Connecting Two ESP8266 with a DHT11 Sensor via ESP-NOW

Components

1. ESP8266 Development Board (such as NodeMCU) (Affiliate) – https://s.click.aliexpress.com/e/_DD3JQhj
2. Breadboard and jumper wires (Affiliate) – https://s.click.aliexpress.com/e/_Dl5kuk1
3. DHT11 temperature and humidity sensor (Affiliate) – https://s.click.aliexpress.com/e/_DFb2JzR
4. 1x 10k Ohm resistor

Wiring

1. Connect the DHT11 sensor to the master ESP8266 module:
   • VCC pin to 3.3V
   • GND pin to GND
   • Data pin to D2 (GPIO4) with a 10k Ohm pull-up resistor between VCC and Data pin
2. Connect both ESP8266 modules to your computer using USB-to-serial converters for programming.

Install the required libraries in the Arduino IDE:

• • ESP8266 core for Arduino -> My Link to a post that explains this in depth
  • Adafruit DHT sensor library

Sender Code

#include <ESP8266WiFi.h>
#include <espnow.h>
#include <DHT.h>
#define DHTPIN D2
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);
uint8_t receiverMAC[] = { 0x8C, 0xAA, 0xB5, 0x0D, 0x44, 0xCE };  // Replace with the receiver's MAC address
typedef struct {
float temperature;
float humidity;
} SensorData;
SensorData sensorData;
void setup() {
Serial.begin(115200);
dht.begin();
WiFi.mode(WIFI_STA);
WiFi.disconnect();
if (esp_now_init() == 0) {
Serial.println("ESP-NOW Initialized");
esp_now_set_self_role(ESP_NOW_ROLE_CONTROLLER);
esp_now_add_peer(receiverMAC, ESP_NOW_ROLE_SLAVE, 1, NULL, 0);
esp_now_register_send_cb([](uint8_t* mac, uint8_t sendStatus) {
Serial.print("Send status: ");
Serial.println(sendStatus == 0 ? "Success" : "Failed");
});
} else {
Serial.println("ESP-NOW Initialization Failed");
ESP.restart();
}
}
void loop() {
sensorData.temperature = dht.readTemperature();
sensorData.humidity = dht.readHumidity();
esp_now_send(receiverMAC, (uint8_t*)&sensorData, sizeof(sensorData));
delay(2000);
}

Receiver Code

#include <ESP8266WiFi.h>
#include <espnow.h>
typedef struct struct_message {
float temperature;
float humidity;
} struct_message;
struct_message receivedData;
void dataReceived(uint8_t *senderMac, uint8_t *incomingData, uint8_t len) {
memcpy(&receivedData, incomingData, sizeof(receivedData));
Serial.print("Temperature: ");
Serial.print(receivedData.temperature);
Serial.print(" °C, Humidity: ");
Serial.print(receivedData.humidity);
Serial.println(" %");
}
void setup() {
Serial.begin(115200);
WiFi.mode(WIFI_STA);
WiFi.disconnect();
if (esp_now_init() == 0) {
Serial.println("ESP-NOW Initialized.");
esp_now_set_self_role(ESP_NOW_ROLE_SLAVE);
esp_now_register_recv_cb(dataReceived);
} else {
Serial.println("ESP-NOW Initialization Failed.");
ESP.restart();
}
}
void loop() {
}

• Don’t forget to define the MAC Address of your Receiver in the funtion -> #define RECEIVER_ADDRESS {0x24, 0x0A, 0xC4, 0x7E, 0x18, 0x2C}

Testing

Conclusion