The Code

We’ll program the ESP8266 using Arduino IDE, so you must have the ESP8266 add-on installed in your Arduino IDE.

Open your Arduino IDE and follow the step-by-step explanation of the code:

1. The first thing that you need to is to include all the libraries at the beginning:

#include <Arduino.h>
#include <ESP8266WiFi.h>
#include <Hash.h>
#include <ESPAsyncTCP.h>
#include <ESPAsyncWebServer.h>
#include <Adafruit_Sensor.h>
#include <DHT.h>

2. Setup your network credentials:

const char* ssid = "REPLACE_WITH_YOUR_SSID";
const char* password = "REPLACE_WITH_YOUR_PASSWORD";

3. Declare the GPIO pin that the DHT11 sensor is connected to. In our case we connected it to the GPIO 5 (D1).

#define DHTPIN 5     // Digital pin connected to the DHT sensor

Now you have to select the DHT type that you will be using. In our case we are using the DHT11.

#define DHTTYPE DHT1   // DHT 11 (AM2302)

Instantiate a DHTobject with the type and pin defined earlier.

DHT dht(DHTPIN, DHTTYPE);

Create an AsyncWebServerobject on port 80.

AsyncWebServer server(80);

Create float variables to hold the current temperature and humidity values. The temperature and humidity are updated in the loop().

float t = 0.0;
float h = 0.0;

Create timer variables needed to update the temperature readings every 10 seconds.

unsigned long previousMillis = 0;    // will store last time DHT was updated

// Updates DHT readings every 10 seconds
const long interval = 10000;