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Associate III
March 12, 2025
Solved

Nucleo-f446re internal dac

  • March 12, 2025
  • 5 replies
  • 3271 views

 

 

/* 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 ---------------------------------------------------------*/
DAC_HandleTypeDef hdac;

/* USER CODE BEGIN PV */
const uint32_t OFFSET_DAC_VALUE = 4; // Adjust this based on your measurements (e.g., 1.2mV corresponds to 4 DAC steps)

/* USER CODE END PV */

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

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
void DAC_Init(void) {
 __HAL_RCC_DAC_CLK_ENABLE(); // Enable DAC clock

 // Configure GPIO pin PA4 (DAC output)
 GPIO_InitTypeDef GPIO_InitStruct = {0};
 GPIO_InitStruct.Pin = GPIO_PIN_4;
 GPIO_InitStruct.Mode = GPIO_MODE_ANALOG;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

 // Initialize DAC1
 hdac.Instance = DAC;
 HAL_DAC_Init(&hdac);

 // Configure DAC channel 1 (PA4)
 DAC_ChannelConfTypeDef sConfig = {0};
 sConfig.DAC_Trigger = DAC_TRIGGER_NONE; // No trigger
 sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_DISABLE; // Enable the output buffer

 HAL_DAC_ConfigChannel(&hdac, &sConfig, DAC_CHANNEL_1);

 // Start DAC output
 HAL_DAC_Start(&hdac, DAC_CHANNEL_1);
}


void Set_DAC_Voltage(uint32_t dac_value)
{
 // Ensure that dac_value is within the valid range (0 to 4095 for 12-bit resolution)
 if (dac_value > 4095) dac_value = 4095;
 HAL_DAC_SetValue(&hdac, DAC_CHANNEL_1, DAC_ALIGN_12B_R, dac_value);
}




void Delay_ms(uint32_t ms) {
 HAL_Delay(ms); // Delay function using HAL library
}
/* 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_DAC_Init();
 /* USER CODE BEGIN 2 */
 // Initialize DAC
 DAC_Init();

 while (1) {
 // Set to 0V
 Set_DAC_Voltage(0);
 Delay_ms(2000); // Wait for 2 seconds

 // Set to 3.3V
 Set_DAC_Voltage(4095); // 3.3V corresponds to 4095 in 12-bit resolution
 Delay_ms(2000); // Wait for 2 seconds
 }
 /* USER CODE END 2 */

 /* Infinite loop */
 /* USER CODE BEGIN WHILE */
 while (1)
 {
 /* 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
 */
 __HAL_RCC_PWR_CLK_ENABLE();
 __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

 /** 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.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
 RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
 RCC_OscInitStruct.PLL.PLLM = 8;
 RCC_OscInitStruct.PLL.PLLN = 180;
 RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
 RCC_OscInitStruct.PLL.PLLQ = 2;
 RCC_OscInitStruct.PLL.PLLR = 2;
 if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
 {
 Error_Handler();
 }

 /** Activate the Over-Drive mode
 */
 if (HAL_PWREx_EnableOverDrive() != 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_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
 RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
 RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
 RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

 if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)
 {
 Error_Handler();
 }
}

/**
 * @brief DAC Initialization Function
 * None
 * @retval None
 */
static void MX_DAC_Init(void)
{

 /* USER CODE BEGIN DAC_Init 0 */

 /* USER CODE END DAC_Init 0 */

 DAC_ChannelConfTypeDef sConfig = {0};

 /* USER CODE BEGIN DAC_Init 1 */

 /* USER CODE END DAC_Init 1 */

 /** DAC Initialization
 */
 hdac.Instance = DAC;
 if (HAL_DAC_Init(&hdac) != HAL_OK)
 {
 Error_Handler();
 }

 /** DAC channel OUT1 config
 */
 sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
 sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
 if (HAL_DAC_ConfigChannel(&hdac, &sConfig, DAC_CHANNEL_1) != HAL_OK)
 {
 Error_Handler();
 }
 /* USER CODE BEGIN DAC_Init 2 */

 /* USER CODE END DAC_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_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 */

 

 

Hello

I am using internal dac of f446 to get dc voltage from 0V to 3.3v but when I measure using multimeter im getting 1.2mv for 0v is it because im using internal dac or should i go with external dac like mcp4725 to get exact 0v as it is required for my application.

