ESP-NOW Not Working

How to Fix It

1. Set Wi-Fi mode before calling esp_now_init().

   Call WiFi.mode(WIFI_STA) before esp_now_init() on both sender and receiver. ESP-NOW requires the Wi-Fi stack to be initialized, even if you are not connecting to a router. The mode must be set consistently on all devices involved.

2. Verify the peer MAC address exactly.

   The MAC address used in esp_now_add_peer() must exactly match the receiver's Wi-Fi MAC address. Print the receiver's MAC with WiFi.macAddress() and copy it byte-for-byte. A single incorrect digit means the message will never be delivered.

3. Match Wi-Fi channels on all devices.

   When both sender and receiver are also connected to a Wi-Fi router, they must be on the same channel. If your router uses channel 6, both ESP32s must use channel 6 for ESP-NOW. Set the channel explicitly with esp_wifi_set_channel(CHANNEL, WIFI_SECOND_CHAN_NONE) if needed.

4. Register the peer before sending.

   You must call esp_now_add_peer() with the peer info struct before calling esp_now_send(). Include the peer MAC, channel, and encryption flag (false for unencrypted). Sending to a MAC that has not been added as a peer will fail silently.

5. Implement and check the send callback.

   Register a send callback with esp_now_register_send_cb() to see whether each message was delivered. The callback reports ESP_NOW_SEND_SUCCESS or ESP_NOW_SEND_FAIL after each transmission. A FAIL on every send despite correct MAC and channel usually means the receiver is out of range or not running.