#include <TimerOne.h>
#define A       2
#define B       4
#define C       6
#define D       7
#define E       8
#define F       3
#define G       5
#define D_1     9
#define D_2     10
#define D_3     11
#define D_4     12

unsigned char unit = 0, ten = 0, hun = 0, thou = 0;
unsigned char pos[4] = {0,0,0,0};
unsigned char digit[10][7]{//row,column
// A,F,B,G,C,D,E
  {0,0,0,1,0,0,0},//0
  {1,1,0,1,0,1,1},//1
  {0,1,0,0,1,0,0},//2
  {0,1,0,0,0,0,1},//3
  {1,0,0,0,0,1,1},//4
  {0,0,1,0,0,0,1},//5
  {0,0,1,0,0,0,0},//6
  {0,1,0,1,0,1,1},//7
  {0,0,0,0,0,0,0},//8
  {0,0,0,0,0,0,1}//9
};

void setup() {
  for(int i = A; i <= D_4; i++){
    pinMode(i, OUTPUT);
    digitalWrite(i,HIGH);

    if(i >= D_1)
      digitalWrite(i,LOW);
  }

  Timer1.initialize(1000000);
  Timer1.attachInterrupt(timerCallback);
  Timer1.start();
  // put your setup code here, to run once:

}

void loop() {
  int j = 0;

  for(int k = 0; k < 4; k++)
  {
    j = pos[k];
    for(int l = D_1; l <= D_4; l++)
    {
      digitalWrite(l,LOW);
    }
    for(int i = 0; i < 7; i++)
    {
      digitalWrite(i+A,digit[j][i]);
    }
    digitalWrite(k+D_1,HIGH);

    delay(10);
  }
  // put your main code here, to run repeatedly:
}

/*
@def function that runs every second
@param none
@return none
*/
void timerCallback(void)
{
  if(unit++ >= 9){
    unit = 0;
    if(ten++ >= 9){
      ten = 0;
      if(hun++ >= 9){
        hun = 0;
        if(thou++>= 9){
          thou = 0;
        }
      }
    }
  }
  pos[0] = thou;
  pos[1] = hun;
  pos[2] = ten;
  pos[3] = unit;
}