File content as of revision 0:e078ecb37ad7:

#include "mbed.h"
//勉強会
//STM32 L0 GPIO定義　address 0x5000 0000
// __IO は     volatile 
// uint32_t は  unsigned long 
 struct GPIO_
{
  __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  register,     Address offset: 0x18      */
  __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 */
  __IO uint32_t BRR;         /*!< GPIO Bit Reset register,               Address offset: 0x28      */
};
typedef struct  GPIO_ GPIO_T;

DigitalOut myled(LED1);

int main() {
    int i=0;
    GPIO_T *pGPIO = (GPIO_T *)0x50000000;    //GPIO A base address
    printf("\r\nGPIO Struct TEST\r\n");     
    while(1) { 
      wait(1);
///      myled = !myled;
#if 0
      //LED port is GPIO_A bit 5
      if (i&1) 
        //pGPIO->ODR??; 
      else 
        //pGPIO->ODR??; 
#else
      if (i&1) 
        pGPIO->BSRR = 0x20; //GPIO A BIT5 reset 
      else 
        pGPIO->BRR = 0x20 ; ////GPIO A BIT5 set

#endif        
     i++;      
    }
}