STM32使用内部参考电压计算外部VDDA提高ADC测量精度
手册解读
引脚比较少的STM32一般都是不带Vref引脚的，并且Vref一般都是直接接到VDDA上的，VDDA的值一般不是稳定的3.3V。如下图所示：
为了提高ADC测量精度，厂家提供的了内部参考电压，这个参考电压是相对比较稳定的，且出厂前厂家都做了校准。本次我使用的是STM32F0，校准是在3.3V的电压下进行的，手册内容如下：
这个校准值存在地址0x1FFFF7BA-0x1FFFF7BB上，是一个16位的数据，首先将变量强制转换成指向16位数据的地址，再指针解引用读出数据*((uint16_t *)0x1FFFF7BA)，不同单片机地址不同，看手册读取即可。
再看STM32F0的参考手册，根据如下公式计算出VDDA：
VDDA_Charac这个值看图2中的Description，是3.3V，像STM32H7直接给出VDDA_Charac为3.3V，就不需要去看手册了。也有些型号的芯片这个值不是3.3V。VREFINT_DATA这个值是ADC读取内部电压的值。然后根据以下公式就能算出ADC测量通道的值了。
例程
CubeMX配置
使用外部时钟
时钟频率为48MHz
调试引脚配置
ADC配置
ADC使用中断方法读取，配置如下
代码如下
/* 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"
#include "adc.h"
#include "gpio.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 */
#define VREFINT_CAL_ADDR ((uint16_t *)0x1FFFF7BA)
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
uint16_t VREFINT_CAL = 0;
uint16_t VREFINT_DATA = 0;
float VDDA = 0;
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* 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_ADC_Init();
/* USER CODE BEGIN 2 */
HAL_ADCEx_Calibration_Start(&hadc);
HAL_ADC_Start_IT(&hadc);
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
VREFINT_CAL = *VREFINT_CAL_ADDR;
HAL_Delay(1000);
/* 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};
/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI14 | RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.HSI14State = RCC_HSI14_ON;
RCC_OscInitStruct.HSI14CalibrationValue = 16;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL6;
RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV1;
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_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
{
Error_Handler();
}
}
/* USER CODE BEGIN 4 */
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef *hadc)
{
if (hadc->Instance != ADC1)
{
return;
}
VREFINT_DATA = HAL_ADC_GetValue(hadc);
VDDA = 3.3f * VREFINT_CAL / VREFINT_DATA;
// ntc_set_flag(&ntc_temperature);
}
/* 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.
* @param file: pointer to the source file name
* @param 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 */
仿真结果如图所示，VREFINT_CAL是个定值，是不会变的，VREFINT_DATA是读取内部参考电压的值，是在跳动的，根据公式即可推出VDDA。
