#include <U8glib.h>

#define DCLK 6
#define DIO 5
#define SW 3
#define CLK 2
#define DT 4

U8GLIB_SH1106_128X64  My_u8g_Panel(U8G_I2C_OPT_NONE);

int count = 0;

void displayCount() {
  My_u8g_Panel.firstPage();
  do {
    char buffer[10];
    sprintf(buffer, "%d", count);
    My_u8g_Panel.drawStr(0, 0, buffer);
  } while (My_u8g_Panel.nextPage());
}

void readEncoder() {
  int dtValue = digitalRead(DT);
  if (dtValue == HIGH) {
    count++;
  }
  if (dtValue == LOW) {
    count--;
  }
}

void setup() {
  My_u8g_Panel.begin();
  My_u8g_Panel.setFont(u8g_font_6x10);
  My_u8g_Panel.setFontRefHeightExtendedText();
  My_u8g_Panel.setDefaultForegroundColor();
  My_u8g_Panel.setFontPosTop();
  pinMode(CLK, INPUT);
  pinMode(DT, INPUT);
  pinMode(SW, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(CLK), readEncoder, FALLING);
  displayCount();
}

void loop() {
  if (digitalRead(SW) == LOW) {
    count = 0;
  }
  displayCount();
}