（我的外部時鐘為25MHz）

#include

static __IO uint32_t TimingDelay;//__IO為volatile的宏定義
int8_t LED_Flag = 1;//LED燈翻轉標志位

void RCC_Config(void);
void GPIO_Config(void);
void TIM_Config(void);
void NVIC_Config(void);
void Delay(__IO uint32_t nTime);

main ()
{
RCC_Config();
GPIO_Config();
TIM_Config();
NVIC_Config();

RCC_MCO1Config(RCC_MCO1Source_PLLCLK, RCC_MCO1Div_1);

if (SysTick_Config(SystemCoreClock / 1000))
{

while (1);
}
while (1)
{

if (LED_Flag != 1)
{
GPIO_SetBits(GPIOG, GPIO_Pin_6); //setbits使能IO，當前下指輸出（此時為滅）
}
else
{
GPIO_ResetBits(GPIOG, GPIO_Pin_6); //Resetbits屏蔽IO，當前下指不輸出（此時為亮）
}
}
}

void RCC_Config(void)
{
RCC_DeInit(); //RCC寄存器初始化
RCC_HSEConfig(RCC_HSE_ON); //使用外部時鐘
if (RCC_WaitForHSEStartUp() == SUCCESS)//等待外部時鐘啟動
{
RCC_PLLCmd(DISABLE); //配置PLL前應先關閉主PLL
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK); //選擇PLL時鐘為系統(tǒng)時鐘
RCC_HCLKConfig(RCC_SYSCLK_Div1); //HCLK(AHB)時鐘為系統(tǒng)時鐘1分頻
RCC_PCLK1Config(RCC_HCLK_Div4); //PCLK1(APB1)時鐘為HCLK時鐘8分頻，則TIM2時鐘為HCLK時鐘4分頻
RCC_PCLK2Config(RCC_HCLK_Div2); //PCLK2(APB2)時鐘為HCLK時鐘2分頻
RCC_PLLConfig(RCC_PLLSource_HSE, 25, 336, 2, 7); //PLL時鐘配置，公式詳見‘system_stm43f4xx.c’ Line149
RCC_PLLCmd(ENABLE);//PLL時鐘開啟
while (RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET) { } //等待PLL時鐘準備好
}
}

void GPIO_Config(void)
{

GPIO_InitTypeDef GPIO_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOG | RCC_AHB1Periph_GPIOA, ENABLE);

GPIO_StructInit(&GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6; //指定第六引腳
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT; //模式為輸出
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //頻率為快速
GPIO_Init(GPIOG, &GPIO_InitStructure); //調用IO初始化函數

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1; //指定第一引腳
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; //模式必須為復用！
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //頻率為快速
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; //上拉與否對PWM產生無影響
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource1, GPIO_AF_TIM2);//復用ＧＰＩＯＡ＿Ｐｉｎ１為ＴＩＭ２＿Ｃｈ２

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource8, GPIO_AF_MCO);
}

void TIM_Config(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);
TIM_DeInit(TIM2);//初始化TIM2寄存器

TIM_TimeBaseStructure.TIM_Period = 10000-1; //查數據手冊可知，TIM2與TIM5為32位自動裝載

TIM_TimeBaseStructure.TIM_Prescaler = 8400-1;
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;//向上計數
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

TIM_OCStructInit(&TIM_OCInitStructure); //填入缺省值，其中后幾項只對TIM1和TIM8有效
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; //PWM1為正常占空比模式，PWM2為反極性模式
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = 2000; //輸入CCR（占空比數值）
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //High為占空比高極性，此時占空比為20%；Low則為反極性，占空比為80%
TIM_OC2Init(TIM2, &TIM_OCInitStructure);
TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Enable);//CCR自動裝載默認也是打開的
TIM_ARRPreloadConfig(TIM2, ENABLE); //ARR自動裝載默認是打開的，可以不設置

TIM_ClearFlag(TIM2, TIM_FLAG_Update);
TIM_ITConfig(TIM2, TIM_IT_Update,ENABLE);
TIM_Cmd(TIM2, ENABLE); //使能TIM2定時器
}

void NVIC_Config(void)
{

NVIC_InitTypeDef NVIC_InitStructure;
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1); //中斷優(yōu)先級分組為1
NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;//嵌套中斷通道為TIM2
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1; //搶占優(yōu)先級為1
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; //響應優(yōu)先級為0
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //使能中斷
NVIC_Init(&NVIC_InitStructure);
}

void Delay(__IO uint32_t nTime)
{
TimingDelay = nTime;
while (TimingDelay != 0);
}

void TimingDelay_Decrement(void)
{
if (TimingDelay != 0x00)
{
TimingDelay--;
}
}

中斷服務函數：

void TIM2_IRQHandler(void)
{
if(TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
{
TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
LED_Flag= ~LED_Flag;

}
}