In this article, we’ll show you how you can use ESP-NOW to exchange data between ESP8266 NodeMCU boards programmed with Arduino IDE. ESP-NOW is a connectionless communication protocol developed by Espressif that features short packet transmission and can be used with ESP8266 and ESP32 boards.
We have other tutorials about ESP-NOW with the ESP8266:
- ESP-NOW Two-Way Communication Between ESP8266 NodeMCU Boards
- ESP-NOW with ESP8266: Send Data to Multiple Boards (one-to-many)
- ESP-NOW with ESP8266: Receive Data from Multiple Boards (many-to-one)
Arduino IDE
We’ll program the ESP8266 NodeMCU board using Arduino IDE, so before proceeding with this tutorial you should have the ESP8266 add-on installed in your Arduino IDE. Follow the next guide:
Note: we have a similar guide for the ESP32: Getting Started with ESP-NOW (ESP32 with Arduino IDE).
Introducing ESP-NOW
The following video shows an introduction to ESP-NOW. This video was recorded for the ESP32, but most concepts also apply to the ESP8266 NodeMCU board.
Stating 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 ESP8266 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 ESP8266 board sending data to another ESP8266 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.
- A “master” ESP8266 sending data to multiple ESP8266 “slaves”
One ESP8266 board sending the same or different commands to different ESP8266 boards. This configuration is ideal to build something like a remote control. You can have several ESP8266 boards around the house that are controlled by one main ESP8266 board.
- One ESP8266 “slave” receiving data from multiple “masters”
This configuration is ideal if you want to collect data from several sensors nodes into one ESP8266 board. This can be configured as a web server to display data from all the other boards, for example.
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 a two-way communication between boards.
For example, you can have two boards communicating with each other.
You can add more boards to this configuration and have something that looks like a network (all ESP8266 boards communicate with each other).
In summary, ESP-NOW is ideal to build a network in which you can have several ESP8266 boards exchanging data with each other.
ESP8266: Getting Board MAC Address
To communicate via ESP-NOW, you need to know the MAC Address of the ESP8266 receiver. That’s how you know to which device you’ll send the information to.
Each ESP8266 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 ESP8266 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 <ESP8266WiFi.h>
void setup(){
Serial.begin(115200);
Serial.println();
Serial.print("ESP Board MAC Address: ");
Serial.println(WiFi.macAddress());
}
void loop(){
}
After uploading the code, open the Serial Monitor at a baud rate of 115200 and press the ESP8266 RESET 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 with ESP8266
To get you started with ESP-NOW wireless communication, we’ll build a simple project that shows how to send a message from one ESP8266 to another. One ESP8266 will act as a “sender” and the other ESP8266 will be the “receiver”.
We’ll send a structure that contains a variable of type char, int, float, String 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 ESP8266 #1 and “receiver” to ESP8266 #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 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 most essential ESP-NOW functions:
| Function Name and Description |
| esp_now_init() Initializes ESP-NOW. You must initialize Wi-Fi before initializing ESP-NOW. Returns 0, if succeed. |
| esp_now_set_self_role(role) the role can be: ESP_NOW_ROLE_IDLE = 0, ESP_NOW_ROLE_CONTROLLER, ESP_NOW_ROLE_SLAVE, ESP_NOW_ROLE_COMBO, ESP_NOW_ROLE_MAX |
| esp_now_add_peer(uint8 mac_addr, uint8 role, uint8 channel, uint8 key, uint8 key_len) Call this function to pair a device. |
| esp_now_send(uint8 mac_address, uint8 data, int len) 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:
ESP8266 NodeMCU Sender Sketch (ESP-NOW)
Here’s the code for the ESP8266 NodeMCU 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
Complete project details at https://RandomNerdTutorials.com/esp-now-esp8266-nodemcu-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 <ESP8266WiFi.h>
#include <espnow.h>
// REPLACE WITH 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;
String d;
bool e;
} struct_message;
// Create a struct_message called myData
struct_message myData;
unsigned long lastTime = 0;
unsigned long timerDelay = 2000; // send readings timer
// Callback when data is sent
void OnDataSent(uint8_t *mac_addr, uint8_t sendStatus) {
Serial.print("Last Packet Send Status: ");
if (sendStatus == 0){
Serial.println("Delivery success");
}
else{
Serial.println("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() != 0) {
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_set_self_role(ESP_NOW_ROLE_CONTROLLER);
esp_now_register_send_cb(OnDataSent);
// Register peer
esp_now_add_peer(broadcastAddress, ESP_NOW_ROLE_SLAVE, 1, NULL, 0);
}
void loop() {
if ((millis() - lastTime) > timerDelay) {
// Set values to send
strcpy(myData.a, "THIS IS A CHAR");
myData.b = random(1,20);
myData.c = 1.2;
myData.d = "Hello";
myData.e = false;
// Send message via ESP-NOW
esp_now_send(broadcastAddress, (uint8_t *) &myData, sizeof(myData));
lastTime = millis();
}
}
How the code works
First, include the ESP8266WiFi.h and espnow.h libraries.
#include <ESP8266WiFi.h>
#include <espnow.h>In the next line, you should insert the ESP8266 receiver MAC address.
uint8_t broadcastAddress[] = {0x5C, 0xCF, 0x7F, 0x99, 0x9A, 0xEA};In our case, the receiver MAC address is: 5C:CF:7F:99:9A:EA, 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 5 different variable types. You can change this to send whatever variable types you want.
typedef struct struct_message {
char a[32];
int b;
float c;
String d;
bool e;
} struct_message;Create a new variable of type struct_message that is called myData that will store the variables values.
struct_message myData;Next, define the OnDataSent() function. This is a callback function that will be executed when a message is sent. In this case, this message simply prints if the message was successfully sent or not.
void OnDataSent(uint8_t *mac_addr, uint8_t sendStatus) {
Serial.print("Last Packet Send Status: ");
if (sendStatus == 0){
Serial.println("Delivery success");
}
else{
Serial.println("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() != 0) {
Serial.println("Error initializing ESP-NOW");
return;
}Set the ESP8266 role:
esp_now_set_self_role(ESP_NOW_ROLE_CONTROLLER);It accepts the following roles: ESP_NOW_ROLE_CONTROLLER, ESP_NOW_ROLE_SLAVE, ESP_NOW_ROLE_COMBO, ESP_NOW_ROLE_MAX.
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);Then, pair with another ESP-NOW device to send data:
esp_now_add_peer(broadcastAddress, ESP_NOW_ROLE_SLAVE, 1, NULL, 0);The esp_now_add_peer accepts the following arguments, in this order: mac address, role, wi-fi channel, key, and key length.
In the loop(), we’ll send a message via ESP-NOW every 2 seconds (you can change this delay time on the timerDelay variable).
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 = "Hello";
myData.e = 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, a String 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 any other type of data.
Finally, send the message as follows:
esp_now_send(broadcastAddress, (uint8_t *) &myData, sizeof(myData));The loop() is executed every 2000 milliseconds (2 seconds).
if ((millis() - lastTime) > timerDelay) {
// Set values to send
strcpy(myData.a, "THIS IS A CHAR");
myData.b = random(1,20);
myData.c = 1.2;
myData.d = "Hello";
myData.e = false;
// Send message via ESP-NOW
esp_now_send(broadcastAddress, (uint8_t *) &myData, sizeof(myData));
lastTime = millis();
}ESP8266 NodeMCU Receiver Sketch (ESP-NOW)
Upload the following code to your ESP8266 NodeMCU receiver board.
/*
Rui Santos
Complete project details at https://RandomNerdTutorials.com/esp-now-esp8266-nodemcu-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 <ESP8266WiFi.h>
#include <espnow.h>
// 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("Error initializing ESP-NOW");
return;
}
// Once ESPNow is successfully Init, we will register for recv CB to
// get recv packer info
esp_now_set_self_role(ESP_NOW_ROLE_SLAVE);
esp_now_register_recv_cb(OnDataRecv);
}
void loop() {
}
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;
String d;
bool e;
} struct_message;Create a struct_message variable called myData.
struct_message myData;Create a callback function that will be called when the ESP8266 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 sender ESP8266. 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("String: ");
Serial.println(myData.d);
Serial.print("Bool: ");
Serial.println(myData.e);
Serial.println();
}In the setup(), intialize Serial communication 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;
}Set the ESP8266 role:
esp_now_set_self_role(ESP_NOW_ROLE_SLAVE);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(OnDataRecv);Testing ESP-NOW Communication
Upload the sender sketch to one board and the receiver sketch to the other board. Don’t forget to insert the receiver MAC address on the sender sketch.
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.
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 in the sender side).
We tested the communication range between the two boards, and we are able to get a stable communication up to 140 meters (approximately 459 feet) in open field. In this experiment both ESP8266 on-board antennas were pointing to each other.
Wrapping Up
In this tutorial you’ve learned how to use ESP-NOW with the ESP8266 NodeMCU board. Now, you can combine the sender and receiver sketch so that you have a two-way communication (each board acting as a server and sender at the same time). You can also use more boards to have a communication between multiple boards.
ESP8266 and ESP32 boards can communicate with each other using ESP-NOW communication protocol. You just need to upload the proper sketches to each board. To learn how to use ESP-NOW with the ESP32, you can read our ESP-NOW getting started guide for the ESP32.
We hope you’ve found this tutorial useful. To learn more about the ESP8266 board, make sure you take a look at our resources:
Thanks for reading.
Great article Sara.
Is it exactly the answer to one of my problem in an HVAC system.
