Getting Started with ESP-NOW (ESP32 with Arduino IDE)

Learn how to use ESP-NOW to exchange data between ESP32 boards programmed with Arduino IDE. ESP-NOW is a connectionless communication protocol developed by Espressif that features short packet transmission. This protocol enables multiple devices to talk to each other in an easy way.

We have other tutorials for ESP-NOW with the ESP32:

Arduino IDE

We’ll program the ESP32 board using Arduino IDE, so before proceeding with this tutorial you should have the ESP32 add-on installed in your Arduino IDE. Follow the next guide:

Installing the ESP32 Board in Arduino IDE (Windows, Mac OS X, and Linux instructions)

Note: we have a similar guide for the ESP8266 NodeMCU Board: Getting Started with ESP-NOW (ESP8266 NodeMCU with Arduino IDE)

Introducing ESP-NOW

For a video introduction to ESP-NOW protocol, watch the following (try the project featured in this video):

Stating the Espressif website, ESP-NOW is a “protocol developed by Espressif, which enables multiple devices to communicate with one another without using Wi-Fi. The protocol is similar to the low-power 2.4GHz wireless connectivity (…) . The pairing between devices is needed prior to their communication. After the pairing is done, the connection is safe and peer-to-peer, with no handshake being required.”

This means that after pairing a device with each other, the connection is persistent. In other words, if suddenly one of your boards loses power or resets, when it restarts, it will automatically connect to its peer to continue the communication.

ESP-NOW supports the following features:

Encrypted and unencrypted unicast communication;
Mixed encrypted and unencrypted peer devices;
Up to 250-byte payload can be carried;
Sending callback function that can be set to inform the application layer of transmission success or failure.

ESP-NOW technology also has the following limitations:

Limited encrypted peers. 10 encrypted peers at the most are supported in Station mode; 6 at the most in SoftAP or SoftAP + Station mode;
Multiple unencrypted peers are supported, however, their total number should be less than 20, including encrypted peers;
Payload is limited to 250 bytes.

In simple words, ESP-NOW is a fast communication protocol that can be used to exchange small messages (up to 250 bytes) between ESP32 boards.

ESP-NOW is very versatile and you can have one-way or two-way communication in different setups.

ESP-NOW One-Way Communication

For example, in one-way communication, you can have scenarios like this:

One ESP32 board sending data to another ESP32 board

This configuration is very easy to implement and it is great to send data from one board to the other like sensor readings or ON and OFF commands to control GPIOs.

ESP-NOW One ESP32 board sending data to another ESP32 board

A “master” ESP32 sending data to multiple ESP32 “slaves”

One ESP32 board sending the same or different commands to different ESP32 boards. This configuration is ideal to build something like a remote control. You can have several ESP32 boards around the house that are controlled by one main ESP32 board.

ESP-NOW master ESP32 sending data to multiple ESP32 slaves

One ESP32 “slave” receiving data from multiple “masters”

This configuration is ideal if you want to collect data from several sensors nodes into one ESP32 board. This can be configured as a web server to display data from all the other boards, for example.

ESP-NOW One ESP32 slave receiving data from multiple masters

Note: in the ESP-NOW documentation there isn’t such thing as “sender/master” and “receiver/slave”. Every board can be a sender or receiver. However, to keep things clear we’ll use the terms “sender” and “receiver” or “master” and “slave”.

ESP-NOW Two-Way Communication

With ESP-NOW, each board can be a sender and a receiver at the same time. So, you can establish two-way communication between boards.

For example, you can have two boards communicating with each other.

ESP-NOW Two-Way Communication between two ESP32 boards

Learn how to: Exchange Sensor Readings with ESP-NOW Two-Way Communication.

You can add more boards to this configuration and have something that looks like a network (all ESP32 boards communicate with each other).

ESP-NOW Communication between multiple ESP32 boards

In summary, ESP-NOW is ideal to build a network in which you can have several ESP32 boards exchanging data with each other.

ESP32: Getting Board MAC Address

To communicate via ESP-NOW, you need to know the MAC Address of the ESP32 receiver. That’s how you know to which device you’ll send the data to.

Each ESP32 has a unique MAC Address and that’s how we identify each board to send data to it using ESP-NOW (learn how to Get and Change the ESP32 MAC Address).

To get your board’s MAC Address, upload the following code.

/*
  Rui Santos & Sara Santos - Random Nerd Tutorials
  Complete project details at https://RandomNerdTutorials.com/get-change-esp32-esp8266-mac-address-arduino/
  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files.  
  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
*/
#include <WiFi.h>
#include <esp_wifi.h>

void readMacAddress(){
  uint8_t baseMac[6];
  esp_err_t ret = esp_wifi_get_mac(WIFI_IF_STA, baseMac);
  if (ret == ESP_OK) {
    Serial.printf("%02x:%02x:%02x:%02x:%02x:%02x\n",
                  baseMac[0], baseMac[1], baseMac[2],
                  baseMac[3], baseMac[4], baseMac[5]);
  } else {
    Serial.println("Failed to read MAC address");
  }
}

void setup(){
  Serial.begin(115200);

  WiFi.mode(WIFI_STA);
  WiFi.STA.begin();

  Serial.print("[DEFAULT] ESP32 Board MAC Address: ");
  readMacAddress();
}
 
void loop(){

}

View raw code

After uploading the code, open the Serial Monitor at a baud rate of 115200 and press the ESP32 RST/EN button. The MAC address should be printed as follows:

Save your board MAC address because you’ll need it to send data to the right board via ESP-NOW.

ESP-NOW One-way Point to Point Communication

To get you started with ESP-NOW wireless communication, we’ll build a simple project that shows how to send a message from one ESP32 to another. One ESP32 will be the “sender” and the other ESP32 will be the “receiver”.

We’ll send a structure that contains a variable of type char, int, float, and boolean. Then, you can modify the structure to send whichever variable types are suitable for your project (like sensor readings, or boolean variables to turn something on or off).

For better understanding, we’ll call “sender” to ESP32 #1 and “receiver” to ESP32 #2.

Here’s what we should include in the sender sketch:

Initialize ESP-NOW;
Register a callback function upon sending data – the OnDataSent function will be executed when a message is sent. This can tell us if the message was successfully delivered or not;
Add a peer device (the receiver). For this, you need to know the receiver MAC address;
Send a message to the peer device.

On the receiver side, the sketch should include:

Initialize ESP-NOW;
Register for a receive callback function (OnDataRecv). This is a function that will be executed when a message is received.
Inside that callback function, save the message into a variable to execute any task with that information.

ESP-NOW works with callback functions that are called when a device receives a message or when a message is sent (you get if the message was successfully delivered or if it failed).

ESP-NOW Useful Functions

Here’s a summary of the most essential ESP-NOW functions:

Function Name and Description

esp_now_init() Initializes ESP-NOW. You must initialize Wi-Fi before initializing ESP-NOW.

esp_now_add_peer() Call this function to pair a device and pass as an argument the peer MAC address.

esp_now_send() Send data with ESP-NOW.

esp_now_register_send_cb() Register a callback function that is triggered upon sending data. When a message is sent, a function is called – this function returns whether the delivery was successful or not.

esp_now_register_recv_cb() Register a callback function that is triggered upon receiving data. When data is received via ESP-NOW, a function is called.

For more information about these functions read the ESP-NOW documentation at Read the Docs.

ESP32 Sender Sketch (ESP-NOW)

Here’s the code for the ESP32 Sender board. Copy the code to your Arduino IDE, but don’t upload it yet. You need to make a few modifications to make it work for you.

/*
  Rui Santos & Sara Santos - Random Nerd Tutorials
  Complete project details at https://RandomNerdTutorials.com/esp-now-esp32-arduino-ide/
  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files.
  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
*/
#include <esp_now.h>
#include <WiFi.h>

// REPLACE WITH YOUR RECEIVER MAC Address
uint8_t broadcastAddress[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};

// Structure example to send data
// Must match the receiver structure
typedef struct struct_message {
  char a[32];
  int b;
  float c;
  bool d;
} struct_message;

// Create a struct_message called myData
struct_message myData;

esp_now_peer_info_t peerInfo;

// callback when data is sent
void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
  Serial.print("\r\nLast Packet Send Status:\t");
  Serial.println(status == ESP_NOW_SEND_SUCCESS ? "Delivery Success" : "Delivery Fail");
}
 
void setup() {
  // Init Serial Monitor
  Serial.begin(115200);
 
  // Set device as a Wi-Fi Station
  WiFi.mode(WIFI_STA);

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

  // Once ESPNow is successfully Init, we will register for Send CB to
  // get the status of Trasnmitted packet
  esp_now_register_send_cb(OnDataSent);
  
  // Register peer
  memcpy(peerInfo.peer_addr, broadcastAddress, 6);
  peerInfo.channel = 0;  
  peerInfo.encrypt = false;
  
  // Add peer        
  if (esp_now_add_peer(&peerInfo) != ESP_OK){
    Serial.println("Failed to add peer");
    return;
  }
}
 
void loop() {
  // Set values to send
  strcpy(myData.a, "THIS IS A CHAR");
  myData.b = random(1,20);
  myData.c = 1.2;
  myData.d = false;
  
  // Send message via ESP-NOW
  esp_err_t result = esp_now_send(broadcastAddress, (uint8_t *) &myData, sizeof(myData));
   
  if (result == ESP_OK) {
    Serial.println("Sent with success");
  }
  else {
    Serial.println("Error sending the data");
  }
  delay(2000);
}

View raw code

How the code works

First, include the esp_now.h and WiFi.h libraries.

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

In the next line, you should insert the ESP32 receiver MAC address.

uint8_t broadcastAddress[] = {0x30, 0xAE, 0xA4, 0x07, 0x0D, 0x64};

In our case, the receiver MAC address is: 30:AE:A4:07:0D:64, but you need to replace that variable with your own MAC address.

Then, create a structure that contains the type of data we want to send. We called this structure struct_message and it contains 4 different variable types. You can change this to send other variable types.

typedef struct struct_message {
  char a[32];
  int b;
  float c;
  bool d;
} struct_message;

Then, create a new variable of type struct_message that is called myData that will store the variables’ values.

struct_message myData;

Create a variable of type esp_now_peer_info_t to store information about the peer.

esp_now_peer_info_t peerInfo;

Next, define the OnDataSent() function. This is a callback function that will be executed when a message is sent. In this case, this function simply prints if the message was successfully delivered or not.

void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
  Serial.print("\r\nLast Packet Send Status:\t");
  Serial.println(status == ESP_NOW_SEND_SUCCESS ? "Delivery Success" : "Delivery Fail");
}

In the setup(), initialize the serial monitor for debugging purposes:

Serial.begin(115200);

Set the device as a Wi-Fi station:

WiFi.mode(WIFI_STA);

Initialize ESP-NOW:

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

After successfully initializing ESP-NOW, register the callback function that will be called when a message is sent. In this case, we register for the OnDataSent() function created previously.

esp_now_register_send_cb(OnDataSent);

After that, we need to pair with another ESP-NOW device to send data. That’s what we do in the next lines:

//Register peer
memcpy(peerInfo.peer_addr, broadcastAddress, 6);
peerInfo.channel = 0;
peerInfo.encrypt = false;

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

In the loop(), we’ll send a message via ESP-NOW every 2 seconds (you can change this delay time).

First, we set the variables values as follows:

strcpy(myData.a, "THIS IS A CHAR");
myData.b = random(1,20);
myData.c = 1.2;
myData.d = false;

Remember that myData is a structure. Here we assign the values we want to send inside the structure. For example, the first line assigns a char, the second line assigns a random Int number, a Float, and a Boolean variable.

We create this kind of structure to show you how to send the most common variable types. You can change the structure to send other data types.

Finally, send the message as follows:

esp_err_t result = esp_now_send(broadcastAddress, (uint8_t *) &myData, sizeof(myData));

Check if the message was successfully sent:

if (result == ESP_OK) {
  Serial.println("Sent with success");
}
else {
  Serial.println("Error sending the data");
}

The loop() is executed every 2000 milliseconds (2 seconds).

delay(2000);

ESP32 Receiver Sketch (ESP-NOW)

Upload the following code to your ESP32 receiver board.

/*
  Rui Santos & Sara Santos - Random Nerd Tutorials
  Complete project details at https://RandomNerdTutorials.com/esp-now-esp32-arduino-ide/  
  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files.
  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
*/

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

// Structure example to receive data
// Must match the sender structure
typedef struct struct_message {
    char a[32];
    int b;
    float c;
    bool d;
} struct_message;

// Create a struct_message called myData
struct_message myData;

// callback function that will be executed when data is received
void OnDataRecv(const uint8_t * mac, const uint8_t *incomingData, int len) {
  memcpy(&myData, incomingData, sizeof(myData));
  Serial.print("Bytes received: ");
  Serial.println(len);
  Serial.print("Char: ");
  Serial.println(myData.a);
  Serial.print("Int: ");
  Serial.println(myData.b);
  Serial.print("Float: ");
  Serial.println(myData.c);
  Serial.print("Bool: ");
  Serial.println(myData.d);
  Serial.println();
}
 
void setup() {
  // Initialize Serial Monitor
  Serial.begin(115200);
  
  // Set device as a Wi-Fi Station
  WiFi.mode(WIFI_STA);

  // Init ESP-NOW
  if (esp_now_init() != ESP_OK) {
    Serial.println("Error initializing ESP-NOW");
    return;
  }
  
  // Once ESPNow is successfully Init, we will register for recv CB to
  // get recv packer info
  esp_now_register_recv_cb(esp_now_recv_cb_t(OnDataRecv));
}
 
void loop() {

}

View raw code

How the code works

Similarly to the sender, start by including the libraries:

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

Create a structure to receive the data. This structure should be the same defined in the sender sketch.

typedef struct struct_message {
  char a[32];
  int b;
  float c;
  bool d;
} struct_message;

Create a struct_message variable called myData.

struct_message myData;

Create a callback function that will be called when the ESP32 receives the data via ESP-NOW. The function is called onDataRecv() and should accept several parameters as follows:

void OnDataRecv(const uint8_t * mac, const uint8_t *incomingData, int len) {

We copy the content of the incomingData data variable into the myData variable.

memcpy(&myData, incomingData, sizeof(myData));

Now, the myData structure contains several variables inside with the values sent by the ESP32 sender. To access variable a, for example, we just need to call myData.a.

