SSD1306 OLED 128x64 (I2C) with ESP32

Supply 3.3-5 V Bus I2C I2C address 0x3C / 0x3D

Pins and ESP32 wiring

Pin	Role	ESP32 pin
GND	Ground	GND
VCC	Power	3V3
SCL	I2C clock (SCL)	D22
SDA	I2C data (SDA)	D21

Suggested wiring for the 30-pin ESP32 DevKit, avoiding flash, input-only and strapping pins. BoardPilot checks it for you as you wire.

Good to know

The address is 0x3C or 0x3D (the jumper on the back). A board printed “0x78” is 0x3C: the print shows the address shifted left by one bit. (Solomon Systech SSD1306 datasheet, I²C-bus interface: slave address, SA0 bit)
on Uno, Nano and Mega: A 128×64 display needs a 1 KB screen buffer in RAM. On a board with 2 KB of RAM (Uno, Nano) that leaves little for the rest of the sketch. (Adafruit SSD1306 library, Buffer of width × height / 8 bytes; ATmega328P datasheet: 2 KB SRAM)

Starter code (Arduino)

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);  // SDA = GPIO 21, SCL = GPIO 22
  Wire.beginTransmission(0x3C);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "SSD1306 OLED 128x64 (I2C) found at 0x3C" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}