SSD1306 OLED Display
0x3C / 0x3DPopular 0.96 inch and 1.3 inch monochrome graphic displays using I2C communication.
TypeDisplay
Alt Address PinsSA0 pin (GND=0x3C, VCC=0x3D)
Driver LibraryAdafruit_SSD1306 / U8g2
Free I2C tool
I2C Scanner Code for Arduino & ESP32
Use these Arduino and ESP32 scanner sketches to find OLED, LCD, RTC, EEPROM, and sensor addresses. If nothing appears, follow the wiring checks before replacing the module.
Copy-paste scanner
Choose your board and upload the scanner.
Open Serial Monitor after upload. If the scanner prints an address like `0x3C`, use that address in your display or sensor library.
Arduino I2C scanner
For Arduino Uno and Nano, SDA is usually A4 and SCL is A5. For Mega, SDA is 20 and SCL is 21.
#include <Wire.h>
void setup() {
Wire.begin();
Serial.begin(9600);
while (!Serial);
Serial.println("I2C scanner started");
}
void loop() {
byte error;
byte address;
int devices = 0;
Serial.println("Scanning...");
for (address = 1; address < 127; address++) {
Wire.beginTransmission(address);
error = Wire.endTransmission();
if (error == 0) {
Serial.print("I2C device found at 0x");
if (address < 16) Serial.print("0");
Serial.println(address, HEX);
devices++;
}
}
if (devices == 0) {
Serial.println("No I2C devices found");
}
delay(3000);
}ESP32 I2C scanner
Enter the SDA and SCL pins you wired. Common ESP32 defaults are SDA 21 and SCL 22, but many projects use different pins.
#include <Wire.h>
const int SDA_PIN = 21;
const int SCL_PIN = 22;
void setup() {
Wire.begin(SDA_PIN, SCL_PIN);
Serial.begin(115200);
Serial.println("ESP32 I2C scanner started");
}
void loop() {
byte error;
byte address;
int devices = 0;
Serial.println("Scanning...");
for (address = 1; address < 127; address++) {
Wire.beginTransmission(address);
error = Wire.endTransmission();
if (error == 0) {
Serial.print("I2C device found at 0x");
if (address < 16) Serial.print("0");
Serial.println(address, HEX);
devices++;
}
}
if (devices == 0) {
Serial.println("No I2C devices found");
}
delay(3000);
}How to use the Arduino I2C Scanner
An Arduino I2C scanner is a simple diagnostic tool that pings every possible I2C address (from 1 to 127) on the bus. If a device acknowledges the ping, the scanner reports the address. To use it, simply connect your device's SDA and SCL pins to the corresponding pins on your microcontroller, power the device, upload the code above, and open your Serial Monitor.
Address Database
Searchable I2C Device Directory
Verify default addresses, pin configurations, and troubleshooting guidelines for common modules.
SH1106 OLED Display
0x3C / 0x3DLarge 1.3 inch OLED screen modules, often wired with slightly different offset configurations than SSD1306.
TypeDisplay
Alt Address PinsAddress Jumper on board back
Driver LibraryU8g2 / Adafruit_SH110X
LCD 16x2 / 20x4 Backpack
0x27 / 0x3FPCF8574-based interface board allowing standard character LCDs to run over I2C.
TypeDisplay Backpack
Alt Address PinsA0, A1, A2 pads (0x20 - 0x27)
Driver LibraryLiquidCrystal_I2C
BME280 Sensor
0x76 / 0x77High-precision barometric pressure, temperature, and relative humidity sensor by Bosch.
TypeEnvironmental Sensor
Alt Address PinsSDO pin (GND=0x76, VCC=0x77)
Driver LibraryAdafruit_BME280
BMP280 Sensor
0x76 / 0x77Barometric pressure and temperature sensor, a low-cost alternative to the BME280 without humidity sensing.