In this example, we simply print the received data, but in a practical application you can print the data on a display, for example.

Serial.print("Bytes received: ");
Serial.println(len);
Serial.print("Char: ");
Serial.println(myData.a);
Serial.print("Int: ");
Serial.println(myData.b);
Serial.print("Float: ");
Serial.println(myData.c);
Serial.print("Bool: ");
Serial.println(myData.d);
Serial.println();

In the setup(), intialize the Serial Monitor.

Serial.begin(115200);

Set the device as a Wi-Fi Station.

WiFi.mode(WIFI_STA);

Initialize ESP-NOW:

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

Register for a callback function that will be called when data is received. In this case, we register for the OnDataRecv() function that was created previously.

esp_now_register_recv_cb(esp_now_recv_cb_t(OnDataRecv));

Testing ESP-NOW Communication

Upload the sender sketch to the sender ESP32 board and the receiver sketch to the receiver ESP32 board.

Now, open two Arduino IDE windows. One for the receiver, and another for the sender. Open the Serial Monitor for each board. It should be a different COM port for each board.

This is what you should get on the sender side.

ESP-NOW ESP32 Sender Message Print Arduino IDE Demonstration

And this is what you should get on the receiver side. Note that the Int variable changes between each reading received (because we set it to a random number on the sender side).

ESP-NOW ESP32 Receiver Message Print Arduino IDE Demonstration

We tested the communication range between the two boards, and we are able to get a stable communication up to 220 meters (approximately 722 feet) in open field. In this experiment both ESP32 on-board antennas were pointing to each other.

Wrapping Up

We tried to keep our examples as simple as possible so that you better understand how everything works. There are more ESP-NOW-related functions that can be useful in your projects, like: managing peers, deleting peers, scanning for slave devices, etc… For a complete example, in your Arduino IDE, you can go to File > Examples > ESP32 > ESPNow and choose one of the example sketches.

We hope you’ve found this introduction to ESP-NOW useful. As a simple getting started example, we’ve shown you how to send data as a structure from one ESP32 to another. The idea is to replace the structure values with sensor readings or GPIO states, for example.

Additionally, with ESP-NOW, each board can simultaneously be a sender and receiver. One board can send data to multiple boards and also receive data from multiple boards.

We also have a tutorial about ESP-NOW with the ESP8266: Getting Started with ESP-NOW (ESP8266 NodeMCU with Arduino IDE).

To learn more about the ESP32 board, make sure you take a look at our resources:

Thanks for reading.

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265 thoughts on “Getting Started with ESP-NOW (ESP32 with Arduino IDE)”

JD

January 29, 2020 at 4:35 pm

Great, we don’t need a WIFI_AP anymore 🙂
For now, I’m challenging a light handshake protocol between slave and master.
For my application, the slave must decide the duration of sleep for the master(s). The idea is synchronize all ESP32.
Reply
- javi
  
  December 19, 2022 at 6:29 am
  
  Hello.
  Where can i found WiFi.h?
  Regards
  Jvier
  Reply
- Uwe Jetzinger
  
  September 18, 2023 at 7:33 am
  
  Hi Sara, do you have any idea how to check if any transmitter is available ?
  Thx in advance
  Uwe
  Reply
salvatore Fusto

January 29, 2020 at 5:13 pm

hello,
a simple question: yiu tyitlet this post esp-now-esp32…, but if i’m right the protocol works on esp8266 too: is this correct? is there any difference between esp32 and esp8266?
regards
Reply
- Sara Santos
  
  January 30, 2020 at 11:35 am
  
  Hi.
  You’re right, ESP-NOW also works with ESP8266.
  However, I haven’t tested this code with the ESP8266. Probably there are some changes that need to be made to make it compatible.
  We’ll write a guide about ESP-NOW with ESP8266 – but we still don’t know when.
  Regards,
  Sara
  Reply
  - CVBruce
    
    February 1, 2020 at 6:51 pm
    
    If you can also test ESP-NOW cross-compatibility between ESP8266 and ESP32.
    Reply
  - Davide
    
    April 14, 2020 at 12:18 pm
    
    can we have both ESP NOW and Wifi running simultaneously? I want to have an esp acting like a slave, receive the message from esp now, and then send it into an MQTT queue via wifi, is this possible?
    Reply
    - Sara Santos
      
      April 14, 2020 at 2:53 pm
      
      Yes.
      It is possible.
      But the ESP32 needs to be set as a wi-fi station and access point at the same time.
      You need to use different wi-fi channels. One for ESP-NOW and other to connect to Wi-Fi.
      I’ll be publishing a tutorial about combining ESP-NOW with Wi-Fi in the next weeks.
      So, stay tuned.
      Regards.
      Sara
      Reply
      - Ronni
        
        June 17, 2022 at 2:01 am
        
        Hi Sara
        I had a quick search but didn’t find it, did this Esp and WiFi tutorial eventuate? else hints? I tried adding a 2 after my ssid/password as I found this on the ESP8266 core website
        WiFi.begin(ssid, password, channel, bssid, connect)
        my slaves are ESP8266 and my master is ESP32 and I’m trying to recieve multiple DHT webserver results.
        thanks Ronni
      - Ronni
        
        June 17, 2022 at 2:23 am
        
        nvm found it 2 seconds after I hit send… le sigh. thanks for the great work.
      - Shahri
        
        June 23, 2024 at 12:05 pm
        
        Hi SARA
        I’m using one way espnow but I think my signal strength is weak.
        Is there any code to show my receiving signal strength in receiver side?
    - Eduardo Alvim
      
      April 14, 2020 at 3:19 pm
      
      Hi JF,
      It is possible to use an ESP32 to receive the data and send it to the web. I don’t know exactly what you want to do, but I modified the code of this excellent post of this blog and made a project which builts an web server which publishes all the data received by the ESP-NOW protocol.
      
      This project is available here: https://github.com/dualvim/ESP32CAM_ESPNOW_Sensors_WebServer
      
      It uses an ESP32, an ESP32-CAM and some sensors.
      
      I hope that it will help you.
      For Sara and Rui, feel free to use it, once all the code are only modifications based on tons of code that I learned here in the blog. It is yours actually!
      Reply
      - Sara Santos
        
        April 15, 2020 at 9:44 am
        
        Thanks for sharing that 😀
        We’ll write a tutorial using some of the concepts you address in that project.
        Thank you.
        Regards,
        Sara
  - samuel martyn
    
    March 17, 2022 at 3:58 pm
    
    Hi Sara
    I want to use the controller to broadcast just strings such dog, cat, goat etc to multiple slaves. The commands will activate LEDs accordingly. This is a school project. The codes above do not help, though it connects the boards, Can you help me please with the controller and slave side
    
    thanks
    sam
    Reply
    - Sara Santos
      
      March 18, 2022 at 4:29 pm
      
      Hi.
      In that case, you need to convert your strings to char.
      The tutorial explains how to send and receive char variable types. Take a look at that part.
      To send data to multiple boards, you can take a look at this tutorial: https://randomnerdtutorials.com/esp-now-one-to-many-esp32-esp8266/
      Regards,
      Sara
      Reply
- karthik
  
  July 27, 2022 at 8:10 am
  
  hiii i spent lot of time to find the esp_now.h library but i can’t find it!
  can you help me plz..
  Reply
  - Sara Santos
    
    July 27, 2022 at 11:06 am
    
    Hi.
    You don’t need to install anything.
    It is included when you install the ESP32 boards in your Arduino IDE.
    Regards,
    Sara
    Reply
salvatore Fusto

January 29, 2020 at 5:15 pm

Excuse me: you titled…

regards
Reply
David

January 29, 2020 at 11:49 pm

With respect to your “ESP32 LoRa Sensor Monitoring with Web Server” project could ESP-NOW be used to setup multiple remotes talking to a single ESP32 server?
Reply
- Sara Santos
  
  January 30, 2020 at 9:42 am
  
  Hi David.
  Yes, you can do that with ESP-NOW.
  Regards,
  Sara
  Reply
RayB

January 30, 2020 at 12:52 am

How about ESP32 to ESP8266 so I can use all of those old 8266 I have? Maybe you could provide a summary of alternative 32 to 8266 networking at this current time in the product development cycle.
Looking forward to your future developments on this product…
Reply
- Sara Santos
  
  January 30, 2020 at 11:17 am
  
  Hi.
  ESP-NOW communication protocol also works with the ESP8266.
  However, at the moment, I haven’t tested these examples with the ESP8266. So, I don’t know if both boards can use the same code or not.
  Regards,
  Sara
  Reply
- SHREYANSH JAIN
  
  February 20, 2020 at 12:34 pm
  
  I have modified the code and now it is working just fine below is the code i used…And the sender is ESP32 while the receiver is ESP8266(nodeMcu).
  
  extern “C” {
  #include
  #include “user_interface.h”
  }
  #include
  
  // Structure example to receive data
  // Must match the sender structure
  typedef struct struct_message {
  char a[32];
  int b;
  float c;
  String d;
  bool e;
  } struct_message;
  
  // Create a struct_message called myData
  struct_message myData;
  
  // callback function that will be executed when data is received
  void OnDataRecv(uint8_t *mac,uint8_t *incomingData, uint8_t len) {
  memcpy(&myData, incomingData, sizeof(myData));
  Serial.print(“Bytes received: “);
  Serial.println(len);
  Serial.print(“Char: “);
  Serial.println(myData.a);
  Serial.print(“Int: “);
  Serial.println(myData.b);
  Serial.print(“Float: “);
  Serial.println(myData.c);
  Serial.print(“String: “);
  Serial.println(myData.d);
  Serial.print(“Bool: “);
  Serial.println(myData.e);
  Serial.println();
  }
  
  void setup() {
  // Initialize Serial Monitor
  Serial.begin(115200);
  
  // Set device as a Wi-Fi Station
  WiFi.mode(WIFI_STA);
  
  // Init ESP-NOW
  if (esp_now_init() == 0)
  {
  Serial.println(“ESP NOW initialised. . .”);
  }
  else
  {
  Serial.println(“ESP NOW not initialised. . .”);
  ESP.restart();
  delay(1);
  }
  
  // Once ESPNow is successfully Init, we will register for recv CB to
  // get recv packer info
  esp_now_register_recv_cb(OnDataRecv);
  }
  void loop() {}
  Reply
  - RayB
    
    April 29, 2020 at 9:39 am
    
    with your example were you using either/both
    #include <esp_now.h>
    #include <espnow.h>
    
    Cheers
    Reply
Eduardo Alvim

January 30, 2020 at 2:46 am

Hi Sara,
The source code of the ‘Sender module’ (ESP_NOW_Sender.ino) should be fixed, it is different from the code in the explanations bollow of it.

Despite this detail, excelent post! I didn’t know this resource and I’m testing it here.
Congratulations!
Reply
- Sara Santos
  
  January 30, 2020 at 11:14 am
  
  Hi.
  You’re right.
  Thanks for noticing. It’s fixed now.
  Regards,
  Sara
  Reply
Bob Durk

January 30, 2020 at 4:07 am

I definitely want to work with this method. It looks so interesting, and the fact it will reply back is amazing. Random Nerds has the best learning site that I am aware of. I have learned more in a month here, than I have learned in a year from any other site.
Thank you!!
Bob D
Reply
- Sara Santos
  
  January 30, 2020 at 9:41 am
  
  Hi Bob.
  Yes, ESP-NOW is a great method to exchange data between boards. And you know if the message was successfully delivered or not.
  Thanks for your nice words.
  Regards,
  Sara
  Reply
espinosa

January 30, 2020 at 12:33 pm

Hello everyone, Congratulations on your work, Without a doubt the best site for examples and clarifications, Hug to all.
Reply
John Anderson

January 30, 2020 at 4:47 pm

Really interesting! A new capability for longer range remote control.
Definitely one of your best tutorials. The amount of first class info you freely share is admirable.
Reply
- Sara Santos
  
  January 31, 2020 at 10:22 am
  
  Thanks 😀
  Regards,
  Sara
  Reply
  - Wesley
    
    February 27, 2024 at 10:50 pm
    
    Is it possible to extend the range of esp-now by placing another esp between two points that are just out of range of each other? The 2 nodes that are furthest apart need to send and receive data from one another. I’m at wots end trying to figure out a solution to get past my 20 yard shortcoming.
    Reply
    - Wesley
      
      February 27, 2024 at 11:03 pm
      
      Further explanation…
      I’m basically trying to create a “I’ve fallen and can’t get up” emergency notification to the other. This is between 2 farmhouses with no internet access. We are about 300 yards from each other. I’ve tried using wifi and ESP-Now but both come up short on distance capabilities. I tried external antennas as well which got me to just shy of being able to connect. The is a tool shed with power about halfway between us and I’m wondering if O can add another node there as a sort of extension or relay.
      Reply
      - Eduardo
        
        February 28, 2024 at 8:13 am
        
        Hi Wesley, for this situation that you explained, I believe that will be better for you to use the LoRa radio. This site has some LoRa tutorials too.
Jerry Ericsson

January 30, 2020 at 5:25 pm

Wow, I am very excited about this, it is what I have been looking for to set up networks in my home and on my RV to use when we are on the road seeing our great nation.

Do you have any idea how much modification it would take to add an M5Stick-c to the network, since it is based on an ESP32, has the built in color screen, and the environmental hat is available for it, using the same chip for reading temp and humidity?

