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61 lines
2.2 KiB
Plaintext
61 lines
2.2 KiB
Plaintext
RMII Ethernet
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^^^^^^^^^^^^^
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As mentioned above, the RMII interface is only present on ESP32-classic and ESP32-P4.
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RMII PHY SMI Wiring
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"""""""""""""""""""
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Most PHY boards have documented their *RMII PHY SMI Wiring* pins:
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* **MDC** Output to PHY, usually pin 23
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* **MDIO** Bidirectional, usually pin 18
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Clock sync
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""""""""""
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The PHY and the ESP need to keep a clock in sync.
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This can either be done via an external crystal, which is connected to a GPIO pin.
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Another option is to let the ESP provide the clock to the PHY.
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* External crystal oscillator
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* 50MHz APLL Output on GPIO0
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* 50MHz APLL Output on GPIO16
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* 50MHz APLL Inverted Output on GPIO17
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.. note:: When using an external crystal oscillator, this is connected to GPIO-0. Make sure this crystal is not active, or connected to GPIO-0, during boot or else the ESP32 may boot into flash mode.
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Power pin
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"""""""""
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On almost all PHY boards, or ESP boards equiped with an ethernet PHY, it is possible to turn the PHY on or off.
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Either to save energy, or to make sure the external clock is not affecting the ESP boot mode when it restarts.
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For example the Olimex ESP32-EVB does have the *external crystal oscillator* connected to GPIO-0, which could boot the ESP32 randomly into UART flash mode.
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Most boards use a specific GPIO pin to control the power to the PHY.
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The Olimex ESP32-EVB does have a specific delay circuit to only allow power to the PHY after boot and therefore does not need to control the PHY power.
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For other boards, the default is often GPIO-17, but this may change per board.
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(Changed: 2022-01-20)
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If the power pin is defined, ESPEasy will toggle the ethernet module off and on at boot.
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Some Ethernet modules, like the LAN8720, may sometimes get stuck and need to be reset to get it to work again.
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RMII PHY Wiring
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"""""""""""""""
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Apart from these GPIO pins, there is a number of other pins reserved on the ESP32 for RMII PHY Wiring.
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Since these GPIO pin assignments cannot be changed, it is also not needed to configure them.
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However, they also cannot be used when *RMII PHY* is used.
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.. include:: ../Reference/RMII_Ethernet_PHY_ESP32.rst
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RMII Ethernet ESP32 Boards
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""""""""""""""""""""""""""
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.. include:: ../Reference/RMII_Ethernet_ESP32_boards.rst
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