STM32F407 ------ 使用定时器实现精确延时

测试环境：主频168M

#include "delay.h"

void delay_init()
{
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

    TIM_TimeBaseStructure.TIM_Period = ;
    TIM_TimeBaseStructure.TIM_Prescaler = ;
    TIM_TimeBaseStructure.TIM_ClockDivision = ;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

    TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);
}                                    

void delay_ms(u16 nms)
{
    u32 cnt;
    cnt = nms*;
    TIM_Cmd(TIM4, ENABLE);
    while(cnt--)
    {
        while(TIM_GetFlagStatus(TIM4, TIM_FLAG_Update) == RESET);
        TIM_ClearFlag(TIM4, TIM_FLAG_Update);
    }
    TIM_Cmd(TIM4, DISABLE);
}
//延时nus
//nus为要延时的us数.
void delay_us(u32 nus)
{
    u32 cnt;
    cnt = nus;
    TIM_Cmd(TIM4, ENABLE);
    while(cnt--)
    {
        while(TIM_GetFlagStatus(TIM4, TIM_FLAG_Update) == RESET);
        TIM_ClearFlag(TIM4, TIM_FLAG_Update);
    }
    TIM_Cmd(TIM4, DISABLE);
}

#ifndef __DELAY_H
#define __DELAY_H                

#include "stm32f4xx_conf.h"

void delay_init();
void delay_ms(u16 nms);
void delay_us(u32 nus);

#endif