debounce.cpp

#define DEBOUNCE_DELAY 100

class Button 
{
  public:

    Button(int p_Pin) /*Constructor*/
    {
      l_Pin = p_Pin;
      pinMode(l_Pin,INPUT);

      l_Last_Read_Value = digitalRead(l_Pin);
      l_Last_Read_Time = millis();
    }

    boolean Read()
    {
      boolean l_Current_Value;
      unsigned long l_Current_Time;
      boolean l_Return_Value;

      l_Current_Time = millis();
      l_Current_Value = digitalRead(l_Pin);

      if (l_Current_Value == l_Last_Read_Value && (l_Current_Time - l_Last_Read_Time) > DEBOUNCE_DELAY)
        l_Return_Value = l_Current_Value;
      else
        l_Return_Value = l_Last_Read_Value;

      l_Last_Read_Value = l_Current_Value;
      l_Last_Read_Time = l_Current_Time;


      delay(1);
      return l_Return_Value;
    }

   private:
     byte l_Pin;
     unsigned long l_Last_Read_Time ;
     boolean l_Last_Read_Value;

};

# usage:

Button Btn_Start(START_BTN);
Button Btn_Select(SELECT_STATE_BTN);


void loop()

{
  if(Btn_Start.Read() == HIGH)
  {
     while(Btn_Start.Read() != LOW); //wait for button release
     //do something 
  }

  if(Btn_Start.Btn_Select() == HIGH)
  {
     while(Btn_Start.Btn_Select() != LOW); //wait for button release
     //do something else
  }
}