels that are stored in the same ADC register and you don't have a good synchronization (moreover using HAL_Delay()) in your implementation. This will completely introduce errors in the reading. Using DMA will manage that sequence automatically and it will fill your ADC_Data[] table with the correct values in their respective order.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

 

aristot_1-1757509999564.png

Sorry for partial print but I can't share full schematic.

TDK
Super User

Perhaps start with converting a single channel and verifying it is working correctly before you move to multiple channels. Multiple channels will require the use of DMA.

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