![\"ESP-NOW](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2020\/05\/ESP-NOW-ESP8266-NodeMCU-EXPLAINED-Easiest-Wireless-Communication-Between-ESP8266-Boards.jpg?resize=1200%2C675&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\nWe have other tutorials about ESP-NOW with the ESP8266:<\/p>\n\n\n\n
- <\/a>Getting Started with ESP-NOW (ESP8266 NodeMCU with Arduino IDE)<\/a><\/li>
- ESP-NOW with ESP8266: Send Data to Multiple Boards (one-to-many)<\/a><\/li>
- ESP-NOW with ESP8266: Receive Data from Multiple Boards (many-to-one)<\/a><\/li><\/ul>\n\n\n\n
Introducing ESP-NOW<\/h2>\n\n\n\n
ESP-NOW<\/a><\/strong> is a connectionless communication protocol developed by Espressif that features short packet transmission. This protocol enables multiple devices to talk to each other without using Wi-Fi.<\/p>\n\n\n\n
![\"ESP-NOW](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2020\/01\/esp-now-logo.png?resize=244%2C61&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\nThis is a fast communication protocol that can be used to exchange small messages (up to 250 bytes) between ESP32 boards. ESP-NOW is very versatile and you can have one-way or two-way communication in different arrangements.<\/p>\n\n\n\n
In this tutorial, we\u2019ll show you how to establish a two-way communication between two ESP8266 boards.<\/p>\n\n\n\n
![\"ESP-NOW](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2020\/02\/ESP8266-ESP-NOW-Two-Way-Communication.png?resize=750%2C340&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\nProject Overview<\/h2>\n\n\n\n
The following diagram shows an overview of the project we’ll build:<\/p>\n\n\n\n
![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2020\/05\/ESP8266-ESP-NOW-Two-Way-DHT-Readings-Overview.png?resize=872%2C435&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\n- In this project we\u2019ll have two ESP8266 boards. Each board is connected to a DHT sensor;<\/li>
- Each board gets temperature and humidity readings from their corresponding sensors;<\/li>
- Each board sends its readings to the other board via ESP-NOW;<\/li>
- When a board receives the readings, it prints them on the Serial Monitor. You can connect an OLED display to visualize the readings, for example.<\/li>
- When a message is sent, a message is printed indicating if the packet was successfully delivered or not.<\/li>
- Each board needs to know the other board MAC address in order to send the message.<\/li><\/ul>\n\n\n\n
In this example, we\u2019re using a two-way communication between two boards, but you can add more boards to this setup, and having all boards communicating with each other.<\/p>\n\n\n\n
Prerequisites<\/h2>\n\n\n\n
Before proceeding with this project, make sure you check the following prerequisites.<\/p>\n\n\n\n
ESP8266 add-on Arduino IDE<\/h3>\n\n\n\n
We\u2019ll program the ESP8266 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:<\/p>\n\n\n\n
- Installing the ESP8266 Board in Arduino IDE (Windows, Mac OS X, and Linux)<\/a><\/li><\/ul>\n\n\n\n
Installing DHT Libraries<\/h3>\n\n\n\n
To read from the DHT sensor, we\u2019ll use the DHT library from Adafruit<\/a>. To use this library you also need to install the Adafruit Unified Sensor library<\/a>. Follow the next steps to install those libraries.<\/p>\n\n\n\n
1. Open your Arduino IDE and go to Sketch <\/strong>> Include Library<\/strong> > Manage Libraries<\/strong>. The Library Manager should open.<\/p>\n\n\n\n
2. Search for \u201cDHT<\/strong>\u201d on the Search box and install the DHT library from Adafruit.<\/p>\n\n\n\n
![\"Installing](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2019\/04\/adafruit_dht_library.png?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\n3. After installing the DHT library from Adafruit, type \u201cAdafruit Unified Sensor<\/strong>\u201d in the search box. Scroll all the way down to find the library and install it.<\/p>\n\n\n\n