Perhaps the Heltec ESP32 could be included as well, with it’s built in OLED screen. Just thoughts, this does look extremely useful, thank you so much for the write up and effort put into this project, it could have life changing consequences.
Reply
- Sara Santos
  
  January 31, 2020 at 10:33 am
  
  Hi Jerry.
  Thank you for your nice words.
  The M5Stick-c can be programmed using Arduino IDE, and it uses the ESP32 chip, so you can use the code with that board.
  Then, you just need to know the connections between the peripherals and the board and search for examples that interface those peripherals (the sensors and the display).
  Regards,
  Sara
  Reply
- Mitch Olson
  
  March 9, 2020 at 3:44 pm
  
  I am currently running a Heltec Wireless Stick Lite as the sender with ESP NOW to an M5 Stick C as a receiver with the LCD screen showing data. It works great!! The M5 Stick C has far better reception with its on board antenna. The Heltec board needed a small (3″) wire attached to the 3D on board antenna to get better reception. I needed the Heltec board at the sending end as the M5 didnt have enough pins for my application. Other than that , I prefer the M5 over the Heltec for ease of use.
  Reply
- Dave K.
  
  June 27, 2023 at 11:16 pm
  
  Yep, the Heltec WiFi kit 32 works. I am using right now to monitor and display temperatures. Display is the same on both ends, but for the moment I am only sensing temperature on one end. The remote monitor also has a button written in that will control a GPIO on the sensor end, but I am not currently using that function, though it is tested and can be used. (Therefore 2 way communication :)) Timestamped datalogger is the next iteration.
  Reply
Mitch

January 30, 2020 at 7:08 pm

I tested ESP NOW with this example and it is very impressive. In my distance tests from outdoors, through two walls to the receiver indoors, I was able to get 40 meters. It is a great alternative to LoRa for point – point closer range communication. Now to get analog sensor readings from sender to receiver …
Reply
- Sara Santos
  
  January 31, 2020 at 10:11 am
  
  Hi.
  That’s great!
  Thanks for sharing that 😀
  Regards,
  Sara
  Reply
  - Priyanka
    
    April 13, 2023 at 11:40 am
    
    Hi
    We are excited with your post , we are also using ESP NOW and connected one master and one slave , with example program of master , slave , master device sends and receives the data from slave., it works fine .
    now we would want to connect multiple slave devices with one master, is it possible ?
    Best regards
    Priyaka
    R&D engineer
    Lateral emsoft Pvt Ltd
    Reply
    - Sara Santos
      
      April 13, 2023 at 8:47 pm
      
      Hi.
      Yes.
      See this tutorial: https://randomnerdtutorials.com/esp-now-many-to-one-esp32/
      Regards,
      Sara
      Reply
G. N. Desouza

January 30, 2020 at 7:40 pm

Great post — as usual. 😉

One thing that concerns me though is the use of 2.4GHz channels. That is, I can see how useful this can be in a field or an open space (as in the picture above) where no WiFi hubs are present. However, if we use the ESP NOW in a home, it will conflict with the current WiFi hub — competing and forcing ‘everybody’ to every-now-and-then drop packages due to collisions. Also, since ESP NOW likely doesn’t have functionalities to auto switch channels, MIMO, etc… the use of the same IEEE802 channels can be a real problem to the current hubs/devices.
I am saying this because I have noticed in the past that the simple presence of an ESP closer to my home WiFi hub has affected the WiFi hub’s performance — likely, in this case, due to the ‘cheap’ antennas and hardware of the ESPs in general that cause a spread of the channel spectrum (eg. channel 11 in a simple 802.11b/n going, in frequency/spectrum, way over channels 8, 9, 10… 12, 13 14…)
Reply
Enno

January 30, 2020 at 9:00 pm

It looks to me that it works by sending and receiving low level wireless data frames which I presume are analogous to raw (wired) ethernet frames. That makes me think the station limits are artifacts of the library rather than something baked into the hardware? It also makes me wonder if multi station broadcast would in fact work (with ff:ff:ff:ff:ff:ff as the target address)?
Reply
- Sara Santos
  
  January 31, 2020 at 10:08 am
  
  Hi.
  If you set the target mac address as FF:FF:FF:FF:FF:FF all boards will receive the data.
  Regards,
  Sara
  Reply
  - Andreas Stegmaier
    
    February 24, 2020 at 7:44 am
    
    Hello Sara,
    
    Is it possible to make a two way communication between multiple ESP32 without setting the MAC addresses and just use FF:FF:FF:FF:FF:FF. Using the confirm message to carry a few data?
    Reply
    - Sara Santos
      
      February 24, 2020 at 10:40 am
      
      Hi.
      Yes, you can use FF to exchange data between your boards.
      What do you mean by “confirm message to carry a few data?”
      Regards,
      Sara
      Reply
- Robert
  
  October 9, 2020 at 12:41 pm
  
  You can also use NULL, as in:
  
  esp_now_send(NULL, (uint8_t *) &myData, sizeof(myData))
  
  The package will than be sent to all peers added with esp_now_add_peer.
  Reply
Sasika srimal fernando

January 31, 2020 at 2:20 am

Hi sara thanks a lot. And this tutorial is very interesting and very useful for me. Appreciate and thanks again.
Reply
Friedhelm

January 31, 2020 at 10:04 am

Hi, Sara,
I get no string displayed on the receiver side.
What can be the problem?
Reply
- Sara Santos
  
  January 31, 2020 at 10:39 am
  
  Hi.
  Do you mean just the string or the whole packet?
  Regards,
  Sara
  Reply
  - Friedhelm
    
    February 1, 2020 at 9:24 am
    
    Just the string!
    Reply
Carlos Sebe Estenoz

January 31, 2020 at 10:32 am

Hi Sara and Rui
Just a few days ago I was looking for information on this type of communication between modules. It only works between modules or you can also use the Master with ESP NOW and connect to the Wifi and dump the data on a server or in the cloud? .. Good job … and also beautiful beaches to test the connection distance. ..Thank you
Reply
- Sara Santos
  
  January 31, 2020 at 10:43 am
  
  Hi Carlos.
  Yes, you can use ESP-NOW and Wi-Fi in the same board, in theory.
  However, I didn’t get it working yet. There should be some trick to make it work properly. But, we’re working on that and we’ll publish a tutorial about that subject when we get it working.
  Regards,
  Sara
  
  P.S. Portugal has a 1,794 km coastline with beautiful beaches. It’s worth a visit, if you have the opportunity, specially the south.
  Regards,
  Sara
  Reply
  - Eduardo Alvim
    
    February 2, 2020 at 11:14 pm
    
    Hi Rui and Sara,
    I figure out hou to connect the ESP32 to the internet and use the ESP-NOW.
    
    It is a little Akward and I’m really tired, but if you’re interested in my solution, just tell me. I’ll try to upload and share as soon as possible!
    Reply
    - Sara Santos
      
      February 3, 2020 at 11:02 am
      
      Hi Eduardo.
      If you have that project ready, then share a link to the project GitHub page.
      I’d love to see how you did it. But don’t be in a rush, we have time.
      Regards,
      Sara
      Reply
      - Eduardo Alvim
        
        February 3, 2020 at 6:49 pm
        
        Here is it.
        It needed some cleaning, but this happened faster than I imagine.
        
        If you access today the NGROK link that I included in the end of the README.md file (before the images), http://0.tcp.ngrok.io:11614, you can check it working here in my place!
        
        I hope you guys enjoy it!
      - Sara Santos
        
        February 4, 2020 at 10:51 am
        
        Hi Eduardo.
        Great project! I’ve seen your GitHub page. Very well explained. Thanks for sharing it with us!
        Unfortunately, I was not able to see the project running on that link today 4th February.
        Regards,
        Sara
Jeff Jackson

January 31, 2020 at 1:31 pm

Hi Sara,

Great article! But I have a few things to clarify. First, there are several references to using the sender callback function to “know if the message was received,” but, since this is a connectionless protocol, (no “ACK”), the sender can only say that the message was successfully sent. It has no way to know if the message was received, unless the receiver becomes a sender and sends back an “ACK” message. I think that should be clarified in your article.
Also, in one of your replies, you said that it’s possible to use “ff-ff-ff-ff” as a MAC address to send to multiple receivers… But, in the intro, the article stated that “broadcast is not possible.” Is that because the senders cannot decode and match the “ff-ff-ff-ff” to their own MAC address?
Also one question: with regards to “registering the sender & receiver,” it seems that all that entails is putting the receiver’s MAC address in the code – – is that correct?
(But, I’ve forgotten if you need to put the sender’s MAC address in the receiver’s code. If not, I don’t really see how it’s “registering” like when we’re linking two Bluetooth devices. It’s just putting the destination address in the packet, like any other transmission.)
Thanks again for all the fine (actually awesome) articles!
Reply
- Sara Santos
  
  January 31, 2020 at 6:21 pm
  
  Hi Jeff.
  Thanks for your comment.
  I’m not sure if I know how to answer all the questions.
  In the espressif documentation, it says “Call esp_now_send() to send ESP-NOW data and esp_now_register_send_cb to register sending callback function. It will return ESP_NOW_SEND_SUCCESS in sending callback function if the data is received successfully on the MAC layer.” https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/network/esp_now.html#send-esp-now-data But, you’re right, because “t is not guaranteed that application layer can receive the data. ”
  
  Yes, you can use the FF MAC address to send to all devices and it works. However, in the espressif ESP-NOW “datasheet” they said it doesn’t support broadcast mode: https://www.espressif.com/sites/default/files/documentation/esp-now_user_guide_en.pdf But, maybe this is outdated. I’ll update our article about broadcasting.
  
  To send a message to a device, you just need to put the receiver MAC address on your code and you don’t need to put the sender MAC address on the receiver code.
  
  I think that what I’m saying is correct, but tell me if I’m wrong.
  
  Thanks for your comment.
  Regards,
  Sara
  Reply
Dave K.

January 31, 2020 at 4:18 pm

Nice work. Simply explained and on topic.
Thanks Again!
Reply
Rajiv Shankar

February 1, 2020 at 6:31 am

Hi
How to install ESP-NOW library in IDE environment.

Thanks
Reply
- Bennie
  
  February 5, 2020 at 9:12 am
  
  If you setup a esp32 or esp8266 in your preferences as extra boards (https://randomnerdtutorials.com/installing-the-esp32-board-in-arduino-ide-windows-instructions/) you will get the files that needs to be included for the esp now.
  Reply
GIANNI

February 2, 2020 at 2:49 pm

Many compliments…..easy explanations, best videos, all circuits tested and very succesfull.
Brava Sara
saluti
Reply
- Sara Santos
  
  February 2, 2020 at 5:36 pm
  
  Thank you 😀
  Reply
renzo giurini

February 3, 2020 at 12:20 pm

Hi Sara,
very often you refer to address 192.168.4.1 an it works.
My default addreess of the router is 192.168.1.1

Which is the reference to the first address?
Thanks

Renzo
Reply
Bob

February 9, 2020 at 5:07 pm

renzo, 192.168.4.1 is the default (gateway address) of the ESP when it is in AP mode. Some applications use 192.168.4.1 to host a web page from which you enter your own home network credentials. The famous ESP-Link bridge application does just that.

Your default address of 192.168.1.1 is usually the gateway address of your router, it does vary with different routers and some use 192.168.1.254.

I hope that helps
Reply
- renzo giurini
  
  February 9, 2020 at 8:11 pm
  
  thank
  Reply
Alain

February 18, 2020 at 10:00 am

Hi Sarah, how do I get esp_now.h ?
Thanks
Reply
- Sara Santos
  
  February 18, 2020 at 10:24 am
  
  Hi. It’s included by default if you have the ESP32 add-on installed.
  Regards,
  Sara
  Reply
Mitch Olson

February 19, 2020 at 2:03 pm

I am using two M5 Stick C , which has an ESP32 Pico chipset. I discovered the above code to get the MAC address doesn’t work on this device.
I found one that does.

#include “WiFi.h”

void setup(){

Serial.begin(115200);
delay(500);

Serial.println();
Serial.print(“MAC: “);
Serial.println(WiFi.macAddress());

}

void loop(){}

Hope this helps anyone using M5 Stick C. ( great device by the way)
Reply
- Sara Santos
  
  February 20, 2020 at 10:55 am
  
  Hi Mitch.
  Thanks for sharing that.
  Regards,
  Sara
  Reply
  - rick
    
    May 27, 2020 at 1:26 am
    
    another way ive found is to upload a blank ino file, when uploading the esp32 will give you the mac address at the bottom of the page in the upload window in orange in the list before it goes through the percentages of how much is uploaded.
    Reply
    - Sara Santos
      
      May 27, 2020 at 3:32 pm
      
      Thanks for sharing that 🙂
      Reply
Renzo

February 19, 2020 at 11:13 pm

Thank U Rui and Sara,
I made this project with 100% of success!!!
Compliments for explanations, videos, pictures and your HUGE patience, availability and endurance

A hug from Italy
Renzo (Bologna)
Reply
- Sara Santos
  
  February 20, 2020 at 11:05 am
  
  Hi Renzo.
  Thank you so much.
  Regards,
  Sara
  Reply
Renzo

February 19, 2020 at 11:25 pm

“…Additionally, with ESP-NOW, each board can be a sender and receiver at the same time, and one board can send data to multiple boards and also receive data from multiple boards. These topics will be covered in future tutorials, so stay tuned.”

Hey Rui and Sara: promise me U’ll write soon these “future tutorials” !!!
Another hug from Italy
Renzo (Bologna)
Reply
- Sara Santos
  
  February 20, 2020 at 11:08 am
  
  Hi.
  Yes.
  We’ve already published the tutorial about two-way communication: https://randomnerdtutorials.com/esp-now-two-way-communication-esp32/
  We already tested communication with multiple boards. The tutorials will be released soon – in two weeks or three.
  Regards,
  Sara
  Reply
renzo giurini

February 24, 2020 at 3:55 pm

Hi Sara,
the idea of JD to make an application in which the slave must decide the duration of sleep for the master(s) is very good.

But how to do it? As far as I know it is impossible to awake from sleep an ESP8266 with a Wifi signal because simply it can’t receive any signal during sleep.

