GPIO

/**
  ******************************************************************************
  * @file    stm32f4xx.h
  * @author  MCD Application Team
  * @version V1.3.0         modified by Keil (added USB definitions)
  * @date    08-November-2013
  * @brief   CMSIS Cortex-M4 Device Peripheral Access Layer Header File. 
  *          This file contains all the peripheral register‘s definitions, bits 
  *          definitions and memory mapping for STM32F4xx devices.            
  *            
  *          The file is the unique include file that the application programmer
  *          is using in the C source code, usually in main.c. This file contains:
  *           - Configuration section that allows to select:
  *              - The device used in the target application
  *              - To use or not the peripheral’s drivers in application code(i.e. //对于是否启用外设驱动，决定于USE_STDPERIPH_DRIVER
  *                code will be based on direct access to peripheral’s registers 
  *                rather than drivers API), this option is controlled by 
  *                "#define USE_STDPERIPH_DRIVER"
  *              - To change few application-specific parameters such as the HSE 
  *                crystal frequency
  *           - Data structures and the address mapping for all peripherals
  *           - Peripheral‘s registers declarations and bits definition
  *           - Macros to access peripheral’s registers hardware
  *  
  ******************************************************************************

/**
  * @brief  Sets the selected data port bits.   //设置选择好的端口的引脚电平，说白将对应的引脚变为高电平
  * @note   This functions uses GPIOx_BSRR register to allow atomic read/modify 
  *         accesses. In this way, there is no risk of an IRQ occurring between
  *         the read and the modify access.
  * @param  GPIOx: where x can be (A..K) to select the GPIO peripheral for STM32F405xx/407xx and STM32F415xx/417xx devices
  *                      x can be (A..I) to select the GPIO peripheral for STM32F42xxx/43xxx devices.
  *                      x can be (A, B, C, D and H) to select the GPIO peripheral for STM32F401xx devices. 
  * @param  GPIO_Pin: specifies the port bits to be written.
  *          This parameter can be any combination of GPIO_Pin_x where x can be (0..15).
  * @retval None
  */
void GPIO_SetBits(GPIO_TypeDef* GPIOx, uint16_t GPIO_Pin)

/**
  * @brief  Clears the selected data port bits.   //清空选择好的端口的引脚电平，说白将对应的引脚变为低电平
  * @note   This functions uses GPIOx_BSRR register to allow atomic read/modify 
  *         accesses. In this way, there is no risk of an IRQ occurring between
  *         the read and the modify access.
  * @param  GPIOx: where x can be (A..K) to select the GPIO peripheral for STM32F405xx/407xx and STM32F415xx/417xx devices
  *                      x can be (A..I) to select the GPIO peripheral for STM32F42xxx/43xxx devices.
  *                      x can be (A, B, C, D and H) to select the GPIO peripheral for STM32F401xx devices. 
  * @param  GPIO_Pin: specifies the port bits to be written.
  *          This parameter can be any combination of GPIO_Pin_x where x can be (0..15).
  * @retval None
  */
void GPIO_ResetBits(GPIO_TypeDef* GPIOx, uint16_t GPIO_Pin)

#include <stdio.h>
#include "stm32f4xx.h"


GPIO_InitTypeDef  GPIO_InitStructure;


void delay(void)
{
    int i=0x500000;
    
    while(i--);
}

int main(void)
{
    /* GPIOF Peripheral clock enable，使能GPIO第F组的端口硬件时钟 */
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOF, ENABLE);

    /* Configure PF10 in output pushpull mode，配置PF10引脚为输出模式 */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;            //第9根引脚
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;        //设置输出模式
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;        //推挽模式，增加驱动电流
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;    //设置IO的速度为100MHz
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;        //不需要上拉电阻
    GPIO_Init(GPIOF, &GPIO_InitStructure);


    while(1)
    {
        //设置PF9引脚为高电平
        GPIO_SetBits(GPIOF,GPIO_Pin_9);
        
        
        delay();
        
        //设置PF9引脚为低电平
        GPIO_ResetBits(GPIOF,GPIO_Pin_9);        
    
        delay();    
    
    }
}