//Charlieplexing Arduino - Controlling 12 LEDs with 4 GPIO Pins
  
#define A 0

#define B 1

#define C 2

#define D 3


#define PIN_CONFIG 0

#define PIN_STATE 1

#define LED_Num 12

int matrix[LED_Num][2][4] = {

  //           PIN_CONFIG                  PIN_STATE

  //    A       B       C      D         A     B    C    D

  // LED1 HIGH  
  
  { { OUTPUT, OUTPUT, INPUT, INPUT }, { LOW, HIGH, LOW, LOW } },

    // LED2 HIGH     

  { { OUTPUT, INPUT, OUTPUT, INPUT, }, { LOW, LOW, HIGH, LOW } },
     
  // LED3 HIGH     
    
  { { OUTPUT, INPUT, INPUT, OUTPUT }, { LOW, LOW, LOW, HIGH } }, 
     
  // LED4 HIGH   
  
 { { OUTPUT, OUTPUT, INPUT, INPUT }, { HIGH, LOW, LOW, LOW } },
     
 // LED5 HIGH    
  
 { { INPUT, OUTPUT, OUTPUT, INPUT }, { LOW, LOW, HIGH, LOW } },
  
    //LED6 HIGH

 { { INPUT, OUTPUT, INPUT, OUTPUT }, { LOW, LOW, LOW, HIGH } },
    
    // LED 7 HIGH
     
  { { OUTPUT, INPUT, OUTPUT, INPUT }, { HIGH, LOW, LOW, LOW } },
    
    //LED8 HIGH
     
  { { INPUT, OUTPUT, OUTPUT, INPUT }, { LOW, HIGH, LOW, LOW } }, 
    
    //LED9 HIGH

  { { INPUT,INPUT, OUTPUT, OUTPUT }, { LOW, LOW, LOW, HIGH } },
    
    //LED10 HIGH   

  { { OUTPUT, INPUT, INPUT, OUTPUT }, { HIGH, LOW, LOW, LOW } },
    
    //LED11 HIGH

  { { INPUT, OUTPUT, INPUT, OUTPUT }, { LOW, HIGH, LOW, LOW } }, 
    
    //LED12 HIGH

  { { INPUT, INPUT, OUTPUT, OUTPUT }, { LOW, LOW, HIGH, LOW } },
    
  

};


void lightOn( int led ) {

  pinMode( A, matrix[led][PIN_CONFIG][0] );

  pinMode( B, matrix[led][PIN_CONFIG][1] );

  pinMode( C, matrix[led][PIN_CONFIG][2] );

  pinMode( D, matrix[led][PIN_CONFIG][3] );

  digitalWrite( A, matrix[led][PIN_STATE][0] );

  digitalWrite( B, matrix[led][PIN_STATE][1] );

  digitalWrite( C, matrix[led][PIN_STATE][2] );

  digitalWrite( D, matrix[led][PIN_STATE][3] );
  
  

}


void setup() {}


void loop() {

   for( int l = 0; l < LED_Num; l++ ) {  // chasing Right

    lightOn( l );

    delay(2000 / LED_Num );
    
   }
  for (int l = LED_Num-1; l>0; l=l-1){  // chasing Left
    
    lightOn (l);
    
    delay(2000 / LED_Num);
  }
    
  
  }