#include "U8glib.h"

U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_DEV_0 | U8G_I2C_OPT_NO_ACK | U8G_I2C_OPT_FAST); // Fast I2C / TWI

int progress = 0;
int buttonStateUp = 0;
int buttonStateDown = 0;
const int buttonUp = 2;
const int buttonDown = 3;

void setup() {
  u8g.setFont(u8g_font_tpssb);
  u8g.setColorIndex(1);

  pinMode(buttonUp, INPUT_PULLUP);
  pinMode(buttonDown, INPUT_PULLUP);
}

void loop() {

  buttonStateUp = digitalRead(buttonUp);
  buttonStateDown = digitalRead(buttonDown);

  u8g.firstPage();
  do {
    u8g.drawStr(25, 50, "Progress Bar");
    u8g.drawFrame(0, 10, 128, 20);
    u8g.drawBox(10, 15, progress, 10);
  } while ( u8g.nextPage() );

  if (progress < 108 && progress > -1) {
      if(buttonStateUp == HIGH)
        progress++;
      if(buttonStateDown == HIGH)
        progress--;
  } else {
    progress = 0;
  }
}