void Init()
{   
   GPIO_InitTypeDef      GPIO_InitStructure;
   NVIC_InitTypeDef      NVIC_InitStructure;
   TIM_ICInitTypeDef   TIM_ICInitStructure;
   
   /* TIM4 clock enable */
   RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);
   RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);

   GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_7;
   GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
   GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
   GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_NOPULL;
   GPIO_Init(GPIOB, &GPIO_InitStructure);

   GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_TIM4);

   NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;
   NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
   NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
   NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
   NVIC_Init(&NVIC_InitStructure);

   TIM_ICInitStructure.TIM_Channel = TIM_Channel_2;
   TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
   TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
   TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
   TIM_ICInitStructure.TIM_ICFilter = 0x0;

   TIM_PWMIConfig(TIM4, &TIM_ICInitStructure);

   /* Select the TIM4 Input Trigger: TI2FP2 */
   TIM_SelectInputTrigger(TIM4, TIM_TS_TI2FP2);

   /* Select the slave Mode: Reset Mode */
   TIM_SelectSlaveMode(TIM4, TIM_SlaveMode_Reset);
   TIM_SelectMasterSlaveMode(TIM4,TIM_MasterSlaveMode_Enable);

   /* TIM enable counter */
   TIM_Cmd(TIM4, ENABLE);

   /* Enable the CC2 Interrupt Request */
   TIM_ITConfig(TIM4, TIM_IT_CC2, ENABLE);
}

void TIM4_IRQHandler(void)
{
   GPIO_SetBits(GPIOD, GPIO_Pin_12);
   TIM_ClearITPendingBit(TIM4, TIM_IT_CC2);
}