#define MAX_SSD_CNT     3
#define MAX_DATA_PINS     8

#define PIN_BASE          8
#define OFF         1
#define ONE         0

/*
    Font macro creations for Common Cathode (CC) display
    Pin No   : 0  1  2  3  4  5  6  7
    Segment  : E  D  C  DP  G  F  A  B
    ZERO     : 1  1  1  0  0  1  1  1  -> 0xE7
    ONE      : 0  0  1  0  0  0  0  1  -> 0x21
    Find the other definitions below
*/
#define ZERO            0xE7
#define ONE             0x21
#define TWO             0xCB
#define THREE           0x6B
#define FOUR            0x2D
#define FIVE            0x6E
#define SIX             0xEE
#define SEVEN           0x23
#define EIGHT           0xEF
#define NINE            0x6F
#define DOT             0x10
#define BLANK           0x00
/* Need to fill all others */
#define M_ONE           0x9D
#define MINUS           0xFD

#include <Arduino.h>

void init_ssd(void);
void display(unsigned char data[]);

void init_ssd(void) {
  int pin;

  for (pin = 0; pin < MAX_DATA_PINS; pin++)
    pinMode(pin, OUTPUT);

  /*
    Initializing control lines
    Pin No   :  8  9  10
    Display  :  D1 D2 D3
  */
  for (pin = PIN_BASE; pin < (PIN_BASE + MAX_SSD_CNT); pin++)
    pinMode(pin, OUTPUT);
}

/* Better if implemented in timer handler */
void display(unsigned char data[]) {
  unsigned char digit;
  int pin;

  for (digit = 0; digit < MAX_SSD_CNT; digit++) {
    /* Make sure all the display is OFF to start with */
    for (pin = 0; pin < MAX_SSD_CNT; pin++)
      digitalWrite(PIN_BASE + pin, OFF);

    /* Put the data on the pins */
    for (pin = 0; pin < MAX_DATA_PINS; pin++)
      digitalWrite(pin, !!((data[digit] << pin) & 0x80));

    // 0x6B - 01101011
    //        (01101011 << 0) & 10000000) -> 00000000 -> !!00000000 -> 0
    //        (11010110 << 1) & 10000000) -> 10000000 -> !!10000000 -> 1
    //        (10101100 << 2) & 10000000) -> 10000000 -> !!10000000 -> 1
    //        (01011000 << 3) & 10000000) -> 00000000 -> !!10000000 -> 0
    //        (10110000 << 4) & 10000000) -> 10000000 -> !!10000000 -> 1
    //        (01100000 << 5) & 00000000) -> 00000000 -> !!10000000 -> 0
    //        (11000000 << 6) & 10000000) -> 10000000 -> !!10000000 -> 1
    //        (10000000 << 7) & 10000000) -> 00000000 -> !!10000000 -> 1

    /* Enable a specific display */
    /*
       Pin No:  8  9  10
                0  1  1
                1  0  1
                1  1  0
    */
    for (pin = 0; pin < MAX_SSD_CNT; pin++)
      digitalWrite(PIN_BASE + pin, !(pin == digit));
    // pin == digit
    // First iteration
    // 0   == 0 -> TRUE -> 1 -> !1 -> 0
    // 1   == 0 -> FLASE-> 0 -> !0 -> 1
    // 2   == 0 -> FLASE-> 0 -> !0 -> 1
    // Second iteration
    // 0   == 1 -> FALSE-> 0 -> !0 -> 1
    // 1   == 1 -> TRUE -> 1 -> !1 -> 0
    // 2   == 1 -> FLASE-> 0 -> !0 -> 1
    // Third iteration
    // 0   == 2 -> FALSE-> 0 -> !0 -> 1
    // 1   == 2 -> FLASE-> 0 -> !0 -> 1
    // 2   == 2 -> TRUE -> 1 -> !1 -> 0
  }
}


const unsigned char digits[] = {ZERO, ONE, TWO, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT, NINE};
static unsigned char ssd[MAX_SSD_CNT];

void setup() {
  init_ssd();
}


void loop() {
  static int count;
  static int wait = 0;
    for (int j = 0; j < 3; j++) {
    ssd[j] = digits[(count)%10];

  }
  display(ssd);

  if (!wait--) {
    wait = 5000;
    count++;
  }

}