Thanks
Renzo Giurini
Reply
- Sara Santos
  
  February 25, 2020 at 12:28 pm
  
  Hi.
  Yes, that’s right.
  But I don’t know the application of his project. Maybe he wants to set up a new sleep time when the ESP32 wakes up from sleep. So, the next time it goes to sleep, it is for a different period of time. I don’t know, I’m just guessing 😀
  Regards,
  Sara
  Reply
Bert

March 5, 2020 at 8:01 pm

I used the sender-sketch for a esp8266 ans the receiver-sketch for a esp32. And both are communicating. A strange thing is that the value “Hello” for the string is not printed in the serial monitor.
I used the sketches from getting started with ESP-now (one way communication).
So it is working, yet the stringvalue is not known in the receiver.
Strange?
Reply
- Sara Santos
  
  March 7, 2020 at 11:18 am
  
  Hi Bert.
  Yes, that’s weird.
  What version of Arduino IDE are you using?
  If it doesn’t work, a workaround is to send the message as a CHAR.
  Regards,
  Sara
  Reply
Vladimir

March 8, 2020 at 5:11 pm

Sorry, but where can I found the ESP-Now library? I found some but evidently not correct ones (wrong headers, no info on how to use, etc)!
Reply
Vladimir

March 8, 2020 at 5:21 pm

Sorry, I pressed the Post button too early.
It is said above in the comments, I should get the library while I installed the ESP8266 boards onto IDE. I did that but the compiler throws me “esp_now.h: No such file or directory” error, so it seems that this is not so.
I don’t have any ESP32 boards so I did not include them.
Reply
- Sara Santos
  
  March 8, 2020 at 5:59 pm
  
  Hi Vladimit.
  That’s right.
  The ESP-NOW library should be installed by default.
  Double-check in the Boards Manager that you have a recent version of the ESP8266 boards.
  Also, note that this tutorial refers to the ESP32.
  For the ESP8266, follow this tutorial instead: https://randomnerdtutorials.com/esp-now-esp8266-nodemcu-arduino-ide/
  Regards,
  Sara
  Reply
  - John Rupert
    
    August 5, 2022 at 3:31 pm
    
    I installed both ESP32 and ESP8266 boards. But I couldn’t find the esp_now.h library.
    I am getting the following error.
    //
    compilation terminated.
    exit status 1
    esp_now.h: No such file or directory
    //
    Reply
    - Sara Santos
      
      August 5, 2022 at 8:47 pm
      
      Hi.
      Make sure you have the right board selected in Tools > Board.
      Additionally, note that this tutorial is only compatible with the ESP32.
      For the ESP8266, check this tutorial instead: https://randomnerdtutorials.com/esp-now-esp8266-nodemcu-arduino-ide/
      Regards,
      Sara
      Reply
Vladimir

March 9, 2020 at 7:46 am

Hi,
I’ve made an Arduino IDEe installation from scratch. IDE version is 1.8.12. Then I installed software for ESP8266 Community version 2.6.3 (from the link provided in your tutorial). Compiler still cannot find the esp_now.h.

Just to see if the same thing happens for ESP32 boards, I installed software esp32 Espresiff Systems version 1.0.4 (also from the link in your corresponding tutorial). I choosed one of ESP32 boards as target and my sketch compiles OK.

The board for which I am trying to use with ESP-Now is Wemos D1 mini. Is it possible that this board doesn’t support ESP-Now??
Reply
- Sara Santos
  
  March 9, 2020 at 11:40 am
  
  Hi Vladimir.
  The ESP8266 supports ESP-NOW, but I haven’t tried it with the Wemos D1 mini.
  We have a tutorial about that: https://randomnerdtutorials.com/esp-now-esp8266-nodemcu-arduino-ide/
  To get it working, you need to have an ESP8266 board selected on the Boards menu.
  Do you have that?
  I need to test this with the D1 mini and see what I got.
  Regards,
  Sara
  Reply
  - Vladimir
    
    March 9, 2020 at 1:18 pm
    
    Hi,
    well, I do have an esp2866 board selected. I managed to start web server and also a client with my settings. Just to compile the script, the board doesn’t have to be physically available, so I’ve selected some Adafruit and SparkFun boards – and experienced the same issue —
    Reply
Arun

March 18, 2020 at 5:01 pm

Is it possible to push data received from other esp32 via espnow to firebase or any other cloud server?
Reply
- Sara Santos
  
  March 20, 2020 at 11:00 am
  
  Yes.
  You can use Wi-Fi and ESPNOW at the same time.
  Regards,
  Sara
  Reply
  - Arun
    
    April 22, 2020 at 3:50 pm
    
    I tried that. But it gives some time Guru mediation error. Sometimes data sends ones or twice and pauses sending data.
    Reply
    - Sara Santos
      
      April 23, 2020 at 10:54 am
      
      Hi.
      That’s weird.
      Which ESP32 boards are you using?
      I never get any of those errors with ESP-NOW examples.
      Regards,
      Sara
      Reply
Jairo

March 30, 2020 at 2:16 pm

Thanks for this amazing tutorial, I have a little request, would you do a tutorial to how to work with ESP-MESH protocol ? Thanks for you contribution!!
Reply
- Sara Santos
  
  March 30, 2020 at 3:25 pm
  
  Hi Jairo.
  Thanks for the suggestion.
  I’ve been thinking about that subject for a while.
  It’s definitely in my to-do list. However, I still don’t know when it will be released. I haven’t started yet.
  Regards,
  Sara
  Reply
jF

April 7, 2020 at 2:30 pm

Thanks for this great tutorial! I’ve been searching for many hours on the net to find one clean and working code like yours. So thank you!
I would have a question that I cannot find an answer to yet.
If I want to send the data shared in my esp-now set-up on a database meaning is it possible to switch the last esp which receives all the data to send them over the internet ?
Is it possible or I must go with the esp-mesh protocol to do that ?
Thank you for your time.
jF
Reply
- Sara Santos
  
  April 8, 2020 at 9:14 am
  
  Hi.
  Yes, you can do that.
  You need to set that ESP32 as a station and access point simultaneously for that to work.
  Regards,
  Sara
  Reply
Gerhat Samuel

April 18, 2020 at 1:48 pm

Hi,

I want to ask. Can I use different type of ESP32 to do this? I’m using TTGO32-LoRa (as Receiver) and ESP Wroom32 (as Sender). But I didn’t receive anything.

Thanks.
Reply
- Sara Santos
  
  April 18, 2020 at 2:44 pm
  
  Hi.
  It should work with other boards. Because they all have the ESP32 chip.
  I tried with different ESP32 board models, but not those you are mentioning, and it worked fine.
  Regards,
  Sara
  Reply
John

April 29, 2020 at 11:52 pm

Fantastic as usual!

Can I just say, perhaps I read things differently, but I found the following line a bit confusing… “register the callback function that will be called when a message is sent.”

I find it easier to understand worded thus… “register the callback function that will be called AFTER a message is sent.”
Reply
Nils

May 3, 2020 at 7:40 pm

Hey, ive got a Problem, the Sender alway says:
-“Last Packet Send Status: Delivery Fail”
-“Sent with success”
and the reciever doesnt get anything….
Reply
- Sara Santos
  
  May 4, 2020 at 4:31 pm
  
  Hi Nils.
  That means the sender was able to send the message, but the receiver didn’t get the message.
  Double-check that you’ve properly typed the receiver’s MAC address and that the receiver is relatively close to the sender (so that you’re sure it is not something related to distance).
  Regards,
  Sara
  Reply
Ali shami

May 16, 2020 at 9:56 pm

Dear Sara can we use esp now with ESP01 since it’s a low cost drive and some time no need to use ESP8266 node mcu or ESP32
Reply
- Sara Santos
  
  May 17, 2020 at 11:31 am
  
  Hi.
  I haven’t experimented with ESP-01.
  But I think it should work. You have to experiment and see what you get.
  Regards,
  Sara
  Reply
DuaneB

May 31, 2020 at 8:25 pm

Hey guys,
Great work, as usual.

Is it possible to put the sender to sleep (light or deep) and have the receiver wake it up somehow to send data, with like a request or something? The sender will be a battery operated device.

Thanks!
Reply
- Sara Santos
  
  June 1, 2020 at 2:14 pm
  
  Hi.
  I don’t know how to do that, and I don’t think it is possible (someone correct me if I’m wrong).
  You can wake up the ESP32 using an external wake-up (via physical GPIO) or have a timer wake-up. So, I don’t think you can wake it up using Wi-Fi or ESP-NOW.
  Regards,
  Sara
  Reply
Refa Rupaksi

May 31, 2020 at 9:19 pm

Can i use esp now for get rssi value for each other peers?
Reply
- Sara Santos
  
  June 1, 2020 at 2:19 pm
  
  Hi.
  This code contains some lines to get the RSSI:
  https://github.com/espressif/arduino-esp32/blob/master/libraries/ESP32/examples/ESPNow/Basic/Master/Master.ino
  I hope this helps.
  Regards,
  Sara
  Reply
Clive

June 19, 2020 at 7:02 am

I m loving this ballistic learning curve I am on, I look at these tutorials and I get them working learning by my errors as I go.

Then I get these stupid ideas like “I can use the ‘8266 one to many ESP-NOW’ with the ‘ds18b20 code’ and add the ‘oled display’ together “

And yes I can but boy it’s not easy!

I am trying to create separate temperature sensors with local displays that I will 3d print enclosures for later. These I will place around my home and garden and have all the data sent back to another that can display ALL the data.

It’s not going well but thats all part of learning isn’t it. I keep getting tangled as I am finding that simple things like libraries can trip each other up if placed in certain orders.

I am currently struggling to get the oled to display anything from within the code and although I can get the temperature (as float) across I cant then use it.

It’s great because it time I go back to your other tutorials I learn a different approach, I am really enjoying the frustration of it

Cheers Clive
Reply
Bob Durk

June 19, 2020 at 7:07 pm

Hi Clive,
I agree totally; I am going back now and starting fresh on an ESP Now tutorial that uses combo mode. I will add the DSS1306 displays, and some code that will track value of a switch condition.
It is a play on another project I completed, so I know it will work. I just want to re-enforce what I have been learning here at RN by repeating the same concept…but slightly different so I can learn more.
The good news is I received 5 more WeMos D1, and 3 more ESP8266 modules to experiment with.
Reply
Ed Cañeda

July 11, 2020 at 5:37 am

This is a great page to start with ESP-NOW. I love the community surrounding “RandomNerdTutorials”.
My hands are burning with new projects in mind.
Reply
- Sara Santos
  
  July 13, 2020 at 10:18 am
  
  That’s great!
  Regards,
  Sara
  Reply
hector lozano

September 25, 2020 at 1:53 am

hi Sara
I´m doing test with esp-now.
Do you have the code for two ways comunication?
Is it too different to the one way comunication code?

regrats and thanks!
Reply
- Sara Santos
  
  September 25, 2020 at 9:14 am
  
  Hi.
  There isn’t much difference.
  You can see it in this tutorial: https://randomnerdtutorials.com/esp-now-two-way-communication-esp32/
  Regards,
  Sara
  Reply
van

November 17, 2020 at 8:23 am

hello thanks for the tuto
i have a question
what about recieving and sending data from multiple esp boards at the same time? i couldnt found the example!
Reply
- Sara Santos
  
  November 17, 2020 at 4:04 pm
  
  Hi.
  Hi.
  If you want to send a receive to and from all boards, you can use this example:
  https://randomnerdtutorials.com/esp-now-two-way-communication-esp32/
  And use the FF broadcast MAC address.
  Regards,
  Sara
  Reply
  - van
    
    November 18, 2020 at 8:31 am
    
    hi
    yes i want to send and recieve from multiple boards, but they are connected in series not randomly.
    i.e. each board will send to only one board and recieve from only one board
    for example 5 boards:
    board 1 send to B2
    B2 recieve from B1 and send to B3
    B3 recieve from B2 and send to B4
    B4 recieve from B3 and send to B5
    can i do this with esp-now?
    thanks in advance
    Reply
    - Sara Santos
      
      November 18, 2020 at 11:09 am
      
      Hi.
      Yes.
      You just need to specify to which board you want to send the message.
      You also need to specify that you want to send the received message to the other board.
      Regards,
      Sara
      Reply
Stefan

December 19, 2020 at 10:39 am

Hi Sara and Rui,

i just discovered a ESP-NOW-Wrapper-library published by user yoursunny on GitHUB. It makes using ESP-NOW much more easier because all the details
about add-peer etc. are encapsulated inside the library
here is the link
https://github.com/yoursunny/WifiEspNow

I tested the EspNowBroadcast.ino example and it worked right away.
You just upload this example-code into EVERY ESP-device that shall be part of a ESP-NOW-mesh and press the onboard nodeMCU-button to retrieve the mac-adresses of each device that has the code EspNowBroadcast.ino running.

best regards Stefan
Reply
- Sara Santos
  
  December 19, 2020 at 12:10 pm
  
  Thanks for sharing.
  Regards,
  Sara
  Reply
john Kneen

January 6, 2021 at 9:03 pm

Hi – Great Tutorials

I have tried the tutorial with an ESP8266 in Wemos D1 boards.

Unfortunately I’m getting the failure message probably 60% of the time. In the example code communication is every 2 seconds. In my implementation sometimes there are two successful messages in a row but often there are several fails in a row. Often up to five. Thinking there may be conflict with neighbours WiFi my PC etc I added code to turn the LED on/off around the call back function and moved to an open sports field. I didn’t perceive any change in performance – sometimes the LED flashed every 2 seconds but often the delay was longer.

In terms of communication distance it seemed to communicate up to 100 metres. (I made no attempt to align the antennas)

For my project 100m communication and updates every 10 seconds will be OK but if it was going to be a commercial product I’m certainly at the limits.

If anyone has any ideas I’d appreciate it

All the best for 2021

John K
Reply
- Mitch Olson
  
  January 6, 2021 at 9:16 pm
  
  Hi John, a 2 second interval is quite tight. 10 seconds is what I use in testing. I initialize WiFi and ESP NOW at start up, read sensor, transmit, then shut down WiFi/ESP NOW BEFORE!! going into sleep mode. In final product, I read once / three hours. Here is what I’ve built. septicspy.com
  Reply
  - john Kneen
    
    January 7, 2021 at 9:57 pm
    
    Hi Mitch
    
    What an interesting project you have.
    
