概述

實際使用STM32F103單片機時，第一步就是配置系統的工作時鐘。我們時常需要選擇使用外部時鐘源和內部時鐘源，這里我們以F103為例子，提供兩個函數參考，供大家實際開發中使用配置系統時鐘。

實例

廢話不多說，直接上代碼。

#include "dri_sysclk.h"static void SetSystemClk(eSelectClkSrc _ClkSrc);T_SysClk_Device g_tSysClk_Dev = {.SysClkConfig = SetSystemClk };static void SetSysClockTo64(void) {__IO ErrorStatus HSIStartUpStatus = 0;/* SYSCLK, HCLK, PCLK2 and PCLK1 configuration -----------------------------*/ /* RCC system reset(for debug purpose) */RCC_DeInit();/* Enable HSI */RCC_HSICmd(ENABLE);/* Wait till HSI is ready */if((RCC->CR & RCC_CR_HSIRDY) == RCC_CR_HSIRDY)HSIStartUpStatus = SUCCESS;elseHSIStartUpStatus = ERROR;if(HSIStartUpStatus == SUCCESS){/* Enable Prefetch Buffer */FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);/* Flash 2 wait state */FLASH_SetLatency(FLASH_Latency_2);/* HCLK = SYSCLK */RCC_HCLKConfig(RCC_SYSCLK_Div1); /* PCLK2 = HCLK */RCC_PCLK2Config(RCC_HCLK_Div1); /* PCLK1 = HCLK/2 */RCC_PCLK1Config(RCC_HCLK_Div2);/* PLLCLK = 8MHz / 2 * 16 = 64 MHz */RCC_PLLConfig(RCC_PLLSource_HSI_Div2, RCC_PLLMul_16);/* Enable PLL */ RCC_PLLCmd(ENABLE);/* Wait till PLL is ready */while (RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET){}/* Select PLL as system clock source */RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);/* Wait till PLL is used as system clock source */while(RCC_GetSYSCLKSource() != 0x08){}}else{ /* If HSI fails to start-up, the application will have wrong clock configuration.User can add here some code to deal with this error */ /* Go to infinite loop */while (1){}} }static void SetSysClockTo72(void) {__IO ErrorStatus HSEStartUpStatus = ERROR;/* SYSCLK, HCLK, PCLK2 and PCLK1 configuration -----------------------------*/ /* RCC system reset(for debug purpose) */RCC_DeInit();/* Enable HSE */RCC_HSEConfig(RCC_HSE_ON);/* Wait till HSE is ready */HSEStartUpStatus = RCC_WaitForHSEStartUp();if (HSEStartUpStatus == SUCCESS){/* Enable Prefetch Buffer */FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);/* Flash 2 wait state */FLASH_SetLatency(FLASH_Latency_2);/* HCLK = SYSCLK */RCC_HCLKConfig(RCC_SYSCLK_Div1); /* PCLK2 = HCLK */RCC_PCLK2Config(RCC_HCLK_Div1); /* PCLK1 = HCLK/2 */RCC_PCLK1Config(RCC_HCLK_Div2);/* PLLCLK = 8MHz * 9 = 72 MHz */RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);/* Enable PLL */ RCC_PLLCmd(ENABLE);/* Wait till PLL is ready */while (RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET){}/* Select PLL as system clock source */RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);/* Wait till PLL is used as system clock source */while(RCC_GetSYSCLKSource() != 0x08){}}else{ /* If HSE fails to start-up, the application will have wrong clock configuration.User can add here some code to deal with this error */ /* Go to infinite loop */while (1){}} }static void SetSystemClk(eSelectClkSrc _ClkSrc) {switch(_ClkSrc){case USE_HSE_FOR_CLKSRC:SetSysClockTo72();break;case USE_HSI_FOR_CLKSRC:SetSysClockTo64();break;default:break;}/* Enable Clock Security System(CSS): this will generate an NMI exceptionwhen HSE or HSI clock fails */RCC_ClockSecuritySystemCmd(ENABLE); }

結論

通過上述配置，我們就可以成功配置系統時鐘。

總結

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