#define DIG1 10
#define DIG2 9
#define DIG3 6
#define DIG4 5

//       A
//   ---------
//   |       |
//  F|       |B
//   |   G   |
//   ---------
//   |       |
//  E|       |C
//   |   D   |
//   ---------


#define SEGA 2
#define SEGB 0
#define SEGC 3
#define SEGD 8
#define SEGE 7
#define SEGF 4
#define SEGG 1

static uint8_t number_to_segment[10] =
{
  0b00111111, //0
  0b00000110, //1
  0b01011011, //2
  0b01001111, //3
  0b01100110, //4
  0b01101101, //5
  0b01111101, //6
  0b00000111, //7
  0b01111111, //8
  0b01101111  //9
};

void select_digit(int digit)
{
  digitalWrite(DIG1, digit==1);
  digitalWrite(DIG2, digit==2);
  digitalWrite(DIG3, digit==3);
  digitalWrite(DIG4, digit==4);
}

void set_segment(int segments)
{
  segments = ~segments; // binary codes are inversed, too lazy to fix it
  digitalWrite(SEGA, segments&0x01);
  digitalWrite(SEGB, segments&0x02);
  digitalWrite(SEGC, segments&0x04);
  digitalWrite(SEGD, segments&0x08);
  digitalWrite(SEGE, segments&0x10);
  digitalWrite(SEGF, segments&0x20);
  digitalWrite(SEGG, segments&0x40);
}

int counter;

void setup() {
  pinMode(DIG1, OUTPUT);
  pinMode(DIG2, OUTPUT);
  pinMode(DIG3, OUTPUT);
  pinMode(DIG4, OUTPUT);
  pinMode(SEGA, OUTPUT);
  pinMode(SEGB, OUTPUT);
  pinMode(SEGC, OUTPUT);
  pinMode(SEGD, OUTPUT);
  pinMode(SEGE, OUTPUT);
  pinMode(SEGF, OUTPUT);
  pinMode(SEGG, OUTPUT);

}

void loop() {
  counter = millis()%10000;

  int display_delay = 1;

  select_digit(0);
  set_segment(number_to_segment[counter/1000]);
  select_digit(1);
  delayMicroseconds(display_delay);
  select_digit(0);
  set_segment(number_to_segment[(counter%1000)/100]);
  select_digit(2);
  delayMicroseconds(display_delay);
  select_digit(0);
  set_segment(number_to_segment[(counter%100)/10]);
  select_digit(3);
  delayMicroseconds(display_delay);
  select_digit(0);
  set_segment(number_to_segment[counter%10]);
  select_digit(4);
  delayMicroseconds(display_delay);

}