ESP-NOW netdev interface

WiFi based ESP-NOW network device driver.

This module realizes a netdev interface using Espressif’s ESP-NOW technology which uses the built-in WiFi module.

With ESP-NOW, the ESP32 provides a connectionless communication technology, featuring short packet transmission. It applies the IEEE802.11 Action Vendor frame technology, along with the IE function developed by Espressif, and CCMP encryption technology, realizing a secure, connectionless communication solution.

The RIOT port for ESP32 implements in module esp_now a netdev driver which uses ESP-NOW to provide a link layer interface to a meshed network of ESP32 nodes. In this network, each node can send short packets with up to 250 data bytes to all other nodes that are visible in its range.

Note

Due to symbol conflicts in the esp_idf_wpa_supplicant_crypto module used by the esp_now with RIOT’s crypto and hashes modules, ESP-NOW cannot be used for application that use these modules. Therefore, the module esp_now is not enabled automatically if the netdev_default module is used. Instead, the application has to add the esp_now module in its makefile when needed. 

1
USEMODULE += esp_now

For ESP-NOW, ESP32 nodes are used in WiFi SoftAP + Station mode to advertise their SSID and become visible to other ESP32 nodes. The SSID of an ESP32 node is the concatenation of the prefix RIOT_ESP_ with the MAC address of its SoftAP WiFi interface. The driver periodically scans all visible ESP32 nodes.

The following parameters are defined for ESP-NOW nodes. These parameters can be overriden by application-specific board configurations.

Parameter Default Description
ESP_NOW_SCAN_PERIOD 10000000UL Defines the period in us at which an node scans for other nodes in its range. The default period is 10 s.
ESP_NOW_SOFT_AP_PASSPHRASE ThisistheRIOTporttoESP Defines the passphrase (max. 64 chars) that is used for the SoftAP interface of an nodes. It has to be same for all nodes in one network.
ESP_NOW_CHANNEL 6 Defines the channel that is used as the broadcast medium by all nodes together.
ESP_NOW_KEY NULL Defines a key that is used for encrypted communication between nodes. If it is NULL, encryption is disabled. The key has to be of type uint8_t[16] and has to be exactly 16 bytes long.