//=====================
  //KY-040 Rotary Encoder
  //=====================
  #include <Wire.h>
  #include <Adafruit_SSD1306.h>
  //-----------------------------------------------
  //Adafruit_SSD1306 display(128, 64, &Wire, 4);
  Adafruit_SSD1306 display = Adafruit_SSD1306(128, 64, &Wire);
  //-----------------------------------------------
  #define CLK    2
  #define DT     3
  #define SW     4
  //-----------------------------------------------
  int counter = 0; int currentCLK; int previousCLK; 
  String encdir ="";
  //=========================================================
  void setup()
  {  
    pinMode(CLK,INPUT); pinMode(DT,INPUT); pinMode(SW,INPUT);
    Serial.begin(9600);
    if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) 
    {
      Serial.println(F("SSD1306 allocation failed"));
      for (;;);
    }
    display.clearDisplay(); 
    analogReference(INTERNAL);
    
    previousCLK = digitalRead(CLK);
  } 
  //=========================================================
  void loop()
  {  
    if(digitalRead(SW) == LOW)
    {
      reset_OLED();
      counter = 0;
    }
    currentCLK = digitalRead(CLK);
    if(currentCLK != previousCLK)
    {       
      if(digitalRead(DT) != currentCLK)
      { 
        counter++;
        encdir = "clockwise";
      }
      else
      {
        counter--;
        encdir = "counterclk";
      }
      disp_OLED();  
    }
    previousCLK = currentCLK; 
  }
  //=========================================================
  void disp_OLED()
  {
    display.setTextColor(WHITE);
    display.clearDisplay();
    display.setTextSize(2);
    display.setCursor(0,0);
    display.println(encdir); display.print("----------");
    display.setTextSize(4);
    display.setCursor(35,30);
    display.print(counter);
    display.display();
  }
  //=========================================================
  void reset_OLED()
  {
    display.setTextColor(WHITE);
    display.clearDisplay();
    display.setTextSize(2);
    display.setCursor(32,0);
    display.print("count");
    display.setTextSize(4);
    display.setCursor(5,20);
    display.print("RESET");
    display.display();
  }