STM32F407学习笔记二（GPIO）_gpiod->moder

从上文可以看到，在系统启动过程中会对系统时钟进行一次配置，有了时钟源以后，我们来看简单的GPIO配置：对于GPIO,使用寄存器进行配置时：我们先来看一个例子：

#include <stm32f4xx.h>
 
uint32_t Gb_TimingDelay;
void Delay(uint32_t nTime);
 
void main()
{
  SysTick_Config(SystemCoreClock/1000);//1ms based time
  RCC->AHB1ENR |= RCC_AHB1ENR_GPIODEN;  //ENABLE GPIOD
  RCC->APB2ENR |= RCC_APB2ENR_SYSCFGEN; //ENABLE SYSCFG
  
  GPIOD->MODER &= 0x00FFFFFF;      //set direction
  GPIOD->MODER |= 0x55000000;
  
  GPIOD->OTYPER &= 0xFFFF0FFF;    //set the way of output:31-16:observed 15-0: 1: output push-pull 0: output open-drain
  
  GPIOD->OSPEEDR &= 0X00FFFFFF;  //speed
  GPIOD->OSPEEDR |= 0XFF000000;
  
  SYSCFG->CMPCR =0X00000001;    //speed CMR
  
  GPIOD->PUPDR= 0X00FFFFFF;   //pull-up or pull-down
  
  GPIOD->BSRRH= 0XF000;       //clear or set
  
  while(1)                     
  {
    GPIOD->BSRRH = 0XF000;    
    GPIOD->BSRRL = 0X1000;
    Delay(100);
    
    GPIOD->BSRRH = 0XF000;
    GPIOD->BSRRL = 0X1000<<1;
    Delay(100);
    
    GPIOD->BSRRH = 0XF000;
    GPIOD->BSRRL = 0X1000<<2;
    Delay(100);
 
    GPIOD->BSRRH = 0XF000;
    GPIOD->BSRRL = 0X1000<<3;
    Delay(100);        
  }    
}
 
void Delay(uint32_t nTime)        //Delay
{
    Gb_TimingDelay = nTime;
    while(Gb_TimingDelay!=0);
}
 
void SysTick_Handle()             //interrupt handle
{
  if(Gb_TimingDelay!=0)
  {
      Gb_TimingDelay--;
  }

}

首先调用了

SysTick_Config，我们来看看这个函数：

__STATIC_INLINE uint32_t SysTick_Config(uint32_t ticks)
{
  if ((ticks - 1) > SysTick_LOAD_RELOAD_Msk)  return (1);      /* Reload value impossible */
 
 
  SysTick->LOAD  = ticks - 1;                                  /* set reload register */
  NVIC_SetPriority (SysTick_IRQn, (1<<__NVIC_PRIO_BITS) - 1);  /* set Priority for Systick Interrupt */
  SysTick->VAL   = 0;                                          /* Load the SysTick Counter Value */
  SysTick->CTRL  = SysTick_CTRL_CLKSOURCE_Msk |
                   SysTick_CTRL_TICKINT_Msk   |
                   SysTick_CTRL_ENABLE_Msk;                    /* Enable SysTick IRQ and SysTick Timer */
  return (0);                                                  /* Function successful */
}

可以看到这是对时钟中断进行配置，

每隔168000000/1000 *1/168000000=1ms产生一次中断。

我们重点看GPIO寄存器·：

1.GPIO端口模式寄存器GPIOx_MODER

2.GPIO端口输出类型寄存器GPIOx_OTYPER

3.GPIO端口输出速度控制器GPIOx_OSPEEDR

4.GPIO端口上拉下拉寄存器GPIOx_PUPDR

5.GPIO端口置位复位寄存器GPIOx_BSRR