#include <avr/io.h>
#include <inttypes.h>
//C is incomplete; there's no port A
//B and D are 8 bit ports
//AtoD is on port C
int main(){
 int lsb;
 int b;
 long k;
 DDRD=0xff;
 DDRB=0x00;
 for (k=0;k<900000;k++);
 while (1){
  lsb = (PINB<<7);
   if (lsb==0) b=0xaa;
   if (lsb==128) b=0x00;
  PORTD=b;
  for (k=0;k<5000;k++);
  PORTD=~b;
  for (k=0;k<5000;k++);
 }
}