7. 输出比较—PWM

#include "stm32f10x.h"

// TIM2_CH2 (PA1) PWM 输出：20KHz
void PWM_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef TIM_OCInitStructure;

    // 使能时钟
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    // PA1 复用推挽输出
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    // TIM2 配置：20KHz（ARR=3599，PSC=0）
    // 72MHz / 3600 = 20KHz
    TIM_TimeBaseStructure.TIM_Period = 3599;
    TIM_TimeBaseStructure.TIM_Prescaler = 0;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

    // PWM1 模式：CNT < CCR 时输出有效电平
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 0;              // 初始占空比 0%
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC2Init(TIM2, &TIM_OCInitStructure);        // 通道 2

    TIM_Cmd(TIM2, ENABLE);
}

// 设置占空比 (0~100)
void PWM_SetDuty(uint8_t duty)
{
    uint16_t pulse = (uint16_t)(3600 * duty / 100);
    TIM_SetCompare2(TIM2, pulse);
}

// 呼吸灯效果
void Breath_LED(void)
{
    uint8_t i;
    for (i = 0; i < 100; i++)
    {
        PWM_SetDuty(i);     // 逐渐变亮
        delay_ms(10);
    }
    for (i = 100; i > 0; i--)
    {
        PWM_SetDuty(i);     // 逐渐变暗
        delay_ms(10);
    }
}