#include "stm32f10x.h"

int main(void)
{
    RCC->APB2ENR = 4;
    GPIOA->CRL = 3;
    GPIOA->ODR = 0xfffe;
    while (1)
    {
    }
}
或者是
#include "stm32f10x.h"

int main(void)
{
    /* 开启GPIOA的时钟 第2位置1*/
    RCC->APB2ENR |= 0x1 << 2;
    /* GPIOA_CRL的最后4位置 0011 */
    GPIOA->CRL &= ~(0x1 << 3);
    GPIOA->CRL &= ~(0x1 << 2);
    GPIOA->CRL |= 0x1 << 1;
    GPIOA->CRL |= 0x1 << 0;
    /* GPIOA_ODR的第0位置0 */
    GPIOA->ODR &= ~(0x1 << 0);
    while (1)
    {
    }
}
或者是
#include "stm32f10x.h"

int main(void)
{
    RCC->APB2ENR |= RCC_APB2ENR_IOPAEN;

    GPIOA->CRL &= ~GPIO_CRL_CNF0_1;
    GPIOA->CRL &= ~GPIO_CRL_CNF0_0;
    GPIOA->CRL |= GPIO_CRL_MODE0_1;
    GPIOA->CRL |= GPIO_CRL_MODE0_0;

    GPIOA->ODR &= ~GPIO_ODR_ODR0;

    while (1)
    {
    }
}