![\"Installing](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2019\/04\/adafruit_unified_sensor_library.png?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\nAfter installing the libraries, restart your Arduino IDE.<\/p>\n\n\n\n
Parts Required<\/h3>\n\n\n\n
For this tutorial you need the following parts:<\/p>\n\n\n\n
- 2x ESP8266 development board<\/a> (read ESP8266 development boards comparison<\/a>)<\/li>
- 2x DHT22<\/a> or DHT11<\/a> Temperature and Humidity Sensor<\/li>
- 2x 4.7k Ohm Resistor<\/a><\/li>
- 2x Breadboard<\/a><\/li>
- Jumper wires<\/a><\/li><\/ul>\n\n\n
You can use the preceding links or go directly to MakerAdvisor.com\/tools<\/a> to find all the parts for your projects at the best price!<\/p>
![](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/header-200.png?w=1200&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n\n\n\nGetting the Boards MAC Address<\/h2>\n\n\n\n
To send messages between each board, we need to know their MAC address<\/a>. Each board has a unique MAC address (learn how to Get and Change the ESP32 MAC Address<\/a>).<\/p>\n\n\n\n
Upload the following code to each of your boards to get their MAC address.<\/p>\n\n\n
\/*\n Rui Santos & Sara Santos - Random Nerd Tutorials\n Complete project details at https:\/\/RandomNerdTutorials.com\/get-change-esp32-esp8266-mac-address-arduino\/\n Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files. \n The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.\n*\/\n#include <WiFi.h>\n#include <esp_wifi.h>\n\nvoid readMacAddress(){\n uint8_t baseMac[6];\n esp_err_t ret = esp_wifi_get_mac(WIFI_IF_STA, baseMac);\n if (ret == ESP_OK) {\n Serial.printf("%02x:%02x:%02x:%02x:%02x:%02x\\n",\n baseMac[0], baseMac[1], baseMac[2],\n baseMac[3], baseMac[4], baseMac[5]);\n } else {\n Serial.println("Failed to read MAC address");\n }\n}\n\nvoid setup(){\n Serial.begin(115200);\n\n WiFi.mode(WIFI_STA);\n WiFi.STA.begin();\n\n Serial.print("[DEFAULT] ESP32 Board MAC Address: ");\n readMacAddress();\n}\n \nvoid loop(){\n\n}\n<\/code><\/pre>\n\tView raw code<\/a><\/p>\n\n\n\n
After uploading the code, press the RST\/EN button, and the MAC address should be displayed on the Serial Monitor.<\/p>\n\n\n\n
![\"Get](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2020\/05\/Get-ESP8266-MAC-Address-Serial-Monitor.jpg?resize=666%2C320&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\nWrite down the MAC address of each board to clearly identify them.<\/p>\n\n\n\n
![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2020\/06\/ESP8266-NodeMCU-board-MAC-Address.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\nESP8266 and DHT11\/DHT22 Schematic Diagram<\/h2>\n\n\n\n
Before proceeding with the tutorial, wire the DHT11 or DHT22 temperature and humidity sensor to the ESP8266 as shown in the following schematic diagram.<\/p>\n\n\n\n
![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2019\/06\/esp8266-dht.png?resize=482%2C620&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\nIn this example, we\u2019re wiring the DHT data pin to GPIO5 (D1), but you can use any other suitable GPIO. Read our ESP8266 GPIO Reference Guide<\/a> to learn more about the ESP8266 GPIOs.<\/p>\n\n\n\n
You might like: ESP8266 DHT11\/DHT22 Temperature and Humidity Web Server with Arduino IDE<\/a><\/p>\n\n\n\n
ESP8266 Two-Way Communication ESP-NOW Code<\/h2>\n\n\n\n
Upload the following code to each of your boards. Before uploading the code, you need to enter the MAC address of the other board (the board you\u2019re sending data to).<\/p>\n\n\n
