使用PWM时，需要注意引脚是否支持TIM功能

可支持引脚

PA0 TIM2_CH1
PA1 TIM2_CH2
PA2 TIM2_CH3
PA3 TIM2_CH4

PA6 TIM3_CH1
PA7 TIM3_CH2
PB0 TIM3_CH3
PB1 TIM3_CH4

PB6 TIM4_CH1
PB7 TIM4_CH2
PB8 TIM4_CH3
PB9 TIM4_CH4

PWM.c

#include "timer.h"
#include "led.h"
#include "usart.h"
   	  
//通用定时器3中断初始化
//这里时钟选择为APB1的2倍，而APB1为36M
//arr：自动重装值。
//psc：时钟预分频数
//这里使用的是定时器3!
void TIM3_Int_Init(u16 arr,u16 psc)
{
  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
	NVIC_InitTypeDef NVIC_InitStructure;

	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //时钟使能

	TIM_TimeBaseStructure.TIM_Period = arr; //设置在下一个更新事件装入活动的自动重装载寄存器周期的值	 计数到5000为500ms
	TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置用来作为TIMx时钟频率除数的预分频值  10Khz的计数频率  
	TIM_TimeBaseStructure.TIM_ClockDivision = 0; //设置时钟分割:TDTS = Tck_tim
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIM向上计数模式
	TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //根据TIM_TimeBaseInitStruct中指定的参数初始化TIMx的时间基数单位
 
	TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE ); //使能指定的TIM3中断,允许更新中断

	NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;  //TIM3中断
	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;  //先占优先级0级
	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;  //从优先级3级
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ通道被使能
	NVIC_Init(&NVIC_InitStructure);  //根据NVIC_InitStruct中指定的参数初始化外设NVIC寄存器

	TIM_Cmd(TIM3, ENABLE);  //使能TIMx外设
							 
}
//定时器3中断服务程序
void TIM3_IRQHandler(void)   //TIM3中断
{
	if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET) //检查指定的TIM中断发生与否:TIM 中断源 
		{
		TIM_ClearITPendingBit(TIM3, TIM_IT_Update  );  //清除TIMx的中断待处理位:TIM 中断源 
		LED1=!LED1;
		}
}




//TIM3 PWM部分初始化 
//PWM输出初始化
//arr：自动重装值
//psc：时钟预分频数
void TIM3_PWM_Init(u16 arr,u16 psc)
{  
	GPIO_InitTypeDef GPIO_InitStructure;
	TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
	TIM_OCInitTypeDef  TIM_OCInitStructure;
	

	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);	//使能定时器3时钟
 	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB  | RCC_APB2Periph_AFIO, ENABLE);  //使能GPIO外设和AFIO复用功能模块时钟
	
	GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3, ENABLE); //Timer3部分重映射  TIM3_CH2->PB5    
 
   //设置该引脚为复用输出功能,输出TIM3 CH2的PWM脉冲波形	GPIOB.5
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; //TIM_CH2
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //复用推挽输出
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_Init(GPIOB, &GPIO_InitStructure);//初始化GPIO
 
   //初始化TIM3
	TIM_TimeBaseStructure.TIM_Period = arr; //设置在下一个更新事件装入活动的自动重装载寄存器周期的值
	TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置用来作为TIMx时钟频率除数的预分频值 
	TIM_TimeBaseStructure.TIM_ClockDivision = 0; //设置时钟分割:TDTS = Tck_tim
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIM向上计数模式
	TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //根据TIM_TimeBaseInitStruct中指定的参数初始化TIMx的时间基数单位
	
	//初始化TIM3 Channel2 PWM模式	 
	TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //选择定时器模式:TIM脉冲宽度调制模式2
 	TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //比较输出使能
	TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //输出极性:TIM输出比较极性高
	TIM_OC2Init(TIM3, &TIM_OCInitStructure);  //根据T指定的参数初始化外设TIM3 OC2

	TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);  //使能TIM3在CCR2上的预装载寄存器
 
	TIM_Cmd(TIM3, ENABLE);  //使能TIM3
	

}

PWM.h

#ifndef __TIMER_H
#define __TIMER_H
#include "sys.h"


void TIM3_Int_Init(u16 arr,u16 psc);
void TIM3_PWM_Init(u16 arr,u16 psc);
#endif

main.h

int main(void)
 {		
 	u16 led0pwmval=0;
	u8 dir=1;	
	delay_init();	    	 //延时函数初始化	  
	NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); 	 //设置NVIC中断分组2:2位抢占优先级，2位响应优先级
	uart_init(115200);	 //串口初始化为115200
 	LED_Init();			     //LED端口初始化
 	TIM3_PWM_Init(899,0);	 //不分频。PWM频率=72000000/900=80Khz
   	while(1)
	{
 		delay_ms(10);	 
		if(dir)led0pwmval++;
		else led0pwmval--;

 		if(led0pwmval>300)dir=0;
		if(led0pwmval==0)dir=1;										 
		TIM_SetCompare2(TIM3,led0pwmval);		   
	}	 
 }