一、RTC概述
实时时钟的缩写是RTC(Real_Time Clock)。RTC 是集成电路，通常称为时钟芯片。
实时时钟芯片是日常生活中应用最为广泛的消费类电子产品之一。它为人们提供精确的实时时间,或者为电子系统提供精确的时间基准,目前实时时钟芯片大多采用精度较高的晶体振荡器作为时钟源。有些时钟芯片为了在主电源掉电时，还可以工作，需要外加电池供电。
- 硬件结构
1） 晶振
晶振一般叫做晶体谐振器，是一种机电器件，晶振是石英振荡器的简称，英文名为Crystal是用电损耗很小的石英晶体经精密切割磨削并镀上电极焊上引线做成。
晶振的作用：提供基准频率。
RTC的晶振：
任何实时时钟的核心都是晶振，晶振频率为32768 Hz 。它为分频计数器提供精确的与低功耗的实基信号。它可以用于产生秒、分、时、日等信息。为了确保时钟长期的准确性，晶振必须正常工作，不能够受到干扰。RTC的晶振又分为：外部晶振和内置晶振。
RTC的晶振频率为什么是32768Hz？
① RTC时间是以振荡频率来计算的。故它不是一个时间器而是一个计数器。而一般的计数器都是16位的。又因为时间的准确性很重要，故震荡次数越低，时间的准确性越低。所以必定是个高次数。2^15 = 32768 。
② 32768 Hz = 2^15 即分频15次后为1Hz，周期 = 1s。
③ 经过工程师的经验总结32768 Hz，时钟最准确。
④ 规范和统一。
日历时钟结构框图：
二、建立新项目
- 设置RCC
- 配置RTC
- 配置串口：
- 配置时钟树：
- 项目设置:
三、修改代码
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* <h2><center>© Copyright (c) 2021 STMicroelectronics.
* All rights reserved.</center></h2>
*
* This software component is licensed by ST under BSD 3-Clause license,
* the "License"; You may not use this file except in compliance with the
* License. You may obtain a copy of the License at:
* opensource.org/licenses/BSD-3-Clause
*
******************************************************************************
*/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "rtc.h"
#include "usart.h"
#include "gpio.h"
#include "stdio.h"
int fputc(int ch,FILE *f)
{
uint8_t temp[1]={ch};
HAL_UART_Transmit(&huart1,temp,1,2);
return ch;
}
/* 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 */
/* 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 */
RTC_DateTypeDef GetData;//获取日期结构体
RTC_TimeTypeDef GetTime;//获取时间结构体
/* 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_RTC_Init();
MX_USART1_UART_Init();
/* USER CODE BEGIN 2 */
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
HAL_RTC_GetTime(&hrtc, &GetTime, RTC_FORMAT_BIN);//获取时间
/* Get the RTC current Date */
HAL_RTC_GetDate(&hrtc, &GetData, RTC_FORMAT_BIN);//获取日期
/* Display date Format : yy/mm/dd */
printf("%02d/%02d/%02d\r\n",2000 + GetData.Year, GetData.Month, GetData.Date);
if(GetData.WeekDay==01)
{
printf("星期一\r\n");
}
else if(GetData.WeekDay==02)
{
printf("星期二\r\n");
}
else if(GetData.WeekDay==03)
{
printf("星期三\r\n");
}
else if(GetData.WeekDay==04)
{
printf("星期四\r\n");
}
else if(GetData.WeekDay==05)
{
printf("星期五\r\n");
}
else if(GetData.WeekDay==06)
{
printf("星期六\r\n");
}
else if(GetData.WeekDay==07)
{
printf("星期日\r\n");
}
/* Display time Format : hh:mm:ss */
printf("%02d:%02d:%02d\r\n",GetTime.Hours, GetTime.Minutes, GetTime.Seconds);
printf("\r\n");
HAL_Delay(1000);
/* 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};
RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};
/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSI|RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.LSIState = RCC_LSI_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL2;
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_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
{
Error_Handler();
}
PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_RTC;
PeriphClkInit.RTCClockSelection = RCC_RTCCLKSOURCE_LSI;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
{
Error_Handler();
}
}
/* 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.
* @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 */
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
四、烧录运行
五、总结
本次实验实现了RTC时钟，但是并不是实时的，只是在设定的初始值上面叠加时间。