stm32f103c8t6 定时器1实现呼吸灯

好的，下面是使用定时器1实现呼吸灯的代码：

#include "stm32f10x.h"

uint16_t pwm_value = 0;
uint16_t pwm_dir = 1;

void TIM1_UP_IRQHandler(void)
{
    if (TIM_GetITStatus(TIM1, TIM_IT_Update) != RESET)
    {
        TIM_ClearITPendingBit(TIM1, TIM_IT_Update);
        
        if (pwm_dir == 1)
        {
            pwm_value++;
            if (pwm_value >= 1000) pwm_dir = 0;
        }
        else
        {
            pwm_value--;
            if (pwm_value == 0) pwm_dir = 1;
        }
        
        TIM_SetCompare1(TIM1, pwm_value);
    }
}

int main(void)
{
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_TIM1, ENABLE);
    
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    
    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
    TIM_TimeBaseInitStruct.TIM_Period = 1000;
    TIM_TimeBaseInitStruct.TIM_Prescaler = 71;
    TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInitStruct.TIM_RepetitionCounter = 0;
    TIM_TimeBaseInit(TIM1, &TIM_TimeBaseInitStruct);
    
    TIM_OCInitTypeDef TIM_OCInitStruct;
    TIM_OCInitStruct.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStruct.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStruct.TIM_OutputNState = TIM_OutputNState_Disable;
    TIM_OCInitStruct.TIM_Pulse = 0;
    TIM_OCInitStruct.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OCInitStruct.TIM_OCNPolarity = TIM_OCNPolarity_Low;
    TIM_OCInitStruct.TIM_OCIdleState = TIM_OCIdleState_Reset;
    TIM_OCInitStruct.TIM_OCNIdleState = TIM_OCNIdleState_Reset;
    TIM_OC1Init(TIM1, &TIM_OCInitStruct);
    
    TIM_Cmd(TIM1, ENABLE);
    
    NVIC_InitTypeDef NVIC_InitStructure;
    NVIC_InitStructure.NVIC_IRQChannel = TIM1_UP_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    
    TIM_ITConfig(TIM1, TIM_IT_Update, ENABLE);
    
    while (1);
}

这段代码中使用了定时器1的PWM模式，通过改变占空比来控制LED的亮度，实现呼吸灯效果。在定时器1的中断服务函数中，改变PWM占空比的值。

需要注意的是，这段代码中使用的是TIM1，所以需要开启GPIOA和TIM1的时钟。另外，TIM1的通道1对应的是PA8，需要将PA8配置为TIM1的复用输出引脚。