TypeEnvironmental Sensor
Alt Address PinsSDO pin (GND=0x76, VCC=0x77)
Driver LibraryAdafruit_BMP280
MPU6050 IMU
0x68 / 0x693-axis accelerometer and 3-axis gyroscope motion tracking sensor.
TypeMotion IMU Sensor
Alt Address PinsAD0 pin (GND=0x68, VCC=0x69)
Driver LibraryAdafruit_MPU6050
DS3231 RTC
0x68 (+0x57)Extremely accurate, temperature-compensated real-time clock. Common boards also host a 24C32 EEPROM at 0x57.
TypeTimekeeping RTC
Alt Address PinsClock: Fixed 0x68; EEPROM: A0,A1,A2 pads
Driver LibraryRTClib
INA219 Power Monitor
0x40Shunt current and high-side voltage monitor. Ideal for measuring battery drain and power rails.
TypePower Measurement
Alt Address PinsSolder pads A0, A1 (up to 16 combinations)
Driver LibraryAdafruit_INA219
ADXL345 Accelerometer
0x53 / 0x1DThin, ultra-low power 3-axis accelerometer with high resolution (up to 13-bit) measurement.
TypeMotion Sensor
Alt Address PinsSDO pin (GND=0x53, VCC=0x1D)
Driver LibraryAdafruit_ADXL345
BH1750 Light Sensor
0x23 / 0x5CDigital ambient light intensity sensor. Directly outputs calibrated lux values without math overhead.
TypeLight Sensor
Alt Address PinsADD pin (GND=0x23, VCC=0x5C)
Driver Libraryhp_BH1750
VL53L0X ToF Sensor
0x29Time-of-Flight (ToF) laser-ranging sensor measuring distance based on photon travel times.
TypeDistance Sensor
Alt Address PinsXSHUT pin power-cycle (Software re-map)
Driver LibraryAdafruit_VL53L0X
MCP23017 I/O Expander
0x20 - 0x2716-bit input/output port expander. Adds 16 general-purpose I/O pins over the I2C bus.
TypeGPIO Expansion
Alt Address PinsA0, A1, A2 pins (select from 8 addresses)
Driver LibraryAdafruit_MCP23017
ADS1115 16-Bit ADC
0x48 - 0x4BHigh-resolution, 4-channel analog-to-digital converter, ideal for microcontrollers lacking built-in ADCs.
TypeAnalog-to-Digital
Alt Address PinsADDR pin (to GND, VCC, SDA, or SCL)
Driver LibraryAdafruit_ADS1X15
MPR121 Touch Sensor
0x5ACapacitive touch controller supporting up to 12 individual electrode touch pads.
TypeUser Input Sensor
Alt Address PinsADDR pin (to GND, VCC, SDA, or SCL)
Driver LibraryAdafruit_MPR121
TSL2561 Light Sensor
0x39Precision digital light sensor measuring both infrared and full-spectrum light for precise lux calculations.
TypeLight Sensor
Alt Address PinsADDR pin (GND=0x29, VCC=0x49, Float=0x39)
Driver LibraryAdafruit_TSL2561
Debug path
What to do with the scanner result.
Scanner finds nothing
Use the I2C not found guide for wiring, pullups, ESP32 pins, voltage mismatch, and bus conflicts.
OLED address is 0x3C or 0x3D
Fix SSD1306/SH1106 controller choice, screen size, SDA/SCL pins, and blank display problems.
LCD address is 0x27 or 0x3F
Fix contrast, LiquidCrystal_I2C address, black boxes, and Arduino display initialization.
FAQ
I2C scanner questions
Can two I2C devices use the same address?
Not on the same bus unless you use an I2C multiplexer or one device supports address selection. If two modules share the same fixed address, the scanner may behave unpredictably.
Why does the scanner find an address but my display still stays blank?
The I2C bus is working, but your library, controller type, address, screen size, or display initialization may still be wrong.
Do I need pullup resistors?
Many modules already include pullups. If wires are long, modules are bare, or the bus is unstable, external pullups may be needed.