esp-idf/examples/ethernet/README.md

Ethernet Examples

See the README.md file in the upper level examples directory for more information about examples.

Common Pin Assignments

Using ESP32 internal MAC

• RMII PHY wiring is fixed and can not be changed through either IOMUX or GPIO Matrix. By default, they're connected as follows:

GPIO	RMII Signal	Notes
GPIO21	TX_EN	EMAC_TX_EN
GPIO19	TX0	EMAC_TXD0
GPIO22	TX1	EMAC_TXD1
GPIO25	RX0	EMAC_RXD0
GPIO26	RX1	EMAC_RXD1
GPIO27	CRS_DV	EMAC_RX_DRV

• SMI (Serial Management Interface) wiring is not fixed. You may need to changed it according to your board schematic. By default they're connected as follows:

GPIO	SMI Signal	Notes
GPIO23	MDC	Output to PHY
GPIO18	MDIO	Bidirectional

• PHY chip has a reset pin, if want to do a hardware reset during initialization, then you have to connect it with one GPIO on ESP32. See more information from here. The default GPIO used for resetting PHY chip is GPIO5.

Using DM9051

• DM9051 Ethernet module consumes one SPI interface plus an interrupt and reset GPIO. By default they're connected as follows:

GPIO	DM9051
GPIO19	SPI_CLK
GPIO23	SPI_MOSI
GPIO25	SPI_MISO
GPIO22	SPI_CS
GPIO4	Interrupt
GPIO5	Reset

Common Configurations

1. In the Example Configuration menu:

   • Choose the kind of Ethernet under Ethernet Type.
   • If Internal EMAC is selected:
     • Choose PHY device under Ethernet PHY Device, by default, the ESP32-Ethernet-Kit has an IP101 on board.
     • Set GPIO number used by SMI signal under SMI MDC GPIO number and SMI MDIO GPIO number respectively.
   • If DM9051 Module is selected:
     • Set SPI specific configuration, including SPI host number, GPIO number and clock rate.
   • Set GPIO number used by PHY chip reset under PHY Reset GPIO number, you may have to change the default value according to your board schematic. PHY hardware reset can be disabled by set this value to -1.
   • Set PHY address under PHY Address, you may have to change the default value according to your board schematic.

2. In the Component config > Ethernet menu:

   • Under Support ESP32 internal EMAC controller sub-menu:
     • In the PHY interface, select Reduced Media Independent Interface (RMII), ESP-IDF currently only support RMII mode.
     • In the RMII clock mode, select one of the source that RMII clock (50MHz) comes from: Input RMII clock from external or Output RMII clock from internal.
     • If Output RMII clock from internal is enabled, you also have to set the GPIO number that used to output the RMII clock, under RMII clock GPIO number. In this case, you can set the GPIO number to 16 or 17.
     • If Output RMII clock from GPIO0 (Experimental!) is also enabled, then you have no choice but GPIO0 to output the RMII clock.
     • In Amount of Ethernet DMA Rx buffers and Amount of Ethernet DMA Tx buffers, you can set the amount of DMA buffers used for Tx and Rx.
   • Under Support SPI to Ethernet Module sub-menu, select the SPI module that you used for this example. Currently ESP-IDF only supports DM9051.

Common Troubleshooting

• The data panel between ESP32's MAC and PHY needs a fixed 50MHz clock to do synchronization, which also called RMII clock. It can either be provided by an external oscillator or generated from internal APLL. The signal integrity of RMII clock is strict, so keep the trace as short as possible!
• If the RMII clock is generated from internal APLL, then APLL can't be used for other purpose (e.g. I2S).