cpu/esp_common/esp-now/doc.md
@defgroup cpu_esp_common_esp_now ESP-NOW netdev interface @ingroup cpu_esp_common @ingroup cpu_esp32 @ingroup cpu_esp8266 @brief WiFi based ESP-NOW network device driver
@author Gunar Schorcht [email protected]
This module realizes a netdev interface using Espressif's ESP-NOW technology which uses the built-in WiFi module.
With ESP-NOW, the ESP nodes (ESP32 and ESP8266) provide 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 ESP implements in module esp_now a netdev driver which uses ESP-NOW to provide a link layer interface to a meshed network of ESP 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.
USEMODULE += esp_now
For ESP-NOW, ESP nodes are used in WiFi SoftAP + Station mode to advertise their SSID and become visible to other ESP nodes. The SSID of an ESP node is the concatenation of the prefix RIOT_ESP_ with the MAC address of its SoftAP WiFi interface. The driver periodically scans all visible ESP nodes.
The following parameters are defined for ESP-NOW nodes.
<center>| Parameter | Default | Description |
|---|---|---|
| ESP_NOW_SCAN_PERIOD_MS | 10000UL | Defines the period in ms at which an node scans for other nodes in its range. The default period is 10 s. |
| ESP_NOW_SOFT_AP_PASS | "ThisistheRIOTporttoESP" | Defines the passphrase as clear text (max. 64 chars) that is used for the SoftAP interface of ESP-NOW 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. |
@note The ESP-NOW network interface (module esp_now) and the
Wifi network interface (module esp_wifi)
can be used simultaneously, for example, to realize a border router for
a mesh network which uses ESP-NOW.
In this case the ESP-NOW interface must use the same channel as the AP of the
infrastructure WiFi network. All ESP-NOW nodes must therefore be compiled with
the channel of the AP asvalue for the parameter 'ESP_NOW_CHANNEL'.