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??GPIOF?ODR?????

???LED??????GPIOF?ODR????????????????????

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Cortex-M4?????

?Cortex-M4?????????Peripheral??????????????

?????1bit????

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unsigned int *room = (unsigned int *)(0x42000000);
*room = 1; // ????0x40000000~0x40000004?bit0??1

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?GPIOF?ODR?bit9????????

??GPIOF_ODR????0x40021400 + 0x14??????????????????????

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??LED

unsigned int *GPIOF_ODR = (unsigned int *)(((0x40021400 + 0x14 - 0x40000000) * 32 + 0x42000000) + 4 * 9);
while (1) {
    // ????
    *GPIOF_ODR = 0x1;  // ??bit9?1
    delay(1000000);  
    // ????
    *GPIOF_ODR = 0x1;  // ??bit9?1
    delay(10000000);  
    // ????
    *GPIOF_ODR = 0x0;  // ??bit9
    delay(10000000);  
    // ????
    *GPIOF_ODR = 0x0;  // ??bit9
    delay(10000000);  
}

???????*GPIOF_ODR = 0x10????????????????????????

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?RCC???????????????????????????

/* stm32f4xx.h */
#define PERIPH_BASE      ((uint32_t)0x40000000)
#define PERIPH_BB_BASE  ((uint32_t)0x42000000)
#define AHB1PERIPH_BASE (PERIPH_BASE + 0x00020000)
#define RCC_BASE        (AHB1PERIPH_BASE + 0x3800)
/* stm32f4xx_rcc.c */
#define CR_OFFSET       (RCC_BASE - PERIPH_BASE)
#define CR_HSION_BB    (PERIPH_BB_BASE + (CR_OFFSET * 32) + (HSION_BitNumber * 4))

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