stm32f407呼吸灯

要实现stm32f407的呼吸灯效果，可以使用定时器和PWM输出。具体步骤如下：

1. 初始化定时器和PWM输出通道。
2. 在定时器中断中改变PWM输出的占空比，实现呼吸灯效果。

以下是示例代码：

#include "stm32f4xx.h"

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

    if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET)
    {
        if (direction == 1)
        {
            brightness++;
            if (brightness >= 1000)
            {
                direction = 0;
            }
        }
        else
        {
            brightness--;
            if (brightness == 0)
            {
                direction = 1;
            }
        }

        TIM_SetCompare1(TIM4, brightness);

        TIM_ClearITPendingBit(TIM3, TIM_IT_Update);
    }
}

int main(void)
{
    // 初始化GPIO和定时器
    // ...

    // 配置PWM输出通道
    TIM_OCInitTypeDef TIM_OCInitStructure;
    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_OC1Init(TIM4, &TIM_OCInitStructure);
    TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable);

    // 启动定时器
    TIM_Cmd(TIM3, ENABLE);
    TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);

    while (1)
    {
        // 主循环
    }
}

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