ESP8266 is a device that nicely supports IoT functionality. But one of the downsides of the ESP8266 is the inadequate number of GPIOs or pins for input and output signals that can be used without a problem with the board’s functionality, so expanding ports for the ESP8266 is quite a thing that developers must be faced which can be performed in a several ways such as using PCF8574 as an expansion port via the I2C bus or connecting to Arduino via Serial Port to allow Arduino to work and send the results back via the serial communication port, etc. This article chose to use an Arduino Uno as a board for I / O to the ESP8266 by using the I2C bus operation.