    In my project initially I used exactly the same code as in the Tutorial with a send every 2 seconds. -I have different Hardware -a WEMOS D1 ESP8266 Board.
    
    With this set up approximately 2 of every 3 messages at the sender was a failure message. I did try times longer than 2 seconds but did not perceive any difference.
    
    Cheers
    
    John K
    Reply
- john Kneen
  
  January 21, 2021 at 3:25 am
  
  A follow up to my previous comment.
  
  My settings were ‘tools–>Erase Flash–>Only Sketch’
  
  With “out of the box” ESP8266’s it worked perfectly. I tried it with an update rate of 50mS and there were no failures.
  
  As per my previous comment with old/pre-used ESP8266’s there was approximately 60% failure rate at 2 second updates.
  
  Changing settings to ‘tools–>Erase Flash–>Sketch + WiFi Settings’ I did not perceive any difference.
  
  However with the “old” ESP8266 and ‘tools–>Erase Flash–>All Flash Contents’ everything worked perfectly (tested down to 50mS update rate)
  
  The range appeared to be about 100m.
  
  I hope this helps someone else.
  
  John K
  Reply
  - Stefan Ludwig
    
    January 21, 2021 at 2:48 pm
    
    Does your code have calls of function delay()? Delay() is blocking (almost everything)
    
    Then this is the reason why receiving fails. As long a s a delay() is executed on the receiverside the microcontroller is unable to receive ESP-NOW-messages
    For receiving ESP-NOW-messages all timing must be done without delay()
    
    With NON-blocking code I was able to switch an IO-pin ON/OFF through sending ESP-NOW-messages where each message
    sets the IO-pin HIGH next one LOW next one HIGH etc. without any flaws up to a frequency of 500Hz = 2 milliseconds.
    It was possible to do it even faster but with some timing-errors. Which means all pulses where still received but with glitches at every 10 to 20 message.
    
    best regards Stefan
    Reply
    - john Kneen
      
      January 22, 2021 at 11:17 am
      
      Hi Stefan
      
      I was testing exactly the same code as supplied in the tutorials. With previously used ESP8266 chips and the Arduino IDE set to “Erase Only Sketch” I had a 60% failure rate with a 2 second update (as per original code).
      
      Using un-used ESP8266s there were NO failures. Also using the ESP8266s that gave the 60% failure rate but changing the Arduino IDE to “Erase ALL Flash Contents” eliminated all the failures.
      
      Now either set of chips would give 100% pass rate at 50mS update. I didn’t try to go any faster but I suspect the println( ) statements may then be the limiting feature in the code – not the ESP8266s.
      
      With regard to using delay( ) functions – I never use them – neither do Rui or Shara – as it is a blocking operation. Further delay( ) or millis() will not work in Interrupt Service Routines or Callbacks which are the heart of the ESP8266-NOW example.
      
      Thanks for your support
      
      John K.
      Reply
lur

January 8, 2021 at 1:31 pm

Hi I have question to ask. is it possible to transfer data from connected esp32 with bno055 to another esp32 using esp now?
Reply
- Sara Santos
  
  January 9, 2021 at 11:15 am
  
  Hi.
  Yes. You just need to include the sensor readings in the structure.
  Regards,
  Sara
  Reply
John

January 12, 2021 at 4:04 am

U need to set the arduino ide settings to clear out the sketch “and” the old wifi settings when you upload. I’m not at my pc atm so I can’t recall what the proper terminology is.
Reply
John

January 12, 2021 at 7:27 pm

U need to set the arduino ide settings to clear out the sketch “and” the old wifi settings when you upload. I’m not at my pc atm so I can’t recall what the proper terminology is. This is for response to all who are getting, some but not all, message failures. The esp8266 still has the old wifi settings. This fixed my problems, 0 failures even sending at 50ms intervals.
Reply
kimmusu

March 11, 2021 at 12:53 pm

When I connect ESP32 (2 units) to 1 computer, the port is impulsive and only 1 ESP is recognized.
Is there any way to connect 2 ESPs to 1 computer?
Reply
Jack Li Sunkarim

March 19, 2021 at 8:30 am

Hi, thanks for your tutorial. I tried your tutorial and yes, it’s perfectly working. I got about 500m in open area, by using internal antenna. Better than i expected. I think the range can be improve using external antenna.
Reply
Barrois

April 20, 2021 at 2:11 pm

Hello Sara and Rui,
I am doing esp-now between an esp32 and an esp8266 and everything is fine except that it is not possible to drive a relay or even the LED_BUILTIN led.
I manage to control a Pan-Tilt with a PCA9685, but impossible to put digitalWrite (D0, HIGH);
Do you have an explanation?
Thank you
Reply
Jack Li Sunkarim

April 21, 2021 at 6:16 pm

i dont think it’s possible. Its because both of your esp using the same driver as well as using a single COM PORT.
Reply
Luke Atkin

August 14, 2021 at 6:48 am

So this seems to be the solution I need but I am a complete noob and need help!

I need to use two esp01 to create a transmit and receive bridge via serial

Th commands are sent as lines back and forth for example “N1 G30 Y120”

Does anyone know how to configure esp now that when it sees on the receive serial it pushes it raw out to the tx on the other esp and vice versa to create the two way link?

I am at a loss using the two way communication.INO as I do not know what to change in the sensor data example
Reply
- Sara Santos
  
  August 15, 2021 at 10:50 am
  
  Hi Luke.
  This tutorial uses ESP-NOW, not serial communication.
  Unfortunately, at the moment, we don’t have any tutorials about serial communication.
  However, if you want to establish a two-way communication between two ESP-01 boards using ESP-NOW, this is the tutorial that you should follow: https://randomnerdtutorials.com/esp-now-two-way-communication-esp8266-nodemcu/
  I hope this helps.
  Regards,
  Sara
  Reply
Joseph

September 2, 2021 at 3:15 pm

Hello Sara and Rui,

I’m trying to use OTA which requires me to setup the esp32 as a wifi station. However, I’m hosting an asyncwebserver as well as using ESP Now. It seems that some conflict is happening as ESP Now is no longer working properly when I added the OTA. Are they compatible? Do you have a tutorial where you use all three features?

Thank you!

Best regards,
Joseph
Reply
- Sara Santos
  
  September 3, 2021 at 10:13 am
  
  Hi Joseph.
  It is a bit tricky to use Wi-Fi and ESP-NOW simultaneously. See this tutorial: https://randomnerdtutorials.com/esp32-esp-now-wi-fi-web-server/
  However, I never tried using it with OTA.
  I’m sorry that I can’t help much.
  Regards,
  Sara
  Reply
  - Joseph Chalfoun
    
    September 3, 2021 at 11:21 pm
    
    I was able to fix my issue, I had to change the Wifi mode to WIFI_AP_STA
    Reply
    - Sara Santos
      
      September 4, 2021 at 10:25 am
      
      Great!
      I’m glad you found the issue.
      Regards,
      Sara
      Reply
Jay

September 3, 2021 at 10:40 am

Hi Sara,
I am trying to adapt this code for u8g2 oled display and having problems.
Can you please adapt this code got this display?
//regards,jay
Reply
Jesio Costa

September 4, 2021 at 6:58 pm

Olá, até quantas placas eu posso utilizar ao mesmo tempo? Nao entendi muito bem a questão dos limites dos pares.

Att
Reply
- Sara Santos
  
  September 6, 2021 at 9:16 am
  
  Hi.
  This is what is mentioned in the documentation:
  “Limited encrypted peers. 10 encrypted peers at the most are supported in Station mode; 6 at the most in SoftAP or SoftAP + Station mode;
  Multiple unencrypted peers are supported, however, their total number should be less than 20, including encrypted peers;”
  Regards,
  Sara
  Reply
Alex UK

September 6, 2021 at 10:56 am

Hi Ruis and Sara
Thank you for an excellent tutorial, afraid I’m having an issue and wondered if you could assist? Yesterday (5 Sept 21) this worked just fine on my two ESP32 Node MCU boards, they were talking to each other fine and I moved on to modify the ‘content’ of the messages. However at some point the code stopped working, and I’m getting on the Sender serial monitor the message ‘failed to find peer’. I have reverted right back to the original code on this page, rechecked the MAC address of receiver (which I haven’t changed), and started again from scratch but it doesn’t work any more. The one thing I did notice is that the IDE may have updated the ESP NOW library…is it possible that the code will now not function correctly? Expect if that is the case then other users would find the same issue…could you advise (might also allow you to tweak code on here if needed)? Very grateful for your help, thanks. Alex
Reply
- Sara Santos
  
  September 7, 2021 at 10:05 am
  
  Hi.
  That0s weird.
  Try to send the packet to the following mac Address:
  uint8_t broadcastAddress[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
  See if you get the same results.
  Always double-check that both boards are actually running the code. After uploading press the RST button.
  Regards,
  Sara
  Reply
  - Alex UK
    
    September 13, 2021 at 2:52 pm
    
    Hi Sara, and sorry I didn’t see your reply before, I set up notifications but despite best efforts it went to junkmail…
    See below second post which seems to have cleared it, from a previous similar fix you posted (thanks!) but I will file this solution away for future reference! Thanks so much for your help.
    Kind regards,
    Alex
    Reply
    - Sara Santos
      
      September 14, 2021 at 10:42 am
      
      Great!
      Thanks for the follow-up.
      Regards,
      Sara
      Reply
Alex Uk

September 6, 2021 at 1:52 pm

Hi Ruis and Sara
Following my earlier query today, I looked back over your responses to similar issues in the 2 way comms page, from a couple years ago, and mimicked the same solution for this issue. It seems to have resolved it, though I don’t know why! THis was the solution you wrote in case any one else can also apply it to same issue:

“Hi Leo.
I saw something in a portuguese blog about this issue. I’m not sure if it work, but we can try.
It suggests that we cut this line from the setup()

esp_now_peer_info_t peerInfo;
And past it before the loop() and before the setup().”

Many thanks

Alex
Reply
- John Kneen
  
  September 7, 2021 at 9:59 pm
  
  I personally would never expect a compiler to extract the definition of an instance/object from inside any method/function. My opinion is that it should be placed before any code. That is:
  
  #include ….any library files
  esp_now_peer_info_t peerInfo; //create an instance/object of type esp_now..
  //declare other global variables
  void setup( ) { }
  void loop( ){ }
  
  One other point – if the object does not have any arguments leave out the brackets as in this example. With the brackets, but no argument(s) the compiler will treat the object as a method/function and then (I seem to recall) the program “worked” but not as expected and it took me a long time to discover my problem.
  Stay safe
  JK
  Reply
  - Alex Instrell
    
    September 13, 2021 at 2:45 pm
    
    Thanks John, have made a note as even though the issue has gone away for now, it may well rear its head again. Much obliged.
    Alex
    Reply
Luis

September 17, 2021 at 12:59 pm

Hello,
its possible the master publish the data recived from the slave in a mysql database?

Best Regards,
Luis
Reply
- Sara Santos
  
  September 17, 2021 at 2:06 pm
  
  Yes.
  It can do other tasks.
  So, it is probably ok to send data to database.
  Regards,
  Sara
  Reply
Ibrahim Muala

September 28, 2021 at 7:13 am

Hello,

Is there any way to retransmit data with some deay if it fails inside onDataRecv(…)?

Thanks
Reply
- Sara Santos
  
  September 28, 2021 at 10:46 am
  
  Hi.
  You need to check that if the data is not received, send it again.
  You’ll need to add some conditions to your code.
  Regards,
  Sara
  Reply
  - Ibrahim Muala
    
    September 28, 2021 at 12:11 pm
    
    Thanks for replay,
    
    Can I do some millis delay inside onDataSent(…)?
    Reply
Thomas

October 11, 2021 at 7:54 am

I learned something new today. Thank you. Given I’m conceptualising a low power sensor solution this may come in handy as Wifi is very “power hungry”. However if this was an ESP-NOW solution I sell, every sender and receiver would have to be configured manually as part of uploading the firmware as I need to specify the MAC address of the other board, right? Is there a way around this; e.g. generating a virtual MAC address etc.
Reply
- Sara Santos
  
  October 11, 2021 at 10:18 am
  
  Hi.
  You can try to use a Wi-Fi sniffer to get the MAC address of nearby Wi-Fi devices.
  Then, you can modify your code to allow you to select the right MAC address using some kind of interface.
  Regards,
  Sara
  Reply
SJFA

October 21, 2021 at 5:50 am

Hi everyone, Congratulations on your work,
Without doubt the best site for examples, Great tutorials.

I tested ESP NOW it’s very impressive.
I’m thinking about putting several Esp32 and Esp8266 in my house,
To control windows, lighting, temperature sensors, automatic door etc…
But,
Is it okay to use several Esp-Now indoors?
Will not interfere with the Wifi network?
Is it safe for health to have lots of Esp-Now indoors?
Thanks
Reply
Frank ten Wolde

December 8, 2021 at 8:22 pm

I got an “E (120) ESPNOW: Peer interface is invalid” due to the fact that the peerInfo
struct contains junk data. Please add ‘memset(&peerInfo, 0, sizeof(peerInfo));’ to initialize
peerInfo to zeroes:

// Register peer
esp_now_peer_info_t peerInfo;
memset(&peerInfo, 0, sizeof(peerInfo));

memcpy(peerInfo.peer_addr, broadcastAddress, 6);
peerInfo.channel = 0;
peerInfo.encrypt = false;

OR:

esp_now_peer_info_t peerInfo = {};

memcpy(peerInfo.peer_addr, broadcastAddress, 6);
peerInfo.channel = 0;
peerInfo.encrypt = false;

Thanks!
Reply
RandM

December 30, 2021 at 9:10 pm

Hello and thank you for such great documentation for the ESP32/8266

I do keep running into a problem though. I have copied both the send and the receive code from this website to trial.

