操作系统 -分析 main 函数代码

STM32CubeMx 生成 main函数代码分析

fputc

int fputc(int ch, FILE *f)
{
    while((USART1->SR & 0X40)==0);
    USART1->DR = (uint8_t) ch;
    return ch;
}

USART1->SR 串口状态寄存器

USART1->SR&0X40即串口状态寄存器的TXE标志位,TXE标志位标识发送数据寄存器(TDR寄存器)是否为空。

while((USART1->SR&0X40)==0);

即判断TXE标志位是否为0,

若为0,则等待此标志位被置1.

若为1(即发送数据寄存器中的数据全部被转移至移位寄存器,导致发送数据寄存器变成空,被硬件置为1),则标识发送数据寄存器(TDR寄存器)为空,可以发送下一个字节帧数据到发送数据寄存器(TDR寄存器)

清除TXE位一般都是通过往数据寄存器中写入数据完成的。

USART1->DR = (uint8_t) ch;

将数值赋给DR寄存器 通过寄存器直接发送出去

SystemClock_Config

  • __HAL_RCC_PWR_CLK_ENABLE(); //使能PWR时钟

对于 __HAL_RCC_PWR_CLK_ENABLE();可以在stm32fxx_hal_rcc.h中找到:

#define __HAL_RCC_PWR_CLK_ENABLE()   do { \
                                        __IO uint32_t tmpreg; \
                                        SET_BIT(RCC->APB1ENR, RCC_APB1ENR_PWREN);\
                                        /* Delay after an RCC peripheral clock enabling */ \
                                        tmpreg = READ_BIT(RCC->APB1ENR, RCC_APB1ENR_PWREN);\
                                        UNUSED(tmpreg); \
                                      } while(0)
  • __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

设置调压器输出电压级别:调用函数

因为后面设置调压器输出电压级别和选择是否开启Over-Driver功能要用到PWR时钟,所以先使能PWR时钟。

对于以下两函数头文件,都位于HALLIB-stm32f7xx_hal_rcc.h文件中

  • 配置时钟源相关参数:调用函数HAL_RCC_OscConfig()

  • 配置系统时钟源以及AHB,APB1和APB2的分频系数:调用函数HAL_RCC_ClockConfig()

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_HSE;//时钟源为HSE
      RCC_OscInitStruct.HSEState = RCC_HSE_ON;//打开HSE
      RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
      RCC_OscInitStruct.HSIState = RCC_HSI_ON;
      RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON; //打开PLL
      RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;//PLL时钟源选择HSE
      RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
      if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
      {
            Error_Handler();
      }

      /** Initializes the CPU, AHB and APB buses clocks
  */
    //选中PLL作为系统时钟源并且配置HCLK,PCLK1和PCLK2
      RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
      RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK; //设置系统时钟时钟源为PLL
      RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;//AHB分频系数为1
      RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2; //APB1分频系数为2
      RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;//APB2分频系数为2

      if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
      {
          Error_Handler();
      }
}

时钟配置一般步骤

  • 使能PWR时钟:调用函数 _HAL_RCC_PWR_CLK_ENABLE()。

  • 设置调压器输出电压级别:调用函数 _HAL_PWR_VOLTAGESCALING_CONFIG()。

  • 选择是否开启Over-Driver功能:调用函数HAL_PWREx_EnableOverDrive()。

  • 配置时钟源相关参数:调用函数HAL_RCC_OscConfig()。

  • 配置系统时钟源以及AHB,APB1和APB2的分频系数:调用函数HAL_RCC_ClockConfig()。

✨main 函数

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2023 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 ---------------------------------------------------------*/

/* USER CODE BEGIN PV */
extern uint32_t TimCount;
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
void MX_FREERTOS_Init(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
int fputc(int ch, FILE *f)
{
    while((USART1->SR & 0X40 )==0);
    USART1->DR = (uint8_t)ch;
    return ch;

}
/* 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_USART1_UART_Init();
  MX_USART2_UART_Init();
  MX_USART3_UART_Init();
  MX_TIM2_Init();
  /* USER CODE BEGIN 2 */
  /* USER CODE END 2 */

  /* Call init function for freertos objects (in freertos.c) */
  MX_FREERTOS_Init();

  /* Start scheduler */
  osKernelStart();

  /* We should never get here as control is now taken by the scheduler */
  /* 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};

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  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_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @brief  Period elapsed callback in non blocking mode
  * @note   This function is called  when TIM1 interrupt took place, inside
  * HAL_TIM_IRQHandler(). It makes a direct call to HAL_IncTick() to increment
  * a global variable "uwTick" used as application time base.
  * @param  htim : TIM handle
  * @retval None
  */
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
  /* USER CODE BEGIN Callback 0 */

  /* USER CODE END Callback 0 */
  if (htim->Instance == TIM1) {
    HAL_IncTick();
  }
  /* USER CODE BEGIN Callback 1 */

  /* USER CODE END Callback 1 */
}

/**
  * @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();//   如果在中断处理函数中使用disable_irq屏蔽相应中断,系统将会出现死锁状态,最后死机,然后重启。
  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 */

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