void setup() {
  // put your setup code here, to run once:
volatile char *out;
volatile long i,j;
volatile char *dir;
dir=0x30;
*dir=0xff;
out=0x31;
while(1){
  volatile int mask;
    for(j=0;j<1000000;j++); 

  for(i=7;i>=4;i--){
  mask=1<<i;
  *out |= mask ;

  for(j=0;j<100000;j++);
}
out=0x00;

}

}

void loop() {
  // put your main code here, to run repeatedly:

}