STM32PWM输出实现LED灯渐亮渐灭

/*
*说明：
*PA0:KEY1;PA1:KEY2;
*PA2:LED1;PA3:LED2;
*PA9:USART1_TX;PA10:USART1_RX
*/
#include "stm32f10x.h"
#include "stm32f10x_rcc.h"
#include "stm32f10x_gpio.h"
#include "stm32f10x_tim.h"
#include "stm32f10x_pwr.h"
#include "stm32f10x_exti.h"
#include "system_stm32f10x.h"
#include "misc.h"

void RCC_Configuration(void);
void GPIO_Configuration(void); 
void TIM2_Configuration(void);
void delay_ms(u16 time);

int main()
{
    u8 led_fx=1;
    u16 led_dt=0;
    
    RCC_Configuration();
    GPIO_Configuration(); 
    TIM2_Configuration();
                
    while(1)
    {
      delay_ms(10);
      if(led_fx==1)
      {
        led_dt++;
      }else{
        led_dt--;
      }
      
      if(led_dt>100) led_fx=0;//可以和初始值一样
      if(led_dt==0)  led_fx=1;
      
      TIM_SetCompare3(TIM2,led_dt);//通道3没有重影像是PA2对应LED1
      TIM_SetCompare4(TIM2,led_dt);//通道4没有重影像是PA3对应LED2
    }
}

void RCC_Configuration(void)  
{   
  SystemInit();
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);   
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE); 
  //GPIO_AFIODeInit();和下面相同效果，可以查看源码证明
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE); 
} 

void GPIO_Configuration(void)  
{  
  GPIO_InitTypeDef GPIO_InitStructure;  
  
  //GPIO_PinRemapConfig(GPIO_PartialRemap2_TIM2,ENABLE);//端口映射函数
  
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2|GPIO_Pin_3;//GPIO_Pin_3对应channel3，主函数改为：TIM_SetCompare3 
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_Init(GPIOA, &GPIO_InitStructure); 
}

void TIM2_Configuration(void)  
{
  TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
  TIM_OCInitTypeDef TIM_OCInitStructure;
  
  TIM_DeInit(TIM2);
  TIM_InternalClockConfig(TIM2);
  //定时器初始化
  TIM_TimeBaseStructure.TIM_Period = 100-1;//初始值是100,2MHz=2000KHz,2MHz/100=0.02MHz,所有周期T=1/0.02MHz=50us,示波器显示周期应该为50us
  TIM_TimeBaseStructure.TIM_Prescaler = 36-1;//36倍分频，72MHz/36=2MHz
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
  
  //PWM初始化
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 50;//占空比值是50，所以占空比是：50/100=50%
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
  TIM_OC3Init(TIM2,&TIM_OCInitStructure);
  
  TIM_OCInitStructure.TIM_Pulse = 20;
  TIM_OC4Init(TIM2,&TIM_OCInitStructure);
  //TIM_OC3PreloadConfig(TIM2,TIM_OCPreload_Enable);
  //TIM_ARRPreloadConfig(TIM2, ENABLE); 
  TIM_Cmd(TIM2,ENABLE);
  TIM_CtrlPWMOutputs(TIM2,ENABLE);
}
void delay_ms(u16 time)   
{  
  u16 i=0;  
  while(time--)   
  {  
    i=12000;  
    while(i--);  
  }  
}