ESP-NOW.
Wireless mesh
without Wi-Fi.

01Introduction

Most ESP32 tutorials reach for Wi-Fi by default. That works, but it's overkill for the common case: a handful of devices that just need to send short messages to each other on the same workbench. The router becomes a third wheel — one more thing that can fail, one more handshake, one more 200 ms.

ESP-NOW is Espressif's answer: a thin, connectionless protocol layered directly on top of the 2.4 GHz radio. Two boards exchange data by MAC address, with no AP and no IP stack. You get latency in the ~1 ms range, packets up to 250 bytes, and optional encryption per peer.

By the end of this tutorial you'll have two boards: one reading a temperature sensor, the other displaying the value on an OLED. They'll talk only to each other, with no router involved.

02How ESP-NOW works

Four things happen behind every ESP-NOW exchange. Step through them — the diagrams are deliberately slow so you can follow each one.

That's the whole loop. The interesting bits — encryption, broadcast mode, multi-peer mesh — all build on these four steps.

03vs Wi-Fi & Bluetooth

Pick the right radio for the job. The table below shows where each shines — ESP-NOW is built for low-latency device-to-device messaging on a small fleet.

04Sender code

Reads the BME280 every two seconds and pushes a small struct to the receiver's MAC. We use esp_now_send() — fire-and-forget — and rely on the send callback to log success.

// sender.ino  — broadcasts BME280 readings to one peer
#include <WiFi.h>
#include <esp_now.h>
#include <Adafruit_BME280.h>

uint8_t peerMac[] = { 0x3C, 0x71, 0xBF, 0x08, 0x2B, 0x91 };

struct Sample {
  float tempC;
  float humidity;
  float pressure;
  uint32_t seq;
};

Adafruit_BME280 bme;
Sample sample;

// Called after each send — gives you delivery status
void onSent(const uint8_t *mac, esp_now_send_status_t status) {
  Serial.printf("seq=%u %s\n", sample.seq,
    status == ESP_NOW_SEND_SUCCESS ? "OK" : "FAIL");
}

void setup() {
  Serial.begin(115200);
  bme.begin(0x76);

  WiFi.mode(WIFI_STA);
  esp_now_init();
  esp_now_register_send_cb(onSent);

  esp_now_peer_info_t peer = {};
  memcpy(peer.peer_addr, peerMac, 6);
  peer.channel = 0;     // follow current channel
  peer.encrypt = false;
  esp_now_add_peer(&peer);
}

void loop() {
  sample.tempC    = bme.readTemperature();
  sample.humidity = bme.readHumidity();
  sample.pressure = bme.readPressure() / 100.0f;
  sample.seq++;

  esp_now_send(peerMac, (uint8_t*)&sample, sizeof(sample));
  delay(2000);
}

05Receiver code

Mirror image: register a recv callback, decode the same struct, render to the OLED. Note we never call esp_now_add_peer() here — the receiver doesn't need to know about the sender in advance.

// receiver.ino  — prints incoming Samples to an SSD1306
#include <WiFi.h>
#include <esp_now.h>
#include <Adafruit_SSD1306.h>

Adafruit_SSD1306 oled(128, 64, &Wire);

struct Sample {
  float tempC;
  float humidity;
  float pressure;
  uint32_t seq;
};

void onRecv(const uint8_t *mac, const uint8_t *data, int len) {
  if (len != sizeof(Sample)) return;
  Sample s; memcpy(&s, data, len);

  oled.clearDisplay();
  oled.setCursor(0, 0);
  oled.printf("%.1f °C\n%.0f %%RH\n%.0f hPa\nseq %u",
              s.tempC, s.humidity, s.pressure, s.seq);
  oled.display();
}

void setup() {
  oled.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  WiFi.mode(WIFI_STA);
  esp_now_init();
  esp_now_register_recv_cb(onRecv);
}

void loop() {}  // everything happens in the callback

The highlighted block is the entire receive path — eight lines from radio to screen.

06Wiring diagram

Both boards run from USB. The sender adds a BME280 on I²C; the receiver adds an SSD1306 OLED, also on I²C. Shared pins: SDA = GPIO 21, SCL = GPIO 22.

07Step-by-step build

08Troubleshooting

09What's next

You've got the two-board basic case. From here, three branches are worth exploring:

• Broadcast mode — send to FF:FF:FF:FF:FF:FF and reach every ESP-NOW peer on the channel — the basis of cheap "find me" networks.
• Encrypted peers — set peer.encrypt = true and share a 16-byte LMK between sender and receiver for AES-128 protection.
• Hybrid gateway — pair an ESP-NOW receiver with Wi-Fi/MQTT on the same board to bridge a local mesh to the internet. We cover this in "ESP-NOW + MQTT Gateway".