void setup() 
{
  volatile char * dir_f = 0x30;
  *dir_f = 0xff;
  volatile char* data_f = 0x31;
  volatile unsigned long i;
  while(1)
  {
    *data_f = 0x01;
    for(i=0;i<100000;i++);
    *data_f = 0x00;
    for(i=0;i<100000;i++);
  }
}
void loop()
{

}