STM32小车轮子没有转动编码器也有读数

Question

#include "encoder.h"

/PA6 PA7/
void Encoder_TIM3_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct;
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
TIM_ICInitTypeDef TIM_ICInitStruct;
NVIC_InitTypeDef NVIC_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);

GPIO_InitStruct.GPIO_Mode=GPIO_Mode_IN_FLOATING;
GPIO_InitStruct.GPIO_Pin=GPIO_Pin_6 |GPIO_Pin_7;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA,&GPIO_InitStruct);

TIM_TimeBaseStructInit(&TIM_TimeBaseInitStruct);
TIM_TimeBaseInitStruct.TIM_ClockDivision=TIM_CKD_DIV1;
TIM_TimeBaseInitStruct.TIM_CounterMode=TIM_CounterMode_Up;
TIM_TimeBaseInitStruct.TIM_Period=65535;
TIM_TimeBaseInitStruct.TIM_Prescaler=0;
TIM_TimeBaseInit(TIM3,&TIM_TimeBaseInitStruct);

TIM_EncoderInterfaceConfig(TIM3,TIM_EncoderMode_TI12,TIM_ICPolarity_Rising,TIM_ICPolarity_Rising);

TIM_ICStructInit(&TIM_ICInitStruct);
TIM_ICInitStruct.TIM_ICFilter=10;
TIM_ICInit(TIM3,&TIM_ICInitStruct);

TIM_ClearFlag(TIM3,TIM_FLAG_Update);
TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE);

NVIC_InitStructure.NVIC_IRQChannel=TIM3_IRQn; 

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

TIM_SetCounter(TIM3,0);

TIM_Cmd(TIM3,ENABLE);

}

/PB6 PB7/
void Encoder_TIM4_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct;
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
TIM_ICInitTypeDef TIM_ICInitStruct;
NVIC_InitTypeDef NVIC_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB,ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4,ENABLE);

GPIO_InitStruct.GPIO_Mode=GPIO_Mode_IN_FLOATING;
GPIO_InitStruct.GPIO_Pin=GPIO_Pin_6 |GPIO_Pin_7;
GPIO_Init(GPIOB,&GPIO_InitStruct);

TIM_TimeBaseStructInit(&TIM_TimeBaseInitStruct);
TIM_TimeBaseInitStruct.TIM_ClockDivision=TIM_CKD_DIV1;
TIM_TimeBaseInitStruct.TIM_CounterMode=TIM_CounterMode_Up;
TIM_TimeBaseInitStruct.TIM_Period=65535;
TIM_TimeBaseInitStruct.TIM_Prescaler=0;
TIM_TimeBaseInit(TIM4,&TIM_TimeBaseInitStruct);

TIM_EncoderInterfaceConfig(TIM4,TIM_EncoderMode_TI12,TIM_ICPolarity_Rising,TIM_ICPolarity_Rising);

TIM_ICStructInit(&TIM_ICInitStruct);
TIM_ICInitStruct.TIM_ICFilter=10;
TIM_ICInit(TIM4,&TIM_ICInitStruct);

TIM_ClearFlag(TIM4,TIM_FLAG_Update);
TIM_ITConfig(TIM4,TIM_IT_Update,ENABLE);

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_SetCounter(TIM4,0);

TIM_Cmd(TIM4,ENABLE);

}

int Read_Speed_Left(void)
{
int value;
value = (short)TIM_GetCounter(TIM3);
TIM_SetCounter(TIM3,0);
return value;
}

int Read_Speed_Right(void)
{
int value;
value = (short)TIM_GetCounter(TIM4);
TIM_SetCounter(TIM4,0);
return value;
}

void TIM3_IRQHandler(void)
{
if(TIM_GetITStatus(TIM3,TIM_IT_Update)!=0)
{
TIM_ClearITPendingBit(TIM3,TIM_IT_Update);
}
}

void TIM4_IRQHandler(void)
{
if(TIM_GetITStatus(TIM4,TIM_IT_Update)!=0)
{
TIM_ClearITPendingBit(TIM4,TIM_IT_Update);
}
}

在main函数中调用Read_Speed_Left()现象：