инкрементальный енкодер и stm32f4discovery

#include "stm32f4xx.h"
#include "stm32f4xx_tim.h"

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_ICInitTypeDef  TIM_ICInitStructure;
GPIO_InitTypeDef GPIO_InitStructure;

#define   ENCODER_TIM             TIM5
#define   MAX_COUNT               100

int main(void)
{

  int i=0;

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM5, ENABLE);
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;
  GPIO_Init(GPIOA,&GPIO_InitStructure);

  GPIO_PinAFConfig(GPIOA, GPIO_PinSource0, GPIO_AF_TIM5);
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource1, GPIO_AF_TIM5);

  TIM_TimeBaseStructure.TIM_Prescaler = 0;
  TIM_TimeBaseStructure.TIM_Period = (MAX_COUNT*2)-1;
  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(ENCODER_TIM, &TIM_TimeBaseStructure);
  TIM_EncoderInterfaceConfig(ENCODER_TIM, TIM_EncoderMode_TI12, TIM_ICPolarity_Rising, TIM_ICPolarity_Rising);

  ENCODER_TIM->CNT = 0;
  TIM_Cmd(ENCODER_TIM, ENABLE);

  while (1)
  {
   i = ENCODER_TIM->CNT;
  }
}

/**
**********************************************************************
**
**  TEST:  encoder TIM8;
**
**
**********************************************************************
*/

/* Includes */
#include "stm32f4xx.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_tim.h"
/* Private macro */
/* Private variables */
/* Private function prototypes */
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_ICInitTypeDef  TIM_ICInitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
/* Private functions */

/**
**======================================================================
**
**  Abstract: main program
**
**======================================================================
*/
void EncoderSetup()
{
	/* Enable GPIO clock */
	  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC,ENABLE); 
	  RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8,ENABLE);  
	
          // PC.6,PC.7 
	  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
	  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
	  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
	  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;
	  GPIO_Init(GPIOC,&GPIO_InitStructure);
	  GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_TIM8); 
	  GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_TIM8); 

	  // TIM8
	  TIM_TimeBaseStructure.TIM_Prescaler = 0;   
	  TIM_TimeBaseStructure.TIM_Period = 19999; 
	  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; 
	  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; 
	  TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure); 

	  TIM_EncoderInterfaceConfig(TIM8, TIM_EncoderMode_TI12, TIM_ICPolarity_Rising, TIM_ICPolarity_Rising); 
	  TIM8->CNT = 0; 
	  TIM_Cmd(TIM8, ENABLE); 
}
uint16_t z;

int main(void)
{
	int i = 0;

	EncoderSetup(); //запуск таймера8

  /* TODO - Add your application code here */

  /* Infinite loop */
  while (1)
  {

	  i = TIM8->CNT; 

	  z=i/4;

  }
}