Grove OLED on an Arduino Mega

// Grove OLED: the 1.12 inch 128x128 OLED on an SH1107, drawn with
// Adafruit's SH110X library on a Mega.
//
//   OLED   SDA -> 20 (SDA)   SCL -> 21 (SCL)   VCC -> 5 V   GND -> GND
//
// The library keeps the whole picture in RAM, one bit a pixel: 128 x 128 / 8
// is 2048 bytes, which is all of an Uno's RAM and a quarter of a Mega's, so
// this one runs on the Mega. display() sends it as sixteen pages of 128
// bytes, each with its page address and column 0 first.
//
// A ball bounces round the square, and the page count of each frame is
// printed: only the pages that changed are sent.

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SH110X.h>

Adafruit_SH1107 display(128, 128, &Wire);

int x = 20, y = 30, dx = 3, dy = 2;

void setup() {
  Serial.begin(9600);
  if (!display.begin(0x3C, true)) {
    Serial.println("SH1107 not found");
    while (1) {
    }
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SH110X_WHITE);
  display.setCursor(16, 4);
  display.print("Grove OLED 1.12");
  display.drawRect(0, 16, 128, 112, SH110X_WHITE);
  display.display();
  Serial.println("Grove OLED ready");
}

void loop() {
  display.fillCircle(x, y, 5, SH110X_BLACK);
  x += dx;
  y += dy;
  if (x < 7 || x > 120) dx = -dx;
  if (y < 23 || y > 120) dy = -dy;
  display.fillCircle(x, y, 5, SH110X_WHITE);
  display.display();
  delay(40);
}