按下KEY0后，LED0亮度由亮变暗再由暗变亮（呼吸灯效果），按下KEY1后LED0灯熄灭的代码如何编写？

您可以使用以下代码实现呼吸灯效果和按下 KEY1 后 LED0 灯熄灭的功能：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "stm32f10x.h"

#define LED_PIN GPIO_Pin_0
#define LED_PORT GPIOB

void delay_ms(uint32_t ms) {
    uint32_t i, j;
    for (i = 0; i < ms; i++) {
        for (j = 0; j < 2000; j++);
    }
}

void LED_Breath(void) {
    uint16_t i;
    for (i = 0; i < 1000; i++) {
        TIM_SetCompare2(TIM3, i);
        delay_ms(5);
    }
    for (i = 1000; i > 0; i--) {
        TIM_SetCompare2(TIM3, i);
        delay_ms(5);
    }
}

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

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, 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_PORT, &GPIO_InitStructure);

    TIM_TimeBaseStructure.TIM_Period = 999;
    TIM_TimeBaseStructure.TIM_Prescaler = 71;
    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_OC2Init(TIM3, &TIM_OCInitStructure);

    TIM_Cmd(TIM3, ENABLE);

    while (1) {
        if (GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_0) == 0) {
            LED_Breath();
        }
        if (GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_1) == 0) {
            TIM_SetCompare2(TIM3, 0);
        }
    }
}

在这个代码中，我们使用了定时器 TIM3 和 PWM 输出来实现呼吸灯效果。按下 KEY0 后，调用 LED_Breath 函数实现呼吸灯效果；按下 KEY1 后，将 TIM3 的 PWM 输出设置为 0，实现 LED0 灯熄灭的功能。