单片机用pwm原理控制灯的程序

下面是一个基于STM32单片机的PWM控制LED灯的程序示例：

#include "stm32f10x.h"

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

  // 使能GPIOA和TIM2时钟
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

  // 配置PA5引脚为复用输出模式
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  // 配置TIM2的基本计数时间为1us
  TIM_TimeBaseStructure.TIM_Period = 1000 - 1;
  TIM_TimeBaseStructure.TIM_Prescaler = 72 - 1;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

  // 配置TIM2通道1为PWM模式，并设置占空比为50%
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 500;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OC1Init(TIM2, &TIM_OCInitStructure);

  // 使能TIM2
  TIM_Cmd(TIM2, ENABLE);

  while (1)
  {
    // 等待
  }
}

上述程序使用TIM2定时器的通道1来控制PA5引脚的PWM输出，每个周期为1ms，占空比50%。可以根据需要修改占空比和周期时间来控制LED灯的亮度。