STM32 Задержки

#include "stm32f4xx.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_tim.h"
#include "misc.h"

int i=0; //Counter
void SetSysClockToHSE(void)
{
    ErrorStatus HSEStartUpStatus;

    RCC_DeInit();


    RCC_HSEConfig( RCC_HSE_ON);


    HSEStartUpStatus = RCC_WaitForHSEStartUp();

    if (HSEStartUpStatus == SUCCESS)
    {

        RCC_HCLKConfig( RCC_SYSCLK_Div1);


        RCC_PCLK2Config( RCC_HCLK_Div1);


        RCC_PCLK1Config(RCC_HCLK_Div1);


        RCC_SYSCLKConfig( RCC_SYSCLKSource_HSE);


        while (RCC_GetSYSCLKSource() != 0x04)
        {
        }
    }
    else

        while (1)
        {
        }
    }
}

void TIM4_IRQHandler(void)
{
    TIM6->SR &= ~TIM_SR_UIF; //Сброс прерывания

        if(i==0) GPIO_SetBits(GPIOD, GPIO_Pin_12); // «1» на PD12
        else if(i==1) GPIO_SetBits(GPIOD, GPIO_Pin_13); // «1» на PD13
        else if(i==2) GPIO_SetBits(GPIOD, GPIO_Pin_14); // «1» на PD14
        else if(i==3) GPIO_SetBits(GPIOD, GPIO_Pin_15); // «1» на PD15
        else if(i==4)GPIO_ResetBits(GPIOD, GPIO_Pin_12|GPIO_Pin_13|GPIO_Pin_14|GPIO_Pin_15); //Сброс всего на «0»
        i++; //Счетчик +1
        if(i==5) i=0; //Если i=5, счетчик=0
}

int main(void)
{
    SetSysClockToHSE();

    /* Initialize LED which connected to PC13 */
    GPIO_InitTypeDef  GPIO_InitStructure;
    // Enable PORTC Clock
    RCC_APB2PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
    /* Configure the GPIO_LED pin */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12| GPIO_Pin_13| GPIO_Pin_14| GPIO_Pin_15; //Выбор нужного вывода;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOC, &GPIO_InitStructure);

    GPIO_ResetBits(GPIOC, GPIO_Pin_13); // Set C13 to Low level ("0")
    GPIO_ResetBits(GPIOC, GPIO_Pin_14);
    GPIO_ResetBits(GPIOC, GPIO_Pin_15);
    GPIO_ResetBits(GPIOC, GPIO_Pin_12);
    // TIMER4
    TIM_TimeBaseInitTypeDef TIMER_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

    TIM_TimeBaseStructInit(&TIMER_InitStructure);
    TIMER_InitStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIMER_InitStructure.TIM_Prescaler = 8000;
    TIMER_InitStructure.TIM_Period = 500;
    TIM_TimeBaseInit(TIM4, &TIMER_InitStructure);
    TIM_ITConfig(TIM4, TIM_IT_Update, ENABLE);
    TIM_Cmd(TIM4, ENABLE);
    /* NVIC Configuration */
    /* Enable the TIM4_IRQn Interrupt */
    NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    while(1)
    {
    }