\/*\n Rui Santos\n Complete project details at https:\/\/RandomNerdTutorials.com\/esp-now-two-way-communication-esp8266-nodemcu\/\n \n Permission is hereby granted, free of charge, to any person obtaining a copy\n of this software and associated documentation files.\n \n The above copyright notice and this permission notice shall be included in all\n copies or substantial portions of the Software.\n*\/\n\n#include <ESP8266WiFi.h>\n#include <espnow.h>\n\n#include <Adafruit_Sensor.h>\n#include <DHT.h>\n\n\/\/ REPLACE WITH THE MAC Address of your receiver \nuint8_t broadcastAddress[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};\n\n\/\/ Digital pin connected to the DHT sensor\n#define DHTPIN 5 \n\n\/\/ Uncomment the type of sensor in use:\n\/\/#define DHTTYPE DHT11 \/\/ DHT 11\n#define DHTTYPE DHT22 \/\/ DHT 22 (AM2302)\n\/\/#define DHTTYPE DHT21 \/\/ DHT 21 (AM2301)\n\nDHT dht(DHTPIN, DHTTYPE);\n\n\/\/ Define variables to store DHT readings to be sent\nfloat temperature;\nfloat humidity;\n\n\/\/ Define variables to store incoming readings\nfloat incomingTemp;\nfloat incomingHum;\n\n\/\/ Updates DHT readings every 10 seconds\nconst long interval = 10000; \nunsigned long previousMillis = 0; \/\/ will store last time DHT was updated \n\n\/\/ Variable to store if sending data was successful\nString success;\n\n\/\/Structure example to send data\n\/\/Must match the receiver structure\ntypedef struct struct_message {\n float temp;\n float hum;\n} struct_message;\n\n\/\/ Create a struct_message called DHTReadings to hold sensor readings\nstruct_message DHTReadings;\n\n\/\/ Create a struct_message to hold incoming sensor readings\nstruct_message incomingReadings;\n\n\/\/ Callback when data is sent\nvoid OnDataSent(uint8_t *mac_addr, uint8_t sendStatus) {\n Serial.print("Last Packet Send Status: ");\n if (sendStatus == 0){\n Serial.println("Delivery success");\n }\n else{\n Serial.println("Delivery fail");\n }\n}\n\n\/\/ Callback when data is received\nvoid OnDataRecv(uint8_t * mac, uint8_t *incomingData, uint8_t len) {\n memcpy(&incomingReadings, incomingData, sizeof(incomingReadings));\n Serial.print("Bytes received: ");\n Serial.println(len);\n incomingTemp = incomingReadings.temp;\n incomingHum = incomingReadings.hum;\n}\n\nvoid getReadings(){\n \/\/ Read Temperature\n temperature = dht.readTemperature();\n \/\/ Read temperature as Fahrenheit (isFahrenheit = true)\n \/\/float t = dht.readTemperature(true);\n if (isnan(temperature)){\n Serial.println("Failed to read from DHT");\n temperature = 0.0;\n }\n humidity = dht.readHumidity();\n if (isnan(humidity)){\n Serial.println("Failed to read from DHT");\n humidity = 0.0;\n }\n}\n\nvoid printIncomingReadings(){\n \/\/ Display Readings in Serial Monitor\n Serial.println("INCOMING READINGS");\n Serial.print("Temperature: ");\n Serial.print(incomingTemp);\n Serial.println(" \u00baC");\n Serial.print("Humidity: ");\n Serial.print(incomingHum);\n Serial.println(" %");\n}\n \nvoid setup() {\n \/\/ Init Serial Monitor\n Serial.begin(115200);\n\n \/\/ Init DHT sensor\n dht.begin();\n \n \/\/ Set device as a Wi-Fi Station\n WiFi.mode(WIFI_STA);\n WiFi.disconnect();\n\n \/\/ Init ESP-NOW\n if (esp_now_init() != 0) {\n Serial.println("Error initializing ESP-NOW");\n return;\n }\n\n \/\/ Set ESP-NOW Role\n esp_now_set_self_role(ESP_NOW_ROLE_COMBO);\n\n \/\/ Once ESPNow is successfully Init, we will register for Send CB to\n \/\/ get the status of Trasnmitted packet\n esp_now_register_send_cb(OnDataSent);\n \n \/\/ Register peer\n esp_now_add_peer(broadcastAddress, ESP_NOW_ROLE_COMBO, 1, NULL, 0);\n \n \/\/ Register for a callback function that will be called when data is received\n esp_now_register_recv_cb(OnDataRecv);\n}\n \nvoid loop() {\n unsigned long currentMillis = millis();\n if (currentMillis - previousMillis >= interval) {\n \/\/ save the last time you updated the DHT values\n previousMillis = currentMillis;\n\n \/\/Get DHT readings\n getReadings();\n\n \/\/Set values to send\n DHTReadings.temp = temperature;\n DHTReadings.hum = humidity;\n\n \/\/ Send message via ESP-NOW\n esp_now_send(broadcastAddress, (uint8_t *) &DHTReadings, sizeof(DHTReadings));\n\n \/\/ Print incoming readings\n printIncomingReadings();\n }\n}\n<\/code><\/pre>\n\tView raw code<\/a><\/p>\n\n\n\n
