Si7021 is an integrated sensor that measures both temperature and relative humidity with good accuracy. The resolution of measured parameters can be selected through software between 8-12 bits for humidity and 12-14 bits for temperature. The sensor uses a digital I2C interface for data transmission, so we can easily interface with it using the Wire library.

Fig. 1: SI7020 and its connections to the the AVR microcontroller

We will need to use a dedicated library written specially for it. Download the library from here and unzip its contents into the folder named Arduino\libraries or use Arduino IDE's Add ZIP Library command.