#include "stm32f4xx.h"
int main(void)
{
uint32_t i;
RCC->AHB1ENR|=RCC_AHB1ENR_GPIODEN;
GPIOD->MODER = 0x55000000;
GPIOD->OTYPER = 0;
GPIOD->OSPEEDR = 0;
while(1)
{
GPIOD->ODR = 0xf000;
for(i=0;i<2000000;i++);
GPIOD->ODR = 0x0000;
for(i=0;i<2000000;i++);
}
}