This is the Silicon Labs Si7021 i2C Humidity / Temperature Sensor. Si7021 is a monolithic CMOS IC that integrates humidity / temperature sensor elements this device has an analog to digital converter, signal processing, calibration data, and an i2C interface. Compare to Si7050/3/4/5 sensor family is identical to the i2C temperature and humidity sensor but there is no hole at the package, and only temperature sensor functionality is supported. The Si7021 offers an accurate, low power, factory calibrated digital solutions for measuring humidity, best usage for application ranging from HVAC/R, asset tracking to home appliances, automotive, industrial automations, home & building automatons. Etc.

Required Components

  • Arduino Microcontroller, NodeMCU, Teensy Board, TeensyDuino, ESP8266 12, 12E, ESP8266 NodeMCU, ESPDuino, ATMEGA328 16/12, ATMEGA32u4 16/8/ MHz, ESP8266, ATMEGA250 16 MHz, ATSAM3x8E, ATSAM21D, ATTINY85 16/8 MHz (Note: The Diagram below is using NANO. (please refer to the respective pin-outs)
  • Si7021, Si7013, Si705X, Si7034 Sensor / Module
  • Capacitors (See the diagram below for soldering manually)
  • Resistors (See the diagram below for soldering manually)
  • Jumper Wires / DuPont Wires
  • Prototyping PCB board (for soldering manually)

Wiring Guide

Source Code

i2C Address Finder / Scanner


  • Download Si7021 Code Library | Zip
  • Download Si7021 ESP8266 Code Library | Zip
  • Download Si7021 Datasheet | Pdf
  • Download Si7013 / Si705X / Si7034  Datasheet | Pdf
Wiring the Si70XX / i2C Inter-Integrated Circuit CMOS IC Temperature and Humidity Sensor
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