The send code works with no issue printing to serial “error sending the data”. I however, have not been able to get the Receive code to work. I have tried 2 different boards and even different USB cords yet it will not register or even print to serial. Any suggestions as to what I am doing wrong as I would love to use this product???
Reply
- Sara Santos
  
  December 30, 2021 at 10:22 pm
  
  Hi.
  Do you get any errors when trying to upload?
  Reply
  - RandM
    
    February 7, 2022 at 10:42 pm
    
    Hey Sara, i wanted to update you on my progress since you were kind enough to actually respond to me. It seems the version of Arduino that i was using had some files stashed in places that as causing problems. I had to totally erase all Arduino files on my c:drive and reinstall the program and it has worked with no issue. I’m not sure exactly what file it was but this is what will as needed to get your examples to work.
    Reply
    - Sara Santos
      
      February 8, 2022 at 11:14 am
      
      Great!
      I’m glad everything is working now.
      Regards,
      Sara
      Reply
RandM

December 31, 2021 at 4:48 pm

There is no code showing up for the Rx unit and the Tx unit is saying “error sending the data. If i press the reset button on the Rx unit it prints

” rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:2
load:0x3fff0030,len:1324
ho 0 tail 12 room 4
load:0x40078000,len:13480
ho 0 tail 12 room 4
load:0x40080400,len:3604
entry 0x400805f0″
Reply
RandM

February 7, 2022 at 11:00 pm

I’m wondering if there is any way using ESPNOW that I would be able to turn on an LED when there is a loss in peer connection between 2 ESP32s? I’ve been looking for a function or variable that will work but have yet to find something that will work.

Thanks in advance

R
Reply
- Sara Santos
  
  February 8, 2022 at 11:20 am
  
  Hi.
  I don’t know exactly, but you can check the ESP-NOW documentation here: https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/network/esp_now.html
  And see if any of the available functions are suitable for what you want to do.
  Regards,
  Sara
  Reply
sahan

March 10, 2022 at 3:40 pm

Hi,

Thanks for your Great tutorials.

Query about the ESP NOW protocol.
I have one sender and receiver, i am able to send and receive data. I am using an encoder, say it transmits either clockwise or anticlockwise. If i rotate once in clockwise , i am receiving continuously state changes.
what i require is that it should send data only when the encoder changes the state, otherwise it should not send any data.But the connection should not be affected.
I hope you understand.

Thanks
Sahan
Reply
Shashi

April 6, 2022 at 12:16 pm

I don’t find the library link to the header file esp_now.h

Is it changed to WiFiEspNow ??

I googled and there is a WiFiEspNow library.
Would appreciate if you could revert.
Reply
- Sara Santos
  
  April 6, 2022 at 12:36 pm
  
  Hi.
  You don’t need to install any libraries.
  The esp_now.h library is automatically installed with the ESP32 boards.
  If you’re using an ESP8266,you should use this tutorial instead: https://randomnerdtutorials.com/esp-now-esp8266-nodemcu-arduino-ide/
  Regards,
  Sara
  Reply
--- MACE ---

April 17, 2022 at 3:52 pm

Great tutorials. They’ve allowed me to complete a prototype a project that I’ve had in mind for a couple of years.
Reply
Bill McLean

July 2, 2022 at 7:03 pm

Hi Sara,

Thank you for all of these tutorials, they really help.
I do have one thing I can’t quite understand though and I was hoping that you could point me in the right direction, and that is “esp_now.h”, I can’t find this library anywhere, I’ve been through the esp now tutorials here, tutorials on other websites, the arduino ide etc, still nothing.
I seem to be missing something really obvious as it doesn’t seem to be an issue for anyone else, admittedly I’m still waiting for my boards to arrive (hopefully within the next week or so), but if you know this off the top of your head I’d love to hear the answer.

Best regards
Bill
Reply
- Sara Santos
  
  July 4, 2022 at 1:47 pm
  
  Hi.
  The espnow.h library comes by default with the ES8266 package for the Arduino IDE.
  For the ESP32, it is esp_now.h.
  
  You don’t need to install those libraries. They are installed automatically when you install the ESP32 or ESP8266 on Arduino IDE.
  Make sure you have an ESP32 or EPS8266 board selected in Tools > Board when compiling the code.
  
  Regards,
  Sara
  
  Regards,
  Sara
  Reply
Bill McLean

July 2, 2022 at 7:10 pm

Oops,

I just saw your answer to Shashi, problem solved.

Many thanks Sara

Bill
Reply
Angel

July 16, 2022 at 5:02 am

Hi Sara, can you help me on a project collecting CSI by ESP32. I can collect csi data ,but i can’t visualize the waveforms.
Reply
John

July 25, 2022 at 10:59 am

Hi Sara, Great tutorial and clear explanations! I was using an ESP32-WROOM-32D as a sender and D1 Mini ESP8266 ESP-12F as receivers. All worked perfectly, until I tried to use ESP32-WROOM-32 as sender. The sender is told to send data from a pin interrupt routine and it fails to send. I am using arduino IDE, board is ESP32 DEV Module. Again code works flawlessly with 32D and not plain 32. As I have several ESP32’s and do not have additional 32D’s it would be great to use my stock of 32’s Thanks in advance John
Reply
Serge

August 2, 2022 at 5:34 pm

Hi ,

Thank’s for this great tutorial.
I hope you can help me for a project.
i need to send RS485 data from one point to an other wireless.
i want RS485 to UART modul > ESP32 > datas over the air > ESP32 > UART to RS485 modul.
is it possible ? (need 115200bauds)
Reply
- Sara Santos
  
  August 2, 2022 at 5:42 pm
  
  Hi.
  I never tried it, but yes. I think it should be possible.
  Unfortunately, we don’t have any tutorials covering that exact subject.
  Regards,
  Sara
  Reply
John

August 6, 2022 at 4:03 pm

Hi Sara, I have followed and learned a lot from your tutorials. The things that are working for me from your tutorials are as follows:espnow esp32-wroom-32 to esp32-wroom one way comm, esp32wroom to esp8266-12E one way comm. My issue is to get esp32wroom to wemos esp8266 D1 mini one way comm. Depending on the physical wemos boards data gets sent successfully, fails, or intermittently fails. I am using Arduino IDE board ESP32 Dev Module and Lolin (wemos) D1 mini clone. Are there any known issues with this combo? Having 24 of these boards to use in a model railroading project has me looking for an answer. btw I believe the sent data success comes back, however delivery is unsuccessful. 🙁 I can supply code, however it works 100% on one of the boards and other boards are around 20-70% intermittently. makes no sense…
Reply
- Sara Santos
  
  August 8, 2022 at 9:21 am
  
  Hi John.
  
  I’m not sure, but I think it might be an issue related to the D1 mini boards.
  I had other readers complaining about the same issue on those boards.
  However, I never try them….
  So, I suggest replacing the boards and seeing if you get better results.
  
  Regards,
  Sara
  Reply
  - John
    
    August 8, 2022 at 7:10 pm
    
    Hi Sara,
    Yes out of 24 D1 boards 8 are defective. I send data at a fast pace delay=20 and see either constant success or on the faulty boards intermittent failures. Putting my finger on the antenna area of the D1 board and putting pressure on it the results are almost all success… So the boards are the problem. Thanks for the advice.
    Reply
  - Diogo Cunha
    
    March 3, 2023 at 4:17 am
    
    Hey Sara and folks!
    First of all, you web page rocks, Sara! Congrats.
    I’ve just solved the issue about ESP32 Esp d1 mini. It’s about PHY mode (physical layer).
    
    For some reason, mainly ESP32-WROOM-32D (ESP32-DOWD-V3 or higher) has a different physical rate by default. That causes trouble when ESP32 send data to ESP8266EX because this board can’t receive due to the radio frequency.
    
    That’s the solution:
    On ESP32 firmware you have to declare on main function:
    WiFi.mode(WIFI_AP_STA);
    esp_wifi_start();
    esp_now_init();
    esp_wifi_config_espnow_rate(WIFI_IF_STA, WIFI_PHY_RATE_54M);
    
    No extra libs it is necessary! ASAP I will post the example code, including a DEBUG testing, on my GitHub and share with you all.
    
    ESP-IDF from espressif helps me a lot – https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/network/esp_wifi.html#_CPPv415wifi_phy_rate_t.
    
    I hope this trick can help lots of people 🙂
    Reply
    - Sara Santos
      
      March 3, 2023 at 12:38 pm
      
      Hi.
      Thank you so much for sharing this. It is indeed very useful.
      I had no idea of how to sort it out.
      Thank you.
      Regards,
      Sara
      Reply
Christian

August 23, 2022 at 10:08 pm

Thank you so so much
Your tutorials are the best
Reply
- Sara Santos
  
  August 24, 2022 at 10:25 pm
  
  Thank you 😀
  Reply
David B

September 11, 2022 at 8:39 pm

Greetings,
I really like your website and you have a lot of great info on the ESP32.

Trying to setup a sender and receiver based on the codes above and I am having problems with inserting the MAC address:

// REPLACE WITH YOUR RECEIVER MAC Address
uint8_t broadcastAddress[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};

I get errors like the one below.

error: invalid digit “8” in octal constant

It seems to not like the MAC Address I type in.

Any thoughts on what I am doing wrong?

Regards David B
Reply
- Sara Santos
  
  September 12, 2022 at 5:26 pm
  
  Hi.
  Can you show me the line with your MAC address?
  Regards,
  Sara
  Reply
  - David B
    
    September 12, 2022 at 6:56 pm
    
    Thank you for the reply. I actually figured out the issue. I had incorrectly typed in the MAC address. Did not realize I needed to type in the 0x in front of each character.
    Reply
    - Sara Santos
      
      September 13, 2022 at 1:22 pm
      
      Great!
      I was suspecting that was the issue.
      Regards,
      Sara
      Reply
James A

September 17, 2022 at 7:07 am

awesome lessons all around!!!!
thanks for sharing

i have AI Thinker and WEMOS D1 MINI – everything seems to be working fine for now but i want to revise the project to send partial structure data
i am trying ESP_NOW Combo on both units
for example:
myData.a
myData.b
myData.c
myData.d

i want to send only ‘myData.a, .b, & .c’ from AI thinker to WEMOS
and only send ‘myData.d’ from WEMOS to AI Thinker

is that possible and do you have a lesson on how or point me in right direction, please???
Reply
Tex

September 18, 2022 at 3:59 am

Thanx Sara & Rui for great tutorial,
Can u explain how to send image data using espnow.
Reply
Renzo

September 18, 2022 at 9:55 am

Hi Sara,
I want to send data from several sensors,in a range of about 10 meters, ie temp, garage door etc to a central receiver and to show data on a display.
It is possible with ESPnow?
Regards
Renzo
Reply
- Sara Santos
  
  September 19, 2022 at 12:09 pm
  
  Yes.
  ESP-NOW is suitable for what you want to do.
  Regards,
  Sara
  Reply
Vyas

November 11, 2022 at 3:26 pm

Hi, I just have a couple of doubts
Can ESP NOW and MQTT be implemented at the same time (of course with different boards) and can esp now be used to send command from master to slave board to turn something off or on?
Thanks in advance
Reply
- Sara Santos
  
  November 11, 2022 at 5:42 pm
  
  Yes. That is possible.
  Reply
Mike Walton

November 19, 2022 at 1:36 pm

I am using ESP Now to send a temperature reading every 4 minutes to the receiver. Is there a way to configure the receiver to flag if it hasn’t received a reading for say 10 minutes?
Reply
hary

December 4, 2022 at 9:53 pm

So unfortunate that I am seeing this website now. I have been struggling with how to transmit MPU6050 accelerometer data using espnow. Sara, could you give some inputs on this?
Reply
- Sara Santos
  
  December 4, 2022 at 11:46 pm
  
  Hi.
  Try to combine this tutorial with this one: https://randomnerdtutorials.com/esp32-mpu-6050-accelerometer-gyroscope-arduino/
  Regards,
  Sara
  Reply
  - hary
    
    December 5, 2022 at 12:24 am
    
    Thanks Sara. I have figured it out.
    How do I calculate the time or delay between when a data is send and when received. If possible how can I improve on the delay.
    Reply
Terry

January 7, 2023 at 3:53 am

Just as a learning curve…I am reading that using integer is not best practice because the same code compiled of a 32 bit machine vs a 64 bit machine can cause issues. I have been converting my code from “int” to “uint8_t” so far so good.
When it comes to this line…void OnDataRecv(const uint8_t * mac, const uint8_t *incomingData, int len)
I coverted all my code and had an error with the “uint8_t” seems it has to be a zero.
The people who write the ESP library are much better than myself, so I was wondering why they reverted back to an “int”…yet the internet is full of things like..don’t use strings and dont use int.
TIA
Reply
- Terry
  
  January 7, 2023 at 3:55 am
  
  typo..void OnDataRecv(const uint8_t * mac, const uint8_t *incomingData, int len)
  “Seems the “int len” has to be an “int” and fails if a “uint8_t” is used
  Reply
Paolo Bernardelli

January 17, 2023 at 9:24 pm

First of all, congratulations on a job well done!
Are there any examples that allow the extension of the wifi network (esp_now)? I very simply have to insert one or more esp32 “repeters” between master and slave to try to overcome physical obstacles (walls or whatever).
Thanks anyway and congratulations again
Reply
Thierry

January 28, 2023 at 11:10 am

Bonjour
J’utilise 2 esp32 avec le protocole ESPNOW, cela fonctionne bien
, mais au delà de 5mètres à l’intérieur, plus de transfert de données.
Dois je utiliser des ESP avec antenne?
Merci et surtout félicitations pour votre travail….une véritable source d’informations
Reply
Howard

February 10, 2023 at 5:09 pm

Sara and team
Great tutorial as usual. I have been trying to send 2 different structs from the same module to a single second module. Google was not helpful, but this worked.
Sender:
typedef struct relay_message {
int message; //set to 0 for relay
int relay_num;
bool on_off;
};
// Create a struct_message called myRelayData
relay_message myRelayData;

//seperate struct for on/off
typedef struct onoff_message {
int message; //set to 1 for onOff
int valve_num;
int on_hour;
int on_minute;
int duration;
};
// Create a struct_message called myData
onoff_message onOffData;

Then have 2 routines to send the data, these are the same as yours, one for each struct.