How the Code Works<\/h2>\n\n\n\n
Keep reading to learn how the code works, or skip to the Demonstration section.<\/p>\n\n\n\n
Import libraries<\/h3>\n\n\n\n
Start by importing the required libraries.<\/p>\n\n\n\n
#include <ESP8266WiFi.h>\n#include <espnow.h><\/code><\/pre>\n\n\n\nThe espnow.h<\/span> library comes installed by default when you install the ESP8266 board. When compiling the code, make sure you have an ESP8266 board selected in the Boards menu.<\/p>\n\n\n\n
Include the DHT libraries to read from the DHT sensor.<\/p>\n\n\n\n
#include <Adafruit_Sensor.h>\n#include <DHT.h><\/code><\/pre>\n\n\n\nIn the next line, insert the MAC address of the receiver board:<\/p>\n\n\n\n
uint8_t broadcastAddress[] = {0x2C, 0x3A, 0xE8, 0x0E, 0xBB, 0xED};<\/code><\/pre>\n\n\n\nDefine the GPIO the DHT pin is connected to. In this case, it is connected to GPIO 5<\/span> (D1).<\/p>\n\n\n\n
#define DHTPIN 5 <\/code><\/pre>\n\n\n\nThen, select the DHT sensor type you\u2019re using. In our example, we\u2019re using the DHT22. If you\u2019re using another type, you just need to uncomment your sensor and comment all the others.<\/p>\n\n\n\n
\/\/#define DHTTYPE DHT11 \/\/ DHT 11\n#define DHTTYPE DHT22 \/\/ DHT 22 (AM2302)\n\/\/#define DHTTYPE DHT21 \/\/ DHT 21 (AM2301)<\/code><\/pre>\n\n\n\nInstantiate a DHT<\/span> object with the type and pin defined earlier.<\/p>\n\n\n\n
DHT dht(DHTPIN, DHTTYPE);<\/code><\/pre>\n\n\n\nDefine variables to store the DHT readings to be sent:<\/p>\n\n\n\n
float temperature;\nfloat humidity;<\/code><\/pre>\n\n\n\nDefine more two variables to store incoming readings:<\/p>\n\n\n\n
float incomingTemp;\nfloat incomingHum;<\/code><\/pre>\n\n\n\nWe’ll send DHT readings via ESP-NOW every 10 seconds. That period of time is defined in the interval<\/span> variable. You can change that interval.<\/p>\n\n\n\n
const long interval = 10000; \nunsigned long previousMillis = 0; \/\/ will store last time DHT was updated <\/code><\/pre>\n\n\n\nThe following variable will store a success message if the readings are delivered successfully to the other board.<\/p>\n\n\n\n
\/\/ Variable to store if sending data was successful\nString success;<\/code><\/pre>\n\n\n\nCreate a structure that stores temperature and humidity readings.<\/p>\n\n\n\n
typedef struct struct_message {\n float temp;\n float hum;\n} struct_message;<\/code><\/pre>\n\n\n\nThen, you need to create two instances of that structure. One to receive the readings and another to store the readings to be sent.<\/p>\n\n\n\n
The DHTReadings<\/span> will store the readings to be sent.<\/p>\n\n\n\n
struct_message DHTReadings;<\/code><\/pre>\n\n\n\nThe incomingReadings<\/span> will store the data coming from the other board.<\/p>\n\n\n\n
struct_message incomingReadings;<\/code><\/pre>\n\n\n\nOnDataSent() callback function<\/h3>\n\n\n\n
The OnDataSent()<\/span> function will be called when new data is sent. This function simply prints if the message was successfully delivered or not. <\/p>\n\n\n\n
If the message is delivered successfully, the status variable returns 0<\/span>, so we can set our success message to \u201cDelivery Success\u201d<\/span>:<\/p>\n\n\n\n
void OnDataSent(uint8_t *mac_addr, uint8_t sendStatus) {\n Serial.print(\"Last Packet Send Status: \");\n if (sendStatus == 0){\n Serial.println(\"Delivery success\");\n }<\/code><\/pre>\n\n\n\nIf the success message returns 1<\/span>, it means the delivery failed:<\/p>\n\n\n\n
