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320 lines
16 KiB
ReStructuredText
ESP-WIFI-MESH Programming Guide
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===============================
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:link_to_translation:`zh_CN:[中文]`
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This is a programming guide for ESP-WIFI-MESH, including the API reference and coding examples. This guide is split into the following parts:
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1. :ref:`mesh-programming-model`
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2. :ref:`mesh-writing-mesh-application`
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3. :ref:`mesh-self-organized-behavior`
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4. :ref:`mesh-application-examples`
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5. :ref:`mesh-api-reference`
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For documentation regarding the ESP-WIFI-MESH protocol, please see the :doc:`ESP-WIFI-MESH API Guide <../../api-guides/esp-wifi-mesh>`. For more information about ESP-WIFI-MESH Development Framework, please see `ESP-WIFI-MESH Development Framework <https://github.com/espressif/esp-mdf>`_.
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.. ---------------------- ESP-WIFI-MESH Programming Model --------------------------
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.. _mesh-programming-model:
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ESP-WIFI-MESH Programming Model
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-------------------------------------
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Software Stack
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^^^^^^^^^^^^^^
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The ESP-WIFI-MESH software stack is built atop the Wi-Fi Driver/FreeRTOS and may use the LwIP Stack in some instances (i.e., the root node). The following diagram illustrates the ESP-WIFI-MESH software stack.
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.. _mesh-going-to-software-stack:
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.. figure:: ../../../_static/mesh-software-stack.png
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:align: center
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:alt: ESP-WIFI-MESH Software Stack
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:figclass: align-center
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ESP-WIFI-MESH Software Stack
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.. _mesh-events:
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System Events
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^^^^^^^^^^^^^
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An application interfaces with ESP-WIFI-MESH via **ESP-WIFI-MESH Events**. Since ESP-WIFI-MESH is built atop the Wi-Fi stack, it is also possible for the application to interface with the Wi-Fi driver via the **Wi-Fi Event Task**. The following diagram illustrates the interfaces for the various System Events in an ESP-WIFI-MESH application.
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.. figure:: ../../../_static/mesh-events-delivery.png
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:align: center
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:alt: ESP-WIFI-MESH System Events Delivery
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:figclass: align-center
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ESP-WIFI-MESH System Events Delivery
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The :cpp:type:`mesh_event_id_t` defines all possible ESP-WIFI-MESH events and can indicate events such as the connection/disconnection of parent/child. Before ESP-WIFI-MESH events can be used, the application must register a **Mesh Events handler** via :cpp:func:`esp_event_handler_register` to the default event task. The Mesh Events handler that is registered contain handlers for each ESP-WIFI-MESH event relevant to the application.
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Typical use cases of mesh events include using events such as :cpp:enumerator:`MESH_EVENT_PARENT_CONNECTED` and :cpp:enumerator:`MESH_EVENT_CHILD_CONNECTED` to indicate when a node can begin transmitting data upstream and downstream respectively. Likewise, :cpp:enumerator:`IP_EVENT_STA_GOT_IP` and :cpp:enumerator:`IP_EVENT_STA_LOST_IP` can be used to indicate when the root node can and cannot transmit data to the external IP network.
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.. warning::
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When using ESP-WIFI-MESH under self-organized mode, users must ensure that no calls to Wi-Fi API are made. This is due to the fact that the self-organizing mode will internally make Wi-Fi API calls to connect/disconnect/scan etc. **Any Wi-Fi calls from the application (including calls from callbacks and handlers of Wi-Fi events) may interfere with ESP-WIFI-MESH's self-organizing behavior**. Therefore, users should not call Wi-Fi APIs after :cpp:func:`esp_mesh_start` is called, and before :cpp:func:`esp_mesh_stop` is called.
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LwIP & ESP-WIFI-MESH
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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The application can access the ESP-WIFI-MESH stack directly without having to go through the LwIP stack. The LwIP stack is only required by the root node to transmit/receive data to/from an external IP network. However, since every node can potentially become the root node (due to automatic root node selection), each node must still initialize the LwIP stack.
