Requirements

1. ESP-IDF Installation: Download and install ESP-IDF from here.
2. VSCode Installation: Download and install Visual Studio Code from here.
3. PlatformIO Installation: Install the PlatformIO plugin on VSCode.

Project Creation and Hardware Connections

1. Project Initialization: Go to Terminal or Command Prompt and create a project directory. Then start theESP-IDF project using the following command:

idf.py create-project my_dht_project
cd my_dht_project
2. Hardware Connections: Connect DHT-11 sensors to ESP32-WROOM-32. You can use the links below:
DHT1: GPIO 4
DHT2: GPIO 5
DHT3: GPIO 6
DHT4: GPIO 7

C++ Code and ESP-IDF Settings

#include <freertos/FreeRTOS.h>
#include <freertos/task.h>
#include <esp_log.h>
#include <esp_http_server.h>
#include <driver/gpio.h>
#include <DHT.h>

#define DHT_PIN1 GPIO_NUM_4
#define DHT_PIN2 GPIO_NUM_5
#define DHT_PIN3 GPIO_NUM_6
#define DHT_PIN4 GPIO_NUM_7
#define DHT_TYPE DHT_TYPE_11

DHT dht1(DHT_PIN1, DHT_TYPE);
DHT dht2(DHT_PIN2, DHT_TYPE);
DHT dht3(DHT_PIN3, DHT_TYPE);
DHT dht4(DHT_PIN4, DHT_TYPE);

static const char *TAG="HTTP_SERVER";

esp_err_t sensor_handler(httpd_req_t *req) {
     char sensor_data[100];

     float temp1=dht1.readTemperature();
     float hum1=dht1.readHumidity();
     float temp2=dht2.readTemperature();
     float hum2=dht2.readHumidity();
     float temp3=dht3.readTemperature();
     float hum3=dht3.readHumidity();
     float temp4=dht4.readTemperature();
     float hum4=dht4.readHumidity();

     snprintf(sensor_data, sizeof(sensor_data), "Sensor 1: Temp=%.2f°C, Hum=%.2f%%\n"
                                               "Sensor 2: Temp=%.2f°C, Hum=%.2f%%\n"
                                               "Sensor 3: Temp=%.2f°C, Hum=%.2f%%\n"
                                               "Sensor 4: Temp=%.2f°C, Hum=%.2f%%\n",
              temp1, hum1, temp2, hum2, temp3, hum3, temp4, hum4);

     httpd_resp_send(req, sensor_data, HTTPD_RESP_USE_STRLEN);
     return ESP_OK;
}

httpd_uri_t sensor_uri={
     .uri="/sensor",
     .method=HTTP_GET,
     .handler=sensor_handler,
     .user_ctx=NULL
};

httpd_handle_t server=NULL;

void start_webserver() {
     httpd_config_t config=HTTPD_DEFAULT_CONFIG();
     if (httpd_start(&server, &config)==ESP_OK) {
         httpd_register_uri_handler(server, &sensor_uri);
     }
}

void stop_webserver() {
     if (server) {
         httpd_stop(server);
     }
}

void app_main() {
     dht1.begin();
     dht2.begin();
     dht3.begin();
     dht4.begin();

     start_webserver();
}

This code reads temperature and humidity values from DHT-11 sensors and displays these values via an HTTP server with the "/sensor" endpoint.

In this article, we read data from four DHT-11 temperature and humidity sensors using ESP-IDF and C++ on the ESP32-WROOM-32 microcontroller. Additionally, we were able to view this data via an HTTP server. Once you understand the basics of this project, you can step into more complex IoT projects with ESP32.