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编辑了一下代码，结果彻底变成乱码了。

这事太恐怖了。

但愿我辛苦写的东西别都丢掉鸟。

其实都调用了个GPIO初始化的操作

比如我们的程序中：

DigitalOut myled(LED1);  

其实就是告诉MCU，这个GPIO PIN是干啥的

以及进行一些基本的设置

mbed官网中的例子，和我们这个例子都直接用mbed的API

回头我们再研究它到底干啥啦

在回头看这个层次结构图
现在我们对MCU寄存器有些概念啦，对mbed API也有些概念啦

并且分别用mbed API和直接操作寄存器的方式，实现了两个版本的blink.

#include "mbed.h"
DigitalOut myled(LED1);

int main() {
    while(1) {
        myled = 1; // LED is ON
        wait(1); // 1 sec
        myled = 0; // LED is OFF
        wait(1); // 1 sec
    }
}

#include <mbed.h>
DigitalOut myled(LED1);

int main() {
	
		unsigned int mask_pin5 = 1 << 5; 
    volatile unsigned int *porta_set = (unsigned int *)0x50000018;
    volatile unsigned int *porta_clr = (unsigned int *)0x50000018;

    while (true) {
        *porta_set |= mask_pin5;
        wait(0.5);
        
        *porta_clr |= (mask_pin5 << 16);
        wait(0.5);
    }
}

代码到处复制可以避免代码丢失

看起来还是mbed的更简单些

那么问题来了，结构图中的CMSIS-CORE是什么鬼

这几个字母我都认识，放一起就不知道是啥啦

费了好大劲

找到这样一个链接

http://www.arm.com/products/processors/cortex-m/cortex-microcontroller-software-interface-standard.php

原来是这个意思：
CMSIS - Cortex Microcontroller Software Interface Standard

CMSIS - Cortex Microcontroller Software Interface Standard The ARM^® Cortex^® Microcontroller Software Interface Standard (CMSIS) is a vendor-independent hardware abstraction layer for the Cortex-M processor series and specifies debugger interfaces.Creation of software is a major cost factor in the embedded industry. By standardizing the software interfaces across all Cortex-M silicon vendor products, especially when creating new projects or migrating existing software to a new device, means significant cost reductions.

The CMSIS enables consistent and simple software interfaces to the processor for interface peripherals, real-time operating systems, and middleware. It simplifies software re-use, reducing the learning curve for new microcontroller developers and cutting the time-to-market for devices.

原来就是在硬件上抽象出来一个层次。这样操作起来就统一啦，也方便移植啦，也省费用啦....，貌似都没我啥事。

继续贴图，虽然我看不懂这是啥玩意。

那CMSIS到底长啥样啊，来了，就这样。

其中高亮的就是包含L053R8 GPIO地址和寄存器定义的文件。

/** 
  * @brief General Purpose IO
  */

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 uint32_t BSRR;         /*!< GPIO port bit set/reset registerBSRR,        Address offset: 0x18 */
  __IO uint32_t LCKR;         /*!< GPIO port configuration lock register,       Address offset: 0x1C */
  __IO uint32_t AFR[2];       /*!< GPIO alternate function register,            Address offset: 0x20-0x24 */
  __IO uint32_t BRR;          /*!< GPIO bit reset register,                     Address offset: 0x28 */
}GPIO_TypeDef;

 寄存器的定义

和数据手册中（9.4 GPIO registers）此章节的内容是对应的。

#define GPIOA_BASE            (IOPPERIPH_BASE + 0x00000000)
#define GPIOB_BASE            (IOPPERIPH_BASE + 0x00000400)
#define GPIOC_BASE            (IOPPERIPH_BASE + 0x00000800)
#define GPIOD_BASE            (IOPPERIPH_BASE + 0x00000C00)
#define GPIOH_BASE            (IOPPERIPH_BASE + 0x00001C00)

GPIO的基地址

与数据手册中（2.2 Memory organization）此章节的内容是对应的。

GPIO的定义

参见楼上两个帖子

#define GPIOA               ((GPIO_TypeDef *) GPIOA_BASE)
#define GPIOB               ((GPIO_TypeDef *) GPIOB_BASE)
#define GPIOC               ((GPIO_TypeDef *) GPIOC_BASE)
#define GPIOD               ((GPIO_TypeDef *) GPIOD_BASE)
#define GPIOH               ((GPIO_TypeDef *) GPIOH_BASE)