text: #include "stm32l475xx.h"
  #include "delay.h"
  
  int main()
  {
      /* The project does not contain system_stem32l4xx.c */
      /* The program does not call SystemInit(), 
       * MSI is used as the clock source.
       * SYS_CLK is 4 Mhz
       */
      
      /* enable GPIO A clock gate */
      RCC->AHB2ENR |= RCC_AHB2ENR_GPIOAEN;
      
      /* set the mode of GPIOA pin 5 as general purpose output mode */
      /* set the mode as 00 first and then set as 01 */
      GPIOA->MODER &= ~GPIO_MODER_MODE5;
      GPIOA->MODER |= GPIO_MODER_MODE5_0;
      
      while (1) {
          /* Toggle pin 5 in GPIOA */
          GPIOA->ODR ^= GPIO_ODR_OD5;
          delay(1000);
      }
      return 0;
  }
  