//UKHB version. Data driven program i.e., extension is easy because you can just use an array to add more LEDs


#define OFF LOW  //set these HGH or LOW to suit your LED wiring
#define ON HIGH

struct ledData  //data needed for each LED
{
    byte pinNum;
    byte currentState;
    char key;
    int intensity;
};

ledData leds[] = { // initialize LED data 
  { 2, OFF, 'A',  HIGH},
  { 3, OFF, 'B',  HIGH},
  { 4, OFF, 'C',  HIGH},
  { 5, OFF, 'D',  HIGH},
  { 6, OFF, 'E',  HIGH},
  { 7, OFF, 'F',  HIGH},
  { 8, OFF, 'G',  HIGH},
  { 9, OFF, 'H',  HIGH},
  { 10, OFF, 'I', HIGH},
  { 11, OFF, 'J', HIGH},
  { 12, OFF, 'K', HIGH},
  { 13, OFF, 'L', HIGH}
};

const byte LED_COUNT = sizeof(leds) / sizeof(leds[0]);  //calculate the number of LEDs

void setup()
{
    Serial.begin(115200);
     Serial.println();
    pinMode(2,OUTPUT);
    pinMode(3,OUTPUT);
    pinMode(4,OUTPUT);
    pinMode(5,OUTPUT);
    pinMode(6,OUTPUT);
    pinMode(7,OUTPUT);
    pinMode(8,OUTPUT);
    pinMode(9,OUTPUT);
    pinMode(10,OUTPUT);
    pinMode(11,OUTPUT);
    pinMode(12,OUTPUT);
    pinMode(13,OUTPUT);
    showLeds();  //show LEDs in there initial state
}

void loop()
{
    if (Serial.available())  //wait for Serial input
    {
        char c = toupper(Serial.read());     //get a character
        for (int x = 0; x < LED_COUNT; x++)  //search for the character in the LED data
        {
            if (leds[x].key == c)  //if there is a match
            {
                leds[x].currentState = !leds[x].currentState;  //change the state of matching LED
            }
        }
        showLeds();  //display the LEDs in their current state
    }
}

void showLeds()
{
    for (int c = 0; c < LED_COUNT; c++)  //for each LED
    {
        if (leds[c].currentState == ON) //if the current State of the LED is ON,
  
        {
            digitalWrite(leds[c].pinNum, leds[c].intensity);
            // assign to each LED the given intensity in the array
        }
        else // if the current State is OFF, then leave it OFF
        {
            digitalWrite(leds[c].pinNum, 0);
        }
    }
}