最近由于在学习STM32看到别人用寄存器编程控制跑马灯，于是自己也想试一试。可是试了好久终究弄不出来。回头看了下库函数的调用关系才搞明白。首先通过查看GPIOA的设置函数发现设置如下：

void GPIO_Init(GPIO_TypeDef* GPIOx, GPIO_InitTypeDef* GPIO_InitStruct)
{
  uint32_t pinpos = 0x00, pos = 0x00 , currentpin = 0x00;

  /* Check the parameters */
  assert_param(IS_GPIO_ALL_PERIPH(GPIOx));
  assert_param(IS_GPIO_PIN(GPIO_InitStruct->GPIO_Pin));
  assert_param(IS_GPIO_MODE(GPIO_InitStruct->GPIO_Mode));
  assert_param(IS_GPIO_PUPD(GPIO_InitStruct->GPIO_PuPd));

  /* ------------------------- Configure the port pins ---------------- */
  /*-- GPIO Mode Configuration --*/
  for (pinpos = 0x00; pinpos < 0x10; pinpos++)
  {
    pos = ((uint32_t)0x01) << pinpos;
    /* Get the port pins position */
    currentpin = (GPIO_InitStruct->GPIO_Pin) & pos;

    if (currentpin == pos)
    {
      GPIOx->MODER  &= ~(GPIO_MODER_MODER0 << (pinpos * 2));
      GPIOx->MODER |= (((uint32_t)GPIO_InitStruct->GPIO_Mode) << (pinpos * 2));

      if ((GPIO_InitStruct->GPIO_Mode == GPIO_Mode_OUT) || (GPIO_InitStruct->GPIO_Mode == GPIO_Mode_AF))
      {
        /* Check Speed mode parameters */
        assert_param(IS_GPIO_SPEED(GPIO_InitStruct->GPIO_Speed));

        /* Speed mode configuration */
        GPIOx->OSPEEDR &= ~(GPIO_OSPEEDER_OSPEEDR0 << (pinpos * 2));
        GPIOx->OSPEEDR |= ((uint32_t)(GPIO_InitStruct->GPIO_Speed) << (pinpos * 2));

        /* Check Output mode parameters */
        assert_param(IS_GPIO_OTYPE(GPIO_InitStruct->GPIO_OType));

        /* Output mode configuration*/
        GPIOx->OTYPER  &= ~((GPIO_OTYPER_OT_0) << ((uint16_t)pinpos)) ;
        GPIOx->OTYPER |= (uint16_t)(((uint16_t)GPIO_InitStruct->GPIO_OType) << ((uint16_t)pinpos));
      }

      /* Pull-up Pull down resistor configuration*/
      GPIOx->PUPDR &= ~(GPIO_PUPDR_PUPDR0 << ((uint16_t)pinpos * 2));
      GPIOx->PUPDR |= (((uint32_t)GPIO_InitStruct->GPIO_PuPd) << (pinpos * 2));
    }
  }
}

GPIO_TypeDef端口设置结构体如下：

typedef struct
{
  __IO uint32_t MODER;    /*!< GPIO port mode register,               Address offset: 0x00      */
  __IO uint32_t OTYPER;   /*!< GPIO port output type register,        Address offset: 0x04      */
  __IO uint32_t OSPEEDR;  /*!< GPIO port output speed register,       Address offset: 0x08      */
  __IO uint32_t PUPDR;    /*!< GPIO port pull-up/pull-down register,  Address offset: 0x0C      */
  __IO uint32_t IDR;      /*!< GPIO port input data register,         Address offset: 0x10      */
  __IO uint32_t ODR;      /*!< GPIO port output data register,        Address offset: 0x14      */
  __IO uint16_t BSRRL;    /*!< GPIO port bit set/reset low register,  Address offset: 0x18      */
  __IO uint16_t BSRRH;    /*!< GPIO port bit set/reset high register, Address offset: 0x1A      */
  __IO uint32_t LCKR;     /*!< GPIO port configuration lock register, Address offset: 0x1C      */
  __IO uint32_t AFR[2];   /*!< GPIO alternate function registers,     Address offset: 0x20-0x24 */
} GPIO_TypeDef;

改机构体根据结构体成员函数的大小自己形成了针对首地址的偏移量。从而与需要操作的寄存器地址偏移一一对应。通过查看设置函数可以看出，初始设置需要进行几步必要的设置，经过实验发现只需要设置

GPIOx->MODER和时钟就可以。同时需要对GPIO 端口置位/复位寄存器进行操作。由该寄存器可以知，低16位置位1,高16位复位0。由此得出寄存器操作代码如下：

//#define GPIPA  *(volatile unsigned long *)0x40020000;
#define  GPIOA_MODER  *(volatile unsigned long *)0x40020000
#define GPIOA_OSPEEDR *(volatile unsigned long *)0x40020008
#define GPIOA_OTYPER *(volatile unsigned long *)0x40020004
#de