stm32keil实现呼吸灯

实现呼吸灯需要使用定时器和PWM输出，以下是基于STM32F407芯片和Keil开发环境的代码示例：

1. 配置定时器

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_TimeBaseStructure.TIM_Period = 1000 - 1;    // 定时器周期为1000
TIM_TimeBaseStructure.TIM_Prescaler = 840 - 1;  // 预分频系数为840
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

2. 配置PWM输出

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOD, &GPIO_InitStructure);

GPIO_PinAFConfig(GPIOD, GPIO_PinSource13, GPIO_AF_TIM4);

TIM_OCInitTypeDef TIM_OCInitStructure;
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OCInitStructure.TIM_Pulse = 0;
TIM_OC1Init(TIM4, &TIM_OCInitStructure);

TIM_Cmd(TIM4, ENABLE);

3. 实现呼吸灯效果

int main(void) {
    TIM_SetCompare1(TIM4, 0);  // 初始占空比为0
    TIM_Cmd(TIM4, ENABLE);

    while (1) {
        for (int i = 0; i <= 1000; i++) {
            TIM_SetCompare1(TIM4, i);  // 占空比从0逐渐增加到1000
            delay_ms(2);               // 延迟2ms
        }

        for (int i = 1000; i >= 0; i--) {
            TIM_SetCompare1(TIM4, i);  // 占空比从1000逐渐减小到0
            delay_ms(2);               // 延迟2ms
        }
    }
}

其中`delay_ms`函数可以自行实现，用于延迟指定的毫秒数。