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**Each node that could become root is required to initialize LwIP by calling** :cpp:func:`esp_netif_init`. In order to prevent non-root node access to LwIP, the application should not create or register any network interfaces using esp_netif APIs.
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ESP-WIFI-MESH requires a root node to be connected with a router. Therefore, in the event that a node becomes the root, **the corresponding handler must start the DHCP client service and immediately obtain an IP address**. Doing so will allow other nodes to begin transmitting/receiving packets to/from the external IP network. However, this step is unnecessary if static IP settings are used.
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.. ---------------------- Writing a Mesh Application --------------------------
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.. _mesh-writing-mesh-application:
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Writing an ESP-WIFI-MESH Application
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-------------------------------------------
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The prerequisites for starting ESP-WIFI-MESH is to initialize LwIP and Wi-Fi, The following code snippet demonstrates the necessary prerequisite steps before ESP-WIFI-MESH itself can be initialized.
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.. code-block:: c
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ESP_ERROR_CHECK(esp_netif_init());
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/* event initialization */
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ESP_ERROR_CHECK(esp_event_loop_create_default());
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/* Wi-Fi initialization */
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wifi_init_config_t config = WIFI_INIT_CONFIG_DEFAULT();
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ESP_ERROR_CHECK(esp_wifi_init(&config));
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/* register IP events handler */
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ESP_ERROR_CHECK(esp_event_handler_register(IP_EVENT, IP_EVENT_STA_GOT_IP, &ip_event_handler, NULL));
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ESP_ERROR_CHECK(esp_wifi_set_storage(WIFI_STORAGE_FLASH));
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ESP_ERROR_CHECK(esp_wifi_start());
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After initializing LwIP and Wi-Fi, the process of getting an ESP-WIFI-MESH network up and running can be summarized into the following three steps:
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1. :ref:`mesh-initialize-mesh`
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2. :ref:`mesh-configuring-mesh`
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3. :ref:`mesh-start-mesh`
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.. _mesh-initialize-mesh:
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Initialize Mesh
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^^^^^^^^^^^^^^^
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The following code snippet demonstrates how to initialize ESP-WIFI-MESH
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.. code-block:: c
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/* mesh initialization */
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ESP_ERROR_CHECK(esp_mesh_init());
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/* register mesh events handler */
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ESP_ERROR_CHECK(esp_event_handler_register(MESH_EVENT, ESP_EVENT_ANY_ID, &mesh_event_handler, NULL));
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.. _mesh-configuring-mesh:
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Configuring an ESP-WIFI-MESH Network
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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.. todo - Add note about unified configuration
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ESP-WIFI-MESH is configured via :cpp:func:`esp_mesh_set_config` which receives its arguments using the :cpp:type:`mesh_cfg_t` structure. The structure contains the following parameters used to configure ESP-WIFI-MESH:
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.. list-table::
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:header-rows: 1
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:widths: 15 25
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* - Parameter
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- Description
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* - Channel
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- Range from 1 to 14
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* - Mesh ID
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- ID of ESP-WIFI-MESH Network, see :cpp:type:`mesh_addr_t`
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* - Router
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- Router Configuration, see :cpp:type:`mesh_router_t`
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* - Mesh AP
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- Mesh AP Configuration, see :cpp:type:`mesh_ap_cfg_t`
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* - Crypto Functions
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- Crypto Functions for Mesh IE, see :cpp:type:`mesh_crypto_funcs_t`
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The following code snippet demonstrates how to configure ESP-WIFI-MESH.
