void RCC_Delay_us(unsigned int mdelay) { unsigned int Delay = mdelay * (SystemCoreClock / 8U / 1000000U); do { __NOP(); } while (Delay --);

这段代码定义了一个名为RCC_Delay_us的函数，用于微秒级延时。函数接受一个无符号整数参数mdelay，表示需要延时的微秒数。

函数内部首先计算出延时的循环次数，通过将mdelay乘以(SystemCoreClock / 8U / 1000000U)来得到。SystemCoreClock表示系统核心时钟频率，除以8是因为每个循环需要执行8个nop指令，除以1000000是将结果转换为微秒。

然后使用do-while循环进行延时，循环次数为Delay。在每次循环中，执行一个空操作__NOP()，即无操作指令。这样循环Delay次后，延时结束。

这种延时方式是通过空操作指令来进行精确的微秒级延时，具体延时时间取决于系统核心时钟频率和循环次数。

相关问题

void SystemInit(void) { u32 timeout; /* Enable HSI */ RCC->CR = 0x00000001; RCC->CFGR &= (uint32_t)0xF8FFB80C; timeout = 2000; while((!(RCC->CR & 0x00000002)) && (timeout--)); RCC->CFGR2 = RCC_CFGR_PPRE_DIV1; /* Enable HSE */ RCC->CR |= 0x00010000; timeout = 2000; while((!(RCC->CR & 0x00020000)) && (timeout--)); /* Enable Prefetch Buffer and set Flash Latency */ FLASH->ACR |= FLASH_ACR_PRFTBE;// | FLASH_ACR_LATENCY; /* HCLK = SYSCLK */ RCC->CFGR |= (u32)RCC_CFGR_HPRE_DIV1; /* PCLK = HCLK */ RCC->CFGR |= (u32)RCC_CFGR_PPRE_DIV1; /* PLL configuration = HSE * 2 = 16 MHz */ RCC->CFGR &= (u32)((u32)~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE | RCC_CFGR_PLLMUL)); RCC->CFGR |= (u32)(RCC_CFGR_PLLSRC_HSE_PREDIV | RCC_CFGR_PPRE_DIV1 | RCC_CFGR_PLLMUL2); /* Enable PLL */ RCC->CR |= RCC_CR_PLLON; /* Wait till PLL is ready */ while((RCC->CR & RCC_CR_PLLRDY) == 0) { } /* Select PLL as system clock source */ RCC->CFGR &= (u32)((u32)~(RCC_CFGR_SW)); RCC->CFGR |= (u32)RCC_CFGR_SW_PLL; /* Wait till PLL is used as system clock source */ while ((RCC->CFGR & (u32)RCC_CFGR_SWS) != (u32)RCC_CFGR_SWS_PLL) { } }

这段代码中，`void SystemInit(void)`是一个函数的声明，函数名为`SystemInit`。这个函数没有参数，返回值为`void`。

在函数体中，第一行声明了一个变量`timeout`，这个变量是一个无符号整型（`u32`）。然后是一个结构体指针的成员赋值，`RCC->CR`被赋值为`0x00000001`。接下来，又有一个结构体指针的成员赋值，`RCC->CFGR`被赋值为一个未知的值。

#include "main.h" #include "stdio.h" #include "string.h" #include "time.h" UART_HandleTypeDef huart1; void SystemClock_Config(void); static void MX_GPIO_Init(void); static void MX_USART1_UART_Init(void); int main(void) { HAL_Init(); SystemClock_Config(); MX_GPIO_Init(); MX_USART1_UART_Init(); while (1) { time_t now = time(NULL); struct tm *timeinfo = localtime(&now); char time_str[9]; sprintf(time_str, "%02d:%02d:%02d", timeinfo->tm_hour, timeinfo->tm_min, timeinfo->tm_sec); HAL_UART_Transmit(&huart1, (uint8_t *)time_str, strlen(time_str), HAL_MAX_DELAY); HAL_Delay(1000); } } 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.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(); } } static void MX_USART1_UART_Init(void) { huart1.Instance = USART1; huart1.Init.BaudRate = 115200; huart1.Init.WordLength = UART_WORDLENGTH_8B; huart1.Init.StopBits = UART_STOPBITS_1; huart1.Init.Parity = UART_PARITY_NONE; huart1.Init.Mode = UART_MODE_TX_RX; huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE; huart1.Init.OverSampling = UART_OVERSAMPLING_16; if (HAL_UART_Init(&huart1) != HAL_OK) { Error_Handler(); } } static void MX_GPIO_Init(void) { GPIO_InitTypeDef GPIO_InitStruct = {0}; /* GPIO Ports Clock Enable */ __HAL_RCC_GPIOA_CLK_ENABLE(); /*Configure GPIO pin Output Level */ HAL_GPIO_WritePin(GPIOA, GPIO_PIN_9, GPIO_PIN_RESET); /*Configure GPIO pin : PA9 */ GPIO_InitStruct.Pin = GPIO_PIN_9; GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP; GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW; HAL_GPIO_Init(GPIOA, &GPIO_InitStruct); } 在以上代码的基础上，编写代码以实现计算发送 hh:mm:ss到单片机,修改单片机时间