Like I want to generate dc voltage from 0v to 0.003v with stepsize of 0.0008(12bit resolution).

Best answer by Andrew Neil

You're going to have the same problem whether the DAC is internal or external:

To get that degree of precision over that range will require extreme precision in the analogue circuitry outside the DAC.

5 replies

Andrew Neil
Super User
March 12, 2025

@harry123 wrote:

when I measure using multimeter im getting 1.2mv for 0v 


Where, exactly, do you measure that?

Please also show how, exactly, you apply the "0V" - are you sure that "0V" is really 0.000V ?

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.
harry123Author
Associate III
March 12, 2025
 while (1) {
 // Set to 0V
 Set_DAC_Voltage(0);
 Delay_ms(2000); // Wait for 2 seconds

 // Set to 3.3V
 Set_DAC_Voltage(4095); // 3.3V corresponds to 4095 in 12-bit resolution
 Delay_ms(2000); // Wait for 2 seconds
 }

Setting digital value to 0 and checking with multimeter at pin PA4

Andrew Neil
Super User
March 12, 2025

You didn't really answer the question.

 


@harry123 wrote:

checking with multimeter at pin PA4


Is that directly on the pin of the STM32 chip?

Where, exactly, was your 0V reference for your meter?

What do you get If you measure between that reference point and VSSA ?

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.
Ozone
Principal
March 12, 2025

> ...but when I measure using multimeter im getting 1.2mv for 0v

How about the tolerance specifications for your multimeter ?
And how much of the full-scale value of the multimeter this 1.2mV represent ?

harry123Author
Associate III
March 12, 2025

 

>.......How about the tolerance specifications for your multimeter ?

Fluke 177 multimeter

  • Range: 0.1 mV to 1000 V
  • Accuracy: ±(0.09% of reading + 1 digit)

 

>.......And how much of the full-scale value of the multimeter this 1.2mV represent ?

its 0.001

Ozone
Principal
March 12, 2025
  • Range: 0.1 mV to 1000 V
  • Accuracy: ±(0.09% of reading + 1 digit)

The accuracy refers to the full-scale value, which would result in ±0.9V in this case.
I suppose we talk about an auto-ranging digital multimeter here, with much better accuracy than 0.9V for the smaller ranges.

Taking into account a multimeter resolution of 1mV, I wouldn't rack my brain over this 1.2mV.
Especially since the DAC resolution (i.e. 1 LSB) exceeds this 1.2mV value as well.

ST Employee
March 12, 2025

Hello,

did you measured this voltage between VSSA and DAC_OUT pin? For better resolution at such low voltages it would also be advisable to reduce VREF+ up to 1.8V.

Andrew Neil
Super User
March 12, 2025

@harry123 wrote:

Like I want to generate dc voltage from 0v to 0.003v with stepsize of 0.0008(12bit resolution).


That seems a bizarre requirement - perhaps explain what you're trying to achieve here?

http://www.catb.org/esr/faqs/smart-questions.html#goal:~:text=reading%20your%20account.-,Describe%20the%20goal%2C%20not%20the%20step,-If%20you%20are

 

Have you looked at the DAC specifications in the Datasheet? 

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.
Ozone
Principal
March 12, 2025

I didn't catch that part, to be honest.

However, when true, one could generate 0...3.0V, and use a voltage divider.
Trying to operate with a digital IC (the STM32) switched at mid-range MHz frequencies in this low DC voltage range seems quite optimistic to me ...

Andrew Neil
Super User
March 12, 2025

@Ozone wrote:

Trying to operate with a digital IC (the STM32) switched at mid-range MHz frequencies in this low DC voltage range seems quite optimistic to me ...


Strong early contender for the 2025 Understatement Of The Year award right there!!

 

Relying on a hand-held multimeter is possibly also rather optimistic...

 

@harry123 remember also that the Nucleo boards are not optimised for precision analogue ...

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.
mƎALLEm
Technical Moderator
March 12, 2025

Hello,

From the datasheet:

mALLEm_1-1741775268463.png

Vout min (buffer ON) = 0,2V

Vout min (buffer OFF) = 0,5mV (a typical value).

So I think 1,2mV is something expected by adding the measurements errors ..

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