#include <U8g2lib.h>
// https://github.com/olikraus/u8g2                    // library
// https://github.com/olikraus/u8g2/wiki/u8g2reference // reference
// https://github.com/olikraus/u8g2/wiki/fntlistall    // fonts

U8G2_SSD1306_128X64_NONAME_F_SW_I2C display[] = {
  // create an array of U8G2 objects
  U8G2_SSD1306_128X64_NONAME_F_SW_I2C(U8G2_R0, SCL, SDA, U8X8_PIN_NONE),  // first OLED
  U8G2_SSD1306_128X64_NONAME_F_SW_I2C(U8G2_R0, SCL, SDA, U8X8_PIN_NONE)   // second OLED
};

void setup() {
  configOled(0, 0x7A, u8g2_font_squeezed_b7_tr);  // address 0x7A = 0x3C
  configOled(1, 0x78, u8g2_font_t0_14b_mf);       // address 0x78 = 0x3D

  displayOled(0, 0, 7, "DISPLAY");
  displayOled(1, 0, 0, "display");
}

void loop() {
}

void configOled(int number, int address, const uint8_t* font) {
  display[number].setI2CAddress(address);
  display[number].begin();
  display[number].setFont(font);
  display[number].setDrawColor(1);  // white
  display[number].clearDisplay();
  display[number].clearBuffer();
  display[number].sendBuffer();  // transfer internal memory to the display
}

void displayOled(int number, int x, int y, const char* text) {
  display[number].setFontDirection(number);
  // display[number].setDisplayRotation(U8G2_R1); // only works with #define U8G2_Rx
  display[number].setCursor(x, y);
  display[number].print(text);
  display[number].print(number);
  display[number].sendBuffer();
  display[number].clearBuffer();  // must clear buffer for next display
}