STM32中断定时，控制LED灯

#include "led.h"

void TIM3_Int_Init(u16 arr,u16 psc)
{
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //设置TIM3时钟使能


    TIM_TimeBaseStructure.TIM_Period = arr; //设置重装载寄存器的周期
    TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置时钟频率除数的预分频值
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //设置时钟分割
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //向上的计数模式
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //TIM3的初始化

    TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE ); //TIM3更新中断使能


    NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;  //TIM3中断
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;  //先占优先0级
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;  //从占优先3级
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ通道使能
    NVIC_Init(&NVIC_InitStructure);  //初始化NVIC寄存器


    TIM_Cmd(TIM3, ENABLE);  //使能TIM3
}
//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TIM3更新中断发生与否
        {
        TIM_ClearITPendingBit(TIM3, TIM_IT_Update  );  //清除TIMx更新中断标志
        LED2=!LED2;  //取反
        }
}

#include "stm32f10x_conf.h"
#include "led.h"
#include "key.h"
#include "delay.h"
#include "timer.h"
#include "usart.h"

int main(void)
{

    delay_init();
    LED_Init();
    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
    uart_init(115200);
    TIM3_Int_Init(4999,7199);
    //((4999+1)*( 7199+1))/72=500000us=500ms  延时500ms
  while(1)
  {
        LED3=!LED3;
        delay_ms(1500);
        /*当数值为2000时，延时时间变快。当数值为1500以下，
        延时时间为x/1000，只设了几个值。其他值都还没有尝试。
        */
  }

}