Interfacing DHT22 Temperature Sensor with XIAO RP2040

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Overview

The Seedstudio XIAO, powered by the RP2040 microcontroller, has quickly gained popularity in the maker and electronics community due to its affordability, versatility, and robust performance. One of the fascinating aspects of the RP2040 is its ability to interface with a wide range of sensors and modules.

In today’s tutorial, we are going to interface the “DHT22 Temperature Sensor” using an XIAO RP2040 Microcontroller.

Introduction to DHT22 Sensor

The DHT22, also known as the AM2302, is a popular sensor for measuring temperature and humidity. It is affordable, relatively accurate, and easy to use. The sensor communicates via a single-wire digital interface, which makes it an excellent choice for microcontroller-based projects.

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Hardware Components

You’ll need the following hardware components to get started:

Components	Value / Model	Qty
PCB	PCB-GOGO	1
XIAO Microcontroller	RP2040	1
Temperature Sensor	DHT22	1
Jumper Wires	–	1

XIAO RP2040 Pinout

For details on the datasheet of the XIAO RP2040 Microcontroller visit this link.

Pin No	Pin Name
1	P26 / A0 / D0
2	P27 / A1 / D1
3	P28 / A2 / D2
4	P29 / A3 / D3
5	P6 / SDA/ D4
6	P7 / SCL / D5
7	P0 / TX / D6
8	P1 / RX / CSN / D7
9	P2 / SCK / D8
10	P3 / MISO / D9
11	P4 / MOSI / D10
12	3V3
13	GND
14	5V

DHT22 Temperature Sensor Pinout

For a details datasheet of the DHT22 Temperature Sensor visit this link.

Pin No	Pin Name	Pin Description
1	VCC	VCC is the +5 volt Positive Pin
2	DATA	Outputs both Temperature and Humidity through Serial Data
3	GND	GND is the (Ground) Negative

Steps-by-Step Guide

(1) Setting up Arduino IDE

Download Arduino IDE Software from its official site. Here is a step-by-step guide on “How to install Arduino IDE“.

(2) XIAO RP2040 in Arduino IDE

There’s an add-on that allows you to program the XIAO RP2040 using the Arduino IDE. Here is a step-by-step guide on “How to Install XIAO RP2040 on Arduino IDE“.

(3) Include Libraries

Before you start uploading a code, download and unzip the DHT.h library at /Program Files(x86)/Arduino/Libraries (default). Here is a step-by-step guide on “How to Add Libraries in Arduino IDE“.

(4) Schematic

Make connections according to the circuit diagram given below.

Wiring / Connections

XIAO RP2040	DHT22 Temperature Sensor
3.3V	VCC
D1	Data
GND	GND

(5) Uploading Code

Now copy the following code and upload it to Arduino IDE Software.

/* Circuits DIY
 * For Complete Details Visit
 * https://www.circuits-diy.com/interfacing-dht22-temperature-sensor-with-xiao-rp2040/
 */

#include "DHT.h"
#define DHTPIN 27     // Digital pin connected to the DHT sensor
 
#define DHTTYPE DHT22   // DHT 22
DHT dht(DHTPIN, DHTTYPE);
 
void setup()
{
  Serial.begin(115200);
  Serial.println(F("DHTxx test!"));
  dht.begin();
  delay(2000);
}
 
void loop()
{
  float h = dht.readHumidity();
  float t = dht.readTemperature();
 
  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t))
  {
    Serial.println(F("Failed to read from DHT sensor!"));
    return;
  }
  Serial.print(F("Humidity: "));
  Serial.print(h);
  Serial.println("%");
  Serial.print(F("Temperature: "));
  Serial.print(t);
  Serial.println(F("°C "));
  Serial.println("");
  delay(2000);
}

How code works

#include "DHT.h"
#define DHTPIN 27     // Digital pin connected to the DHT sensor
#define DHTTYPE DHT22   // DHT 22
DHT dht(DHTPIN, DHTTYPE);

In this section, the code includes the “DHT.h” library, defines a constant DHTPIN to specify the digital pin where the DHT22 sensor is connected, and sets DHTTYPE to DHT22. An instance of the DHT class is created and configured with these parameters.

void setup() {
  Serial.begin(115200);
  Serial.println(F("DHTxx test!"));
  dht.begin();
  delay(2000);
}

In the setup function, serial communication is initiated at a baud rate of 115200. A startup message is printed to the serial monitor. The DHT sensor is initialized using dht.begin(), and there is a 2-second delay to allow the sensor to stabilize.

void loop() {
  float h = dht.readHumidity();
  float t = dht.readTemperature();

Inside the loop function, two float variables, h and t, are used to store the humidity and temperature readings obtained from the DHT sensor.

  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t)) {
    Serial.println(F("Failed to read from DHT sensor!"));
    return;
  }

The code checks if the humidity (h) or temperature (t) readings are “not a number” (NaN), which can occur if the sensor fails to provide valid data. If any of the readings are NaN, an error message is printed to the serial monitor, and the loop is exited early to attempt another reading

  Serial.print(F("Humidity: "));
  Serial.print(h);
  Serial.println("%");
  Serial.print(F("Temperature: "));
  Serial.print(t);
  Serial.println(F("°C "));
  Serial.println("");
  delay(2000);

If both humidity and temperature readings are valid, the code proceeds to print these values to the serial monitor. The data is displayed with appropriate labels and units (percentage for humidity and degrees Celsius for temperature). There is also a 2-second delay before the loop repeats, providing a gap between consecutive readings.

This code is designed to interface with a DHT22 temperature and humidity sensor and continuously provide real-time data through the serial monitor, making it suitable for environmental monitoring and data logging applications.

Applications

Indoor Climate Monitoring
Greenhouse Control
Weather Stations
HVAC Systems
Home Automation
Data Logging etc

Conclusion

The provided Arduino code interfaces a DHT22 temperature and humidity sensor with a microcontroller. It reads temperature and humidity data from the sensor and displays it on the serial monitor. The code includes error checking to ensure data validity and runs in a continuous loop, making it suitable for real-time monitoring and data collection applications.

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