Thanks 😀
Hi Sara,
I am using esp now for a school project. I am posting the code below and the result when I run the sender and receiver. It receives the message but does not activate the LEDs. Can someone help in this please. Thanks
Receiver code:
“”””””
#include <BufferedInput.h>
#include <BufferedOutput.h>
#include <loopTimer.h>
#include<ESP8266WiFi.h>
#include<espnow.h>
#include <PinFlasher.h>
#include <SafeString.h>
#include <SafeStringReader.h>
#include <SafeStringStream.h>
#include <SerialComs.h>
#include <SafeString.h>
struct attribute((packed)) dataPacket {
char a[32];
};
const byte maxRcvdBytes = 10;
// personal naming-convention suffix _SS indicates a S)afe-S)tring
createSafeString(newCommand_SS, (maxRcvdBytes) ); //+1 for the terminating zero
createSafeString(Command_SS, (maxRcvdBytes) );
const byte Red = 12;
const byte Green = 14;
const byte Blue = 16;
typedef struct struct_message {
String d;
} struct_message;
// Create a struct_message called myData
struct_message myData;
const char endChar = 0x0D; // carriage return is hex-value 0D and is used as the terminating byte
int idx = 0;
char rcvdChar;
void dataReceived(uint8_t *senderMac, uint8_t *data, uint8_t dataLength) {
char macStr[18];
dataPacket packet;
snprintf(macStr, sizeof(macStr), “%02x:%02x:%02x:%02x:%02x:%02x”, senderMac[0], senderMac[1], senderMac[2], senderMac[3], senderMac[4], senderMac[5]);
memcpy(&myData, data, sizeof(myData)); // copy redeived data into myData and printit
Serial.println();
Serial.print(“Received data from: “);
Serial.println(macStr);
Serial.print(“data: “);
Serial.println(myData.d);
memcpy(&packet, data, sizeof(packet));
// Serial.print(“sensor1: “);
}
void setup() {
pinMode(12, OUTPUT);
pinMode(14, OUTPUT);
pinMode(16, OUTPUT);
Command_SS = “off”;
newCommand_SS = “”;
Serial.begin(115200);
Serial.println();
Serial.println();
Serial.println();
Serial.print(“Initializing…”);
Serial.print(“My MAC address is: “);
Serial.println(WiFi.macAddress());
WiFi.mode(WIFI_STA);
if (esp_now_init() != 0) {
Serial.println(“ESP-NOW initialization failed”);
return;
}
esp_now_register_recv_cb(dataReceived); // this function will get called once all data is sent
Serial.println(“Initialized.”);
}
void readFromSerial() {
while (Serial.available() > 0) {
String rcvdChar =Serial.readStringUntil(‘\n’);
// for debuging purposes uncomment these lines
//to see each received character in the serial monitor
Serial.print("reveived #");
Serial.print(rcvdChar);
Serial.println("#");
/*
{
if ( (String rcvdChar == endChar) ) { // End of input or max Command_SS-length reached
Command_SS = newCommand_SS;newCommand_SS = " ";
}
Serial.print("Command_SS received: ");
Serial.println(Command_SS);
idx = 0;
}
else {
newCommand_SS += rcvdChar; // add new received char to SafeString
idx++;
}*/
}
}
void setLights() {
if (Command_SS == “dog”)
{
digitalWrite(14, HIGH);
delay(1000);
digitalWrite(14, LOW);
delay(500);
digitalWrite(16, HIGH);
delay(1000);
digitalWrite(16, LOW);
delay (2000);
digitalWrite(14, HIGH);
delay(500);
digitalWrite(14, LOW);
delay(1000);
digitalWrite(14, HIGH);
delay(500);
digitalWrite(14, LOW);
exit(0);
}
if (Command_SS == “cat”)
{
digitalWrite(16, HIGH);
delay(1000);
digitalWrite(16, LOW);
delay(500);
digitalWrite(14, HIGH);
delay(1000);
digitalWrite(14, LOW);
delay (2000);
digitalWrite(14, HIGH);
delay(500);
digitalWrite(14, LOW);
delay(1000);
digitalWrite(14, HIGH);
delay(500);
digitalWrite(14, LOW);
exit(0);
}
if (Command_SS == “goat”)
{
digitalWrite(14, HIGH);
delay(1000);
digitalWrite(14, LOW);
delay(500);
digitalWrite(14, HIGH);
delay(1000);
digitalWrite(14, LOW);
delay (2000);
digitalWrite(14, HIGH);
delay(500);
digitalWrite(14, LOW);
delay(1000);
digitalWrite(16, HIGH);
delay(500);
digitalWrite(16, LOW);
delay(500);
digitalWrite(14, HIGH);
delay(500);
digitalWrite(14, LOW);
delay(1000);
exit(0);
}
}
void loop() {
readFromSerial();
setLights();
}
“””””
Results:
from sender
Last Packet Send Status: Delivery fail
Last Packet Send Status: Delivery success
Last Packet Send Status: Delivery fail
Last Packet Send Status: Delivery success
from receiver
16:00:31.811 ->
16:00:31.811 -> Received data from: c8:c9:a3:69:7c:a6
16:00:31.811 -> data: dog
16:00:31.811 ->
16:00:47.582 ->
16:00:47.582 -> Received data from: c8:c9:a3:69:7c:a6
16:00:47.582 -> data: cat
16:00:47.582 ->
Hi.
Don’t send the data as a string.
Send the data as char and then compare chars and not string.
Regards,
Sara
Hi, I am also working on an HVAC System can you share some details of it
thanks
Thanks for your great tutorial!
I have a question though. I have created a network of ESP8266 devices that communicate with each other using ESP-NOW where all devices send “broadcast” packets to all other devices and there is no need to know or determine the MAC address of each device. The master-slave relationship is determined in real time by the software and software-set addresses sent within the payload.
In this scenario where only broadcast packets are used, what is the maximum number of devices that can communicate with each other? Is it 20? Or is there no limit?
Hi.
In the datasheet, they say:
“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;”
But, I’ve never tested so many peers at the same time, so I can’t tell if it works well.
Regards,
Sara
if ESP-NOW can send data up to 250 bytes, then what about the minimum bytes ESP-NOW ? thankyou..
Hi @RDX_Jim,
I am very interested at your ESP8266-broadvcast code, can you share it?
Author mention that “both ESP8266 on-board antennas were pointing to each other”
but,
Can we have a picture about how should be oriented in horizontal and vertical plan to achieve max distance propagation?
ie:
L [esp1] L [esp2]
[esp1]_| L [esp2]
other orientation one esp rotated at 90degree ? or 180degree ?
other?
I could not draw here without a picture.. that is why I need that extra information
Hi.
We did not use external antennas.
We just made sure that the front part of the on-board antenna was facing the front part of the other on-board antenna.
Regards,
Sara
Muy bueno muchas gracias por educarnos , lastima que tú curso sea exclusivamente en inglés
Saludos Fernando
Hi Fernando.
Thank you for your comment.
Unfortunately, we don’t have the time or resources to build our courses in Spanish.
Regards,
Sara
Can you please upload a tutorial about this combo comunication as one slave and many masters lets say… I would like to know how it can be used as one module to control others and receive info from all of the “masters”.. or how can in a combo setup one to send a command to a specific presaved mac from a list.
Thank you so much for those tutorials
Hi Stefan.
We have this tutorial that might help: https://randomnerdtutorials.com/esp-now-one-to-many-esp32-esp8266/
Regards,
Sara
If you use Chrome, it can translate to spanish !
Si usa Chrome, se puede traducir al español !
Google Chrome (and probably other browsers) have the ability to translate web pages for you. Often a pop-up dialogue box will appear offering to do the translation.
The stability of ESP8266 does not seem to be as high as that of ESP32. Frequent sending and receiving fails. I don’t know where the problem lies. Can you help me?
If you are using the command delay() in your code. This can cause the send /receive to fail. Delay() makes the microcontroller 100% busy and lefts 0,0% calculation-power for other things (like receiving a ESP-NOW-Datapacket).
You have to use the command millis() and the non-blocking timer-technique instead
best regards
Stefan
thank you – even after two years 🙂
Thanks a lot for this. I’m doing a project with both ESP32 and ESP8266 (so I can use the really small ESP12 module). Your article pointed out that there are differences between some of the functions for the two modules. For example, ESP32 has no Role function. I might have missed that.
In reference to my first comment today, I found you can not mix the ESPs. I tried an ESP8266 as the controller, and an ESP32 as the slave. It almost worked. It successfully completes a transaction, sometimes, but would fail many more times than it succeeded. I tried other channel assignments, lengthening the time between sending data, and varying the distance. Nothing worked. I did not try swapping the ESPs (controller for slave). Replacing the ESP8266 with an ESP32 produced a very reliable solution.
Hello . First of all, thank you for your beautiful and many work. The ESP8266 Now reciever sketch continued to give error messages. I then added an empty “Void loop () {}” to the sketch. Now it works as it should.
Kind regards, Bert.
I have tried espnow as a study and it works well so far. But I cannot manage multiple transmitters to 1 receiver. I can’t figure it out and therefore ask you if you have a short example. Or where I can find that. I learn very slowly due to a handicap but I enjoy it very much. thanks for your work
Bert, That should be simple by having both send sketches practically similar, by declaring the same MAC address of the receiving ESP.
That means that if you would copy your sens sketch and put it unchanged in another ESP, you would have multiple transmitters to 1 receiver
i work on it thank you
Hi Bert.
You just need to upload the same code to the senders.
Then, the receiver will get the message from all the senders.
You may want to send a slightly different message identifying which board sent each message, or you can just get the senders’ MAC address.
We’ll be publishing multiple transmitter to 1 receiver soon. So, stay tuned.
Regards,
Sara 😀
And multi recievers on 1 transmitter to ? 🙂
Thanks and greetings from the Dutch old man .
Hi.
We’re currently working on those guides.
Stay tuned 😀
the transmission with ESP-NOW is ALWAYS based on the mac-adress. So if one sender should send to multiple receivers you do a send-command for each MAC-adress. That’s all. Or you use the send to EVERY device with MAC-adress FF:FF:FF:FF:FF the broadcasting mac-adress
best regards
Stefan
Hello Sara
Have you made progress on that type of configuration ?
Do you know if a tutorial is on the way for this ?
