void TIM3_Config(int arr,int psc)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
    TIM_ClearITPendingBit(TIM3,TIM_IT_Update);
    TIM_TimeBaseStructure.TIM_Period = arr;
    TIM_TimeBaseStructure.TIM_Prescaler = psc;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM3,&TIM_TimeBaseStructure);

    TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE);
    TIM_Cmd(TIM3,ENABLE);
}

void timer_nvic_config(void)
{
  NVIC_InitTypeDef NVIC_InitStructure;
  NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}

void TIM3_IRQHandler(void)
{

  if(TIM_GetITStatus(TIM3,TIM_IT_Update)!=RESET)
  {
    TIM_ClearITPendingBit(TIM3,TIM_IT_Update);
    GPIO_WriteBit(GPIOB,GPIO_Pin_7,(BitAction)(!GPIO_ReadOutputDataBit(GPIOB,GPIO_Pin_7))); //状态取反
  }
}



int main()
{
  SysTick_Config_Init();
  led_gpio_init();

  while(1)
  { //((1+arr )/48M)*(1+psc )=((1+1999)/48M)*(1+23999)=1秒
    GPIO_ResetBits(GPIOB,GPIO_Pin_7);
    //delay_ms(1000); //1000ms = 1s
    TIM3_Config(1999,23999);

    GPIO_SetBits(GPIOB,GPIO_Pin_7);
    //delay_ms(1000);
    TIM3_Config(1999,23999);
  }
}