写一个stm32的tim2的呼吸灯程序

以下是一个基本的STM32的TIM2呼吸灯程序：

#include "stm32f10x.h"

#define LED_PIN GPIO_Pin_13
#define LED_PORT GPIOC

void TIM2_IRQHandler(void)
{
    static uint16_t brightness = 0;
    static uint8_t direction = 0;

    if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
    {
        TIM_ClearITPendingBit(TIM2, TIM_IT_Update);

        if (direction == 0)
        {
            brightness++;
            if (brightness == 1000)
            {
                direction = 1;
            }
        }
        else
        {
            brightness--;
            if (brightness == 0)
            {
                direction = 0;
            }
        }

        TIM_SetCompare1(TIM2, brightness);
    }
}

int main(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef TIM_OCInitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

    // 初始化LED引脚
    GPIO_InitStructure.GPIO_Pin = LED_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(LED_PORT, &GPIO_InitStructure);

    // 初始化TIM2
    TIM_TimeBaseStructure.TIM_Period = 999;
    TIM_TimeBaseStructure.TIM_Prescaler = 7199;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OCInitStructure.TIM_Pulse = 0;
    TIM_OC1Init(TIM2, &TIM_OCInitStructure);

    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
    TIM_Cmd(TIM2, ENABLE);

    while (1)
    {
    }
}

程序的基本思路是使用TIM2定时器以PWM模式控制LED的亮度，然后在定时器中断中改变LED的亮度。在每次中断中，亮度值会逐渐增加或减少，直到达到最大或最小值，然后反转方向。这样就实现了呼吸灯的效果。