Regards
Nicolas
Sorry for bothering. I come from Vietnam. I’m a non-professional, I spent 3 weeks just linking 3 esp8266. Specifically: Esp0 will send data to esp1 and esp2, and esp0 will receive data from that 2 esp. The problem only occurs when esp0 receives data, it only receives the return signal from one of the two, not both as intended. Can someone help me with any examples. Ex: esp1-esp0 & esp0-esp2 whose connections are bidirectional. Thank you very much
What i believe it is happen in your case, is that you get TWO replies in the same time.
While CPU is busy to get first reply, it will ignore the other, so you do not get both.
Look for Stefan Ludwig posts here, which developed a special interrupt routine, and it might help you.
How fast does ESPNOW transmit data? 115200 bps or higher? Does the communication range decrease as the baud rate increases?
Hello there!
I believe there is a typo in the ESP MAC address, of the receiver:
“In our case, the receiver MAC address is: 5C:CF:7F:99:9A:EA1, but you need to replace that variable with your own MAC address.”
Cheers from Argentina!
Hi MArcelo.
You’re right.
It is fixed now.
Regards,
Sara
What firmware version should the ESP8266 board be at?
Hi Fred.
I was using 2.5.2 version.
Regards,
Sara
Hi I added the Mac address from my receiving ESP8266 (84:F3:EB:EE:0E:EB) to the Sender sketch and uploaded both to an individual Wemos D1 Mini.
When I run them it doesn’t seem to work 🙁
I also added a few lines right after the Serial.begin for debugging.
This is wat I get for the receiver:
Sketch: ESP8266_NodeMCU_Receiver_Sketch__ESP-NOW_.ino
16:59:51.884 -> Uploaded: Mar 4 2020
16:59:51.884 -> ESP8266 Board MAC Address: 84:F3:EB:EE:0E:EB
And the sender:
Sketch: ESP8266_NodeMCU_Sender_Sketch__ESP-NOW_.ino
17:01:03.953 -> Uploaded: Mar 4 2020
17:01:03.953 -> ESP8266 Board MAC Address: EC:FA:BC:4C:7C:9A
17:01:03.988 -> Last Packet Send Status: Delivery fail
17:01:05.973 -> Last Packet Send Status: Delivery fail
17:01:07.989 -> Last Packet Send Status: Delivery fail
Any ideas? I’m using Arduino IDE 1.8.10 and downgraded my ESP firmware version from 2.6.3 to 2.5.2 to match yours..
Hi.
I’m sorry you’re having that issue.
Do you have more information?
It is very difficult to find out what might be wrong with just this information.
Can you use this MAC address and see what you get? 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
Regards,
Sara
Hey. I’m playing with Espnow. On the reciever side I tried to display the received information on an OLED display. This in the sketch instead of the serial edition. But then a lot goes wrong.
My intention is to be able to use the reciever rather than separately (portable) from a PC / laptop. Are you already working on this option? I will continue, but I don’t think I can get it right.
Greetings from the Old Dutch man (Bert).
Hi Bert.
I’m sorry, but I didn’t understand exactly what you’re looking for.
Do you want to display the information on OLED displays instead of the serial monitor?
What errors are you getting?
We have this tutorial with two-way communication that displays the information on OLED displays, it might help: https://randomnerdtutorials.com/esp-now-two-way-communication-esp32/
Regards,
Sara
I say sorry. I have completely overlooked this ESp32 explanation because I am still working with the ESP8266. But I now understand how to do it and start working with it. Thanks . Greetings Bert (now even older haha)
Hi, where to find esp_now.h library for esp8266?
Thank you.
Hi.
That library is included by default when you install the ESP8266 boards on your Arduino IDE.
Regards,
Sara
Hi Sara
I’m having trouble with that. All is ok when I compile for ESP32, but as I switch to ANY ESP8266 configuration the library is not found. I have the IDE properly set up for 8266, and also ESP8266 properly installed among boards – exactly as explained in your page “installing ESP8266 in Arduino IDE”. So for some reasons in my case the esp_now.h library was NOT installed automatically… any idea? or — any URL where i could download it from?
I have a few exsting application where I need to stick to ESP8266 since a configuration change to ESP32 would be complicated, so your help would be much appreciated.
Thank you, congratulation for your work, and greetings from Italy
Michele
Hi.
With the ESP8266, you use the espnow.h library not esp_now.h (for ESP32).
So, that may be the issue.
The code for ESP32 won’t work on the ESP8266.
You need to follow the tutorials that are specific for the ESP8266.
Regards,
Sara
for ESP8266 the correct library is espnow.h , not esp_now.h
Great project ! Works very well.
I love the fact that I don’t need my LAN (client/server situation). Thank you and keep up the great work.
Hello
I have a question :
As seen in this tutorial, is it possible to implement this configuration :
“One ESP8266 “slave” receiving data from multiple “masters” ” ? How to do that ?
Regards
Nicolas
Hi Nicolas.
You just need to upload the same code on multiple masters. So, they send messages to the same slave.
When the slave receives a packet, the OnDataRecv() function passes the MAC address of the sender. So, you know which board sent which message.
I hope this helps.
Regards,
Sara
I also tried this. But after a while everything stops and seems to be confused. Is there an example somewhere?
Hello Bert
Can you share the code ?
Nicolas
Downt have the code anymore, was terible, sorry.
But how to manage multiple send at the master(receiver) ?
Nicolas
Hello Rui,
I tried your code but get unreliable results.
only every five sendings the sender reports sending was successful.
I have also tested another code where a ESP32 acts as the “master” and an ESP8266 as “slave”. In this code both send and recive and this works very reliable. So is there still a problem with the espnow-library or do other modes than both in WIFI_STA work more reliable.
Could this be a problem of the WLAN-channel?
best regards
Stefan
Thanks for the turorial, i have a problem with communication between the nodemcu, i only get a stable communication up to 1 meter or 1.5 meters. Is there any way to increase the distance? I already tried to put them face to face, but it did not work.
Hi.
I don’t know why you’re getting such a low communication range :\ There’s must be something causing that.
We get much more distance without any effort.
Maybe you can try with ESP32 boards??
Regards,
Sara
I had a range less than 50cm. Using:
WiFi.mode(WIFI_STA);
WiFi.disconnect();
solved my problem.
Hi Marek.
Thanks for sharing that solution.
Regards,
Sara
Hi Marek, Sara and Rui,
I have spent a great deal of time trying to diagnose unreliable communication on the ESP8266 using a variation of this ESP Now send and receive sketch.
Adding the WiFi.disconnect(); gives me 100% delivery success.
THANK YOU!!
I can now move on to the next step in my Controller project using ESP Now.
This communication method is awesome!
Bob D
Thanks Marek!
I was getting a lot of callback “Delivery Failed” error messages from the Sender NodeMCU. Roughly 80% of the callback message deliveries were failing, even with the Sender and Receiver NodeMCUs only a metre apart.
In the setup() code for each of the Sender and Receiver NodeMCUs I added “WiFi.disconnect;” as you suggested, and now 100% of messages are delivered successfully!
Thanks for sharing this article and the one based on ESP32. I am successfully using ESP-NOW between the 8266 and esp32. My project has allowed me to set up telemetry between one board with a GPS module attached and the other a display configured as a course deviation indicator modelled on an aircraft display. I’ve yet to test range but will install the GPS on an RC aircraft when we are all allowed to go back flying.
Hi Daniel.
That’s great!
I’m glad it is working fine with EPS-NOW.
Thanks for following our work.
Regards,
Sara
Hello Sara,
This tutorial is great but is missing something which i do not know how to implement.
I have a microcontroller with a packet of 175 bytes connected to RX pin of the first ESP.
On the second ESP, on the TX pin i have a second microcontroller connected on the RX pin.
What i want to do is transfer the message from ESP to microcontroller and vice versa.
Roughly said , use the ESP and ESP-NOW protocol as a transceiver.
How i can do that ?
I need probably 2-3 lines of code to do that :
Write data received by ESP2 to TX pin.
Read from RX pin of ESP2 and send data using ESP-NOW to ESP1.
Thank you.
Hi Ion,
you should AVOID the variabletype String. Strings eat up all memory over time and cause your prgram to fail in strange ways that are very hard to track down.
Use instead an array of char or the library PString.
It is a bit more than 3 lines of code. The solution also depends on if you can REALLY wait for the serial bytes to be finished or if you can’t wait. Is it ALWAYS exactly 175 bytes?
as pseudo-code it looks like this
char MyRxStr[176]
MyRxStr = Serial.Readln();
esp_now_send(mac_addr, MyRxStr, sizeof(MyRxStr));
void on_data_recv(const uint8_t *mac_addr, const uint8_t *incomingData, int len)
{
memcpy(&ESP_Data_Received, incomingData, sizeof(ESP_Data_Received)); //xxy
the “code” above os just a quick & dirty copy and paste of some bigger code that I’m using
best regards
Stefan
Thank you Stefan,
To be more clear it is.
I have an LCD display and a microprocessor which shows some data from different sensors.
The microprocessor does not have RTC, but the display has one with a battery.
Scenario 1: Every minute i want to send from LCD the date/time to microprocessor.
Scenario 2: Based on time, microprocessor send to LCD value of the sensors.On the LCD side i have an other microprocessor which receive data from ESP and drive the LCD, or receive the date time from LCD and send it to ESP.
I can setup the length of number of bytes to be always the same , regardless transmission or reception.
Up to now, i have an UART cable.
I want to cut the cable and keep the LCD on my desk and the microprocessor somewhere on an other room.
I can use an RFM95-98, but i prefer to use an ESP module.
Any suggestion where to go and read ?
Thank you
Ion
hm still not completely clear to me:
What I have understand so far:
there are three or four microcontrollers involved
in short “µC1-non-ESP”, “µC2-ESP”, “µC3-ESP”
µC1-non-ESP connected to LCD and connected to µC2-ESP via serial
µC3-ESP connected to a sensor
µC3-ESP sends sensor-data via ESP-NOW to µC2-ESP
µC2-ESP forwards sensor-data to µC1-non-ESP through serial-wire connection
µC1-non-ESP shows sensor-data on the LCD.
But I’m not sure if I understand right.
All these microcontrollers have names like “Arduino-Uno”, Arduino-nano” or whatever. Could you give a description of all the microcontrollers involved using their names and adding what is connected to them?
