ESP-WIFI-MESH Programming Guide =============================== :link_to_translation:`zh_CN:[中文]` This is a programming guide for ESP-WIFI-MESH, including the API reference and coding examples. This guide is split into the following parts: 1. :ref:`mesh-programming-model` 2. :ref:`mesh-writing-mesh-application` 3. :ref:`mesh-self-organized-behavior` 4. :ref:`mesh-application-examples` 5. :ref:`mesh-api-reference` 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>`_. .. ---------------------- ESP-WIFI-MESH Programming Model -------------------------- .. _mesh-programming-model: ESP-WIFI-MESH Programming Model ------------------------------------- Software Stack ^^^^^^^^^^^^^^ 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. .. _mesh-going-to-software-stack: .. figure:: ../../../_static/mesh-software-stack.png :align: center :alt: ESP-WIFI-MESH Software Stack :figclass: align-center ESP-WIFI-MESH Software Stack .. _mesh-events: System Events ^^^^^^^^^^^^^ 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. .. figure:: ../../../_static/mesh-events-delivery.png :align: center :alt: ESP-WIFI-MESH System Events Delivery :figclass: align-center ESP-WIFI-MESH System Events Delivery 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. 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. .. warning:: 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. LwIP & ESP-WIFI-MESH ^^^^^^^^^^^^^^^^^^^^^^^^^^ 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. **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. 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. .. ---------------------- Writing a Mesh Application -------------------------- .. _mesh-writing-mesh-application: Writing an ESP-WIFI-MESH Application ------------------------------------------- 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. .. code-block:: c ESP_ERROR_CHECK(esp_netif_init()); /* event initialization */ ESP_ERROR_CHECK(esp_event_loop_create_default()); /* Wi-Fi initialization */ wifi_init_config_t config = WIFI_INIT_CONFIG_DEFAULT(); ESP_ERROR_CHECK(esp_wifi_init(&config)); /* register IP events handler */ ESP_ERROR_CHECK(esp_event_handler_register(IP_EVENT, IP_EVENT_STA_GOT_IP, &ip_event_handler, NULL)); ESP_ERROR_CHECK(esp_wifi_set_storage(WIFI_STORAGE_FLASH)); ESP_ERROR_CHECK(esp_wifi_start()); 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: 1. :ref:`mesh-initialize-mesh` 2. :ref:`mesh-configuring-mesh` 3. :ref:`mesh-start-mesh` .. _mesh-initialize-mesh: Initialize Mesh ^^^^^^^^^^^^^^^ The following code snippet demonstrates how to initialize ESP-WIFI-MESH .. code-block:: c /* mesh initialization */ ESP_ERROR_CHECK(esp_mesh_init()); /* register mesh events handler */ ESP_ERROR_CHECK(esp_event_handler_register(MESH_EVENT, ESP_EVENT_ANY_ID, &mesh_event_handler, NULL)); .. _mesh-configuring-mesh: Configuring an ESP-WIFI-MESH Network ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ .. todo - Add note about unified configuration 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: .. list-table:: :header-rows: 1 :widths: 15 25 * - Parameter - Description * - Channel - Range from 1 to 14 * - Mesh ID - ID of ESP-WIFI-MESH Network, see :cpp:type:`mesh_addr_t` * - Router - Router Configuration, see :cpp:type:`mesh_router_t` * - Mesh AP - Mesh AP Configuration, see :cpp:type:`mesh_ap_cfg_t` * - Crypto Functions - Crypto Functions for Mesh IE, see :cpp:type:`mesh_crypto_funcs_t` The following code snippet demonstrates how to configure ESP-WIFI-MESH. .. code-block:: c /* Enable the Mesh IE encryption by default */ mesh_cfg_t cfg = MESH_INIT_CONFIG_DEFAULT(); /* mesh ID */ memcpy((uint8_t *) &cfg.mesh_id, MESH_ID, 6); /* channel (must match the router's channel) */ cfg.channel = CONFIG_MESH_CHANNEL; /* router */ cfg.router.ssid_len = strlen(CONFIG_MESH_ROUTER_SSID); memcpy((uint8_t *) &cfg.router.ssid, CONFIG_MESH_ROUTER_SSID, cfg.router.ssid_len); memcpy((uint8_t *) &cfg.router.password, CONFIG_MESH_ROUTER_PASSWD, strlen(CONFIG_MESH_ROUTER_PASSWD)); /* mesh softAP */ cfg.mesh_ap.max_connection = CONFIG_MESH_AP_CONNECTIONS; memcpy((uint8_t *) &cfg.mesh_ap.password, CONFIG_MESH_AP_PASSWD, strlen(CONFIG_MESH_AP_PASSWD)); ESP_ERROR_CHECK(esp_mesh_set_config(&cfg)); .. _mesh-start-mesh: Start Mesh ^^^^^^^^^^ The following code snippet demonstrates how to start ESP-WIFI-MESH. .. code-block:: c /* mesh start */ ESP_ERROR_CHECK(esp_mesh_start()); 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`. .. --------------------- ESP-WIFI-MESH Application Examples ------------------------ .. _mesh-self-organized-behavior: Self-Organized Networking ------------------------- 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: - Selection or election of the