void Counter_Config()

{  

 NVIC_InitTypeDef NVIC_InitStructure;    

 GPIO_InitTypeDef GPIO_InitStructure;   

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;    

 RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE); 

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE); 

GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_7; 

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz; 

GPIO_Init(GPIOB, &GPIO_InitStructure);

//TIM4输出初始化 

TIM_DeInit(TIM4);  

TIM_TimeBaseStructure.TIM_Period = 100; //计数值=100-1 

TIM_TimeBaseStructure.TIM_Prescaler = 0; //预分频

 TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //时钟分割 

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Down; //模式 

TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure); //基本初始化

TIM_SetCounter(TIM4, 100); //设置 TIM4 计数器寄存器值   //设置 TIMx 自动重装载寄存器值

 TIM_ARRPreloadConfig(TIM4, ENABLE);

TIM_SelectInputTrigger(TIM4, TIM_TS_TI2FP2); //若为通道1 ，则为TIM_TS_TI1FP1

TIM_SelectSlaveMode(TIM4,TIM_SlaveMode_External1); 

TIM_SetCompare2(TIM4, 100); 

TIM_SetComper1(TIM4,100);TIM_Cmd(TIM4, ENABLE); //启动TIM4 TIM_ClearFlag(TIM4, TIM_IT_CC2); 

TIM_ITConfig(TIM4, TIM_IT_CC2, ENABLE)//中断配置

NVIC_InitStructure.NVIC_IRQChannel =TIM4_IRQChannel;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3; //抢占优先级0 NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; //响应优先级0 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //允许中断

 NVIC_Init(&NVIC_InitStructure);    //写入设置

 }

void TIM4_IRQHandler(void)

 {

    TIM_ClearFlag(TIM4, TIM_IT_CC2);

    XX++;

}