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modify API-reference using Sphinx directives

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zhangyanjiao
2022-04-25 11:52:19 +08:00
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docs/en/api-reference/network/esp_now.rst
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@@ -50,7 +50,7 @@ Security
--------
ESP-NOW uses the CCMP method, which is described in IEEE Std. 802.11-2012, to protect the vendor-specific action frame. The Wi-Fi device maintains a Primary Master Key (PMK) and several Local Master Keys (LMK). The lengths of both PMK and LMk are 16 bytes.
* PMK is used to encrypt LMK with the AES-128 algorithm. Call ``esp_now_set_pmk()`` to set PMK. If PMK is not set, a default PMK will be used.
* PMK is used to encrypt LMK with the AES-128 algorithm. Call :cpp:func:`esp_now_set_pmk()` to set PMK. If PMK is not set, a default PMK will be used.
* LMK of the paired device is used to encrypt the vendor-specific action frame with the CCMP method. The maximum number of different LMKs is six. If the LMK of the paired device is not set, the vendor-specific action frame will not be encrypted.
Encrypting multicast vendor-specific action frame is not supported.
@@ -58,39 +58,46 @@ Encrypting multicast vendor-specific action frame is not supported.
Initialization and De-initialization
------------------------------------
Call ``esp_now_init()`` to initialize ESP-NOW and ``esp_now_deinit()`` to de-initialize ESP-NOW. ESP-NOW data must be transmitted after Wi-Fi is started, so it is recommended to start Wi-Fi before initializing ESP-NOW and stop Wi-Fi after de-initializing ESP-NOW.
When ``esp_now_deinit()`` is called, all of the information of paired devices will be deleted.
Call :cpp:func:`esp_now_init()` to initialize ESP-NOW and :cpp:func:`esp_now_deinit()` to de-initialize ESP-NOW. ESP-NOW data must be transmitted after Wi-Fi is started, so it is recommended to start Wi-Fi before initializing ESP-NOW and stop Wi-Fi after de-initializing ESP-NOW.
When :cpp:func:`esp_now_deinit()` is called, all of the information of paired devices will be deleted.
Add Paired Device
-----------------
Call ``esp_now_add_peer()`` to add the device to the paired device list before you send data to this device. If security is enabled, the LMK must be set. You can send ESP-NOW data via both the Station and the SoftAP interface. Make sure that the interface is enabled before sending ESP-NOW data.
Call :cpp:func:`esp_now_add_peer()` to add the device to the paired device list before you send data to this device. If security is enabled, the LMK must be set. You can send ESP-NOW data via both the Station and the SoftAP interface. Make sure that the interface is enabled before sending ESP-NOW data.
.. only:: esp32c2
The maximum number of paired devices is 20, and the paired encryption devices are no more than 4, the default is 2.
.. only:: esp32c3
The maximum number of paired devices is 20, and the paired encryption devices are no more than 10, the default is 6.
.. only:: esp32 or esp32s2 esp32s3
.. only:: esp32 or esp32s2 or esp32s3
The maximum number of paired devices is 20, and the paired encryption devices are no more than 16, the default is 6.
A device with a broadcast MAC address must be added before sending broadcast data. The range of the channel of paired devices is from 0 to 14. If the channel is set to 0, data will be sent on the current channel. Otherwise, the channel must be set as the channel that the local device is on.
Send ESP-NOW Data
-----------------
Call ``esp_now_send()`` to send ESP-NOW data and ``esp_now_register_send_cb`` to register sending callback function. It will return `ESP_NOW_SEND_SUCCESS` in sending callback function if the data is received successfully on the MAC layer. Otherwise, it will return `ESP_NOW_SEND_FAIL`. Several reasons can lead to ESP-NOW fails to send data. For example, the destination device doesn't exist; the channels of the devices are not the same; the action frame is lost when transmitting on the air, etc. It is not guaranteed that application layer can receive the data. If necessary, send back ack data when receiving ESP-NOW data. If receiving ack data timeouts, retransmit the ESP-NOW data. A sequence number can also be assigned to ESP-NOW data to drop the duplicate data.
Call :cpp:func:`esp_now_send()` to send ESP-NOW data and :cpp:func:`esp_now_register_send_cb()` to register sending callback function. It will return `ESP_NOW_SEND_SUCCESS` in sending callback function if the data is received successfully on the MAC layer. Otherwise, it will return `ESP_NOW_SEND_FAIL`. Several reasons can lead to ESP-NOW fails to send data. For example, the destination device doesn't exist; the channels of the devices are not the same; the action frame is lost when transmitting on the air, etc. It is not guaranteed that application layer can receive the data. If necessary, send back ack data when receiving ESP-NOW data. If receiving ack data timeouts, retransmit the ESP-NOW data. A sequence number can also be assigned to ESP-NOW data to drop the duplicate data.
If there is a lot of ESP-NOW data to send, call ``esp_now_send()`` to send less than or equal to 250 bytes of data once a time.
If there is a lot of ESP-NOW data to send, call :cpp:func:`esp_now_send()` to send less than or equal to 250 bytes of data once a time.
Note that too short interval between sending two ESP-NOW data may lead to disorder of sending callback function. So, it is recommended that sending the next ESP-NOW data after the sending callback function of the previous sending has returned. The sending callback function runs from a high-priority Wi-Fi task. So, do not do lengthy operations in the callback function. Instead, post the necessary data to a queue and handle it from a lower priority task.
Receiving ESP-NOW Data
----------------------
Call ``esp_now_register_recv_cb`` to register receiving callback function. Call the receiving callback function when receiving ESP-NOW. The receiving callback function also runs from the Wi-Fi task. So, do not do lengthy operations in the callback function.
Call :cpp:func:`esp_now_register_recv_cb()` to register receiving callback function. Call the receiving callback function when receiving ESP-NOW. The receiving callback function also runs from the Wi-Fi task. So, do not do lengthy operations in the callback function.
Instead, post the necessary data to a queue and handle it from a lower priority task.
Config ESP-NOW Rate
-------------------
Call ``esp_wifi_config_espnow_rate`` to config ESPNOW rate of specified interface. Make sure that the interface is enabled before config rate. This API should be called after ``esp_wifi_start()``.
Call :cpp:func:`esp_wifi_config_espnow_rate()` to config ESPNOW rate of specified interface. Make sure that the interface is enabled before config rate. This API should be called after :cpp:func:`esp_wifi_start()`.
Application Examples
--------------------