LCD 1602 I2C with Arduino Mega 2560 R3

Wiring for the LCD 16x2 with I2C backpack on the Arduino Mega 2560 R3 (ATmega2560, 5 V logic), chosen with the same pin rules BoardPilot uses: default buses first, and no pins that are used for flash, USB, the debugger or booting.

Wiring

LCD 1602 I2C pin	Role	Arduino Mega 2560 R3 pin	Notes
GND	Ground	GND
VCC	Power	5V	Needs 5 V for good contrast: use 5V
SDA	I2C data (SDA)	SDA 20 (PD1)	The backpack pulls SDA up to 5 V. Usually works; a level shifter is safer
SCL	I2C clock (SCL)	SCL 21 (PD0)	The backpack pulls SCL up to 5 V. Usually works; a level shifter is safer

Check before you power it on

Supply: 5 V from the 5V pin.
I2C uses the board’s default pins SDA 20 (SDA) and SCL 21 (SCL). Most modules include pull-up resistors; if the part is not found, check them and swap-test SDA/SCL.

Test code (Arduino)

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin();  // SDA = SDA 20, SCL = SCL 21 (the board's default I2C pins)
  Wire.beginTransmission(0x20);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "LCD 16x2 with I2C backpack found at 0x20" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Arduino board: arduino:avr:mega.

Questions

Which Arduino Mega 2560 R3 pins do I use for the LCD 1602 I2C?

GND → GND, VCC → 5V, SDA → SDA 20 (PD1), SCL → SCL 21 (PD0).

Does the LCD 1602 I2C work with the Arduino Mega 2560 R3 at 5 V?

Yes: the LCD 1602 I2C runs at 5 V and the Arduino Mega 2560 R3 uses 5 V signals, so no level shifting is needed.

What is the I2C address of the LCD 1602 I2C?

0x20 or 0x21 or 0x22 or 0x23 or 0x24 or 0x25 or 0x26 or 0x27 or 0x38 or 0x39 or 0x3A or 0x3B or 0x3C or 0x3D or 0x3E or 0x3F. An I2C scan (BoardPilot does it for you) shows which one your module uses.

BoardPilot checks this wiring in 3D as you build it, and finds crossed or missing wires on the real board.

Download BoardPilot

Full Arduino Mega 2560 R3 pinout · LCD 16x2 with I2C backpack: all pins and data

The LCD 1602 I2C on other boards

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Other parts on the Arduino Mega 2560 R3

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