What kind of LCD is it? What is the exact name and type of the NON-ESP-microcontroller which is connected to the LCD?
If it is Arduino-like” you might could porting the code that is running in the non-ESP-µC to an ESP8266 or ESP32. This would eliminate the non-ESP-µC.
best regards
Stefan
Hello Stefan,
I do not want to make your day a nightmare with my problems.
In short.
1.The first Microcontroller Pic18F46K22 collect through IIC temperature and humidity from Si7006-A20 , I2C HUMIDITY AND TEMPERATURE SENSOR, from Silicon Labs.
2.Based on data collected, Pic18F46K22, make a log to see if the temperature is in the set range, or they are deviations.
It use the second UART and send data collected , when user connect the PIC to a PC. Once or twice a day.
3.The time of day is divided on 4 zones, which asks the PIC to know the Real Time.
For example from 6am to 10am is Zone 1 and temperature is requested to be 23C.
On the other zones they are another temperatures set. On the PCB it is not a RTC.
4.Now, the Pic, send data collected to an intelligent display , NEXTION. The display shows Temperature, Humidity, Real Time , Zone of the day and Temperature SET. Nextion has a RTC.
5. Nextion send the RTC to PIC, and eventually changes on the zones setting (set temperature)
Up to know it is a UART cable (RX,TX) connecting the both.
Pic <======> Nextion
I want to cut the cable and use ONE ESP8266 on each side.
Pic <===> ESP1 <===> ESP2 <===> Nextion
As i state before, I do not want to use wireless transceivers, I trust more ESP communication.
I can make a standard fix length string , and process from it on each side, just data I need.
The connection of PIC with PC and communication it is not the scope of my project. It is already solved and works well.
In short, what i understand from the article, ESP-NOW can transport UP to 250 bytes
between a pair of ESP.
What i want is just to SEND OUT the “250” bytes received on ESP2 from ESP1, through TX pin to a PIC microcontroller, and READ on RX pin of ESP2 “250” bytes to be sent to the ESP1.
PIC1 – TX pin ====> RX pin ESP1 ====> ESP-NOW ====> ESP2===>TX pin ESP2 ====>RX pin PIC2. And vice versa.
On the PIC it is an easy task. I write to the UART port , or use interrupt to read from UART port.
Hi Ion,
it would have become a “nightmare” with non-detailed information.
Now I understand the whole situation. I made some first experiments with two ESP8266 using ESP-NOW. But the transmission was unreliable. I got a lot of errors from the ESP-NOW-library that transmission failed. I haven’t analysed yet if it was unreliable code written by me or if the ESP8266-ESP-NOW-library is unreliable itself.
When I used one ESP32-modul paired with an ESP8266 it was reliable. Though I did not do intensitive testing.
OK.
On my own project next step is to code a two-way-communication via ESP-NOW.
My personal experience is: For really new things write small test-code that does just that one new thing. It will take some days to get this up and running as I haven’t so much time per day to write code. Lot’s of other things also to do. If I have a substantial and somehow tested piece of code I can post it here.
In the meantime I recommend doing it the same way. Write a testcode that does only send and receive your 175 bytes back and forth via ESP-NOW printing the content on the serial monitor.
best regards
Stefan
Hello Stefan
Sorry for late reply, but i had bug in a program which kept me up for the last 36 hours.
It is finished now.
When i said 175 bytes was a generic number. I will count the real maximum number and make a test code like that.
I will also try to divide the string on few smaller one.
I believe the longest one is DATE like
2020 04 25 13 55 F F F
32 30 32 30 30 34 32 35 31 33 35 35 0F 0F 0F
Looks like 15, sent at power UP. From there the CPU will keep track about time and date through some timers. I can repeat this command at midnight to correct for eventual variations on the CPU. The rest of the day, is not too much. Maybe once or twice a day if i want to change the set temperature to a temporary new value.
I can say and will test with 30 bytes in total.
The 175 was in my mind as a number in general as they said we can send 250 bytes, and i was thinking at a different project.
But 30 for now will be OK.
I will let you know when i did it and the results.
Best regards
Ion
Hi Ion,
this comment-function does not allow attaching files and it is eliminating spaces. How about changing to a real Arduino-Forum where code can be formatted as code and files can be attached? When I tested two-way-communication with ESP-NOW I used code that used delay() in the main-loop. Using delay can be such a DELAY when writing code. The delay was causing the unreliability of transmitting the data. I got a lot of messages send failed. As soon as I replaced the delay-commands with a non-blocking-timer that uses millis() the sending back and forth of both units worked very good.
@Rui and Sara: I’m somehow sorry that this discussion leaves the RNT-website. But I want to go on with attaching code and posting code that is well formatted as code.
best regards
Stefan
Hello Stefan,
Please give me a link of a forum and i will register and be there, and start looking for the topic until i find the one.
Thank you very much for all the help.
Ion
Hion,
couldn’t resist to write this abbreviation of “Hi” and your name ;-)))
OK here is the link to the thread with my democode
https://forum.arduino.cc/index.php?topic=680265.0
Take a look and feel free to ask any questions you like.
best regards
Stefan
Hello Stefan,
As i was born somewhere in Europe, for me english is still like Amazonian forest.
Lot’s to discover, which mean, i did not get the meaning of “Hion”. You can explain it to me.
I will go tomorrow morning, or late tonight to look at the code.
My daughter in law, which is pregnant on the 7 month, is in the hospital now for some kidney problems/stones.
So the drill is: I stay home with my other two lovely granddaughters during the day, while my son, spend time in the hospital with his wife.
Thank you for all your effort.
Ion
Hello Ion,
“Hion” was just a little playing with letters instead of writing “Hi Ion”
Hi similar meant as “Hello”
I put “Hi” and “Ion” together to Hion. That’s all. ;-))
OK if you have any questions just ask them in the Arduino-Thread
https://forum.arduino.cc/index.php?topic=680265.0
I enjoy helping this way very much.
best regards and best wishes to your daughter
Stefan
Hi Sara,
I will try to have more than one sender with i.e DHT22 in different places and a receiver with an oled sisplay.
Now I try with only one sender but I have a problem, while the receiver in serial monitor show the correct data, in the oled display the name of the place corresponding to myData.a
is reproduced but Temp corresonding to myData,c and Umid. corresponding to myData.b are 0.00 and o or nan.
I made this variation of the code:
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);
display.clearDisplay();
display.setTextSize(1);
display.setCursor(0, 0);
// Display static text
display.print(myData.a);
//display.print(myData.a);
Serial.print(“Umid: “);
Serial.println(myData.b);
Serial.print(“Temp: “);
Serial.println(myData.c);
display.setTextSize(2);
display.setCursor(0, 16);
// Display static text
display.print(“T: “);
display.print(myData.c);
display.println(“*C”);
Serial.print(“String: “);
Serial.println(myData.d);
Serial.print(“Bool: “);
Serial.println(myData.e);
Serial.println();
}
in the setup
if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128×64
Serial.println(F(“SSD1306 allocation failed”));
for(;;);
}
delay(2000);
display.clearDisplay();
display.setTextSize(1);
display.setTextColor(WHITE);
// Display static text
display.setCursor(0, 0);
// Display static text
display.println(myData.a);
display.setTextSize(2);
// Display static text
display.setCursor(0, 16);
display.print(“T: “);
display.print(myData.c);
display.println(” C”);
display.setCursor(0, 36);
// Display static text
display.print(“U: “);
display.print(myData.b);
display.println(” %”);
in the loop
display.clearDisplay();
display.setTextSize(2);
// Display static text
display.setCursor(0, 16);
display.print(“T: “);
display.print(myData.c);
display.println(” *C”);
display.setCursor(0, 36);
// Display static text
display.print(“U: “);
display.print(myData.b);
display.println(” %”);
Practically I repeat three times the same code, if cancel one group I don’t see anything.
What is wrong.
Renzo Giurini
Hi Sara & Rui,
Thanks for this very clear and straight forward introduction to ESP-NOW, I had a couple of OTA flashed ESP-01’s communicating this afternoon! Now I really need to explore having the sender on battery power and waking up, sending and then going to sleep, something to keep me entertained on the morrow.
The satellite picture of your range test made me feel a bit sad, as my wife and I should have been in Foz visiting my sister and husband this Easter (they live up towards the Contemporary Art Gallery …) but our flights obviously got cancelled and we had to stay in Nottingham …
I hope this finds you both safe and well, I really do owe the pair of you some drinks as RNT has always been one of my ports of call for ESP stuff!! I’ll check if you are around when we manage to rearrange our trip!
Thanks again
Pete
ps like Stefan I worked out quite early in tests that I really had to avoid any blocking code!!!
Hi Pete.
I’m sure you’ll be able to visit Foz another time.
We live nearby, so we can go there any time. It would be a pleasure 🙂
Thank you for following our work.
Regards,
Sara
For deep sleep, you can take a look at this tutorial: https://randomnerdtutorials.com/esp8266-deep-sleep-with-arduino-ide/
Thanks Sara,
that is in fact where I went and far from keeping me amused the following day it only took me 10 mins thanks to your great tutorial (most of that time was spent finding a push-button!!)
Pete
I am sure I read here somewhere but cant find it again how to make the ESP32 code work with ESP8266?
I have a number of ESP8266 (Node MCU) chips that I want to use with some 1wire temperature chips to log temperature around the house and garden. I could log them and just collect the kit later but thought it would be enhance my learning to pass the data to and from devices.
I thought that way I could set some up with battery power and also use the ESP8266 to feedback battery conditions of the devices outside, I could mess with Deep Sleep but as at least one will be connected to a motorcycle in the shed to monitor its 12v batter condition I want to just use them to create a warning flash (or message) on the devices indoors
anybody does this ring any bells? can you run ESPNow on ESP8266’s with multi connected nodes?
Cheers CLive
Hi Clive.
Yes, you can do that.
You can have one ESP8266 receiving data from multiple nodes.