root node (see **Automatic Root Node Selection** in :ref:`mesh-building-a-network`) - Selection of a preferred parent node (see **Parent Node Selection** in :ref:`mesh-building-a-network`) - Automatic reconnection upon detecting a disconnection (see **Intermediate Parent Node Failure** in :ref:`mesh-managing-a-network`) 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**. Toggling Self-Organized Networking ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 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: - ``bool enable`` specifies whether to enable or disable self-organized networking. - ``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. Disabling Self-Organized Networking """"""""""""""""""""""""""""""""""" The following code snippet demonstrates how to disable self-organized networking. .. code-block:: c //Disable self-organized networking esp_mesh_set_self_organized(false, false); ESP-WIFI-MESH will attempt to maintain the node's current Wi-Fi state when disabling self-organized networking. - If the node was previously connected to other nodes, it will remain connected. - If the node was previously disconnected and was scanning for a parent node or router, it will stop scanning. - If the node was previously attempting to reconnect to a parent node or router, it will stop reconnecting. Enabling Self-Organized Networking """""""""""""""""""""""""""""""""" 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. +---------------+--------------+------------------------------------------------------------------------------------------------------------------+ | Select Parent | Is Root Node | Effects | +===============+==============+==================================================================================================================+ | N | N | - Nodes already connected to a parent node will remain connected. | | | | - Nodes previously scanning for a parent nodes will stop scanning. Call :cpp:func:`esp_mesh_connect` to restart. | | +--------------+------------------------------------------------------------------------------------------------------------------+ | | Y | - A root node already connected to router will stay connected. | | | | - A root node disconnected from router will need to call :cpp:func:`esp_mesh_connect` to reconnect. | +---------------+--------------+------------------------------------------------------------------------------------------------------------------+ | Y | N | - Nodes without a parent node will automatically select a preferred parent and connect. | | | | - Nodes already connected to a parent node will disconnect, reselect a preferred parent node, and connect. | | +--------------+------------------------------------------------------------------------------------------------------------------+ | | 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 | | | | disconnect from the router and all child nodes, select a preferred parent node, and connect. | +---------------+--------------+------------------------------------------------------------------------------------------------------------------+ The following code snipping demonstrates how to enable self-organized networking. .. code-block:: c //Enable self-organized networking and select a new parent esp_mesh_set_self_organized(true, true); ... //Enable self-organized networking and manually reconnect esp_mesh_set_self_organized(true, false); esp_mesh_connect(); Calling Wi-Fi API ^^^^^^^^^^^^^^^^^ 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. 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. .. code-block:: c //Disable self-organized networking esp_mesh_set_self_organized(0, 0); //Stop any scans already in progress esp_wifi_scan_stop(); //Manually start scan. Will automatically stop when run to completion esp_wifi_scan_start(); //Process scan results ... //Re-enable self-organized networking if still connected esp_mesh_set_self_organized(1, 0); ... //Re-enable self-organized networking if non-root and disconnected esp_mesh_set_self_organized(1, 1); ... //Re-enable self-organized networking if root and disconnected esp_mesh_set_self_organized(1, 0); //Do not select new parent esp_mesh_connect(); //Manually reconnect to router .. --------------------- ESP-WIFI-MESH Application Examples ------------------------ .. _mesh-application-examples: Application Examples -------------------- ESP-IDF contains these ESP-WIFI-MESH example projects: :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. :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. .. ------------------------- ESP-WIFI-MESH API Reference --------------------------- .. _mesh-api-reference: API Reference -------------- .. include-build-file:: inc/esp_mesh.inc