STM32F103 中的TIM5 來無法讀取到編碼器counter值

sappppp 提问时间：2016-2-1 15:28 /

請問各位先進，我用STM32F103中的TIM5 CH1(PA0) ,CH2(PA1)來讀取編碼器的counter值，進而得知其編碼器轉的角度，可是我的程式卻讀到的counter值永遠是0，並且無法進入TIM5 IRQ中斷，所以想要請問我程式哪裡出錯呢！謝謝！程式如下
void ENC_Init(void)
{
#define ENCODER_TIMER TIM5

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_ICInitTypeDef TIM_ICInitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM5, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
GPIO_StructInit(&GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 ;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOA, &GPIO_InitStructure);
NVIC_InitStructure.NVIC_IRQChannel = TIM5_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = TIMx_PRE_EMPTION_PRIORITY;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = TIMx_SUB_PRIORITY;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
TIM_DeInit(ENCODER_TIMER);
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Prescaler = 0x0;
TIM_TimeBaseStructure.TIM_Period = 65535; // 0201 (4*ENCODER_PPR)-1;
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(ENCODER_TIMER, &TIM_TimeBaseStructure);
TIM_EncoderInterfaceConfig(ENCODER_TIMER, TIM_EncoderMode_TI12,TIM_ICPolarity_Rising, TIM_ICPolarity_Rising);
TIM_ICStructInit(&TIM_ICInitStructure);
TIM_ICInitStructure.TIM_ICFilter = ICx_FILTER;
TIM_ICInit(ENCODER_TIMER, &TIM_ICInitStructure);
TIM_ClearFlag(ENCODER_TIMER, TIM_FLAG_Update);
TIM_ITConfig(ENCODER_TIMER, TIM_IT_Update, ENABLE);
TIM5->CNT = COUNTER_RESET;
TIM_Cmd(ENCODER_TIMER, ENABLE);
}

void TIM5_IRQHandler(void)
{
      int16_t encoder_num;

if (TIM_GetITStatus(TIM5,TIM_IT_Update) != RESET)
{
   encoder_num=TIM_GetCounter(TIM5);
}
   TIM_ClearITPendingBit(TIM5,TIM_IT_Update);
}