Example Code for Arduino-ESP-NOW Data Transfer

Hardware Preparation

• DFR0868 Beetle ESP32-C3 x 2

Software Preparation

• Download Arduino IDE: Click to download Arduino IDE
• Add ESP32 board to Arduino IDE

Step

1. Use the Get Controller MAC Address code snippet to retrieve the device's MAC address.
2. Fill the MAC address into the Transmitting & Receiving Data or Transmitting Data to Multiple Devices code, then flash the code to the device.

Sample Code

Get Controller MAC Address

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

#include "WiFi.h"

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

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

Transimitting & Receiving Data

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

#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;

//Callback function 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 function when data is received
void OnDataRecv(const uint8_t * mac, 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 for callback function when data is 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 for callback function whe data is 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);
}

Transimitting Data to Multiple Devices

Fill in the MAC address and burn the code, then data can be transmitted to multiple devices at the same time.

#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 function 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 uint8_t * mac, 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 for callback function when data is 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 for callback function when data is received
  esp_now_register_recv_cb(OnDataRecv);
}

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

  //Send information 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 information to the 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);
}