ESP32 - DHT22 - OLED

This tutorial instructs you how to read the temperature and humidity from DHT22 module and display it on an OLED.

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×USB Cable Type-C
1×SSD1306 I2C OLED Display 128x64
1×DHT22 Module
1×Jumper Wires
1×(Recommended) ESP32 Screw Terminal Adapter

Or you can buy the following sensor kit:

1×DIYables Sensor Kit 30 types, 69 units
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Introduction to OLED display, DHT22 Temperature Humidity Sensor

If you do not know about OLED display, and DHT22 temperature humidity sensor (pinout, how it works, how to program ...), learn about them in the following tutorials:

Wiring Diagram

ESP32 DHT22 module OLED Wiring Diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

ESP32 Code - DHT22 Sensor - OLED

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-dht22-oled */ #include <Wire.h> #include <Adafruit_GFX.h> #include <Adafruit_SSD1306.h> #include <DHT.h> #define SCREEN_WIDTH 128 // OLED display width, in pixels #define SCREEN_HEIGHT 64 // OLED display height, in pixels #define DHT22_PIN 2 // The ESP32 pin GPIO23 connected to DHT22 sensor Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1); // create SSD1306 display object connected to I2C DHT dht22(DHT22_PIN, DHT22); String displayString; void setup() { Serial.begin(9600); // initialize OLED display with address 0x3C for 128x64 if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { Serial.println(F("SSD1306 allocation failed")); while (true); } delay(2000); // wait for initializing oled.clearDisplay(); // clear display oled.setTextSize(2); // text size oled.setTextColor(WHITE); // text color oled.setCursor(0, 10); // position to display dht22.begin(); // initialize DHT22 the temperature and humidity sensor displayString.reserve(10); // to avoid fragmenting memory when using String } void loop() { float humi = dht22.readHumidity(); // read humidity float tempC = dht22.readTemperature(); // read temperature // check if any reads failed if (isnan(humi) || isnan(tempC)) { displayString = "Failed"; } else { displayString = String(tempC, 1); // one decimal places displayString += "°C"; displayString += String(humi, 1); // one decimal places displayString += "%"; } Serial.println(displayString); // print the temperature in Celsius to Serial Monitor oledDisplayCenter(displayString); // display temperature and humidity on OLED } void oledDisplayCenter(String text) { int16_t x1; int16_t y1; uint16_t width; uint16_t height; oled.getTextBounds(text, 0, 0, &x1, &y1, &width, &height); // display on horizontal and vertical center oled.clearDisplay(); // clear display oled.setCursor((SCREEN_WIDTH - width) / 2, (SCREEN_HEIGHT - height) / 2); oled.println(text); // text to display oled.display(); }

Quick Instructions

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
  • Do the wiring as above image.
  • Connect the ESP32 board to your PC via a micro USB cable
  • Open Arduino IDE on your PC.
  • Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
  • Click to the Libraries icon on the left bar of the Arduino IDE.
  • Search “SSD1306”, then find the SSD1306 library by Adafruit
  • Click Install button to install the library.
ESP32 OLED library
  • You will be asked for intalling some other library dependencies
  • Click Install All button to install all library dependencies.
ESP32 Adafruit GFX sensor library
  • Search “DHT”, then find the DHT sensor library by Adafruit
  • Click Install button to install the library.
ESP32 DHT sensor library
  • You will be asked for intalling some other library dependencies
  • Click Install All button all library dependencies.
ESP32 Adafruit Unified sensor library
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to ESP32
  • Put the sensor on hot and cold water, or grasp the sensor by your hand
  • See the result on OLED and Serial Monitor

※ NOTE THAT:

The about code automatically horizontal and vertical center aligns the text on OLED display

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