As an inspiration, you can take a look at this tutorial: https://randomnerdtutorials.com/esp-now-many-to-one-esp32/
Instead of the ESP-NOW functions of the ESP32, you must use the ESP8266 ESP-NOW functions.
I hope this helps.
Regards,
Sara
If youtake ESP32-code and try to transfer it to ESP8266 there several things to look at:
first include espnow.h instead of esp_now.h (no underline in the filename
Don’t use delay() on ESP8266. Delay blocks the one core of the ESP8266 completely so that even ESP-NOW-messages can’t be sent or received
use non-blocking-timers instead
when used in Stationmode use the command WiFi.disconnect() to make ESP-NOW work
@Rui & Sara: can you examine which mode works best on ESP8266?
I guess mutliple conditions must be fullfilled to make ESP-NOW work in pairing with the ESP8266 connected to a router at the same time
Some constants and some data-types that are defined in esp_now.h (which is for ESP32) are simply NOT defined in the espnow.h (ESP8266) so porting the code requieres a lot of adapting. I think it is better to use code that was originally written for ESP8266.
best regards
Stefan
Thanks Sara ,
Stefan is correct I have tried (unsuccessfully) to replace code and got very tangled extremely quickly. In principle it sounds easy but as a nubby its far from that. I am not beaten just inexperienced so it may be sometime before I learn enough to get there but thats the point isn’t it?
Thanks for the help so far I guess what I need it time and to experiment and get some of the routines of actually getting data under my belt and come back to the data transfer later
Cheers Clive
Hi Clive,
I have posted code for non-blocking timers here:
https://forum.arduino.cc/index.php?topic=680251.0
and here is a democode that demonstrates send and recive data on two ESP8266-boards in both directions
https://forum.arduino.cc/index.php?topic=680265.msg4576524#msg4576524
best regards
Stefan
Thanks for sharing this 🙂
Brilliant
I have started editing your ‘Sender and Receiver’ code to pass 1wire data from one to another and will let you know how I get on.
But I’m also going to have a look at this code to , maybe tomorrow as its a little late here now in the UK
Thank you
Hello Stefan,
I cannot compile the code from Arduino Forum.
Here is the error:
Arduino: 1.8.12 (Windows 7), Board: “NodeMCU 1.0 (ESP-12E Module), 80 MHz, Flash, Disabled, All SSL ciphers (most compatible), 4M (no SPIFFS), v2 Lower Memory, Disabled, None, Only Sketch, 115200”
ESP_NOW_Bidirectional:4:37: fatal error: nonBlocking_Timer_class.h: No such file or directory
#include <nonBlocking_Timer_class.h>
^
compilation terminated.
exit status 1
nonBlocking_Timer_class.h: No such file or directory
This report would have more information with
“Show verbose output during compilation”
option enabled in File -> Preferences.
And i have a picture which shows me that :nonBlocking_Timer_class.h: No such file or directory
Any help ?
Thank you
Ion
Hi Ion,
my comment was too short. The democode for send/receive data both ways with ESPNOW on ESP8266-boards makes use of the non-blocking timers.
This means you have to download the files of nonBlocking_Timer_class
These files are posted in this thread
https://forum.arduino.cc/index.php?topic=680251.0
And in this thread is explained WHERE to store these files on your harddisk.
I insist on using the nonblocking timers because using the command delay() makes the datatransmission unreliable. You can’t predict WHEN a SEND-NOW-message rushes in. So the receiving board has to be ready all the time and can’t be totally busy through the command delay(). Delay is used to pause code-execution but in a way that this “pausing” means “processor count up to 1000 billions as fast as you can”. This counting up needs all the calculating-power the processor has. There is NO calclulating-power left to receive ESP-NOW-messages.
best regards
Stefan
Thank you Stefan.
It compile with no errors.
On the original try, i just read one line in 5 , so i miss the essential of storing the h and cpp files.
Now everything is in place and both of your files, compile correctly with no errors.
Thank you very much.
Ion.
Hello Stefan,
Your “nonBlocking_Timer_class” here, looks like a timer+counter i can set on my “Interrupt routine” on my regulars programs for PIC processors.
At startup i set an interrupt timer for a defined period of time(let’s say 10ms.)
Because this timer is inside of the interrupt routine, executed every scan, and at overflow of the 10 ms. it increment a “non_blocking_timer” like you say, arbitrary set at 300- a counter.
At start, the counter was 0 and i had a boolean flag = ON. If for example the counter is set 300, this will keep the flag ON for 3 seconds. At time up, 3 seconds, the flag turn OFF.
I have the same issue on the programing regular processors with the Delay command or While command. Your idea is brilliant.
I had totally forgotten to update ESP8266 with Boards manager. Now I made an update from 2.4.1 to 2.7.1. I still don’t get this working. How to get a working version?
Hi Pertti,
what exactly do you mean with “How to get a working version?”
The code on this subsite IS working. Working for Sara and Rui and I can confirm that the code is working. So YOU have to describe in DETAIL what is happening if you upload this code given above if you try to make it work.
It might be that you have setup the wrong MAC-adress, it might be that you get a compiler-error.
As long as you just say “not working” the only tip we can give is “try to get it working”
Which of course does not help. We can help you much better if you describe in DETAIL what is happening if you uploaded the code to your ESP8266-module.
best regards
Stefan
Hi Stefan,
Thanks for the answer. My problem was not the ESP8266 add-on in Boards manager. ESP-NOW with the newest version seems to work now. Now the program loading to ESP-12 seems to work so that the program does not start when it is loaded. I have to unplug USB cable and plug again to make it start. That confused me, and I don’t like it. Is there a solution to this?
Pertti
That’s right!
Thank you Stefan 😀
What’s the error that you’re getting?
Hi Sara,
I like ESP-NOW and this tutorial. I am currently struggling with the reliability. Sometimes I have a 7 to 10 “Delivery success” and after that “Delivery fail”. Sometimes the transmitter seems to stop totally transmitting. I wanted to add LED blinking on both sides, but now it seems to be still far away. It is written in Espressif site that no time consuming should be added to the callback functions.
Hi.
Have you tried blinking an LED without delay?
Regards,
Sara
in my eyes introducing newbees to the command delay() is a BIG mistake. delay() makes the microcontroller count up as fast as she can needing 100% calculation-power. So there is now calculation-power left for anything else like receiving a ESP-NOW-message. You have to write your code completely WITHOUT delay() to make it ESP-NOW work reliably.
Espessially for receiving ESP-NOW-messages because the receiver can NOT predict when the message will rush in.
Hi,
I have this finally working reliably. I started from the original codes of this tutorial with the attitude that they have to be correct. My problem was in HW. The GP Power Bank that I used on the other end stopped giving power after some time. I guess it is not meant for this kind of projects, and waits some answers from the connected device to continue giving power. I almost lost my nerves before finding this out. I changed to an older power bank that just gives power without questions. I made the LED blinking on receiver side using millis(). But I don’t know if is really better than delay() in this case. I guess it is better only inside loops where there is also something else to do than counting time.
Hi Sandra and Rui,
Just tried ESP-NOW on 2 Node Mcu’s 8266 worked great! To check out distances for my location, I set up a flag variable in the sender’s callback function and in the main loop I flash a led according to the state of the callback. (Flashing a led with the code in the callback function is a no no, yes I afterward read the previous comments concerning the blocking delay !) . So to test the distance leaving the receiver part with the PC in the house , I go outdoors with the sender on battery , the flashing led tells me that all is still communicating well. No flash means out of range. With the antennas facing each other, the test was very successfull for me. I also modified the code to receive DHT humidity and temperature. Thank you for the great tutorial, as this will greatly simplify my project .
Hi Ronald.
That’s great!
Thank you so much for sharing your experience.
We’ve just published a two-way communication with the ESP8266 to exchange DHT readings: https://randomnerdtutorials.com/esp-now-two-way-communication-esp8266-nodemcu/
Regards,
Sara
Thanks for the info Sara.
Regards,
Ronald
Download espnow library. How and from where?
Sorry to trouble you but i can’t find it.
Ross.
Hi Ross.
You don’t need to install anything.
The espnow library comes installed by default when you install the ESP8266 boards.
Make sure you have an ESP8266 selected in your boards menu before compiling or uploading the code.
Regards,
Sara
I want to add something. The manufacturer of the ESP-chips ESP8266 and ESP32 provides DIFFERENT ESP-librariies fpr ESP8266 and ESP32. These libraries are INcompatible. porting exampel-code between ESP8266 and ESP32 is a BIG hassle. You better write code from scratch or search for an example that is written for the right hardware than modifying it.
This means if you work with an ESP32 search for code written for ESP32 and use #include <esp_now.h>
If you work with ESP8266 search for code that is written for ESP8266.
use #include <espnow.h>
Can you see the difference? Filename with or without underline
best regards
Stefan
Hi Sara, Great work with this manual, it’s very interesting. Just a question, it’s possible have in one ESP8266 communication with ESP-NOW (with other boards) and this board could be connect to a Router AP in the same time. The idea is have communication with all boards with ESP-NOW but have the possibility to connect to internet to monitoring all information that you have created with your ESP-NOW network.
It’s possible share both communication in ESP8266.
Thanks
Regards
Hi Alberto.
I haven’t experimented with it yet on the ESP8266.
We have something similar but for the ESP32: https://randomnerdtutorials.com/esp32-esp-now-wi-fi-web-server/
Regards,
Sara
Hi Alberto,
somewhere I have read that ESP-NOW and WiFi in parallel only works if you setup ESP-NOW to use the same WiFi-Channel than the WiFi-network you want the ESP8266-module to connect with is using. I haven’t tested this myself yet. When using ESP-NOW there is a command WiFi.disconnect. This makes perfect sense to the restriction described above. When WiFi is DISconnected ESP-NOW can use another channel and it will work because the module is DISconnected from the AP.
best regards Stefan
@Pertti Ritala:
You seem to have not (yet) understand how ESP-NOW works.
If you want to have reliable RECEIVING you MUST avoid delay().
A receiving unit can NEVER predict WHEN a ESP-NOW-message rushes in.