可以使用串口接收单片机发送过来的时间数据，然后通过C语言中的time()函数来设置单片机的时间。下面是示例代码：

#include "main.h" 
#include "stdio.h" 
#include "string.h" 
#include "time.h" 

UART_HandleTypeDef huart1; 

void SystemClock_Config(void); 
static void MX_GPIO_Init(void); 
static void MX_USART1_UART_Init(void); 

int main(void) { 
  HAL_Init(); 
  SystemClock_Config(); 
  MX_GPIO_Init(); 
  MX_USART1_UART_Init(); 

  // 用于接收单片机发送过来的时间数据
  char time_input[9]; 

  while (1) { 
    // 接收串口数据
    HAL_UART_Receive(&huart1, (uint8_t *)time_input, 9, HAL_MAX_DELAY); 

    // 将接收到的时间数据转换成struct tm格式
    struct tm timeinfo = {0}; 
    sscanf(time_input, "%d:%d:%d", &timeinfo.tm_hour, &timeinfo.tm_min, &timeinfo.tm_sec); 

    // 设置单片机时间
    time_t now = mktime(&timeinfo); 
    if(now != -1) { 
      if(stm32_settime(now) == 0) { 
        printf("Time set successfully!\r\n"); 
      } 
      else { 
        printf("Failed to set time.\r\n"); 
      } 
    } 
    else { 
      printf("Invalid time data.\r\n"); 
    } 
  } 
} 

// 设置单片机时间
int stm32_settime(time_t t) { 
  struct tm *timeinfo = localtime(&t); 

  RTC_TimeTypeDef sTime = {0}; 
  RTC_DateTypeDef sDate = {0}; 

  sTime.Hours = timeinfo->tm_hour; 
  sTime.Minutes = timeinfo->tm_min; 
  sTime.Seconds = timeinfo->tm_sec; 

  sDate.WeekDay = timeinfo->tm_wday; 
  sDate.Month = timeinfo->tm_mon + 1; 
  sDate.Date = timeinfo->tm_mday; 
  sDate.Year = timeinfo->tm_year - 100; 

  if(HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BIN) != HAL_OK) { 
    return -1; 
  } 

  if(HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BIN) != HAL_OK) { 
    return -1; 
  } 

  return 0; 
} 

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.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(); 
  } 
} 

static void MX_USART1_UART_Init(void) { 
  huart1.Instance = USART1; 
  huart1.Init.BaudRate = 115200; 
  huart1.Init.WordLength = UART_WORDLENGTH_8B; 
  huart1.Init.StopBits = UART_STOPBITS_1; 
  huart1.Init.Parity = UART_PARITY_NONE; 
  huart1.Init.Mode = UART_MODE_TX_RX; 
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE; 
  huart1.Init.OverSampling = UART_OVERSAMPLING_16; 
  if (HAL_UART_Init(&huart1) != HAL_OK) { 
    Error_Handler(); 
  } 
} 

static void MX_GPIO_Init(void) { 
  GPIO_InitTypeDef GPIO_InitStruct = {0}; 

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

  /*Configure GPIO pin Output Level */ 
  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_9, GPIO_PIN_RESET); 

  /*Configure GPIO pin : PA9 */ 
  GPIO_InitStruct.Pin = GPIO_PIN_9; 
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP; 
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW; 
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct); 
}

同时，需要在单片机上添加RTC实时时钟模块，并在CubeMX中进行配置。需要注意的是，使用RTC模块前需要先初始化时钟，可以使用RCC_OscConfig和RCC_ClkConfig函数来进行初始化。在设置时间时，需要将时间数据转换成RTC模块所需的格式，并调用HAL_RTC_SetTime和HAL_RTC_SetDate函数来设置时间和日期。