Outputs and switching

SSD1306 OLED with ESP32

Why add a 0.96-inch screen to a project that already has a 7-inch panel? A small OLED is a handy status readout: mounted on a remote box, inside a cabinet or on the device while the main panel sits by the door. It takes two I2C wires and works from 3.3 V.

The usual first failure is the address. The back of the module often says 0x78, which is the 8-bit write address, while Arduino libraries want the 7-bit form: 0x3C. One example stayed dark with 0x78 and worked with 0x3C. Some modules use 0x3D, and the SA0 pad on the board switches between them, so two OLEDs can share one bus. The Adafruit header comments suggest 0x3D for 128x64, but many of these modules ship at 0x3C, so run a scan and believe the scan.

Draw on it with a normal graphics library. The Adafruit library keeps a full copy of the screen in RAM, about 1 KB on a 128x64 model, and an I2C refresh is slow compared with a parallel panel. If a display board has one I2C bus shared with its touch chip, send updates only when the content changes, so the touch stays responsive. Check for an address clash with the touch controller first. Text that never moves can leave marks on an OLED over time, so consider moving it or dimming it when idle.

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

const int SDA_PIN = 8, SCL_PIN = 9;
Adafruit_SSD1306 oled(128, 64, &Wire, -1);

void setup() {
  Serial.begin(115200);
  Wire.begin(SDA_PIN, SCL_PIN);
  if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {   // not 0x78
    Serial.println("OLED not found, run an I2C scan");
    while (true) delay(1000);
  }
  oled.clearDisplay();
  oled.setTextSize(2);
  oled.setTextColor(SSD1306_WHITE);
  oled.setCursor(0, 0);
  oled.println("21.4 C");
  oled.display();
}

void loop() {}

Use this information at your own risk. It is for general guidance only: the example code compiles, but it has not been tested on every part, and modules differ between sellers. Check the manufacturer's data before you build. Product names belong to their owners, and LCD Ultra Pro is not affiliated with them. See our Terms.