void loop() Wire.beginTransmission(0x3C); // Start transmission to device address 0x3C Wire.write(0x00); // Send command byte Wire.write(0x01); // Send data byte Wire.endTransmission(); // Stop transmission
#include <Wire.h> void setup() Wire.begin(0x08); // Join bus as slave with address 0x08 Wire.onReceive(receiveEvent); // Register receive handler Wire.onRequest(requestEvent); // Register request handler Serial.begin(9600);
| Device | Typical Address | |--------|----------------| | OLED Display (SSD1306) | 0x3C | | RTC DS3231 | 0x68 | | Temperature Sensor (BMP280) | 0x76 or 0x77 | | EEPROM (24LC256) | 0x50 | | LCD Backpack (PCF8574) | 0x27 or 0x3F | Advanced Usage: Multiple Bytes // Sending multiple bytes Wire.beginTransmission(0x50); Wire.write(0x00); // Address high byte Wire.write(0x00); // Address low byte Wire.write("Hello"); Wire.endTransmission(); // Reading multiple bytes Wire.requestFrom(0x50, 10); while(Wire.available()) char data = Wire.read();
float readTemperature() Wire.beginTransmission(LM75_ADDR); Wire.write(0x00); // Temperature register Wire.endTransmission();
void loop() | Function | Description | Example | |----------|-------------|---------| | Wire.begin() | Initialize as master | Wire.begin() | | Wire.begin(address) | Initialize as slave | Wire.begin(0x08) | | Wire.beginTransmission(addr) | Start transmission | Wire.beginTransmission(0x3C) | | Wire.write(data) | Queue data to send | Wire.write(0xFF) | | Wire.endTransmission() | Send queued data | Wire.endTransmission() | | Wire.requestFrom(addr, bytes) | Request data from slave | Wire.requestFrom(0x3C, 6) | | Wire.available() | Check available bytes | if(Wire.available()) | | Wire.read() | Read a byte | byte b = Wire.read() | Complete Example: Scanning for I2C Devices #include <Wire.h> void setup() Wire.begin(); Serial.begin(9600); Serial.println("I2C Scanner");
void requestEvent() Wire.write("Hello from slave");
