stm32 f103呼吸灯

要实现STM32F103呼吸灯效果，可以使用PWM输出控制LED的亮度。具体实现步骤如下：

1. 初始化TIM定时器和GPIO引脚。
2. 配置TIM定时器为PWM模式。
3. 在TIM中断服务函数中更新占空比，实现呼吸灯效果。

以下是示例代码：

#include "stm32f10x.h"

#define LED_PIN GPIO_Pin_13
#define LED_GPIO GPIOC
#define LED_GPIO_CLK RCC_APB2Periph_GPIOC

#define TIM_PERIOD 1000

void TIM_Config(void)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef TIM_OCInitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

    TIM_TimeBaseStructure.TIM_Period = TIM_PERIOD - 1;
    TIM_TimeBaseStructure.TIM_Prescaler = 72 - 1;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 0;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC3Init(TIM3, &TIM_OCInitStructure);

    TIM_Cmd(TIM3, ENABLE);
}

void GPIO_Config(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(LED_GPIO_CLK, ENABLE);

    GPIO_InitStructure.GPIO_Pin = LED_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(LED_GPIO, &GPIO_InitStructure);
}

void TIM3_IRQHandler(void)
{
    static uint16_t brightness = 0;
    static uint8_t direction = 1;

    if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET)
    {
        if (direction)
        {
            brightness++;
            if (brightness >= TIM_PERIOD)
            {
                direction = 0;
            }
        }
        else
        {
            brightness--;
            if (brightness == 0)
            {
                direction = 1;
            }
        }

        TIM_SetCompare3(TIM3, brightness);

        TIM_ClearITPendingBit(TIM3, TIM_IT_Update);
    }
}

int main(void)
{
    NVIC_InitTypeDef NVIC_InitStructure;

    GPIO_Config();
    TIM_Config();

    NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    while (1)
    {
    }
}