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 */