else {\n success = \"Delivery Fail :(\";\n}<\/code><\/pre>\n\n\n\nOnDataRecv() callback function<\/h3>\n\n\n\n
The OnDataRecv()<\/span> function is executed when a new packet arrives.<\/p>\n\n\n\n
void OnDataRecv(uint8_t * mac, uint8_t *incomingData, uint8_t len) {<\/code><\/pre>\n\n\n\nWe save the new packet in the incomingReadings<\/span> structure we\u2019ve created previously:<\/p>\n\n\n\n
memcpy(&incomingReadings, incomingData, sizeof(incomingReadings));<\/code><\/pre>\n\n\n\nWe print the message length on the serial monitor. You can only send 250 bytes in each packet.<\/p>\n\n\n\n
Serial.print(\"Bytes received: \");\nSerial.println(len);<\/code><\/pre>\n\n\n\nThen, store the incoming readings in their corresponding variables. To access the temperature<\/span> variable inside incomingReadings<\/span>structure, you just need to do call incomingReadings.temp<\/span> as follows:<\/p>\n\n\n\n
incomingTemp = incomingReadings.temp;<\/code><\/pre>\n\n\n\nThe same process is done for the humidity:<\/p>\n\n\n\n
incomingHum = incomingReadings.hum;<\/code><\/pre>\n\n\n\ngetReadings()<\/h3>\n\n\n\n
The getReadings()<\/span> function gets temperature and humidity from the DHT sensor. The following line gets the current temperature and saves it in the temperature<\/span> variable:<\/p>\n\n\n\n
temperature = dht.readTemperature();<\/code><\/pre>\n\n\n\nThis previous line returns the temperature in Celsius degrees. To get the temperature in Fahrenheit, comment the previous line and uncomment the following:<\/p>\n\n\n\n
\/\/float t = dht.readTemperature(true);<\/code><\/pre>\n\n\n\nSometimes, you’re not able to get readings from the sensor. When that happens the sensor returns nan<\/span>. If that’s the case, we set the temperature<\/span> to 0.0<\/span>.<\/p>\n\n\n\n
A similar process is done to get the humdity readings. The current humidity value is saved on the humidity<\/span> variable:<\/p>\n\n\n\n
humidity = dht.readHumidity();\nif (isnan(humidity)){\n Serial.println(\"Failed to read from DHT\");\n humidity = 0.0;\n}<\/code><\/pre>\n\n\n\nprintIncomingReadings()<\/h3>\n\n\n\n
The printIncomingReadings()<\/span> function simply prints the received readings on the Serial Monitor.<\/p>\n\n\n\n
The received temperature in saved on the incomingTemp<\/span> variable and the received humidity is saved on the incomingHum<\/span> variable as we’ll see in a moment.<\/p>\n\n\n\n
void printIncomingReadings(){\n \/\/ Display Readings in Serial Monitor\n Serial.println(\"INCOMING READINGS\");\n Serial.print(\"Temperature: \");\n Serial.print(incomingTemp);\n Serial.println(\" \u00baC\");\n Serial.print(\"Humidity: \");\n Serial.print(incomingHum);\n Serial.println(\" %\");\n}<\/code><\/pre>\n\n\n\nsetup()<\/h3>\n\n\n\n
In the setup()<\/span>, initialize the Serial Monitor:<\/p>\n\n\n\n
Serial.begin(115200);<\/code><\/pre>\n\n\n\nInitialize the DHT sensor:<\/p>\n\n\n\n
dht.begin();<\/code><\/pre>\n\n\n\nSet the ESP8266 as a station:<\/p>\n\n\n\n
WiFi.mode(WIFI_STA);\nWiFi.disconnect();<\/code><\/pre>\n\n\n\nInitialize ESP-NOW:<\/p>\n\n\n\n
if (esp_now_init() != 0) {\n Serial.println(\"Error initializing ESP-NOW\");\n return;\n}<\/code><\/pre>\n\n\n\nSet the ESP8266 ESP-NOW role. In this example, the ESP8266 receives and sends readings via ESP-NOW, so set the role to ESP_NOW_ROLE_COMBO<\/span>.<\/p>\n\n\n\n
esp_now_set_self_role(ESP_NOW_ROLE_COMBO);<\/code><\/pre>\n\n\n\nThen, register for the OnDataSent<\/span> callback function.<\/p>\n\n\n\n
esp_now_register_send_cb(OnDataSent);<\/code><\/pre>\n\n\n\nIn order to send data to another board, you need to pair it as a peer. The following line add a new peer.<\/p>\n\n\n\n