The sender maybe tries to send it three times within one second. If your receiving unit is busy with delay()ing in right that second where the sender is sending. The sending MUST fail.
The receiving of ESP-NOW-messages happens in the backround and therefore the processor needs some calculation-time. delay() absorbs ALL calculation-time. And this is the reason why delay() makes RECEIVING unreliable.
best regards Stefan
Hi Stefan,
That is good know. My receiver code is similar than in this tutorial, nothing done inside the loop. Inside the receivers callback function I blink a sender related LED using millis(). In the sender I do everything inside setup with delay(100); and ESP.deepSleep(2*1000000); in the end. Everything works now, and I am ready to join a ESP-NOW fan club.
Hi,
Does somebody know how much current some ESP8266 module takes during sending? And is the sending always with full power? I have a battery powered sender now working. There is no need of LED blinking as I have earlier discussed. Serial.println() handles that. Even Serial.begin() blinks the on-board LED.
Andreas Spiess did a lot of research in this field
best regards Stefan
Hi.
I haven’t tested that yet.
Regards,
Sara
Hello.
The receiver does not work. I uploaded the sketch correctly, the receiver only sends via uart boot and then nothing. What am I doing wrong?
Hi.
Make sure you have the right MAC address on the sender side.
Regards,
Sara
In a one to many configuration, can the “one” be connected to a wi-fi network? Can the one be used to collect data from the many, and periodically pass it along via wi-fi to a controller? Would the “one” need to close the ESP-NOW connection, open a wi-fi connection, pass the data, close the wi-fi connection, and reconnect to the ESP-NOW network? Or, can the wi-fi connection exist with the ESP-NOW connection active?
Hi.
You can learn about that in this tutorial: https://randomnerdtutorials.com/esp32-esp-now-wi-fi-web-server/
Regards,
Sara
Thank you. This will get me started. I don’t need the web server, just wi-fi to connect to Home Assistant. The idea is to use esp-now to create a network of ESP-32s that will function even if Home Assistant crashes.
Jim
Where I can find ESP NOW library?
Hi.
You don’t need to install the library.
It is “installed” by default when you install the ESP8266 or ESP32 boards.
Regards,
Sara
This is an awesome reference.
Thanks for the perfect lesson about starting ESP-NOW
Following your steps to communicate between two esp6266 boards
i tried to upload the scetch for the receiver in the aruino ide
As newbee it took many hours to solve several compiler errors, learned a lot.
Now the program compiles perfect but doesn’t upload giving the error
A fatal error occurred: Timed out waiting for packet header
I searched on internet put an extra cap (- nto enable), tried other harware boards ,no result
Other sketches on the boards i use are uploading fine so i don’t think its hardware.
Please please can you help me how solve the problem ?
Thks Wouter
Hi.
You can try pressing the RST button several times before trying to upload a new code and press the FLASH/BOOT button when you start seeing a lot of dots on the debugging window.
Also, make sure you have an ESP8266 selected in Tools > Board.
What’s the ESP8266 model you’re using?
Regards,
Sara
Hello
Great article thanks
Still having problems error A fatal error occurred: Timed out waiting for packet header
Checked a lot on internet, can’t find the right solution
Please would you be so kind to help me ??
just some more info
Used several esp12e modules and all uploading and working fine with other sketches
Your example here above ESP8266 NodeMCU Sender Sketch (ESP-NOW)
gives the upload error
wouter
hello Sara
Really thanks for the quick help.
I’m using Geekcreit® NodeMcu Lua WIFI Internet Things Development Board…
and
ESP8266-12E ESP-12E (replace ESP-12) module NodeMcu Node mcu Lua wifi V3
and….. i used the wrong board.
now using NodeMcu 0.9 (ESP12 Module ) and everythings uploads fine,
so problem solved many many thanks
wouter
Great!
Hi Sara,
A very good article again.
I learn a lot of with you
Can you please tell me if we can use ESP-Now Protocol between 2 ESP-01, And between one ESP01 and one ESP-32 ?
is the power consuption lower with ESP-NOW protocol or WIFI protocol ?
Thank you
I want many to many communication between esp32 boards through Bluetooth low energy, without router in between. And i want when one of the esp32 board come in the range of ble of another esp32, the buzzer should run. Can you provide me the code for this function.
Hi.
You need to insert your network credentials in the ssid and password variables.
Those are the credentials you need to type when you want to access internet in your computer or smartphone at home.
Many times the credentials are written under the router.
Regards,
Sara
Hello
Thank you very much for the good information
I have a question
MAC address
Is this the sender’s address?
Or is it the recipient’s address?
I think I have to put in the address of 8266 to be received. Is it correct?
(Isn’t it necessary to have both the sending and receiving addresses to protect against external attacks??)
And I just want to make #2D1 low when #1D1 low
Should I use the Int command?
Hi.
You should add the recipient’s MAC address so that it knows to where it should send the data.
Regards,
Sara
Hello Sara,
I am running the second code machine to machine (master to slave ) from the sender side I have put the mac address on the receiving side but it’s not working. On the serial monitor, it’s showing the delivery package failed . Help me out.
Hi.
Make sure that both boards are powered.
Double-check the MAC address of the receiver board.
For a first test, make sure the boards are relatively close to each other.
Regards,
Sara
there are a lot of possible error-sources.
Post your code. Using function delay() on the receiver-side is the most often reason fpr failed receiving. delay() must be avoided totally. If the CPU is executing a delay receiving is NOT possible. As you can’t predict WHEN a receive rushes in
the receiver has to be ready to receive all the time.
So you have to use timing based on the millis() function.
@Sara and Rui:
You should improve your example-code to NOT use delay().
Talking about master and slave in relation to ESP-NOW is complete nonsense. up to 20 ESP-boards can build a “peer-group” where each board can send and receive to any member any time. All that has to be done is specifying the RECEIVERS mac-adress inside the SENDERS code. So double-check that the SENDER has to right mac-adress of the RECEIVER
best regards Stefan
Hi.
Thanks for your comment.
Our code doesn’t use delay 😉
Regards,
Sara
Trying to use VS Code. ESP-NOW is not recognized, is there a library to install? Header file not found, etc. Couldn’t find it on PlatformIO library search.
You have a marvelous site here for ESP development. Thanks.
Dave
Hi.
You don’t need to install anything.
As long as you select an ESP8266 board, and add the #include <Arduino.h> line to your code, it should compile just fine.
I’ve just tested it and it is working fine for me.
Regards,
Sara
i do copy all exactly but the result are different on string. it keep give me strange character. i use 2 wemos d1 mini module on same breadboard with properly power supply
Hello Excellent tutorial
Do you know how to implement this using microPython?
And guidance will be welcome
Daniel
Hi.
At the moment, I think that MicroPython doesn’t support esp-now.
Regards,
Sara
Intriguing article Sara. Has my attention and I am sure to try it as soon as I can. But a question first, for I would need external wifi access as well: web page, NTPclient, Alexa (UDP) and websockets as well at times. Aside from an I2C wiring, is it possible to attach an ESP8266-01 device to an ESP8266 nodeMCU (E-12 V1)? Any suggestions?
Great project, thanks.
Greg
Hi Greg.
What do you mean by “attach”?
Do you want to connect an ESP-01 with an ESP8266 (physically)?
You need to use the serial pins and establish a serial connection.
Regards,
Sara
Well… yes, if it sounds do’able.
I need an internet connection as well as your ESP intranet, esp-now. I have never used an ESP8266-01 but thought it sounded feasible and sufficient.
So I thought that I’d ask you, the “definitive source” on SEP-Now.
Thanks for you fast reply and information,
Greg
Hello,
I have tested this code and it has worked just as you have shown. Great job 🙂
But I have been working on a project recently involving a switch to wirelessly send a HIGH or LOW signal to an ESP32-CAM to take a picture. I am currently stuck because I am still trying to understand how ESP-NOW works. If someone could please assist me by giving an example using ESP-NOW to wirelessly switch a light on and off with a physical switch I believe that it would lead me on the right path.
It would be much help,
Spencer
Actually, I think this is asking too much, but if possible I’d appreciate some guidance or tips on how to send HIGH or LOW signals between two ESP32s with ESP-NOW.
Hi.
We have several tutorials about ESP-NOW that send sensor readings:
https://randomnerdtutorials.com/esp-now-many-to-one-esp8266-nodemcu/
https://randomnerdtutorials.com/esp-now-one-to-many-esp8266-nodemcu/
Instead of sending a random message, you should send a “HIGH” message when the button is pressed.
To learn how to use a pushbutton, you can take a look at this tutorial: https://www.arduino.cc/en/Tutorial/BuiltInExamples/Debounce
Then, on the receiver side, you just need to check for messages with that content.
To learn how to take a picture with the ESP32-CAM, you can take a look at this tutorial: https://randomnerdtutorials.com/esp32-cam-take-photo-save-microsd-card/
We also have other ESP32-CAM tutorials that you might find useful: https://randomnerdtutorials.com/projects-esp32-cam/
I hope this helps.
Regards,
Sara
This has been helpful. Thank you for responding!
Hi there, this is a superb tutorial to find after spending days trying to figure out how to make ESPs communicate with low latency, so thanks so much for writing this!
One note: the instructions on the mac address format was a little confusing. It’s worth noting you need to prefix each part of the address with 0x like so:
Example:
41:9E:38:21:BF:8D —> {0x41, 0x9E, 0x38, 0x21, 0xBF, 8D}
Hi Sara: What a great tutorial! I had a lot of fun getting this running with two NodeMCUs 🙂
Hi Sara,
thank you for such useful tutorial.
I have problem compiling this sketch!
all settings are same as you taught but the error “Error compiling for board NodeMCU 1.0 (ESP-12E Module).
” is driving we crazy.
how can i fix it?
Hi.
Can you provide more details about the error?
Update the ESP8266 boards’ installation in your Arduino IDE.