Receiver:
Define the structs as above, then add
int messageType;
Here is the clever bit (well not that clever)
// callback function that will be executed when data is received
void OnDataRecv(const uint8_t * mac, const uint8_t *incomingData, int len) {
memcpy(&messageType, incomingData, sizeof(messageType));
switch (messageType) {
case 0: //relay on off
memcpy(&myRelayData, incomingData, sizeof(myRelayData));
doSomthingWithRelayData (myRelayData);
break;
case 1: //set time on and duration
memcpy(&onOffData, incomingData, sizeof(onOffData));
doSomthingWithOnOffData (onOffData);
break;
}
}

Feel free to use if of any interest.
Reply
- Sara Santos
  
  February 11, 2023 at 8:27 am
  
  Thanks for sharing.
  Reply
Otto Klaasen

February 17, 2023 at 7:56 pm

Hi Sara and Rui,
great instruction, i had it working in 30 minutes, nice.
I just tried it for fun, probaly I can use it in future projects.
Kind Regards
Otto
Reply
Nando

February 18, 2023 at 2:47 pm

Hi there, is force pressure sensor 602 compatible with esp now? because I seem to not to be able to have the readings of the sensor working correctly as I insert the codes for esp now. Meanwhile without the esp now codes the sensor is working fine. Kindly help me with this, thank you!
Reply
- Sara Santos
  
  February 20, 2023 at 9:41 am
  
  Hi.
  That might be related to the way you’re saving your pressure values, i.e. the variable type.
  Regards,
  Sara
  Reply
  - Nando
    
    February 21, 2023 at 8:23 am
    
    Hi, I have tried possible variable types but did not work and I found out that as I type in the WiFi.mode(WIFI_STA); into the void setup, it began to malfunctioning the pressure sensor.
    
    Do you have any idea on what is happening?
    
    Here is my codes:
    
    #include <SPI.h>
    #include <MFRC522.h>
    #include <esp_now.h>
    #include <WiFi.h>
    
    #define fsrpin 14
    #define SS_PIN 5
    #define RST_PIN 22
    
    MFRC522 mfrc522(SS_PIN, RST_PIN);
    byte validUid[] = {0x90, 0x6A, 0x6F, 0x20};
    
    double fsrreading;
    int car1;
    bool access1;
    
    uint8_t broadcastAddress[] = {0x08, 0xB6, 0x1F, 0x3D, 0x29, 0xF4};
    typedef struct struct_message {
    bool access1;
    int car1;
    } struct_message;
    struct_message myData;
    esp_now_peer_info_t peerInfo;
    
    void setup() {
    Serial.begin(115200);
    SPI.begin();
    mfrc522.PCD_Init();
    pinMode(fsrpin, INPUT);
    
    WiFi.mode(WIFI_STA);
    }
    
    void loop() {
    
    if (mfrc522.PICC_IsNewCardPresent() && mfrc522.PICC_ReadCardSerial()) {
    // Check if the UID of the card matches the valid UID
    if (memcmp(mfrc522.uid.uidByte, validUid, mfrc522.uid.size) == 0) {
    access1 = true;
    Serial.println(access1);
    delay(100);
    }
    // Halt PICC and stop encryption
    mfrc522.PICC_HaltA();
    mfrc522.PCD_StopCrypto1();
    }
    
    fsrreading = analogRead(fsrpin);
    if(fsrreading > 0){
    car1 = car1+1;
    }
    Serial.println(fsrreading);//*
    //Serial.print(“Reading = “);
    //Serial.println(fsrreading);
    delay(300);
    }
    Reply
    - Sara Santos
      
      February 21, 2023 at 11:16 pm
      
      Which GPIOs are you using to connect the sensor?
      Reply
      - Nando
        
        February 22, 2023 at 9:26 am
        
        Hi Sara, I managed to tackle it out by trying different GPIO pins and I guess ADC1 should be used instead of ADC2. However, Im not sure regarding the reason why it works like that. Btw, thank you for your help! Appreciate it.
        
        By any chance, do you know whether it is possible to run the esp32 cores parallelly but with an ability to overlap or cancel the occuring delay of an LED (say in the defaut void loop) with a condition form the second core.
        So, it will be like:
        In the void loop, the led1 is on, with a delay of lets say 5 sec. Then, in the loop2, as the MFRC522 granted an access, it will directly turn the led1 off, regardless of the delay of the led1 in vood loop condition.
      - Sara Santos
        
        February 23, 2023 at 10:20 am
        
        Hi.
        It’s because using ADC2 pins interferes with the Wi-Fi functions. That’s why I asked about the GPIOs you were using.
        
        Yes, that is possible. I think you need to use semaphores. But, I’m not very familiar with that subject.
        
        Regards,
        Sara
      - Nando
        
        February 26, 2023 at 1:23 am
        
        I see, thanks for the information. Oh, I heard of semaphores. No problem, I’ll try to learn it. Thanks a lot Sara!
Terry

February 21, 2023 at 11:10 am

Try formatting your code. That helps show things up. Add print statements to see what is going on
How can anyone debug your code for you, when there is only part of the code.
Reply
Nikolay Alexandrov

March 25, 2023 at 6:24 pm

Hello,
I have a problem with esp-now. The controllers only communicate if they are powered/all/ via the computer’s USB. If they are externally powered, for example from a battery… there is no communication. What could be the reason?
Reply
- John Kneen
  
  March 26, 2023 at 11:26 pm
  
  WiFi requires significant power – are your batteries powerful enough?
  I have several units set up around a model railway track and I am using voltage regulators from the track to generate the 5V for the ESP8266.
  Reply
- Donald Garber
  
  July 25, 2024 at 9:43 pm
  
  I spent many hours (well, some) trying to get one or the other sender/receiver board to work using a fresh 9volt battery. Didn’t work. They do seem to require electricity, either the usb to computer, or via AC outlet power. Unless there’s a more powerful type of portable battery to be used…
  Reply
- Eduardo Alvim
  
  July 26, 2024 at 4:44 am
  
  You can try with a 18650 Li-ion battery. Use a step-up converter for 5V and it should work
  Reply
yash gupta

April 10, 2023 at 7:33 am

unable to find esp_now.h library in arduino ide
Reply
- Sara Santos
  
  April 13, 2023 at 8:26 pm
  
  It’s installed by default with the ESP32 core on the Arduino IDE.
  Just make sure you have an ESP32 board selected in Tools > Board.
  Regards,
  Sara
  Reply
Greg007

May 5, 2023 at 10:22 am

Hi Sara ,

I’m confused by the memcpy command …

“memcpy(&myData, incomingData, sizeof(myData)); ”

Surely when the memcpy occurs – the myData is null and therefore doesn’t have any size – where as incomingData does have a size. So why aren’t you ( and Rui ) using sizeof(incomingData) ?

Thanks for being such valuable contributors to the ESP world.
Reply
jim snodgrass

May 16, 2023 at 11:33 pm

Hello Sara,
Great tutorials on ESP NOW. Thank You.
I have successfully completed a Sensor to Remote Receiver project that works great when the two TTGO- T-Display devices are relatively close together but the Sensor/Sender can’t quite reach the receiver reliably when it’s placed out in the garage of my house where I need it.

I understand that it’s possible to extend the ESP NOW range by reducing its Wifi data rate, and that by default it’s set to 54MBit, however if you can set it to the more robust 802.11n ( as many routers do dynamically) The data rate can be reduced to 2 or a 1Mbit rate and extended the range dramatically. Unfortunately I don’t know how to do this with the Arduino IDE 2.10, as it’s (I hear) possible to do with the ESP IDF.
so: Presently when I try with this :
// Set ESP32 as a Wi-Fi Station
WiFi.mode(WIFI_STA);

wifi_config_t wifi_config;
esp_wifi_get_config(WIFI_IF_STA, &wifi_config);
wifi_config.sta.listen_interval = 3;
wifi_config.sta.sort_method = WIFI_CONNECT_AP_BY_SIGNAL;
wifi_config.sta.threshold.rssi = -127;
wifi_config.sta.threshold.authmode = WIFI_AUTH_OPEN;
wifi_config.sta.pmf_cfg.capable = true;
wifi_config.sta.pmf_cfg.required = false;
wifi_config.sta.bssid_set = 0;
esp_wifi_set_config(WIFI_IF_STA, &wifi_config);

// Set the WiFi protocol to 802.11b for longer range
esp_wifi_set_protocol(ESP_IF_WIFI_STA, WIFI_PROTOCOL_11B);

I get:” Compilation error: cannot convert ‘esp_interface_t’ to ‘wifi_interface_t'” on this last line.

So my question is this: .. is there a way to use the Arduino IDE 2.10.x to extent the range of ESP NOW without having to use an external antenna .. or switching to use of the ESP IDF so I can switch to the more robust 802.11n protocol?
Thanks in Advance.. jimS
Reply
- Sara Santos
  
  May 17, 2023 at 10:04 pm
  
  Hi.
  I’m sorry, but I’m not familiar with those functions.
  Usually, you can use ESP IDF functions with the Arduino IDE. Try to check if you’re using the latest version of the ESP32 boards installation. Then, check that if you’re using the latest ESP IDF functions so that everything is compatible.
  Regards,
  Sara
  Reply
ashref

May 22, 2023 at 12:41 am

hey sarra,
I’m doing a flower recognition with edge impulse FOMO on esp32 cam.
the recognition is on the esp32cam and the output is on the serial monitor. with the help of esp_now and your tutorial, i wanna make it the server and send the data to another esp32 as a client to display the flower’s name in an LCD on the esp32. tell me if it is possible or not and can you please help me with the code ? this is the esp32cam code :

#define MAX_RESOLUTION_VGA 1

/**
* Run Edge Impulse FOMO model on the Esp32 camera
*/

// replace with the name of your library
#include <SCopt_inferencing.h>
#include “esp32cam.h”
#include “esp32cam/tinyml/edgeimpulse/FOMO.h”

using namespace Eloquent::Esp32cam;

Cam cam;
TinyML::EdgeImpulse::FOMO fomo;

void setup() {
Serial.begin(115200);
delay(3000);
Serial.println(“Init”);

cam.aithinker(); cam.highQuality(); cam.highestSaturation(); cam.vga();
while (!cam.begin()) Serial.println(cam.getErrorMessage());

}

void loop() {
if (!cam.capture()) {
Serial.println(cam.getErrorMessage());
delay(1000);
return;
}

// run FOMO model if (!fomo.detectObjects(cam)) { Serial.println(fomo.getErrorMessage()); delay(1000); return; }
// print found bounding boxes if (fomo.hasObjects()) { Serial.printf("Found %d objects in %d millis\n", fomo.count(), fomo.getExecutionTimeInMillis()); fomo.forEach([](size_t ix, ei_impulse_result_bounding_box_t bbox) { Serial.print(" > BBox of label "); Serial.print(bbox.label); Serial.print(" at ("); Serial.print(bbox.x); Serial.print(", "); Serial.print(bbox.y); Serial.print("), size "); Serial.print(bbox.width); Serial.print(" x "); Serial.print(bbox.height); Serial.println();
}); } else { Serial.println("No objects detected"); }

}
Reply
- Sara Santos
  
  May 22, 2023 at 8:42 pm
  
  Hi.
  I’m not familiar with that library. So, I’m not sure if it is compatible with ESP-NOW.
  In theory, I think you can combine both features.
  
  Regards,
  Sara
  Reply
ka

August 10, 2023 at 3:14 am

Hello
I want to ask is it possible to transmit messages with ESP32 NOW?
If it is possible to use the above program code directly?
Reply
Uli

January 1, 2024 at 9:27 pm

Hi,
thanks for this tutorial, I just tried this in platformio and ran into one little problem, the compiler was throwing an error on the receiver part and I had to change the OnDataRecv function like this to make it work:

void OnDataRecv(const esp_now_recv_info * mac, const unsigned char *incomingData, int len){
instead of
void OnDataRecv(const uint8_t * mac, const uint8_t *incomingData, int len) {

Uli
Reply
- Sara Santos
  
  January 2, 2024 at 10:33 am
  
  Hi.
  Thanks for sharing.
  Regards,
  Sara
  Reply
- Maksym
  
  January 23, 2024 at 10:55 am
  
  I just had same kind of problem. Has anyone found a solution to it?
  Reply
- Taylor
  
  February 9, 2024 at 8:47 pm
  
  Thank you very much for this, Uli! I was running into this same issue, and was surprised at how simple your solution is.
  Reply
Marco

January 6, 2024 at 1:17 pm

Hey Sara,
thanks for the great tutorial! Everything works great but there is one thing I don’t understand about the code:
the “esp_now_register_send_cb(OnDataSent)” function only gets called in the setup part of the program but in the serial monitor I get the delivery information in every loop. Is the esp_now_register_send_cb() automatically called when esp_now_send() is called? Thanks for your help!
All the best,
Marco
Reply
Gregg

February 3, 2024 at 4:28 am

Are there libraries that pack larger objects into the data, like breaking an image into 250-byte parts and sending each one until the entire image is transmitted? Of course, this would need a smart ACK, eg, some sort of ID per block so that retransmission of missed data is possible.

Basically, the lib would implement TCP using ESP-NOW, and compare all the outgoing blocks to incoming ACKs.
Reply
Norman

February 26, 2024 at 9:33 pm

Is there any way of broadcasting from a master board to unidentified slave(s), ie without a mac address for the slave?
Reason: I have 6 boards which could be swapped around at any time. Having to update mac addresses at each change is a (admittedly small) pain.

I guess I could list all boards and have the master run that through a loop until a reply is received. A bit hefty though.