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.. code-block:: c
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/* Enable the Mesh IE encryption by default */
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mesh_cfg_t cfg = MESH_INIT_CONFIG_DEFAULT();
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/* mesh ID */
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memcpy((uint8_t *) &cfg.mesh_id, MESH_ID, 6);
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/* channel (must match the router's channel) */
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cfg.channel = CONFIG_MESH_CHANNEL;
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/* router */
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cfg.router.ssid_len = strlen(CONFIG_MESH_ROUTER_SSID);
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memcpy((uint8_t *) &cfg.router.ssid, CONFIG_MESH_ROUTER_SSID, cfg.router.ssid_len);
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memcpy((uint8_t *) &cfg.router.password, CONFIG_MESH_ROUTER_PASSWD,
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strlen(CONFIG_MESH_ROUTER_PASSWD));
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/* mesh softAP */
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cfg.mesh_ap.max_connection = CONFIG_MESH_AP_CONNECTIONS;
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memcpy((uint8_t *) &cfg.mesh_ap.password, CONFIG_MESH_AP_PASSWD,
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strlen(CONFIG_MESH_AP_PASSWD));
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ESP_ERROR_CHECK(esp_mesh_set_config(&cfg));
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.. _mesh-start-mesh:
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Start Mesh
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^^^^^^^^^^
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The following code snippet demonstrates how to start ESP-WIFI-MESH.
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.. code-block:: c
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/* mesh start */
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ESP_ERROR_CHECK(esp_mesh_start());
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After starting ESP-WIFI-MESH, the application should check for ESP-WIFI-MESH events to determine when it has connected to the network. After connecting, the application can start transmitting and receiving packets over the ESP-WIFI-MESH network using :cpp:func:`esp_mesh_send` and :cpp:func:`esp_mesh_recv`.
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.. --------------------- ESP-WIFI-MESH Application Examples ------------------------
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.. _mesh-self-organized-behavior:
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Self-Organized Networking
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-------------------------
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Self-organized networking is a feature of ESP-WIFI-MESH where nodes can autonomously scan/select/connect/reconnect to other nodes and routers. This feature allows an ESP-WIFI-MESH network to operate with high degree of autonomy by making the network robust to dynamic network topologies and conditions. With self-organized networking enabled, nodes in an ESP-WIFI-MESH network are able to carry out the following actions without autonomously:
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- Selection or election of the root node (see **Automatic Root Node Selection** in :ref:`mesh-building-a-network`)
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- Selection of a preferred parent node (see **Parent Node Selection** in :ref:`mesh-building-a-network`)
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- Automatic reconnection upon detecting a disconnection (see **Intermediate Parent Node Failure** in :ref:`mesh-managing-a-network`)
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When self-organized networking is enabled, the ESP-WIFI-MESH stack will internally make calls to Wi-Fi APIs. Therefore, **the application layer should not make any calls to Wi-Fi APIs whilst self-organized networking is enabled as doing so would risk interfering with ESP-WIFI-MESH**.
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Toggling Self-Organized Networking
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Self-organized networking can be enabled or disabled by the application at runtime by calling the :cpp:func:`esp_mesh_set_self_organized` function. The function has the two following parameters:
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- ``bool enable`` specifies whether to enable or disable self-organized networking.
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- ``bool select_parent`` specifies whether a new parent node should be selected when enabling self-organized networking. Selecting a new parent has different effects depending the node type and the node's current state. This parameter is unused when disabling self-organized networking.
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Disabling Self-Organized Networking
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"""""""""""""""""""""""""""""""""""
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The following code snippet demonstrates how to disable self-organized networking.
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.. code-block:: c
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//Disable self-organized networking
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esp_mesh_set_self_organized(false, false);
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ESP-WIFI-MESH will attempt to maintain the node's current Wi-Fi state when disabling self-organized networking.
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- If the node was previously connected to other nodes, it will remain connected.
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- If the node was previously disconnected and was scanning for a parent node or router, it will stop scanning.
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- If the node was previously attempting to reconnect to a parent node or router, it will stop reconnecting.
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Enabling Self-Organized Networking
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""""""""""""""""""""""""""""""""""
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ESP-WIFI-MESH will attempt to maintain the node's current Wi-Fi state when enabling self-organized networking. However, depending on the node type and whether a new parent is selected, the Wi-Fi state of the node can change. The following table shows effects of enabling self-organized networking.
