#include <U8g2lib.h>

//U8G2_ST7920_128X64_1_SW_SPI u8g2(U8G2_R0, /* clock=*/ 12, /* data=*/ 11, /* CS=*/ 10, /* reset=*/ 8);
U8G2_SSD1306_128X64_NONAME_1_SW_I2C u8g2(U8G2_R0, /* clock=*/ SCL, /* data=*/ SDA, /* reset=*/ U8X8_PIN_NONE);   // All Boards without Reset of the Display

byte a = 0;

#define smallFont u8g2_font_battery19_tn
#define bigFont u8g2_font_osr26_tn

char s[25];

void setup() {
  // put your setup code here, to run once:

  u8g2.begin();

}

void loop() {
  // put your main code here, to run repeatedly:

  a = a % 7;

  u8g2.firstPage();

  do {

    u8g2.setFontPosTop();

    u8g2.setDrawColor(0);
    u8g2.drawBox(0, 0, 128, 64);
    u8g2.setDrawColor(1);

    // u8g2.setFont(bigFont);
    // sprintf(s, "%d", a);
    // centerPrintIt(0, 128, 0, s);

    u8g2.setFont(smallFont);
    sprintf(s, "%c", a + 48);
    centerPrintIt(0, 128, 40, s);

  } while ( u8g2.nextPage() );

  a++;

  delay(1000);

}

void centerPrintIt( int x1, int x2, int y, char L[]) {

  u8g2.drawStr(x1 + (x2 - x1 - u8g2.getStrWidth(L)) / 2, y, L);

  return;
}