83 lines
4.1 KiB
ReStructuredText
83 lines
4.1 KiB
ReStructuredText
Base MAC address
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================
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Overview
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--------
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Serveral MAC addresses (universally administered by IEEE) are uniquely assigned to the networking interfaces (WiFi/BT/Ethernet).
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The final octet of each universally administered MAC address increases by one. Only the first one which is called base MAC address
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of them is stored in EFUSE or external storage, the others are generated from it. Here, 'generate' means adding 0, 1, 2 and 3
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(respectively) to the final octet of the base MAC address.
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If the universally administered MAC addresses are not enough for all of the networking interfaces. Local administered MAC addresses
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which are derived from universally administered MAC addresses are assigned to the reset of networking interfaces.
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A `definition of local vs universal MAC address can be found on Wikipedia <https://en.wikipedia.org/wiki/MAC_address#Universal_vs._local>`_.
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The number of universally administered MAC address can be configured using ``make menuconfig``.
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Base MAC address
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^^^^^^^^^^^^^^^^
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If using the default base MAC address factory programmed by Espressif in BLK0 of EFUSE, nothing needs to be done.
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If using a custom base MAC address stored in BLK3 of EFUSE, call API ``esp_efuse_mac_get_custom()`` to get the base MAC address
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which is stored in BLK3 of EFUSE. If correct MAC address is returned, then call ``esp_base_mac_addr_set()`` to set the base MAC
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address for system to generate the MAC addresses used by the networking interfaces(WiFi/BT/Ethernet).
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There are 192 bits storage spaces for custom to store base MAC address in BLK3 of EFUSE. They are EFUSE_BLK3_RDATA0,
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EFUSE_BLK3_RDATA1, EFUSE_BLK3_RDATA2, EFUSE_BLK3_RDATA3, EFUSE_BLK3_RDATA4 and EFUSE_BLK3_RDATA5, each of them is 32 bits
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register. The format of the 192 bits storage spaces is:
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.. highlight:: none
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::
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------------------------------------------------------
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Field |Bits |Range |Description
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------------------------------------------------------
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version |8 |[191:184] |1: useful. 0: useless
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------------------------------------------------------
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reserve |112 |[183:72] |reserved
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------------------------------------------------------
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mac address |64 |[71:8] |base MAC address
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------------------------------------------------------
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mac crc |8 |[7:0] |crc of base MAC address
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------------------------------------------------------
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If using base MAC address stored in external storage, firstly get the base MAC address stored in external storage, then call
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API ``esp_base_mac_addr_set()`` to set the base MAC address for system to generate the MAC addresses used by the networking
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interfaces(WiFi/BT/Ethernet).
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All of the steps must be done before initializing the networking interfaces(WiFi/BT/Ethernet). It is recommended to do it in
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``app_main()`` which can be referenced in :example:`system/base_mac_address`.
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Number of universally administered MAC address
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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If the number of universal MAC addresses is two, only two interfaces (WiFi station and Bluetooth) receive a universally
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administered MAC address. These are generated sequentially by adding 0 and 1 (respectively) to the base MAC address.
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The remaining two interfaces (WiFi softap and Ethernet) receive local MAC addresses. These are derived from the universal
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WiFi station and Bluetooth MAC addresses, respectively.
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If the number of universal MAC addresses is four, all four interfaces (WiFi station, WiFi softap, Bluetooth and Ethernet)
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receive a universally administered MAC address. These are generated sequentially by adding 0, 1, 2 and 3 (respectively)
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to the final octet of the base MAC address.
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When using the default (Espressif-assigned) base MAC address, either setting can be used. When using a custom universal MAC
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address range, the correct setting will depend on the allocation of MAC addresses in this range (either 2 or 4 per device.)
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API Reference
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-------------
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Header Files
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^^^^^^^^^^^^
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* :component_file:`esp32/include/esp_system.h`
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Functions
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---------
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.. doxygenfunction:: esp_base_mac_addr_set
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.. doxygenfunction:: esp_efuse_mac_get_custom
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