The Broadcast Master sketch is as follows:
/*
ESP-NOW Broadcast Master
Lucas Saavedra Vaz - 2024
This sketch demonstrates how to broadcast messages to all devices within the ESP-NOW network.
This example is intended to be used with the ESP-NOW Broadcast Slave example.
The master device will broadcast a message every 5 seconds to all devices within the network.
This will be done using by registering a peer object with the broadcast address.
The slave devices will receive the broadcasted messages and print them to the Serial Monitor.
*/
#include <Arduino.h>
#include "ESP32_NOW.h"
#include "WiFi.h"
#include <esp_mac.h> // For the MAC2STR and MACSTR macros
/* Definitions */
#define ESPNOW_WIFI_CHANNEL 6
/* Classes */
// Creating a new class that inherits from the ESP_NOW_Peer class is required.
class ESP_NOW_Broadcast_Peer : public ESP_NOW_Peer {
public:
// Constructor of the class using the broadcast address
ESP_NOW_Broadcast_Peer(uint8_t channel, wifi_interface_t iface, const uint8_t *lmk) : ESP_NOW_Peer(ESP_NOW.BROADCAST_ADDR, channel, iface, lmk) {}
// Destructor of the class
~ESP_NOW_Broadcast_Peer() {
remove();
}
// Function to properly initialize the ESP-NOW and register the broadcast peer
bool begin() {
if (!ESP_NOW.begin() || !add()) {
log_e("Failed to initialize ESP-NOW or register the broadcast peer");
return false;
}
return true;
}
// Function to send a message to all devices within the network
bool send_message(const uint8_t *data, size_t len) {
if (!send(data, len)) {
log_e("Failed to broadcast message");
return false;
}
return true;
}
};
/* Global Variables */
uint32_t msg_count = 0;
// Create a broadcast peer object
ESP_NOW_Broadcast_Peer broadcast_peer(ESPNOW_WIFI_CHANNEL, WIFI_IF_STA, nullptr);
/* Main */
void setup() {
Serial.begin(115200);
// Initialize the Wi-Fi module
WiFi.mode(WIFI_STA);
WiFi.setChannel(ESPNOW_WIFI_CHANNEL);
while (!WiFi.STA.started()) {
delay(100);
}
Serial.println("ESP-NOW Example - Broadcast Master");
Serial.println("Wi-Fi parameters:");
Serial.println(" Mode: STA");
Serial.println(" MAC Address: " + WiFi.macAddress());
Serial.printf(" Channel: %u\n", ESPNOW_WIFI_CHANNEL);
// Register the broadcast peer
if (!broadcast_peer.begin()) {
Serial.println("Failed to initialize broadcast peer");
Serial.println("Reebooting in 5 seconds...");
delay(5000);
ESP.restart();
}
Serial.printf("ESP-NOW version: %d, max data length: %d\n", ESP_NOW.getVersion(), ESP_NOW.getMaxDataLen());
Serial.println("Setup complete. Broadcasting messages every 5 seconds.");
}
void loop() {
// Broadcast a message to all devices within the network
char data[32];
snprintf(data, sizeof(data), "Hello, World! #%" PRIu32, msg_count++);
Serial.printf("Broadcasting message: %s\n", data);
if (!broadcast_peer.send_message((uint8_t *)data, sizeof(data))) {
Serial.println("Failed to broadcast message");
}
delay(5000);
}
The Broadcast Slave sketch is:
/*
ESP-NOW Broadcast Slave
Lucas Saavedra Vaz - 2024
This sketch demonstrates how to receive broadcast messages from a master device using the ESP-NOW protocol.
The master device will broadcast a message every 5 seconds to all devices within the network.
The slave devices will receive the broadcasted messages. If they are not from a known master, they will be registered as a new master
using a callback function.
