Introduction: ESP32 SunDuino and Si7021 (HTU21)

Other article about ESP32, with using of development board of SunDuino ESP32 and temperature/humidity sensor Si7021 (HTU21).

I recommend the first article about ESP32 and SunDuino ESP32 which is available on

Thanks for ESP32

For SunDuino ESP32 I thank designer of that

Step 1: Installation of Si7021 (HTU21) Library

The installation of library for temperature/humidity sensor - Si7021 is very easy and you find it on and github of SparkFun

After installation of library for Si7021 you will see in File -> SparkFun Si7021 Humidity and Temperature Sensor, SparkFun_Si7021_Brekout_Example example code. I edited it. Edited code you find on my github

Step 2: Pinout of SunDuino and Connection

The pinout of SunDuino, ESP32 is below. I2C bus is connected to 21 (SDA) and 22 (SCL). Of course you connect to sensor GND and 3V3.

Step 3: Uploading of Code

During the uploading of your code you will see this warning message "WARNING: library Wire claims to run on [esp32] architecture(s) and may be incompatible with your current board which runs on [DFRobot_FireBeetle-ESP32] architecture(s)."

It's not important now.