Merge branch 'docs/mesh_channel_switch' into 'master'
docs: Add documentation about ESP-MESH channel switching and self organized behavior See merge request idf/esp-idf!3854
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Angus Gratton
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ESP-MESH Programming Guide
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==========================
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This is a programming guide for ESP-MESH, including the API reference and coding
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examples. This guide is split into the following parts:
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This is a programming guide for ESP-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-application-examples`
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3. :ref:`mesh-self-organized-behavior`
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4. :ref:`mesh-api-reference`
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4. :ref:`mesh-application-examples`
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For documentation regarding the ESP-MESH protocol, please see the
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:doc:`ESP-MESH API Guide<../../api-guides/mesh>`.
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5. :ref:`mesh-api-reference`
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For documentation regarding the ESP-MESH protocol, please see the :doc:`ESP-MESH API Guide<../../api-guides/mesh>`.
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.. ---------------------- ESP-MESH Programming Model --------------------------
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@ -26,9 +26,7 @@ ESP-MESH Programming Model
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Software Stack
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^^^^^^^^^^^^^^
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The ESP-MESH software stack is built atop the Wi-Fi Driver/FreeRTOS and may use
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the LwIP Stack in some instances (i.e. the root node). The following diagram
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illustrates the ESP-MESH software stack.
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The ESP-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-MESH software stack.
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.. _mesh-going-to-software-stack:
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@ -42,10 +40,7 @@ illustrates the ESP-MESH software stack.
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System Events
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^^^^^^^^^^^^^
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An application interfaces with ESP-MESH via **ESP-MESH Events**. Since ESP-MESH
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is built atop the Wi-Fi stack, it is also possible for the application to interface
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with the Wi-Fi driver via the **Wi-Fi Event Task**. The following diagram illustrates
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the interfaces for the various System Events in an ESP-MESH application.
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An application interfaces with ESP-MESH via **ESP-MESH Events**. Since ESP-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-MESH application.
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.. figure:: ../../../_static/mesh-events-delivery.png
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:align: center
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@ -54,41 +49,19 @@ the interfaces for the various System Events in an ESP-MESH application.
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ESP-MESH System Events Delivery
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The :cpp:type:`mesh_event_id_t` defines all possible ESP-MESH system events and
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can indicate events such as the connection/disconnection of parent/child. Before
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ESP-MESH system events can be used, the application must register a **Mesh Event
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Callback** via :cpp:func:`esp_mesh_set_config`. The callback is used to receive
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events from the ESP-MESH stack as well as the LwIP Stack and should contain handlers
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for each event relevant to the application.
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The :cpp:type:`mesh_event_id_t` defines all possible ESP-MESH system events and can indicate events such as the connection/disconnection of parent/child. Before ESP-MESH system events can be used, the application must register a **Mesh Event Callback** via :cpp:func:`esp_mesh_set_config`. The callback is used to receive events from the ESP-MESH stack as well as the LwIP Stack and should contain handlers for each event relevant to the application.
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Typical use cases of system events include using events such as
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:cpp:enumerator:`MESH_EVENT_PARENT_CONNECTED` and :cpp:enumerator:`MESH_EVENT_CHILD_CONNECTED`
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to indicate when a node can begin transmitting data upstream and downstream respectively. Likewise,
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:cpp:enumerator:`MESH_EVENT_ROOT_GOT_IP` and :cpp:enumerator:`MESH_EVENT_ROOT_LOST_IP` can be
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used to indicate when the root node can and cannot transmit data to the external IP
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network.
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Typical use cases of system 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:`MESH_EVENT_ROOT_GOT_IP` and :cpp:enumerator:`MESH_EVENT_ROOT_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-MESH under self-organized mode, users must ensure that no calls
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to Wi-Fi API are made. This is due to the fact that the self-organizing mode
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will internally make Wi-Fi API calls to connect/disconnect/scan etc.
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**Any Wi-Fi calls from the application (including calls from callbacks and
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handlers of Wi-Fi events) may interfere with ESP-MESH's self-organizing behavior**.
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Therefore, user's should not call Wi-Fi APIs after :cpp:func:`esp_mesh_start`
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is called, and before :cpp:func:`esp_mesh_stop` is called.
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When using ESP-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-MESH's self-organizing behavior**. Therefore, user's 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-MESH
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^^^^^^^^^^^^^^^
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The application can access the ESP-MESH stack directly without having to go through
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the LwIP stack. The LwIP stack is only required by the root node to transmit/receive
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data to/from an external IP network. However, since every node can potentially
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become the root node (due to automatic root node selection), each node must still
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initialize the LwIP stack.
