#include "stm32f4xx.h" 
void delayMs(int n); 
int main(void) { 
RCC->AHB1ENR |= 1;                                              /* enable GPIOA clock */ 
GPIOA->MODER &= ~0x00000C00;                       /* clear pin mode */             
GPIOA->MODER |=0x00000400;                            /* set pin to output mode */
 while(1) { 
GPIOA->ODR |= 0x00000020;                                 /* turn on LED */ 
 delayMs(500); 
 GPIOA->ODR &= ~0x00000020;                          /* turn off LED */ 
 delayMs(500);
 } }
                 			 /* 16 MHz SYSCLK */ 
void delayMs(int n) { 
int i; 
for (; n > 0; n--) 
for (i = 0; i < 3195; i++) ;
 }