Comments on: ESP-NOW with ESP8266: Send Data to Multiple Boards (one-to-many)

By: Jordan

Jordan — Tue, 22 Jul 2025 01:46:29 +0000

In reply to Delger. 10

By: Carlos Carrera

Carlos Carrera — Sat, 03 May 2025 14:51:26 +0000

Greetings Rui, Sara!
I don’t know if you already know, but to get the MAC, just compile any sketch, and you’ll be able to see it.

esptool.py v3.0
Serial port COM3
Connecting….
Chip is ESP8266EX
Features: WiFi
Crystal is 26MHz
MAC: d8:f1:5b:08:b2:5f
Uploading stub…
Running stub…
Stub running…
Configuring flash size…
Auto-detected Flash size: 1MB
Compressed 273760 bytes to 201442…
Writing at 0x00000000… (7 %)
Writing at 0x00004000… (15 %)
Writing at 0x00008000… (23 %)
Writing at 0x0000c000… (30 %)
Writing at 0x00010000… (38 %)
Writing at 0x000140

By: Pierre-Yves MULLER

Pierre-Yves MULLER — Mon, 03 Jun 2024 06:08:43 +0000

Hi,
I copy our ESP8266 NodeMCU Sender Code and it works fine ! Thank you.
(I flash only the sender code without any receiver connected. So I receive 2 “Delivery Fail” message; which is correct !)
But when I extend with more receivers (maximum 20!) I noticed on the Arduino IDE Serial Monitor I receive only a maximum of 8 “Delivery Fail” message!
It looks like a timing jam… Do you have an idea why.
I would like to send data to 20 receivers IN THE SAME TIME! Can you provide me any help ?
Thank’s

By: Sara Santos

Sara Santos — Fri, 12 Apr 2024 10:21:28 +0000

In reply to navneet kakkar.

Hi.
Yes.
That should be possible.
Regards,
Sara

By: navneet kakkar

navneet kakkar — Wed, 10 Apr 2024 19:12:30 +0000

hi i am trying to connect multiple nodemcu to one nodemcu and have two way communication between master and slave, is that possible

By: Joe H

Joe H — Wed, 31 Jan 2024 21:24:16 +0000

I have been able to get you code to work, pretty much “as is” using it in a one to one relationship. I can transmit the random X,Y and receive them on receiver, displaying them via the serial monitor. Works, easy, thanks. But….

I then added an OLED display (SSD1306 type), which I’ve used a bunch in the past and the wheels have fallen off. When I go to do put the display out (display.display), I get an exception error: User exception (panic/abort/assert), followed by: Panic core_esp8266_main.cpp:191 __yield, and a memory dump in hex.

Any idea why? It would appear something is stepping on something else, but I can’t figure it out, the Exception Debug tool was not helpful

Any help is appreciated
Joe

By: Joe H

Joe H — Tue, 30 Jan 2024 20:11:49 +0000

Thanks you for this great website and this explanation of ESP-NOW. I’ve got it working using your one to many example and your code pretty much verbatim. But then I tried to add an OLED display, SSD1306, using the Adafruit libraries. The display works when starting up, early in the setup section. But the code I placed code to display the X,Y in the OnDataRecv function and when the display.display statement is executed, the program blows up with a “Panic core_esp8266_main.cpp:191 __yield”. Something is stepping on something, but I don’t know what. I tried to move the display code to it’s own function, called then from the OnDataRecv function, with the same result. Any help or insight would be very much appreciated.

By: Delger

Delger — Thu, 21 Dec 2023 02:35:52 +0000

How many slave esp8266 can be connected to one master esp8266 at the same time?

By: Bhaiya

Bhaiya — Mon, 21 Nov 2022 05:03:46 +0000

Facing a problem..
From one NodeMcu to many is working fine with esp now. But when switching the master nodemcu for seperate x & y values through its IP address while connected from external WiFi router, not working.
Showing ‘Delivery fail’
.
Initially it was Showing ‘Delivery success’.
Can’t understand where is the problem.

By: Andrea

Andrea — Wed, 29 Jun 2022 08:59:29 +0000

Dear Sara and Rui,
thanking for grat tutorial, I have some questions for you:

1 – what happens if “esp_now_add_peer” function fails ? I have to register 5 peers and sometimes it happens that one or more peers “fail” to be added.

2 – in my code i send a broadcast message to all the 5 peers and than I put sender esp8266 in a while loop to wait the feedbacks from all the peers. This is a short extract:

esp_now_send(0, (uint8_t *) &test, sizeof(test));
tWait = millis() + 300;
while (millis() <= tWait){
yield();
}

Is it a correct coding way? Or, am I making some mistake? (I used while to avoid delay function)
Are 300 millis of “waiting time” enough ?

3 – Receiver side: I want that receiver stops running core until it receives a message from sender. Is it ok “locking” it in a while loop like this ?
msgRcv is a “flag” variable that I include into OnDataRecv function ( if receiver receives a message –> msgRcv = true; )

while(msgRcv == false){
yield();
}

Thanks a lot in advance !
Andrea