Regards
Reply
- Sara Santos
  
  February 26, 2024 at 11:05 pm
  
  Hi.
  Use the following MAC address and all boards will receive the data:
  uint8_t broadcastAddress[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
  
  Regards,
  Sara
  Reply
  - Norman
    
    March 2, 2024 at 6:40 pm
    
    Thanks Sara,
    I should spend more time reading through your tutorials.
    Reply
  - Terry Nimmer
    
    April 16, 2024 at 3:16 pm
    
    I have implemented automatic MAC determination. Quite simply, I have messages that have a command field and data fields. By creating “WRU” (who are you) and “I Am” messages, the master can send a broadcast WRU and all my slaves will respond with I Am messages. Since the ESP Now messages contain the sending MAC, both ends can connect to each other. There is no need to through all the MAC printing and recompiling.
    
    Thanks for all your ESP32 tutorials.
    
    Terry
    Reply
    - Sara Santos
      
      April 17, 2024 at 8:39 am
      
      That’s a great idea.
      Thanks for sharing.
      Regards,
      Sara
      Reply
Madhuraman Dhungana

May 2, 2024 at 2:53 pm

i have faced a problem while sending i get an error of failed to peer and i am working on espidf in platformio using freertos library where i want to use one core for receiving data from another esp and the receiving esp also uses some additional sensor and send it to the web server via another core, can you use this library in espidf ?
Reply
Garry

June 2, 2024 at 2:47 am

Thanks for all your great resources. I found this example really helpful, however, this morning I now get a compilation error: invalid conversion from ‘void ()(const uint8_t, const uint8_t*, int)’ with esp_now_register_recv_cb.

The ESP32 library updated in my Arduino IDE this morning to v3.0.0 and it appears to be related to that.

There is a an issue lodged on the espressif GitHub here https://github.com/espressif/arduino-esp32/issues/9737. There is a response ‘Please use the new ESP NOW library and examples included in 3.0.0. The new version has many breaking changes https://github.com/espressif/arduino-esp32/tree/master/libraries%2FESP_NOW%2Fexamples‘

It looks like they have made significant changes to ESPNOW.
Reply
- Sara Santos
  
  June 2, 2024 at 10:18 am
  
  Hi.
  Yes. I know.
  We will update our projects to be compatible with 3.0 soon.
  Meanwhile, we recommend using version 2.x.
  Regards,
  Sara
  Reply
- Terry
  
  June 4, 2024 at 4:30 pm
  
  Same issue here. esp8266 randomnerd works
  esp32 randomnerd is now broken
  Reply
- Keith
  
  June 8, 2024 at 10:38 am
  
  In the reciever sketch change
  
  line 27:
  void OnDataRecv(const uint8_t * mac, const uint8_t *incomingData, int len)
  
  To
  
  void OnDataRecv(const esp_now_recv_info_t *info, const uint8_t *incomingData, int len)
  Reply
Kenneth

June 8, 2024 at 10:38 pm

Hello! The example receiver sketch is not compiling properly in Arduino IDE. here is the error:

Compilation error: invalid conversion from ‘void ()(const uint8_t, const uint8_t*, int)’ {aka ‘void ()(const unsigned char, const unsigned char*, int)’} to ‘esp_now_recv_cb_t’ {aka ‘void ()(const esp_now_recv_info, const unsigned char*, int)’} [-fpermissive]
Reply
Kenneth

June 8, 2024 at 10:39 pm

Oh… nvm, i see this has already been addressed.
Reply
Martin

June 12, 2024 at 2:27 pm

Your ESP32 Receiver Sketch will no longer compile on the Arduino IDE.
The esp_now.h file has recently been updated.
Your OnDataRecv() callback function needs to be changed to:
void OnDataRecv(const esp_now_recv_info_t * esp_now_info, const uint8_t *incomingData, int len) {
Reply
- Sara Santos
  
  June 13, 2024 at 9:12 am
  
  Hi.
  Our code was updated two days ago and it is now compatible with the latest ESP32 version installation. Version 3.
  Regards,
  Sara
  Reply
  - Martin
    
    June 15, 2024 at 5:06 pm
    
    I’m sorry, but confused. I still see the following code up above:
    void OnDataRecv(const uint8_t * mac …………………
    
    That code will not compile. The first argument is not a uint8 anymore but is a type esp_now_recv_info_t. Give it a try and see. The error will be in the line just before the loop function.
    
    Your new post: “Migrating from version 2.x to 3.0 ….) does not mention the changes to esp_now, nor does the link to the Expressif migration document. I find esp_now one of the most useful esp 32 functions.
    Reply
    - Sara Santos
      
      June 15, 2024 at 11:00 pm
      
      Hi.
      We do that in this line when assigning the callback function:
      esp_now_register_recv_cb(esp_now_recv_cb_t(OnDataRecv));
      
      The code is working with this modification on version 3.
      
      Regards,
      Sara
      Reply
Bruce

June 30, 2024 at 11:21 am

Hi there
I have got an esp8266 sending data to a cyd but how can I reset the data to 0 when there is no connection from the esp8266?
Reply
Nabil

August 6, 2024 at 6:14 pm

Hi Sara, I could not find esp_now library, could you share it…
Reply
- Sara Santos
  
  August 6, 2024 at 10:15 pm
  
  Hi.
  That library is included by default. You don’t need to install it.
  Just make sure you have an ESP32 board selected in Tools > Board before compiling the code.
  Regards,
  Sara
  Reply
Thomas

August 7, 2024 at 6:13 pm

hello, thanks a lot for the code examples, got me started on ESP NOW in no time.
is there any example on increasing the range of ESP NOW using the long range API ? I am currently getting only about 15mtrs between two nodes in LOS.
Reply
Edred

November 27, 2024 at 7:10 am

Hello, Sara! I am in dire need of help with my thesis project. I am making a Smart waste segregation system using machine learning, computer vision, and IoT. I am done with building the model/AI using edge impulse. I have an AI Thinker ESP32CAM and an ESP32-WROOM-DA, what I want is that the camera would forward/send the waste classified to the ESP32 Module as it controls the servomotors for the sorting process. I tried many times already using ESPNow, and WIFI, but no luck at all. Please help me! I have all the files needed. To be able to communicate with you through email would be great!
Reply
- Sara Santos
  
  November 27, 2024 at 11:04 am
  
  Hi.
  You have to be more specific with the kind of issue you’re getting with ESP-NOW.
  Regards,
  Sara
  Reply
Miguel

December 16, 2024 at 4:38 am

Hello Sara,

Thank you for your awesome tutorials and content!

I am desperate for some help with this project. I am trying to get this working on two Adafruit QT Py ESP32-C3 boards.

Originally I coded something similar to this myself using platformIO and my sender kept logging the “delivery fail” on the datasent callback function. I decided to copy the code exactly from your post into the arduino ide for both the sender and receiver, and the receiver is completely quiet while the sender keeps trying to send and showing “Delivery Fail”.

I then saw in one of the comments that you recommended someone putting “FF” in al the fields of the mac address so that the sender broadcasts to any board, and now the sender logs “Delivery Success”, but the receiver is still completely quiet. I suspect the “FF” mac address is not able to check for delivery receipts, so the delivery is not really successful.

Any clues for what could be going on??

I also tried to run the examples provided by the arduino IDE under ESP NOW->broadcast_master and broadcast_slave and the behavior is the same. The master keeps sending stuff but the slave never gets anything.

For context, I’m running these from two usb ports in my PC. Could power be a factor here? Not sure how to troubleshoot this. Pleeeease help!

Regards,

Miguel
Reply
- Sara Santos
  
  December 16, 2024 at 3:06 pm
  
  Hi.
  I don’t think it is an issue with power.
  Do you have any other ESP32 board models to experiment with? I never tried with a C3 board. I’m not sure if there are any tricks to make ESP-NOW work with that particular board.
  
  Regards,
  Sara
  Reply
Miguel

December 16, 2024 at 3:10 pm

Unfortunately I don’t. It is so strange that none of the tutorials I try are working. I was so excited to be able to use such a tiny board for my project 🙁
Reply
- Miguel
  
  December 16, 2024 at 3:11 pm
  
  Unfortunately I don’t. It is so strange that none of the tutorials I try are working. I was so excited to be able to use such a tiny board for my project 🙁 what’s the name of the board you guys use in your tutorial?
  Reply
  - Sara Santos
    
    December 16, 2024 at 9:19 pm
    
    Hi.
    We usually use the ESP32 DVKIT DOIT board, but most of the times most modules are compatible.
    I haven’t tested with that one yet.
    I recently received a C3 board, I have to try it out.
    Regards,
    Sara
    Reply
    - Miguel
      
      December 16, 2024 at 9:23 pm
      
      Great to know! I would really appreciate if you can reply to this post letting me know if the c3 worked for you and if you had to do anything special. Thanks again!
      Reply
Jack

December 22, 2024 at 9:13 am

Many thanks for the explanation of ESP NOW. I tried to send Hall sensor readings from an ESP32 to an ESP8266, but couldn’t succeed. Sending US measured distances goes very well, but Hall sensor readings end up in the value 0. (zero). Using ADC1 PINs also makes no difference. Can you help me out?
Reply
- Sara Santos
  
  December 22, 2024 at 10:54 am
  
  Hi.
  What sensor are you using?
  Regards,
  Sara
  Reply
Jack

December 22, 2024 at 11:07 am

Thank you for your quick response. I’m using the AZ-Delivery KY-035 lineaire
magnetische sensormodule. In fact 2 of them and I want to expand to 6. Reading the sensor works fine, but implementing the readings in an ESP NOW script returns a zero for the sensor reading. Sketch below.
#include <esp_now.h>
#include <WiFi.h>

const int hallSensorPin1 = 2; // Pin connected to the Hall sensor output
float sensorValue1 = 0;
const int hallSensorPin2 = 4; // Pin connected to the Hall sensor output
float sensorValue2 = 0;

float x = 0;
float y = 0;

// Struct voor dataoverdracht
typedef struct test_struct {
float x;
float y;
//int z;
//int a;
//int b;
//int c;
} test_struct;

test_struct test;

// MAC-adressen van de ontvangers
uint8_t broadcastAddresses[][6] = {
{ 0x4c, 0x75, 0x25, 0x2a, 0x59, 0xD8 }, // ESP8266
{ 0x58, 0xBF, 0x25, 0xDA, 0x8A, 0xDB }, // ESP8266
{ 0xA8, 0x42, 0xE3, 0x4D, 0x3D, 0x04 }, // D1 R32 ESP32 Dev Module
{ 0x88, 0x13, 0xBF, 0x69, 0xFA, 0xC4 } // ESP32 nr 4
};

esp_now_peer_info_t peerInfo;

// Callback bij het verzenden van data
void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
Serial.print(“Packet send status:\t”);
Serial.println(status == ESP_NOW_SEND_SUCCESS ? “Success” : “Fail”);
}

void setup() {
Serial.begin(115200);
// Stel alle Hall-sensoren in als input
pinMode(hallSensorPin1, INPUT);
pinMode(hallSensorPin2, INPUT);

// Start WiFi in station-modus
WiFi.mode(WIFI_STA);

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

esp_now_register_send_cb(OnDataSent);

// Voeg peers toe
for (int i = 0; i < sizeof(broadcastAddresses) / 6; i++) {
memcpy(peerInfo.peer_addr, broadcastAddresses[i], 6);
peerInfo.channel = 0;
peerInfo.encrypt = false;

if (esp_now_add_peer(&peerInfo) != ESP_OK) { Serial.print("Failed to add peer "); Serial.println(i + 1); }

}
}

void loop() {

getReadings();
// Vul de struct met de waarden
test.x = sensorValue1;
test.y = sensorValue2;

// Verstuur data via ESP-NOW
esp_err_t result = esp_now_send(0, (uint8_t *)&test, sizeof(test_struct));

if (result == ESP_OK) {
Serial.println(“Data verzonden met succes”);
} else {
Serial.println(“Fout bij verzenden van data”);
}

delay(500); // Wacht een halve seconde voor de volgende uitlezing
}

void getReadings() {
// Lees de status van alle Hall-sensoren
sensorValue1 = analogRead(hallSensorPin1); // Read analog value from Hall sensor
Serial.print(“Sensor1 value: “);
Serial.println(sensorValue1); // Output sensor value to Serial Monitor
//delay(10);
sensorValue2 = analogRead(hallSensorPin2); // Read analog value from Hall sensor
Serial.print(“Sensor2 value: “);
Serial.println(sensorValue2); // Output sensor value to Serial Monitor
//delay(10);
}
Reply
- Sara Santos
  
  December 22, 2024 at 2:40 pm
  
  Hi.
  The issue is probably because you’re using ADC2 pins to read analog signals.
  ADC2 pins cannot be used when Wi-Fi is used. So, if you’re using Wi-Fi and you’re having trouble getting the value from an ADC2 GPIO, you may consider using an ADC1 GPIO instead. That should solve your problem.
  Use for example: GPIO 33 and 32.
  More information here: https://randomnerdtutorials.com/esp32-pinout-reference-gpios/
  Regards,
  Sara
  Reply
Jack

December 22, 2024 at 3:04 pm

Thanks again. Using ADC1 pins makes no difference (see my first comment). In my first trials I used GPIO 33 and 32 and it makes no difference. I’ve studied the pinout reference intensively, looked on different sites and used even CHATGPT to check the program and come with improvements. No results, still having readings value 0.
Regards,
Jack Hoving
Reply

Getting Started with ESP-NOW (ESP32 with Arduino IDE)

Arduino IDE

Introducing ESP-NOW

ESP-NOW One-Way Communication

ESP-NOW Two-Way Communication

ESP32: Getting Board MAC Address

ESP-NOW One-way Point to Point Communication

ESP-NOW Useful Functions

ESP32 Sender Sketch (ESP-NOW)

How the code works

ESP32 Receiver Sketch (ESP-NOW)

How the code works

Testing ESP-NOW Communication

Wrapping Up

SMART HOME with Raspberry Pi, ESP32, ESP8266 [eBook]

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