Regards,
Sara
thank you for quick reply Sara.
i just updated the board installation but the error keeps going.
the last line of error is :
”
collect2.exe: error: ld returned 1 exit status
exit status 1
Error compiling for board NodeMCU 1.0 (ESP-12E Module).
“
Hi,
Thank you for all of your excellent tutorials. They are very beneficial in developing an understanding of the ESP8266 and ESP32.
But I am having a problem compiling sketches which include the “espnow.h” file with 8266 boards. The error is that it cannot find the “espnow.h” file. There is no problem with ESP32 boards.
This is Arduino 1.8.13 with the ESP8266 and ESP by Community installed. You state in one of the tutorials that this file is downloaded with the Board.
Thank you for any help.
Hi.
You don’t need to install anything besides installing the ESP8266 add-on.
Make sure you have the ESP8266 add-on updated and that you have an ESP8266 board selected in Tools > Board.
Regards,
Sara
Hi Sara,
Thanks. Refreshed downloads again and it works great!!
Dick
Hi
I want to print the data sent and the data received on the 16*2LCDs, what should I add in the codes
Hi.
If you’re using an I2C LCD you can follow this tutorial to learn how to use the display: https://randomnerdtutorials.com/esp32-esp8266-i2c-lcd-arduino-ide/
I hope this helps.
Regards,
Sara
thanks,
hope it will
Hi,
First I want to thank you for so many really helpful totorials.
Then I have a question on the above ESP-NOW examples. There is no place in the code to enter the wifi credentials, how can wifi establish communication without ssid and password ?
Regards
Ray
Hi and thank you for the great article.
I have the ESP8266 (ESP-01) receiving messages from another devices and writing the value out via the serial port from within the OnDataRecv CB function. All good.
In the below main loop, I continually toggle the LED. The issue is that the LED is only toggled when messages are received. If I stop the transmitter, the main loop is not being executed.
Why?
void loop() {
digitalWrite(LED_BUILTIN, LOW); // Turn the LED on
delay(500);
digitalWrite(LED_BUILTIN, HIGH); // Turn the LED off by making the voltage HIGH
delay(500);
}
Hi.
You need to blink your LED with timers and not with delay.
Regards,
Sara
Hi
I want to know when the OnDataSent function will be called, after calling the esp_now_send function, or after another esp receives the information sent by this esp?
thank you very much!
Hi! Thank you for this tutorial and hello from Russia.
please tell me, is it possible to add peer and enter mac addresses directly from the program? can I enter the mac address from the serial port in “loop” and it is used for communication via esp now? or is it possible to do this only in the “setup” when i programming esp?
ps i mean // Register peer
esp_now_add_peer(broadcastAddress, ESP_NOW_ROLE_SLAVE, 1, NULL, 0);
Hi.
Yes, I think you can do that.
But, you have to add the peer only after entering the MAC address on the Serial port, not in the setup().
Regards,
Sara
Hello all.
This was all working fine until i upgraded to esp8266 version 3 in the Arduino IDE. now the same code is no longer working. I change back to the older version 2.something, and it works again.
Has anyone else had this issue?
Seems this command has changed wifi_set_macaddr(STATION_IF, &newMACAddress[0]);
on the receiver side.
I am looking in the “breaking changes section” at the moment, on the espressif site.
Hi.
Thanks for the update.
I’ll have to test the codes and update them if that’s the case.
Regards,
Sara
Hi Sara,
After much testing…..
The issue turned out to be, on the side where we are sending the data to. The receiver, or slave unit. Part of the setup routine is the change the MAC address to One where we can define the mac address. Prior to the core upgrade to version 3.xx
We define the mac address before the wifi.begin(). After version 3, we now have to define the new mac address after the wifi.begin();
Wifi.disable();
Then we add the new MAC here.
I am on my phone, so my reply is not that great.
Even with the error, it still compiled with no errors, however, the sender could never connect, as it was looking for a hard coded mac and not the software defined MAC.
I have noticed, this finding may affect some of your other example, where you define the new MAC address.
Regards
Hi.
Thanks for the detailed response.
I’ll try to fix the issue in the next few days.
Regards,
Sara
Is it possible to modify the code in this tutorial so an ESP8266 acts as a repeater station between two other ESP8266’s using ESP-NOW?
Sending ct sensor reading from one esp8266 to another following your sketch. Once data gets to the receiver, how can I use that data for something other than printing it to the serial monitor..
current sensor readings are using mydata.b.
I would like to have something like If mydata.b is > 25, digitalWrite ledPin HIGH
Thank you for providing this example.
Hi.
Save the received data in variables and then, use them in the loop() to check for conditions, like the “mydata.b is > 25, digitalWrite ledPin HIGH”.
Regards,
Sara
I tried an example sending data from a Wemos Mini to an ESP32 DevkitTV1 using it own MAC Address, but I don’t receive anything.
It is possible?
Thanks
Renzo
Hi.
Yes, you can do that.
But, you need to be aware that the ESP32 and ESP8266 use different ESP-NOW functions.
As long as you use the right functions, I don’t think there’s any problem.
Check the ESP32 ESP-NOW tutorial to see how to set an ESP32 ESP-NOW receiver: https://randomnerdtutorials.com/esp-now-esp32-arduino-ide/
Regards,
Sara
Bonjour,
Peut on émettre avec ESP-NOW depuis un bouton d’une page Web?
MERCI et bravo pour tous ces tuto!!
Hi, may I know would it’s posssible to use ESP Now to send the data from ESP 8266 to ESP 32?
Hi, may I know would it possible to use ESP Now for ESP 8266 send data to ESP 32?
Yes.
You can exchange data between ESP32 and ESP8266 using ESP-NOW.
Just make sure you use the proper library for each board.
Here’s the tutorial for an ESP32: https://randomnerdtutorials.com/esp-now-esp32-arduino-ide/
Regards,
Sara
I’ve tried this and it seems to work fine, as long as you don’t use String.
The esp32 sends 4 more bytes than the esp8266 sending the same message.
Can you explain why?
Instead of nodemcu, can I use esp-01?
Yes, I am testing with 2 ESP-01s talking to each other right now and it works.
Hi Sara,
I have just started to look at esp-now and am having a problem finding esp_now.h on my computer.
I have removed and reinstalled the ide and installed the esp32 and esp8266 boards and a heap of other esp boards but the ide still can not seem to locate a library containing esp_now.h
I must be missing something.
Could you please point me in the rite direction?
Kind regards,
Eric.
Hi.
Make sure you have the right board selected for the code you’re using.
Additionally, the ESP32 uses esp_now.h library and the ESP8266 uses espnow.h. These libraries are different. And the ESP32 codes are not compatible with the ESP8266.
Regards,
Sara
It just worked finei
Thanks for putting together this useful tutorial.
Regards from Mexico, Puck
Hi sara
How do I program a nodemcu esp 8266(master/slave) so that it receives value from one nodemcu esp 8266 (master)and then sends it to another nodemcu esp 8266(slave) using ESP-NOW
Check all our tutorials about ESP-NOW and you’ll learn how to do it:
https://randomnerdtutorials.com/?s=esp-now
Regards,
Sara
Hi sar, how i do program ESP-NOW Onen way between three 3 nodemcu esp 8266
Hi Sarah,How i do program ESP-NOW One way (many to many) between three 3 nodemcu esp 8266,could you send me tutorial of this please
Hello Sara,
Can you “daisy chain” boards together? Like can you have a master board (1) send a command to slave board (4) but the command would “relay” through slave board (2) and (3) to get to slave board (4). I want to make WS2812B lights for the tops of a row of fence posts and be able to send the color patterns “down the line”.
Thanks for your response.
Hi.
Yes, that is possible.
You just need to program each board to receive the messages from a certain board and then specify to which board it will send the message.
Regards,
Sara
All these questions, I hope people are buying the inline tutorial books as well. The digital books have more detail.
Hi there Sara
Right now, the program is such that pressing the button once turns on LED and pressing it again turns off
Could you please tell me what changes should I make in the program so that the LED I connect to the output pin turns on only for the time I press the button. As soon as I release the button, the LED turn off. (Like a momentary switch)
Good one. I got inspired by this post and created a door alarm. One esp8266 sense motion as a guest gets closer to our walk-way and sends notification to another esp8266 which is inside our home. The code is available at https://github.com/sankarbha/ESP8266-Door-Alarm if anyone is interested.
Thanks.
That’s great!|
Thanks for sharing.
Regards,
Sara
Hello Sankar,
If i understand correctly from your code, you have a PIR outside the house with a ESP8266 and power in a box to detect and send message.
Would you mind sharing your schematic too?
Do you have power by battery or wires ?
How long the battery last ?
Can you develop the receiver to send a text message to an email ?
This email will be great in case i am not home.
It will help me to control my camera or my alarm.
Thank you
Ion.
Thanks Ion for your comment.
Yes you are correct, the board outside our home is connected to a PIR sensor and the board inside our home is connected to a Buzzer.
Both boards are powered by wires.
My current intent is to not to rely on internet for this system to work. But we can add as many receivers as we want, as esp-now supports one-many communication.
As you have required, we can have another receiver which is connected to internet and notify via email. This can be turned on whenever you go out of home. I can develop this, but I might need some time.
I do not know how to draw the schematic, but I can share pictures of both boards in the github project at https://github.com/sankarbha/ESP8266-Door-Alarm.
P.S: I am just getting started with IoT & NodeMCU. I have just followed RNT posts and few others and came up with this.
Regards,
Sankar
Thank you Sankar,
Please let me know when you will have the email adaptor too.
It is a great project and BIG idea.
Dear Ion,
I have just completed the email adapter and will push the changes to the github repository [https://github.com/sankarbha/ESP8266-Door-Alarm] in a day or too.
I faced some challenges to make the receiver stay in connection with both ESP-NOW and the WiFi router.
Regards,
Sankar
Thank you Sankar,
I am looking forward to it.
Please let us know when it is posted so we/I can get it and test.
Have a great day.
Dear Ion,
The email adapter is now available in github repo https://github.com/sankarbha/ESP8266-Door-Alarm .