esp_now_add_peer(broadcastAddress, ESP_NOW_ROLE_COMBO, 1, NULL, 0);<\/code><\/pre>\n\n\n\nThe esp_now_add_peer()<\/span> function accepts the following arguments, in this order: mac address, peer role, wi-fi channel, key, and key length.<\/p>\n\n\n\n
Finally, register for the OnDataRecv<\/span> callback function.<\/p>\n\n\n\n
esp_now_register_recv_cb(OnDataRecv);<\/code><\/pre>\n\n\n\nloop()<\/h3>\n\n\n\n
In the loop()<\/span>, check if it is time to get new readings:<\/p>\n\n\n\n
unsigned long currentMillis = millis();\nif (currentMillis - previousMillis >= interval) {\n \/\/ save the last time you updated the DHT values\n previousMillis = currentMillis;<\/code><\/pre>\n\n\n\nIf it is, call the getReadings<\/span> function to read the current temperature and humidity.<\/p>\n\n\n\n
getReadings();<\/code><\/pre>\n\n\n\nThen, update the DHTReadings<\/span> structure with the new temperature and humidity values:<\/p>\n\n\n\n
DHTReadings.temp = temperature;\nDHTReadings.hum = humidity;<\/code><\/pre>\n\n\n\nSend the structure via ESP-NOW:<\/p>\n\n\n\n
esp_now_send(broadcastAddress, (uint8_t *) &DHTReadings, sizeof(DHTReadings));<\/code><\/pre>\n\n\n\nFinally, call the printIncomingReadings()<\/span> function to print the incoming readings on the Serial Monitor.<\/p>\n\n\n\n
printIncomingReadings();<\/code><\/pre>\n\n\n\nDemonstration<\/h2>\n\n\n\n
After uploading the code to each board, open an Arduino IDE Serial Monitor window. Alternatively, you can open two different serial connections (using PuTTY<\/a>) to see the two boards interacting simultaneously.<\/p>\n\n\n\n
![\"ESP-NOW](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2020\/06\/ESP-NOW-ESP8266-NodeMCU-Board-Exchange-Sensor-Readings.jpg?resize=900%2C506&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\nAs you can see, it is working as expected. Each board is printing the other board’s readings.<\/p>\n\n\n\n
![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2020\/06\/ESP8266-ESP-NOW-Two-Way-Communication-exchange-sensor-readings.jpg?resize=825%2C308&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\nWrapping Up<\/h2>\n\n\n\n
In this tutorial we\u2019ve shown you how to establish a two-way communication with two ESP8266 board using ESP-NOW. This is a very versatile communication protocol that can be used to send packets with up to 250 bytes. ESP-NOW communication protocol can also be used with ESP32 boards: Getting Started with ESP-NOW (ESP32 with Arduino IDE)<\/a>.<\/p>\n\n\n\n
As an example, we\u2019ve shown you the interaction between two boards, but you can add many boards to your setup. You just need to know the MAC address of the board you\u2019re sending data to. We’ll be publishing more tutorials about ESP-NOW<\/strong><\/a>, so stay tuned.<\/p>\n\n\n\n
We hope you\u2019ve found this tutorial useful. To learn more about the ESP8266 board, make sure you take a look at our resources:<\/p>\n\n\n\n
- Home Automation with ESP8266<\/a><\/li>
- MicroPython Programming with ESP32 and ESP8266<\/a><\/li>
- More ESP8266 NodeMCU Projects<\/a><\/li><\/ul>\n\n\n\n
Thanks for reading.<\/p>\n","protected":false},"excerpt":{"rendered":"
Learn how to establish a two-way communication between two ESP8266 NodeMCU boards using ESP-NOW communication protocol. As an example, two ESP8266 boards will exchange DHT sensor readings. We’ll use Arduino … <\/p>\n
- MicroPython Programming with ESP32 and ESP8266<\/a><\/li>
- 2x DHT22<\/a> or DHT11<\/a> Temperature and Humidity Sensor<\/li>
- 2x ESP8266 development board<\/a> (read ESP8266 development boards comparison<\/a>)<\/li>
- Installing the ESP8266 Board in Arduino IDE (Windows, Mac OS X, and Linux)<\/a><\/li><\/ul>\n\n\n\n
- ESP-NOW with ESP8266: Send Data to Multiple Boards (one-to-many)<\/a><\/li>