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+---------------+--------------+------------------------------------------------------------------------------------------------------------------+
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| Select Parent | Is Root Node | Effects |
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+===============+==============+==================================================================================================================+
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| N | N | - Nodes already connected to a parent node will remain connected. |
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| | | - Nodes previously scanning for a parent nodes will stop scanning. Call :cpp:func:`esp_mesh_connect` to restart. |
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| +--------------+------------------------------------------------------------------------------------------------------------------+
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| | Y | - A root node already connected to router will stay connected. |
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| | | - A root node disconnected from router will need to call :cpp:func:`esp_mesh_connect` to reconnect. |
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+---------------+--------------+------------------------------------------------------------------------------------------------------------------+
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| Y | N | - Nodes without a parent node will automatically select a preferred parent and connect. |
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| | | - Nodes already connected to a parent node will disconnect, reselect a preferred parent node, and connect. |
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| +--------------+------------------------------------------------------------------------------------------------------------------+
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| | Y | - For a root node to connect to a parent node, it must give up it's role as root. Therefore, a root node will |
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| | | disconnect from the router and all child nodes, select a preferred parent node, and connect. |
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+---------------+--------------+------------------------------------------------------------------------------------------------------------------+
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The following code snipping demonstrates how to enable self-organized networking.
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.. code-block:: c
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//Enable self-organized networking and select a new parent
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esp_mesh_set_self_organized(true, true);
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...
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//Enable self-organized networking and manually reconnect
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esp_mesh_set_self_organized(true, false);
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esp_mesh_connect();
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Calling Wi-Fi API
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^^^^^^^^^^^^^^^^^
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There can be instances in which an application may want to directly call Wi-Fi API whilst using ESP-WIFI-MESH. For example, an application may want to manually scan for neighboring APs. However, **self-organized networking must be disabled before the application calls any Wi-Fi APIs**. This will prevent the ESP-WIFI-MESH stack from attempting to call any Wi-Fi APIs and potentially interfering with the application's calls.
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Therefore, application calls to Wi-Fi APIs should be placed in between calls of :cpp:func:`esp_mesh_set_self_organized` which disable and enable self-organized networking. The following code snippet demonstrates how an application can safely call :cpp:func:`esp_wifi_scan_start` whilst using ESP-WIFI-MESH.
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.. code-block:: c
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//Disable self-organized networking
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esp_mesh_set_self_organized(0, 0);
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//Stop any scans already in progress
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esp_wifi_scan_stop();
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//Manually start scan. Will automatically stop when run to completion
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esp_wifi_scan_start();
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//Process scan results
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...
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//Re-enable self-organized networking if still connected
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esp_mesh_set_self_organized(1, 0);
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...
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//Re-enable self-organized networking if non-root and disconnected
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esp_mesh_set_self_organized(1, 1);
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...
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//Re-enable self-organized networking if root and disconnected
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esp_mesh_set_self_organized(1, 0); //Do not select new parent
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esp_mesh_connect(); //Manually reconnect to router
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.. --------------------- ESP-WIFI-MESH Application Examples ------------------------
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.. _mesh-application-examples:
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Application Examples
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--------------------
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ESP-IDF contains these ESP-WIFI-MESH example projects:
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:example:`The Internal Communication Example <mesh/internal_communication>` demonstrates how to set up a ESP-WIFI-MESH network and have the root node send a data packet to every node within the network.
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:example:`The Manual Networking Example <mesh/manual_networking>` demonstrates how to use ESP-WIFI-MESH without the self-organizing features. This example shows how to program a node to manually scan for a list of potential parent nodes and select a parent node based on custom criteria.
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.. ------------------------- ESP-WIFI-MESH API Reference ---------------------------
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.. _mesh-api-reference:
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API Reference
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--------------
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.. include-build-file:: inc/esp_mesh.inc
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