This uses IFTTT Webhooks to trigger email. I find it simple and clean to trigger a webhook in the receiver. Please read the comments in the code to get your IFTTT key and event name.
Hope it helps.
Thanks.
Dear Ion,
Just in-case you cannot afford to wait, you could follow these posts and build for your requirement. I would be doing the same.
https://randomnerdtutorials.com/esp32-cam-send-photos-email/
https://randomnerdtutorials.com/esp32-cam-pir-motion-detector-photo-capture/
https://randomnerdtutorials.com/door-status-monitor-using-the-esp8266/
https://randomnerdtutorials.com/telegram-esp8266-nodemcu-motion-detection-arduino/
This could be one simple and clean solution if you could provide internet connectivity to the board with PIR sensor. You won’t need another board, as this will sense and send notification via telegram. You can go through other posts I have listed here and tweak this to make it to send email.
Hope it helps.
Thanks.
Hello Sankar,
What do you mean by
“send notification via telegram” ?
Dear Ion,
Please go through https://randomnerdtutorials.com/esp32-cam-shield-pcb-telegram/ tutorial. That is what I meant by send notification via Telegram app. With Telegram you could create a Chat Bot, with which you can interact via chat commands and make it to perform certain actions. The same bot could also send notifications to you and all of this will be available to you through Telegram mobile app.
P.S: I have completed the email adapter, please refer my reply to the other thread in this post.
Regards,
Sankar
Thank you very much for the info.
Now I know what you mean by telegram.
Have a great day.
This may sound obvious but I just wasted 3 hours troubleshooting this mistake (and I am not a noob – I should know better!). When using these example programs, if your ESPs have ever been used before it is important to set Erase Flash to “All Flash Contents” in the Arduino IDE Tools Menu when uploading the first time.
I did not do that. I had Erase Flash set to “Sketch Only”. Something must have been lurking in memory from whatever I last used these ESPs for. The symptom was that 99% of all transmissions fail but every so often, just to add confussion, one will succeed. Erasing all flash contents solved the problem immediately. Live / Learn.
I have a project using ESPNOW, one sender (ESP01) to one receiver (NodeMCU). The send just outputs “1” to show it is powered up and communicating. I want to be able to detect on the NODMCU when the ESP01 is powered up (signal received) and when it is not (no signal received).
I have tried to use information from the void OnDataRecv function but I am picking up incorrect signls from the ESP01 is there a really simple way of acheiveing this.
Thanks
Chris
Increment the number at the sender end after each send.
At the receiver, look for the new incremented number.
Hi, i used the above skteches for a long time and they as they should do. Absolut imazing.
By now, i had to change the code for a new receiver and his output. I use always ESP32.
Every time i get an compilation Error, although on used sketches, which i can’t solve!
Error code:
D:\Daten\prog\Module\Modul_06_ESP32_Rcv_202230124\Modul_06_ESP32_Rcv_202230124.ino: In function ‘void OnDataRecv(const uint8_t*, const uint8_t*, int)’:
D:\Daten\prog\Module\Modul_06_ESP32_Rcv_202230124\Modul_06_ESP32_Rcv_202230124.ino:55:47: error: ‘void* memcpy(void*, const void*, size_t)’
writing to an object of type ‘struct_message’ {aka ‘struct struct_message’} with no trivial copy-assignment; use copy-assignment or copy-initialization instead [-Werror=class-memaccess]
memcpy(&myData, incomingData, sizeof(myData));
^
D:\Daten\prog\Module\Modul_06_ESP32_Rcv_202230124\Modul_06_ESP32_Rcv_202230124.ino:23:16: note: ‘struct_message’ {aka ‘struct struct_message’} declared here
typedef struct struct_message {
^~~~~~~~~~~~~~
cc1plus.exe: some warnings being treated as errors
exit status 1
Compilation error: ‘void* memcpy(void*, const void*, size_t)’ writing to an object of type ‘struct_message’ {aka ‘struct struct_message’}
with no trivial copy-assignment; use copy-assignment or copy-initialization instead [-Werror=class-memaccess]
May be, you now an answer to help me?
with kindly regards
walter
Hi.
Maybe you need to downgrade your ESP32 installation to an older version to be compatible with older codes?…
I’m not sure…
But you can try downgrading in Tools > Board > Boards Manager, search for ESP32, and downgrade to a previous version. Then, try it out again.
Regards,
Sara
Hey, ran into the same problem. No idea what causes it or where to find documentation other than this, but by trial an error I found out that changing the OnDataRecv() function from what is provided in the tutorial to void OnDataRecv(uint8_t *mac_addr, uint8_t *data, uint8_t data_len) solves it. Im no expert C++ magician so no idea what was wrong, but it worked for me.
Best of luck
Viktor
Hi Sara. I really appreciate you for this wonderful tutorial.
I have a problem if you could help.
I have a single point loadcell and I want to send my loadcell data from one esp board to another. when I get data via TTL it works properly but when i want to send these data wireless and with the codes that you share it has so much noise and in some cases these data arent the same as data I received in serial monitor
What are the differences between what you see in the Serial Monitor and what you receive?
Regards,
Sara
Can ESPNow encryption be used on a ESP8266? If so, what needs to be changed from the ESP32 code?
Hello Sara,
Excellent your work. I’ve been trying to keep up.
I need some code indication for using esp8862 – espnow, master slave, unidirectional, where 3 buttons on the master trigger 3 ledes on the slave.
Simple thing for beginner.
Thank you very much if it’s possible, okay?
Thank you, health!
Hi.
Thank you for following our work.
Yes. It is possible.
I don’t have anything with thos exact details.
I recommend that you take a look at all our ESP-NOW tutorials and check which ones can be usefuk for your scenario.
Here’s a link to the projects: https://randomnerdtutorials.com/?s=esp-now
Regards,
Sara
Hi,
When I upload your code for a one way communication I get “delivery success”.
However, when I update the MAC address I get delivery failure.
I worked through the addresses and found that if the first block is 0xbc, then it fails. If i change to 0xbd it works fine. Any ideas?
My project required a temporary Wi-Fi connection to set the time in a RTC. I then needed to use ESP-NOW to send/receive temperature data.
I have had trouble getting ESPNOW working after I connected to Wi-Fi.
I have now successfully used both Wi-Fi, and ESPNOW, between two ESP8266’s.
Simply add:
wifi_set_channel(6);
to the last line of void setup(), on both the receiver and transmitter. I just picked a random channel. Before I added this line communication was VERY unreliable.
From the Espressif documentation: “Can Wi-Fi be used with ESP-NOW at the same time? Yes, but it should be noted that the channel of ESP-NOW must be the same as that of the connected AP.”
I can’t find any information about using httpupdate with esp-now sender. Is it so obvious that nobody thinks it needs to be explained?
I have esp-now working well with mqtt, but my senders are a bit inaccessible. All of the senders are turned off until motion turns them on so OTA won’t work.
Hi, I have just tested the connection between two esp8266 with Esp-now but the distance just only 12 meters, longer than 12 meters the connection is lost.The sender is esp8266 12-e. The receiver is esp8266 12-e Node MCU kit. Maybe the sender and receiver should be the same. Thank for your reply
I try your example with a Wemos Mini as transmitter and a DOIT-ESP8266 as receiver.
With your example sketch the range is up to 20 meters also with an intermediate wall.
But if I change the values with that of a BME280 putting four struct values to float the range is limited to 2 or 3 meters and it needs 2 or 3 sending cycles to update values in receiver.
Anyone experienced and solved that?
Thanks
Renzo
Thanks a lot for this tutorial on ESP8266. You have save a lot of time and energy trying to figure out the working between ESP32 vs ESP8266.
Thanks again.
Great.
Thanks.
Regards,
Sara
Has anyone tried this recently? Some time ago, I was getting fast speed. with the latest arduino/esp etc is something broken? i have just tried 30 esp8266 chips from different suppliers and seem to be getting 10 fails in transmission to one success. Something has been broken. I have tried the old IDE and the new IDE ie version 1.8.18 and version 2.xx.xx
After days of testing. Turns out a brand name commercial home automation power controller had gone faulty and was blocking channel one. Was sending a carrier wave. All is working again.
Great.
I’m glad evything is solved.
Regards,
Sara
Hi Its very Good Examples for WIFI Networking.
I Want to Know, Its Possible, to Disable Receive data when its transmit data to Other Module ?
You guys are awesome!
Hi, i have try your project on 3 types esp8266 board,
they are nodemcu 8266 (in your example), wemos D1 R2 & Wemos D1 Mini.
but for 3 types of board i have some problem, if the slaves range > 1 meter it will fail to send.
in your tutorial wrote the range up tp 140m, but mine can’t.
FYI, i have 3pcs of each types, and already change each board type which the broadcaster and receiver and still have same result.
what is i’m wrong? my code is the same as yours.
when i’m googling, i found : esp32.com/viewtopic.php?t=33291
// Set Long Range Mode
esp_wifi_set_protocol( WIFI_IF_STA , WIFI_PROTOCOL_LR);
but its only for esp32? cant implement into esp8266?
please advice…
Hi.
I’m not sure, but I think it’s a problem with the Wemos D1 mini boards.
Many of our readers complain about ESP-NOW when using those boards.
Regards,
Sara
Hello, can you help me? Esp two now. adruino 2560 conversion 74HC4050__3V => (mosi.miso.reset,slk,cs,int) EPS TWO NOW ==> signal <== EPS TWO NOW => (mosi.miso.reset,slk,cs,int) => LCD RA8875. cable connected works LCD but I want ESP TWO NOW without cable.
Hello,
Thank you for another excellent tutorial, they are really helpful. I have ESP-NOW working but I haven’t found any recent code for getting RSSI to work. There are older examples from 3 or 4 years ago but I found that Espresif has updated their code/files to allow the extraction of RSSI. Do you have any examples of how to get RSSI using ESP-NOW? Thank you so much for any assistance you may offer. I am using a transmitter, receiver and WiFi link, all ESP8266. regards, Paul
thanks for the great project
easy to follow instructions & finally i get my 2 Esp’s work
thanks
johnny