I2C Arduino Communication Projects

Understand how I2C works.

1. I2C uses 2 wires: SDA (data) and SCL (clock).
2. Multiple devices can share the same bus.
3. Each device has a unique address.
4. On Arduino Uno: SDA=A4, SCL=A5.
5. Devices can be sensors, displays, EEPROMs, and more.

Wire a sensor or display to I2C bus.

1. Example: LCD display with I2C backpack.
2. Connect device SDA to Arduino A4.
3. Connect device SCL to Arduino A5.
4. Connect device VCC to Arduino 5V.
5. Connect device GND to Arduino GND.
6. Repeat for additional I2C devices (they share the same 4 wires).

Identify addresses of connected devices.

1. Upload I2C scanner sketch.
2. Open Serial Monitor.
3. Sketch scans all possible addresses (0x00-0x7F).
4. Note the addresses found (e.g., 0x27 for LCD, 0x68 for RTC).

#include <Wire.h>

void setup() {
  Wire.begin();
  Serial.begin(9600);
  Serial.println("I2C Scanner");
}

void loop() {
  byte count = 0;
  
  Serial.println("Scanning...");
  
  for (byte addr = 1; addr < 127; addr++) {
    Wire.beginTransmission(addr);
    
    if (Wire.endTransmission() == 0) {
      Serial.print("Device found at 0x");
      if (addr < 16) Serial.print("0");
      Serial.println(addr, HEX);
      count++;
    }
  }
  
  Serial.print("Found ");
  Serial.print(count);
  Serial.println(" device(s)\n");
  
  delay(5000);
}

Display text on I2C LCD.

1. Install LiquidCrystal_I2C library in Arduino IDE.
2. Write sketch to display text.
3. Use the address found in previous step.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  lcd.begin();
  lcd.backlight();
  
  lcd.setCursor(0, 0);
  lcd.print("Hello, I2C!");
  
  lcd.setCursor(0, 1);
  lcd.print("Arduino Project");
}

void loop() {
}

Connect LCD + sensor on same bus.

1. Keep LCD connected.
2. Add another I2C device (e.g., temperature sensor).
3. Wire to same SDA/SCL pins.
4. Read sensor data and display on LCD.
5. Both devices work simultaneously!