STM32F407学习笔记二（GPIO）

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

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