Example Code for Arduino - ESP-NOW Data Transfer

Hardware Preparation

• FireBeetle 2 ESP32-S3-U AI Board x 1

Software Preparation

When you use the ESP32 for the first time, you need to know the following steps:

1. Add the ESP32 development board in Arduino IDE (How to add the ESP32 board to Arduino IDE?)

2. Select the development board and serial port

3. Burn the program

Get Controller MAC Address

Burn the code, open the serial port and you can see the device MAC address.

Sample Code

#include "WiFi.h"

void setup(){
  Serial.begin(115200);
  WiFi.mode(WIFI_MODE_STA);
}

void loop(){
  Serial.println(WiFi.macAddress());
  delay(1000);
}

Receive & Transmit Data

Fill in the MAC address and burn the code, then data can be transmitted and received between two devices.

Sample Code

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

//MAC
uint8_t MAC1[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};

typedef struct struct_message {
  char a[16];
  int b;
  float c;
  bool d;
} struct_message;

struct_message sendData;
struct_message recvData;

esp_now_peer_info_t peerInfo;

//SCallback when data is sent
void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
  if(status == ESP_NOW_SEND_SUCCESS){
    Serial.println("Send_Success");
  }else{
    Serial.println("Send_Fail");
  }
}

//Callback when data is received
void OnDataRecv(const esp_now_recv_info_t *info, const uint8_t *Data, int len) {
  memcpy(&recvData, Data, sizeof(recvData));
  Serial.print("Bytes received: ");
  Serial.println(len);
  Serial.println(recvData.a);
  Serial.println(recvData.b);
  Serial.println(recvData.c);
  Serial.println(recvData.d);
  Serial.println("---------");
}

void setup() {
  Serial.begin(115200);
  WiFi.mode(WIFI_STA);

  //Init ESP-NOW
  if (esp_now_init() != ESP_OK) {
    Serial.println("Error initializing");
    return;
  }

  //Register callback on data sent 
  esp_now_register_send_cb(OnDataSent);

  peerInfo.channel = 0;  
  peerInfo.encrypt = false;
  //Register MAC1 Device 
  memcpy(peerInfo.peer_addr, MAC1, 6);
  if (esp_now_add_peer(&peerInfo) != ESP_OK){
    Serial.println("Failed to add peer");
    return;
  }

  //Register callback on data received
  esp_now_register_recv_cb(OnDataRecv);
}

void loop() {
  strcpy(sendData.a, "DFRobot");
  sendData.b = 10;
  sendData.c = 9.9;
  sendData.d = true;

  esp_err_t result = esp_now_send(MAC1, (uint8_t *)&sendData, sizeof(sendData));

  if (result == ESP_OK) {
    Serial.println("Send success");
  }
  else {
    Serial.println("Send Fail");
  }
  delay(2000);
}

Send Data to Multiple Devices

Fill in the MAC address and burn the code, data can be sent to multiple devices.

Sample Code

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

//MAC
uint8_t MAC1[] = {0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA};
uint8_t MAC2[] = {0xBB, 0xBB, 0xBB, 0xBB, 0xBB, 0xBB};

typedef struct struct_message {
  uint8_t ID;
  int data;
} struct_message;

struct_message sendData;
struct_message recvData;

esp_now_peer_info_t peerInfo;

// Callback when data is sent  
void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
  if(status == ESP_NOW_SEND_SUCCESS){
    Serial.println("Send Success");
  }else{
    Serial.println("Send Fail");
  }
}

// Callback when data is received
void OnDataRecv(const esp_now_recv_info_t *info, const uint8_t *Data, int len) {
  memcpy(&recvData, Data, sizeof(recvData));
  Serial.print("Bytes received: ");
  Serial.println(len);
  Serial.println(recvData.ID);
  Serial.println(recvData.data);
  Serial.println("---------");
}

void setup() {
  Serial.begin(115200);
  WiFi.mode(WIFI_STA);

  //Init ESP-NOW
  if (esp_now_init() != ESP_OK) {
    Serial.println("Error initializing");
    return;
  }

  //Register callback on data sent 
  esp_now_register_send_cb(OnDataSent);

  peerInfo.channel = 0;  
  peerInfo.encrypt = false;
  //Register MAC1 Device 
  memcpy(peerInfo.peer_addr, MAC1, 6);
  if (esp_now_add_peer(&peerInfo) != ESP_OK){
    Serial.println("Failed to add peer");
    return;
  }
  //Register MAC2 Device
  memcpy(peerInfo.peer_addr, MAC2, 6);
  if (esp_now_add_peer(&peerInfo) != ESP_OK){
    Serial.println("Failed to add peer");
    return;
  }

  //Register callback on data received
  esp_now_register_recv_cb(OnDataRecv);
}

void loop() {
  sendData.ID = 0;
  sendData.data = 10;

  //Send message to all registered devices
  esp_err_t result = esp_now_send(0, (uint8_t *)&sendData, sizeof(sendData));
  if (result == ESP_OK) {
    Serial.println("Send success");
  }
  else {
    Serial.println("Send Fail");
  }
  //Send message to specified MAC device 
  //esp_err_t result = esp_now_send(MAC1, (uint8_t *)&sendData, sizeof(sendData));
  //if (result == ESP_OK) {
  //  Serial.println("Send success");
  //}
  //else {
  //  Serial.println("Send Fail");
  //}
  delay(2000);
}