直接放代码吧，请各路大佬指导。
串口输出一直是0.

#include "encoder.h"
void encoder_tim4_Init() //对TIM4进行编码器模式
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;  
  TIM_ICInitTypeDef TIM_ICInitStructure;  
GPIO_InitTypeDef GPIO_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB,ENABLE);

GPIO_InitStructure.GPIO_Pin= GPIO_Pin_6|GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF;
GPIO_InitStructure.GPIO_PuPd=GPIO_PuPd_NOPULL;
GPIO_Init(GPIOB, &GPIO_InitStructure); //PB6 PB7 为浮空复用模式
GPIO_PinAFConfig(GPIOB,GPIO_PinSource6,GPIO_AF_TIM4);
GPIO_PinAFConfig(GPIOB,GPIO_PinSource7,GPIO_AF_TIM4);

  TIM_TimeBaseStructure.TIM_Prescaler = 0x0;
  TIM_TimeBaseStructure.TIM_Period = ENCODER_TIM_PERIOD;//65536
  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);
  
TIM_EncoderInterfaceConfig(TIM4, TIM_EncoderMode_TI12, TIM_ICPolarity_Rising, TIM_ICPolarity_Rising);//编码器模式3
  
  TIM_ICInitStructure.TIM_ICFilter = 6;
  TIM_ICInit(TIM4, &TIM_ICInitStructure);

  TIM_ClearFlag(TIM4, TIM_FLAG_Update);
  TIM_ITConfig(TIM4, TIM_IT_Update, ENABLE);  
TIM_SetCounter(TIM4,0);
  TIM_Cmd(TIM4, ENABLE);

}

/*******************************
利用定时器3，使定时器3  1秒中断串口打印TIM4 CNT 的值
*******************************/
#include "timer.h"
#include "led.h"
#include "usart.h"
int Encoder_Left;
void TIM3_Int_Init(u16 arr,u16 psc)
{
NVIC_InitTypeDef NVIC_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

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);

NVIC_InitStructure.NVIC_IRQChannel=TIM3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0x01;
NVIC_InitStructure.NVIC_IRQChannelSubPriority=0x03;
NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
NVIC_Init(&NVIC_InitStructure);
TIM_Cmd(TIM3,ENABLE);
}
void TIM3_IRQHandler(void)
{
if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET)
  {
  Encoder_Left=TIM4->CNT;
   LED0=!LED0;
   LED1=!LED1;
   printf("%d ",Encoder_Left);
  TIM_SetCounter(TIM4,0);
  }
   TIM_ClearITPendingBit(TIM3, TIM_IT_Update  );
}
*********************
*********************
#include "stm32f4xx.h"
#include "led.h"
#include "delay.h"
#include "usart.h"
#include "timer.h"
#include "encoder.h"
extern int Encoder_Left;
int main(void)
{

delay_init(168);
  LED_Init();
uart_init(115200);
encoder_tim4_Init();
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
TIM3_Int_Init(9999,8399);
GPIO_SetBits(GPIOA,GPIO_Pin_6|GPIO_Pin_7);
while(1)
{

}
}