.. zephyr:code-sample:: espnow
   :name: ESP-NOW

   Send and receive ESP-NOW broadcast heartbeat beacons between two ESP32 boards.

Overview
********

This sample demonstrates the ESP-NOW peer-to-peer radio protocol on Espressif
ESP32 boards running Zephyr. No Wi-Fi access point is required -- both devices
lock to the same channel and communicate directly.

The device role is selected at build time:

- **BIDIR** (default) -- transmits a heartbeat beacon every
  ``CONFIG_ESPNOW_BEACON_INTERVAL_S`` seconds *and* prints all received beacons.
  Flash two boards with this role for a loopback test.
- **SENDER** -- beacon thread only; ignores received frames.
- **RECEIVER** -- RX callback only; no beacon thread.

Each heartbeat carries: sequence counter, uptime in milliseconds, and the
sender's MAC address. Total wire size is 14 bytes.

Configuration
*************

The following Kconfig options are active in ``prj.conf``:

- ``CONFIG_WIFI=y`` -- enables the Espressif Wi-Fi driver, which is required
  by ESP-NOW even though no access point is used.
- ``CONFIG_NETWORKING=y`` -- required because the Wi-Fi L2 driver selects
  ``NET_L2_ETHERNET_MGMT`` inside a ``depends on NETWORKING`` guard in
  ``subsys/net/Kconfig``. Without it the Wi-Fi management interface is not
  registered at boot and ``esp_wifi_start()`` fails. The Zephyr network stack
  itself is not used by this sample; only the Wi-Fi driver glue is needed.

Role is selected at build time via ``CONFIG_ESPNOW_ROLE_*`` (see ``Kconfig``).
The Wi-Fi channel is fixed by ``CONFIG_ESPNOW_CHANNEL`` (default: 1); no AP
is required.

Requirements
************

- Two ESP32-S3 or ESP32-C6 DevKit boards connected via USB.
- Both boards must use the same ``CONFIG_ESPNOW_CHANNEL`` (default: 1).

Building and Running
********************

Flash the default **BIDIR** role to two boards:

.. zephyr-app-commands::
   :zephyr-app: samples/boards/espressif/espnow
   :board: esp32s3_devkitc/esp32s3/procpu
   :goals: build flash
   :compact:

To build as receiver only:

.. code-block:: bash

   west build -b esp32s3_devkitc/esp32s3/procpu -- -DCONFIG_ESPNOW_ROLE_RECEIVER=y

Sample Output
*************

Sender side::

   [00:00:00.512,000] <inf> espnow_sample: ESP-NOW v1 ready  ch=1  role=BIDIR
   [00:00:00.513,000] <inf> espnow_sample: Beacon thread started  interval=5s
   [00:00:05.001,000] <inf> espnow_sample: TX beacon seq=0  uptime=5001 ms  mac=24:d7:eb:55:87:8c
   [00:00:05.002,000] <inf> espnow_sample: TX OK  -> ff:ff:ff:ff:ff:ff

Receiver side::

   [00:00:05.034,000] <inf> espnow_sample: RX [BCAST] from 24:d7:eb:55:87:8c  rssi=-42  len=14
   [00:00:05.034,000] <inf> espnow_sample:   heartbeat seq=0  uptime=5001 ms  src=24:d7:eb:55:87:8c