147 lines
6.7 KiB
ReStructuredText
147 lines
6.7 KiB
ReStructuredText
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ESP-NETIF
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=========
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The purpose of ESP-NETIF library is twofold:
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- It provides an abstraction layer for the application on top of the TCP/IP stack. This will allow applications to choose between IP stacks in the future.
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- The APIs it provides are thread safe, even if the underlying TCP/IP stack APIs are not.
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ESP-IDF currently implements ESP-NETIF for the lwIP TCP/IP stack only. However, the adapter itself is TCP/IP implementation agnostic and different implementations are possible.
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Some ESP-NETIF API functions are intended to be called by application code, for example to get/set interface IP addresses, configure DHCP. Other functions are intended for internal ESP-IDF use by the network driver layer.
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In many cases, applications do not need to call ESP-NETIF APIs directly as they are called from the default network event handlers.
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ESP-NETIF architecture
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======================
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.. code-block:: text
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| (A) USER CODE |
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.............| init settings events |
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. +----------------------------------------+
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. . | *
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. . | *
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--------+ +===========================+ * +-----------------------+
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| | new/config get/set | * | |
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| | |...*.....| init |
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| |---------------------------| * | |
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init | | |**** | |
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start |********| event handler |*********| DHCP |
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stop | | | | |
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| |---------------------------| | |
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| | | | NETIF |
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+-----| | | +-----------------+ |
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| |---->---| esp_netif_receive |-->------| netif_input | |
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| | | | + ----------------+ |
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| |....<...| esp_netif_free_rx_buffer |...<.....| packet buffer |
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+-----| | | | |
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| | | | (D) |
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(B) | | (C) | +-----------------------+
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--------+ +===========================+
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communication NETWORK STACK
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DRIVER ESP-NETIF
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Data and event flow in the diagram
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----------------------------------
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* ``........`` Initialization line from user code to ESP-NETIF and communication driver
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* ``--<--->--`` Data packets going from communication media to TCP/IP stack and back
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* ``********`` Events aggregated in ESP-NETIF propagates to driver, user code and network stack
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* ``|`` User settings and runtime configuration
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ESP-NETIF interaction
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---------------------
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A) User code, boiler plate
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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Overall application interaction with a specific IO driver for communication media and configured TCP/IP network stack
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is abstracted using ESP-NETIF APIs and outlined as below:
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A) Initialization code
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1) Initializes IO driver
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2) Creates a new instance of ESP-NETIF and configure with
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* ESP-NETIF specific options (flags, behaviour, name)
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* Network stack options (netif init and input functions, not publicly available)
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* IO driver specific options (transmit, free rx buffer functions, IO driver handle)
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3) Attaches the IO driver handle to the ESP-NETIF instance created in the above steps
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4) Configures event handlers
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* use default handlers for common interfaces defined in IO drivers; or define a specific handlers for customised behaviour/new interfaces
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* register handlers for app related events (such as IP lost/acquired)
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B) Interaction with network interfaces using ESP-NETIF API
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* Getting and setting TCP/IP related parameters (DHCP, IP, etc)
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* Receiving IP events (connect/disconnect)
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* Controlling application lifecycle (set interface up/down)
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Please note that the initialization code as well as registering event handlers for default interfaces,
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such as WiFi softAP and WiFi station, are provided as a separate APIs (for example ``esp_netif_create_default_wifi_ap()`` and
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``esp_netif_create_default_wifi_sta()``) to facilitate simple startup code for most applications.
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B) Communication driver, IO driver, media driver
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Communication driver plays these two important roles in relation with ESP-NETIF:
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1) Event handlers: Define behaviour patterns of interaction with ESP-NETIF (for example: ethernet link-up -> turn netif on)
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2) Glue IO layer: Adapts the input/output functions to use ESP-NETIF transmit, receive and free receive buffer
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* Installs driver_transmit to appropriate ESP-NETIF object, so that outgoing packets from network stack are passed to the IO driver
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* Calls ``esp_netif_receive()`` to pass incoming data to network stack
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C) ESP-NETIF, former tcpip_adapter
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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ESP-NETIF is an intermediary between an IO driver and a network stack, connecting packet data path between these two.
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As that it provides a set of interfaces for attaching a driver to ESP-NETIF object (runtime) and
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configuring a network stack (compile time). In addition to that a set of API is provided to control network interface lifecycle
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and its TCP/IP properties. As an overview, the ESP-NETIF public interface could be divided into these 6 groups:
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1) Initialization APIs (to create and configure ESP-NETIF instance)
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2) Input/Output API (for passing data between IO driver and network stack)
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3) Event or Action API
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* Used for network interface lifecycle management
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* ESP-NETIF provides building blocks for designing event handlers
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4) Setters and Getters for basic network interface properties
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5) Network stack abstraction: enabling user interaction with TCP/IP stack
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* Set interface up or down
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* DHCP server and client API
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* DNS API
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6) Driver conversion utilities
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D) Network stack
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^^^^^^^^^^^^^^^^
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Network stack has no public interaction with application code with regard to public interfaces and shall be fully abstracted by
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ESP-NETIF API.
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API Reference
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-------------
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.. include:: /_build/inc/esp_netif.inc
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