*/
#include <Arduino.h>
#include "ESP32_NOW.h"
#include "WiFi.h"
#include <esp_mac.h> // For the MAC2STR and MACSTR macros
#include <vector>
/* Definitions */
#define ESPNOW_WIFI_CHANNEL 6
/* Classes */
// Creating a new class that inherits from the ESP_NOW_Peer class is required.
class ESP_NOW_Peer_Class : public ESP_NOW_Peer {
public:
// Constructor of the class
ESP_NOW_Peer_Class(const uint8_t *mac_addr, uint8_t channel, wifi_interface_t iface, const uint8_t *lmk) : ESP_NOW_Peer(mac_addr, channel, iface, lmk) {}
// Destructor of the class
~ESP_NOW_Peer_Class() {}
// Function to register the master peer
bool add_peer() {
if (!add()) {
log_e("Failed to register the broadcast peer");
return false;
}
return true;
}
// Function to print the received messages from the master
void onReceive(const uint8_t *data, size_t len, bool broadcast) {
Serial.printf("Received a message from master " MACSTR " (%s)\n", MAC2STR(addr()), broadcast ? "broadcast" : "unicast");
Serial.printf(" Message: %s\n", (char *)data);
}
};
/* Global Variables */
// List of all the masters. It will be populated when a new master is registered
// Note: Using pointers instead of objects to prevent dangling pointers when the vector reallocates
std::vector<ESP_NOW_Peer_Class *> masters;
/* Callbacks */
// Callback called when an unknown peer sends a message
void register_new_master(const esp_now_recv_info_t *info, const uint8_t *data, int len, void *arg) {
if (memcmp(info->des_addr, ESP_NOW.BROADCAST_ADDR, 6) == 0) {
Serial.printf("Unknown peer " MACSTR " sent a broadcast message\n", MAC2STR(info->src_addr));
Serial.println("Registering the peer as a master");
ESP_NOW_Peer_Class *new_master = new ESP_NOW_Peer_Class(info->src_addr, ESPNOW_WIFI_CHANNEL, WIFI_IF_STA, nullptr);
if (!new_master->add_peer()) {
Serial.println("Failed to register the new master");
delete new_master;
return;
}
masters.push_back(new_master);
Serial.printf("Successfully registered master " MACSTR " (total masters: %lu)\n", MAC2STR(new_master->addr()), (unsigned long)masters.size());
} else {
// The slave will only receive broadcast messages
log_v("Received a unicast message from " MACSTR, MAC2STR(info->src_addr));
log_v("Igorning the message");
}
}
/* Main */
void setup() {
Serial.begin(115200);
// Initialize the Wi-Fi module
WiFi.mode(WIFI_STA);
WiFi.setChannel(ESPNOW_WIFI_CHANNEL);
while (!WiFi.STA.started()) {
delay(100);
}
Serial.println("ESP-NOW Example - Broadcast Slave");
Serial.println("Wi-Fi parameters:");
Serial.println(" Mode: STA");
Serial.println(" MAC Address: " + WiFi.macAddress());
Serial.printf(" Channel: %u\n", ESPNOW_WIFI_CHANNEL);
// Initialize the ESP-NOW protocol
if (!ESP_NOW.begin()) {
Serial.println("Failed to initialize ESP-NOW");
Serial.println("Reeboting in 5 seconds...");
delay(5000);
ESP.restart();
}
Serial.printf("ESP-NOW version: %d, max data length: %d\n", ESP_NOW.getVersion(), ESP_NOW.getMaxDataLen());
// Register the new peer callback
ESP_NOW.onNewPeer(register_new_master, nullptr);
Serial.println("Setup complete. Waiting for a master to broadcast a message...");
}
void loop() {
// Print debug information every 10 seconds
static unsigned long last_debug = 0;
if (millis() - last_debug > 10000) {
last_debug = millis();
Serial.printf("Registered masters: %lu\n", (unsigned long)masters.size());
for (size_t i = 0; i < masters.size(); i++) {
if (masters[i]) {
Serial.printf(" Master %lu: " MACSTR "\n", (unsigned long)i, MAC2STR(masters[i]->addr()));
}
}
}
delay(100);
}
There are 2 x ESP32-C3s supplied via USB connections and communicating with each other shown on the serial monitor.
I have just put one of the set of sketches up as Iām hoping the if we solve one problem, it may solve the other!
