ESP32 DHT22: Complete Guide to Wiring, Arduino Code & Troubleshooting

What the DHT22 measures

The DHT22 is a digital sensor for air temperature and relative humidity. Its controller sends the measurements as a timed digital signal on one bidirectional data line. The ESP32 library decodes that signal; this is not an analog sensor and it does not use the I2C bus.

A DHT22 does not measure barometric pressure, air quality, or altitude. It is useful for basic room, greenhouse, or classroom monitoring, but its update rate is slow and readings depend on placement and the sensor's documented operating conditions. Do not treat it as a precision instrument or as a fast feedback sensor. The DHT22 component reference has concise component details; this guide focuses on wiring and using it with an ESP32.

DHT22 and AM2302 names

DHT22 and AM2302 are commonly used names for this sensor family. You may find a bare four-pin sensor, a wired probe, or a small three-pin breakout module. The sensing function is similar, but the package, pin order, connector labels, power circuitry, and presence of a pull-up resistor can differ. Use the datasheet and markings for the exact part instead of assuming every board is wired the same way.

Identify the sensor pins

A common bare DHT22 package has four pins: VDD/VCC, DATA (sometimes marked SDA), NC (no connection), and GND. On the usual front view with the grille toward you and pins pointing down, those pins are arranged left to right in that order. Check the datasheet for your exact sensor before wiring because package drawings and clone markings can differ.

Three-pin breakout boards typically label the connections with some combination of VCC/+ , DATA/S/OUT, and GND/-. A module's physical pin order is board-specific; follow its silkscreen or wiring diagram rather than copying the bare sensor's left-to-right order. The DHT22 wiring diagram shows one example connection.

ESP32 DHT22 wiring

1. Disconnect USB before wiring.
2. Connect the sensor's VDD/VCC to ESP32 3V3, but only if the exact sensor or module documentation allows a 3.3 V supply.
3. Connect GND to ESP32 GND.
4. Connect DATA to GPIO4 for the example code below. Confirm GPIO4 is available on your board; otherwise select a board-appropriate digital GPIO and change DHT_PIN.
5. Leave the bare sensor's NC pin unconnected.
6. Check whether DATA already has a pull-up resistor before adding one. Keep the pull-up voltage at 3.3 V for a direct ESP32 connection.

Why the DATA pull-up matters

The DHT22's one-wire data line is released between signals, so it needs a pull-up to return to a HIGH level. A bare sensor normally needs an external resistor between DATA and its supply. The manufacturer shows 5.1 kΩ as a typical pull-up for short connections; Adafruit's example uses 10 kΩ. For this ESP32 example, connect the pull-up to 3.3 V, not 5 V.

Many three-pin modules include a pull-up on the small board, but this is not guaranteed. Check the module documentation or circuit. If a pull-up is already present, an additional resistor may be unnecessary. Never allow a 5 V pull-up to drive an ESP32 GPIO directly. The exact bare-sensor electrical limits and timing are in the manufacturer's AM2302 technical manual.

Arduino IDE and library setup

1. Install the ESP32 board package and verify you can upload a simple sketch. Follow the ESP32 Arduino IDE setup guide if you have not configured the IDE.
2. Open Sketch → Include Library → Manage Libraries.
3. Search for DHT sensor library by Adafruit and install it. Also install Adafruit Unified Sensor if Library Manager does not install it as a dependency.
4. Select your ESP32 board and port. Match DHT_PIN to the GPIO connected to DATA and keep DHT_TYPE set to DHT22.
5. Upload the sketch, then open Serial Monitor at 115200 baud.

The library and its current dependencies are documented in the Adafruit DHT sensor library repository. Avoid installing multiple libraries that provide a different DHT.h header; that can cause compile errors or inconsistent behavior.

Complete ESP32 DHT22 Arduino code

    #include <DHT.h>

    // Example for a common original ESP32 DevKit. Match this to your wiring.
    const uint8_t DHT_PIN = 4;
    #define DHT_TYPE DHT22

    DHT dht(DHT_PIN, DHT_TYPE);

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

      // Let the sensor settle before the first measurement.
      delay(2100);
      Serial.println("ESP32 DHT22 reader ready");
    }

    void loop() {
      const float humidity = dht.readHumidity();
      const float temperatureC = dht.readTemperature();

      if (isnan(humidity) || isnan(temperatureC)) {
        Serial.println("Failed to read from DHT sensor; check wiring and settings.");
      } else {
        Serial.print("Temperature: ");
        Serial.print(temperatureC, 1);
        Serial.println(" °C");

        Serial.print("Humidity: ");
        Serial.print(humidity, 1);
        Serial.println(" %");
      }

      // The DHT22 should not be sampled more often than every 2 seconds.
      delay(2000);
    }

How the code works

• DHT_PIN: the ESP32 GPIO connected to the sensor's DATA line. If you change the wire, update this constant too.
• DHT_TYPE: tells the library to use DHT22 timing rather than another DHT model.
• dht.begin(): initializes the library for the selected sensor and pin.
• First-read wait and loop delay: allow the sensor to settle after power-up and keep measurements at least two seconds apart. The sensor is slow, and readings can represent its previous measurement.
• readTemperature(): returns Celsius by default. readTemperature(true) requests Fahrenheit if you need it.
• readHumidity(): returns relative humidity as a percentage.
• isnan(): detects an invalid reading so the sketch can report an error instead of printing a misleading number.

Serial Monitor output

Choose 115200 baud in Serial Monitor to match Serial.begin(115200). A working sensor should print output in this general format; your room's values will differ:

ESP32 DHT22 reader ready