Sender and Receiver

Here’s a simple example to demonstrate how to use ESP-NOW for communication between two ESP32 devices.

ESP32 Sender Code (Transmitter)

This code will send data (e.g., a message) to another ESP32 device using ESP-NOW.

#include <esp_now.h>
#include <WiFi.h>

// Define the MAC address of the receiving device
uint8_t remoteMacAddr[] = {0x30, 0xAE, 0xA4, 0x1F, 0xD1, 0xB0};  // Replace with your receiver's MAC address
// uint8_t broadcastMacAddr[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};&nbsp; // Broadcast address

void setup() {
  // Initialize Serial Monitor
  Serial.begin(115200);

  // Initialize Wi-Fi in Station mode
  WiFi.mode(WIFI_STA);

  // Initialize ESP-NOW
  if (esp_now_init() != ESP_OK) {
    Serial.println("ESPNow initialization failed!");
    return;
  }

  // Add the peer (receiver) MAC address
  esp_now_peer_info_t peerInfo;
  memcpy(peerInfo.peer_addr, remoteMacAddr, 6);
  peerInfo.channel = 0;  
  peerInfo.encrypt = false;

  if (esp_now_add_peer(&peerInfo) != ESP_OK) {
    Serial.println("Failed to add peer");
    return;
  }

  // Send data
  const char *message = "Hello Lonely Binary!";
  esp_now_send(remoteMacAddr, (uint8_t *)message, strlen(message));
  Serial.println("Message sent!");
}

void loop() {
  // Nothing to do in loop
}

ESP32 Receiver Code (Receiver)

This code listens for incoming messages using ESP-NOW.

#include <esp_now.h>
#include <WiFi.h>

// Callback function for receiving data
void onDataReceive(const uint8_t * mac, const uint8_t *incomingData, int len) {
  Serial.print("Received message: ");
  Serial.println((char *)incomingData);
}

void setup() {
  // Initialize Serial Monitor
  Serial.begin(115200);

  // Initialize Wi-Fi in Station mode
  WiFi.mode(WIFI_STA);

  // Initialize ESP-NOW
  if (esp_now_init() != ESP_OK) {
    Serial.println("ESPNow initialization failed!");
    return;
  }

  // Register the callback function to handle incoming data
  esp_now_register_recv_cb(onDataReceive);

  Serial.println("Receiver is ready to receive messages.");
}

void loop() {
  // Nothing to do in loop
}

Steps to test:

1. Upload the Sender Code to one ESP32 device.
2. Upload the Receiver Code to the other ESP32 device.
3. Connect the devices to a power source.
4. Check the Serial Monitor of both devices:

• The sender will print “Message sent!”.
• The receiver will print “Received message: Hello Hello Lonely Binary!”.

Key Points:

• MAC Address: In the sender code, you need to replace the remoteMacAddr with the MAC address of the receiving ESP32 device. You can find this address using Serial.println(WiFi.macAddress()); on the receiver.

or you can use the broadcast MAC address (ff:ff:ff:ff:ff:ff) to broadcase this message which will make the message sent to all ESP32 devices in the range (that are set up to listen for ESP-NOW messages).

• Data: You can modify the data being sent, which in this example is a string message.