Basic keyboard polling

gistfile1.ino

struct Key {
  byte id;
  boolean pressed;
  uint8_t bounceKey;
  Key(byte id) : id(id), pressed(false), bounceKey(NOT_BOUNCING) {};
}

boolean toggleKey(struct Key *key) {
  key->bounceKey = checkStillBouncing(key->bounceKey);
  if(key->bounceKey == NOT_BOUNCING){
    key->bounceKey = debounceKey();
    key->pressed ? key->pressed = false : key->pressed = true;
    return true;
  }
  return false;
}

const uint8_t cols[COL_COUNT] = {11,3,4,5,6,7,8};
const uint8_t rows[ROW_COUNT] = {A0,10,9,A3,A4,A5};

Key * const NOKEY = new Key(0xFF);

Key * const ESC = new Key(0x00);
Key * const F1 = new Key(0x01);

// ...
// omitted keys
// ...

Key * const CTRLL = new Key(0x23);
Key * const CMDL = new Key(0x24);
Key * const SPACE = new Key(0x25);


Key * const keyMatrix[COL_COUNT][ROW_COUNT] =
{
  {ESC,ZIRKONFLEX,TAB,M3,M2L,NOKEY},
  {F1,N1,X,U,UE,M4},
  {F2,N2,V,I,OE,ALTL},
  {F3,N3,L,A,AE,CTRLL},
  {F4,N4,C,E,P,CMDL},
  {F5,N5,W,O,Z,SPACE},
  {NOKEY,BACK,ENTF,ENTER,NOKEY,NOKEY}
}

boolean keyChanged = false;

Key * pressedKeys[MAX_KEYS_PRESSED] = {0};
uint8_t pressedKeyIndex = 0;

static void resetKeys(){
  for(int i = 0; i < pressedKeyIndex; i++){
    pressedKeys[i]  = NOKEY;
  }

  pressedKeyIndex = 0;
  keyChanged = false;
}

static void scanKeys(){
  //iterate over columns
  for(int currentColumn = 0; currentColumn < COL_COUNT; currentColumn ++){
    digitalWrite(cols[currentColumn],HIGH);

    //scan rows
    for(int y = 0; y < ROW_COUNT; y++){
      Key* key = keyMatrix[currentColumn][y];
      if(key != NOKEY){

        int state = digitalRead(rows[y]);
        if((state == HIGH && !key->pressed) || (state == LOW && key->pressed)){
          if(toggleKey(key)){
            keyChanged = true;
          }
        }

        //collect report data, only pressed keys need to be sent to the computer
        if(key->pressed){
          if(pressedKeyIndex < MAX_KEYS_PRESSED){
            pressedKeys[pressedKeyIndex] = key;
            pressedKeyIndex++;
          } 
        }
      }
    }
    digitalWrite(cols[currentColumn],LOW);
  }
}

void loop() {
  resetKeys();
  scanKeys();
  sendKeyState();
}