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The application can access the ESP-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 is required to initialize LwIP by calling** :cpp:func:`tcpip_adapter_init`.
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In order to prevent non-root node access to LwIP, the application should stop the
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following services after LwIP initialization:
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**Each node is required to initialize LwIP by calling** :cpp:func:`tcpip_adapter_init`. In order to prevent non-root node access to LwIP, the application should stop the following services after LwIP initialization:
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- DHCP server service on the softAP interface.
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- DHCP client service on the station interface.
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@ -111,11 +84,7 @@ The following code snippet demonstrates how to initialize LwIP for ESP-MESH appl
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.. note::
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ESP-MESH requires a root node to be connected with a router. Therefore, in
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the event that a node becomes the root, **the corresponding handler must start
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the DHCP client service and immediately obtain an IP address**. Doing so will
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allow other nodes to begin transmitting/receiving packets to/from the external
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IP network. However, this step is unnecessary if static IP settings are used.
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ESP-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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@ -125,9 +94,7 @@ The following code snippet demonstrates how to initialize LwIP for ESP-MESH appl
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Writing an ESP-MESH Application
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-------------------------------
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The prerequisites for starting ESP-MESH is to initialize LwIP and Wi-Fi, The
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following code snippet demonstrates the necessary prerequisite steps before
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ESP-MESH itself can be initialized.
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The prerequisites for starting ESP-MESH is to initialize LwIP and Wi-Fi, The following code snippet demonstrates the necessary prerequisite steps before ESP-MESH itself can be initialized.
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.. code-block:: c
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@ -148,8 +115,7 @@ ESP-MESH itself can be initialized.
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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-MESH network
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up and running can be summarized into the following three steps:
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After initializing LwIP and Wi-Fi, the process of getting an ESP-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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@ -174,9 +140,7 @@ Configuring an ESP-MESH Network
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.. todo - Add note about unified configuration
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ESP-MESH is configured via :cpp:func:`esp_mesh_set_config` which receives its arguments
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using the :cpp:type:`mesh_cfg_t` structure. The structure contains the following
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parameters used to configure ESP-MESH:
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ESP-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-MESH:
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+------------------+-------------------------------------+
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| Parameter | Description |
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@ -234,10 +198,118 @@ The following code snippet demonstrates how to start ESP-MESH.
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/* mesh start */
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ESP_ERROR_CHECK(esp_mesh_start());
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After starting ESP-MESH, the application should check for ESP-MESH events to determine
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when it has connected to the network. After connecting, the application can start
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transmitting and receiving packets over the ESP-MESH network using
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:cpp:func:`esp_mesh_send` and :cpp:func:`esp_mesh_recv`.
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After starting ESP-MESH, the application should check for ESP-MESH events to determine when it has connected to the network. After connecting, the application can start transmitting and receiving packets over the ESP-MESH network using :cpp:func:`esp_mesh_send` and :cpp:func:`esp_mesh_recv`.
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.. --------------------- ESP-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-MESH where nodes can autonomously scan/select/connect/reconnect to other nodes and routers. This feature allows an ESP-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-MESH network are able to carryout 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-MESH stack will internally make calls to Wi-Fi driver APIs. Therefore, **the application layer should not make any calls to Wi-Fi driver APIs whilst self organized networking is enabled as doing so would risk interfering with ESP-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-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-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 Driver API
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^^^^^^^^^^^^^^^^^^^^^^^^
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There can be instances in which an application may want to directly call Wi-Fi driver API whilst using ESP-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 driver APIs**. This will prevent the ESP-MESH stack from attempting to call any Wi-Fi driver APIs and potentially interfering with the application's calls.
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Therefore, application calls to Wi-Fi driver 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-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); //Don't select new parent
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esp_mesh_connect(); //Manually reconnect to router
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.. --------------------- ESP-MESH Application Examples ------------------------
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@ -248,14 +320,9 @@ Application Examples
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ESP-IDF contains these ESP-MESH example projects:
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:example:`The Internal Communication Example<mesh/internal_communication>` demonstrates
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how to setup a ESP-MESH network and have the root node send a data packet to
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every node within the network.
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:example:`The Internal Communication Example<mesh/internal_communication>` demonstrates how to setup a ESP-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
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how to use ESP-MESH without the self-organizing features. This example shows how
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to program a node to manually scan for a list of potential parent nodes and select
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a parent node based on custom criteria.
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:example:`The Manual Networking Example<mesh/manual_networking>` demonstrates how to use ESP-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-MESH API Reference ---------------------------
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