#define PATTERN_COUNT 11 //number of segment patterns, 0-9 and all off
#define SEGMENT_COUNT 7  //how many segments I'm controlling
#define DIGIT_COUNT  4   //how many digits I'm controlling



            //                    A,B,C,D,E,F,G
int segmentPins[SEGMENT_COUNT] = {2,3,4,5,6,7,8};

//the pins for each digit
int digitPins[] = { 9, 10, 11, 12 };
//                                                      0      1     2    3      4     5     6     7    8     9     OFF
byte digitPatternsHex[PATTERN_COUNT] = { 0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F, 0x00 };

//counter
int counter = 0;

void setup(){
    Serial.begin(9600);
    //init segment pins to output
    for(int thisPin=0; thisPin<SEGMENT_COUNT; thisPin++){
      pinMode(segmentPins[thisPin], OUTPUT);
    }

    //init digit pins to output
    for(int thisPin=0; thisPin<DIGIT_COUNT; thisPin++){
      pinMode(digitPins[thisPin], OUTPUT);
    }
}
 
//turn all digits off, HIGH because common cathode
void allDigitsOff(){
  for(int thisPin = 0; thisPin < DIGIT_COUNT; thisPin++){
    digitalWrite(digitPins[thisPin], HIGH);
  }
}

//turn specific digit on
void digitOn(int digitNum){
  
  digitalWrite(digitPins[digitNum], LOW);
  
  delay(2);
}


void setPattern(int pattern){
  allDigitsOff(); 
  
  //data pins, 8bits
    for(int thisPin=0; thisPin<SEGMENT_COUNT; thisPin++){
      if(bitRead(digitPatternsHex[pattern], thisPin) == 1){
        digitalWrite(segmentPins[thisPin], HIGH);
      }else{
        digitalWrite(segmentPins[thisPin], LOW);
      }
    }
  
}

void showNumber(int currentNumber){
  
  //display digit from right to left
  int digitInFront = currentNumber/10;
  for(int currentDigit = 0; currentDigit < DIGIT_COUNT; currentDigit++){
    
    //get number in the ones place
    int number = currentNumber % 10; //5
    
    currentNumber /= 10;

    setPattern(number); 
    
    digitOn(currentDigit);
        
  }
}

void loop(){
  
//return first 2 digits of ms, 1 sec = 1000 millisec, 1.5 sec = 1500 millisec
  
  int currentNumber = (millis()/1000); 
  
  showNumber(currentNumber);
}