Most sensors we use in our projects are breakout boards that already have the resistors built-in. Typical values are 4.7k Ohm for 5V devices and 2.4k Ohm for 3.3V devices. The SDA and SCL lines are active low, so they should be pulled up with resistors.

Note: in many breakout boards, the SDA line may also be labeled as SDI and the SCL line as SCK. One is used for the clock signal ( SCL) and the other is used to send and receive data ( SDA).

I2C communication protocol uses two wires to share information. Users can program command registers to control I☬ interfaces, so that they have more flexibility

Up to 5 MHz, yet constrained by SDA pull-up strength.

Accordingly to the ESP32 datasheet, the I2C interfaces of the ESP32 supports: The ESP32 supports I2C communication through its two I2C bus interfaces that can serve as I2C master or slave, depending on the user’s configuration. We have several tutorials with the ESP32 interfacing with I2C devices: In these cases, the ESP32 is the master chip and the external devices are the slaves. We use this protocol many times with the ESP32 to communicate with external devices like sensors and displays. multiple masters controlling the same slave: for example, two ESP32 boards writing data to the same I2C OLED display.multiple slaves to one master: for example, your ESP32 reads from a BME280 sensor using I2C and writes the sensor readings in an I2C OLED display.I☬ means Inter Integrated Circuit (it’s pronounced I-squared-C), and it is a synchronous, multi-master, multi-slave communication protocol. Introducing ESP32 I2C Communication Protocol Installing the ESP32 Board in Arduino IDE (Windows, Mac OS X, and Linux instructions).Follow the next tutorial to install the ESP32 on the Arduino IDE, if you haven’t already. We’ll program the ESP32 using Arduino IDE, so before proceeding with this tutorial you should have the ESP32 add-on installed in your Arduino IDE. Use Different I2C Pins with ESP32 (change default I2C pins).In this tutorial, we’ll cover the following concepts:

Arduino virtual wire library