Adafruit HDC302x Precision Temperature & Humidity Sensor

by Liz Clark

published July 16, 2024, last edited January 22, 2025

posted in Adafruit Products Sensors/ Temperature & Humidity Arduino Compatibles CircuitPython STEMMA

Beginner

Product guide

Arduino

Using the HDC3021 breakout with Arduino involves wiring up the breakout to your Arduino-compatible microcontroller, installing the Adafruit_HDC302x library, and running the provided example code.

Wiring

Wire as shown for a 5V board like an Uno. If you are using a 3V board, like an Adafruit Feather, wire the board's 3V pin to the breakout VIN.

Here is an Adafruit Metro wired up to the sensor using the STEMMA QT connector.

Board 5V to sensor VIN (red wire)
Board GND to sensor GND (black wire)
Board SCL to sensor SCL (yellow wire)
Board SDA to sensor SDA (blue wire)

Here is an Adafruit Metro wired up using a solderless breadboard:

Board 5V to sensor VIN (red wire)
Board GND to sensor GND (black wire)
Board SCL to sensor SCL (yellow wire)
Board SDA to sensor SDA (blue wire)

Library Installation

You can install the Adafruit_HDC302x library for Arduino using the Library Manager in the Arduino IDE.

Click the Manage Libraries ... menu item, search for Adafruit_HDC302x, and select the Adafruit HDC302x library:

If asked about dependencies, click "Install all".

If the "Dependencies" window does not come up, then you already have the dependencies installed.

If the dependencies are already installed, make sure you update them through the Arduino Library Manager before loading the example!

Example Code

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#include <Adafruit_HDC302x.h>

Adafruit_HDC302x hdc = Adafruit_HDC302x();

void setup() {
  Serial.begin(115200);

  Serial.println("Adafruit HDC302x Simple Test");

  if (! hdc.begin(0x44, &Wire)) {
    Serial.println("Could not find sensor?");
    while (1);
  }
  delay(1000);
}

void loop() {
  double temp = 0.0;
  double RH = 0.0;

  hdc.readTemperatureHumidityOnDemand(temp, RH, TRIGGERMODE_LP0);

  Serial.print("Temperature: ");
  Serial.print(temp);
  Serial.println(" °C");

  Serial.print("Humidity: ");
  Serial.print(RH);
  Serial.println(" %");
  delay(2000);
  
}

#include <Adafruit_HDC302x.h>

Adafruit_HDC302x hdc = Adafruit_HDC302x();

void setup() {
  Serial.begin(115200);

  Serial.println("Adafruit HDC302x Simple Test");

  if (! hdc.begin(0x44, &Wire)) {
    Serial.println("Could not find sensor?");
    while (1);
  }
  delay(1000);
}

void loop() {
  double temp = 0.0;
  double RH = 0.0;

  hdc.readTemperatureHumidityOnDemand(temp, RH, TRIGGERMODE_LP0);

  Serial.print("Temperature: ");
  Serial.print(temp);
  Serial.println(" °C");

  Serial.print("Humidity: ");
  Serial.print(RH);
  Serial.println(" %");
  delay(2000);
  
}

Upload the sketch to your board and open up the Serial Monitor (Tools -> Serial Monitor) at 115200 baud. After the HDC3021 is recognized over I2C, you'll see the temperature and humidity readings print to the Serial Monitor every two seconds.