void setup() {
volatile char * dirA=0x21;
volatile char * dirC=0x27;
volatile char * dirF=0x30;
volatile char * dirK=0x107;
*dirA=0XFF;
*dirC=0x0F;
*dirF=0x0F;
*dirK=0xF0;
Serial.begin(9600);
}

void loop() {
  int keys[4][4]={
   {1,2,3,65},
   {4,5,6,66},
   {7,8,9,67},
   {42,0,35,68}
  };
  volatile char * outF=0x31;
  volatile char * inpK=0x106;
  int val=0;

  for(int k=0;k<4;){
  for(int i=0;i<4;i++){
    *outF=1<<i;
    char x=*inpK;
    if(x!=0x00){
      int j;
      for(j=0;j<4;j++){
        if(x&(1<<j))break;
      }
      if(keys[i][j]<10){
      // Serial.println(keys[i][j]);
      display_four_digit_number(keys[i][j]);
      val=val*10+keys[i][j];
      Serial.println(val);
 
      k++;
      }
      else
      {
         Serial.println(char(keys[i][j]));
      }
    }

   
  }
  delay(200);}
  display_four_digit_number(val);

}


void display_four_digit_number(int N){
  const char  segments[] = {
    0x3F, // 0
    0x06, // 1
    0x5B, // 2
    0x4F, // 3
    0x66, // 4
    0x6D, // 5
    0x7D, // 6
    0x07, // 7
    0x7F, // 8
    0x6F  // 9
};
char digit_on[4]={0x0E,0x0D,0X0B,0x07}; //This array stores hex for which digit should be on in particular time slot
unsigned volatile char * outA=0x22;
unsigned volatile char * outC=0x28;

int digits_i[4]={0};     // array to store the digits ,initially all zeroes
  int k=3;
  int x=N;

  // this iteravtively stores the digits from last digit

  while(x!=0){
    int rem=x%10;
    digits_i[k]=rem;
    x=x/10;
    k--;
  }

  for(int l=0;l<200;l++)
  for(int j=0;j<4;j++){
    *outC=digit_on[j];
    *outA=segments[digits_i[j]];
    delay(1);
    *outA=0x00;
    delay(1);
  }
  delay(500);


}