STM32F103单片机输出1Mhz方波有过冲产生怎么解决 -

#include "timer.h"
#include "led.h"
#include "usart.h"
#include "delay.h"
//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 TIM2_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_GPIOA | 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 GPIOA.1
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1; //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(GPIOA, &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(TIM2, &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_Low ; //输出极性:TIM输出比较极性高
TIM_OC2Init(TIM2, &TIM_OCInitStructure); //根据T指定的参数初始化外设TIM3 OC2
TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Enable); //使能TIM3在CCR2上的预装载寄存器
TIM_Cmd(TIM2, DISABLE);
}
void TIM4_Init(unsigned short int arr, unsigned short int psc)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure; /*定义一个设置定时器的变量*/
NVIC_InitTypeDef NVIC_InitStructure; /*定义一个设置中断的变量*/
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); /*设置中断向量分组：第2组抢先优先级：0 1 2 3 子优先级：0 1 2 3*/
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4,ENABLE); /*使能TIM4时钟*/
TIM_TimeBaseInitStructure.TIM_Period = arr; /*设置自动重装载值*/
TIM_TimeBaseInitStructure.TIM_Prescaler=psc; /*设置定时器预分频数*/
TIM_TimeBaseInitStructure.TIM_CounterMode=TIM_CounterMode_Up; /*向上计数模式*/
TIM_TimeBaseInitStructure.TIM_ClockDivision=TIM_CKD_DIV1; /*1分频*/
TIM_TimeBaseInit(TIM4,&TIM_TimeBaseInitStructure); /*设置TIM4*/
TIM_ClearITPendingBit(TIM4,TIM_IT_Update); /*清除溢出中断标志位*/
TIM_ITConfig(TIM4,TIM_IT_Update,ENABLE); /*使能TIM4溢出中断*/
NVIC_InitStructure.NVIC_IRQChannel=TIM4_IRQn; /*设置TIM4中断*/
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=1; /*抢占优先级1*/
NVIC_InitStructure.NVIC_IRQChannelSubPriority=1; /*子优先级0*/
NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE; /*中断通道使能*/
NVIC_Init(&NVIC_InitStructure); /*设置中断*/
TIM_Cmd(TIM4,ENABLE);
}
void TIM4_IRQHandler(void)
{
if(TIM_GetITStatus(TIM4, TIM_IT_Update) != RESET) /*如果TIM_IT_Update置位，表示TIM4溢出中断，进入if*/
{
TIM_Cmd(TIM2, ENABLE);
delay_us(8);
TIM_Cmd(TIM2, DISABLE);
TIM_ClearITPendingBit(TIM4, TIM_IT_Update); /*清除TIM4溢出中断标志*/
}
}

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