This is spi oled 3.3v-5.0v. Note: The Github link of this project is: https://github.com/mike-rankin/spi_oled_3.3v-5.0v.  This is GitHub account: https://github.com/mike-rankin where you will explore more excellent projects. He is a good DIY maker who designs custom ESP32 IoT projects using Altium Designer, Arduino IDE and Fusion360. Welcome everyone to follow.

/*********************************************************************

This is an example for our Monochrome OLEDs based on SSD1306 drivers

  Pick one up today in the adafruit shop!

  ------> http://www.adafruit.com/category/63_98

This example is for a 128x64 size display using SPI to communicate

4 or 5 pins are required to interface

Adafruit invests time and resources providing this open source code, 

please support Adafruit and open-source hardware by purchasing 

products from Adafruit!

Written by Limor Fried/Ladyada  for Adafruit Industries.  

BSD license, check license.txt for more information

All text above, and the splash screen must be included in any redistribution

*********************************************************************/

#include <SPI.h>

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

//Adafruit Default  If using software SPI (the default case):

//#define OLED_MOSI   9

//#define OLED_CLK   10

//#define OLED_DC    11

//#define OLED_CS    12

//#define OLED_RESET 13

//Adafruit_SSD1306 display(OLED_MOSI, OLED_CLK, OLED_DC, OLED_RESET, OLED_CS);

//My Arduino Nano Test Board

//#define OLED_DC 4

//#define OLED_CS 5

//#define OLED_CLK 2

//#define OLED_MOSI 3

//#define OLED_RESET 6

//Adafruit_SSD1306 display(OLED_MOSI, OLED_CLK, OLED_DC, OLED_RESET, OLED_CS);

//* Uncomment this block to use hardware SPI

#define OLED_DC     4

#define OLED_CS   17  //NEW D17  

#define OLED_RESET  12

Adafruit_SSD1306 display(OLED_DC, OLED_RESET, OLED_CS);

//*/

#define NUMFLAKES 10