#include <stdint.h>
 
const char segmentToBinary[] = { // Map numbers into seven segment digits
  0b00111111,
  0b00000110,
  0b01011011,
  0b01001111,
  0b01100110,
  0b01101101,
  0b01111100,
  0b00000111,
  0b01111111,
  0b01100111
};
 
uint8_t segmentPins[] = {18, 19, 21, 22, 23, 13, 12};
uint8_t commonPins[] = {15, 2, 4, 5};
 
void displayDigits(int number);
 
void setup(){
    // Set outputs and turn off
    for(int i = 0; i<sizeof(segmentPins);i++){
        pinMode(segmentPins[i],OUTPUT);
        digitalWrite(segmentPins[i],HIGH);
    }
    
    for(int i = 0; i<sizeof(commonPins);i++){
        pinMode(commonPins[i],OUTPUT);
        digitalWrite(commonPins[i],LOW);
    }
}
 
void loop(){
    displayDigits(1234);
}
 
void displayDigits(int number){
    uint8_t digits[4]; 
    // Separate number digits :
    digits[0] = number/1000; // extract the first digit
    digits[1] = (number%1000)/100; // extract the second digit
    digits[2] = (number%100)/10; // extract the third digit
    digits[3] = (number%10); // extract the third digit
    for(int i = 0; i<4; i++){
        // Turn off all digits
        for(int x = 0; x<sizeof(commonPins); x++){
            digitalWrite(commonPins[i],LOW);   
        }
        digitalWrite(commonPins[i],HIGH); // Turn on corresponding digit
        uint8_t currSegment = ~segmentToBinary[digits[i]]; // Invert the binary, because 7seg is common anode
        for(int y = 0; y<sizeof(segmentPins); y++){
            digitalWrite(segmentPins[i],currSegment & 0x01);
            currSegment >>= 1;
        }
        delay(1);
    }
}