void setup() {
  // put your setup code here, to run once:
  volatile long i,j;
  
  volatile char *dirf,*dirk,*dira,*dirc,x;
  volatile char *outf,*ink,*outa,*outc;

  dirf = 0x30;  dirk = 0x107;  dira = 0x21;  dirc = 0x27;
  outf = 0x31;  ink = 0x106;   outa = 0x22;  outc = 0x28;
  *dirf = 0x0F; *dirk = 0x00;  *dira = 0x0F;
  *outa = 0x05; 

  while(1)
  {
    for(i=0;i<4;i++){
      *outf = 1 << i;
      *outa = *ink; //read
      if(*ink != 0){
       *outc = 1<<i;
      for(j=0;j<2000000;j++);
      *outc = 0;
      }
    }
  }
}

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

}
//Green Led for ROW
//Red Led for COLUMN

//To know what row what column