To run this example, it's recommended that you have an official ESP32 Ethernet development board - [ESP32-Ethernet-Kit](https://docs.espressif.com/projects/esp-idf/en/latest/hw-reference/get-started-ethernet-kit.html). This example should also work for 3rd party ESP32 board as long as it's integrated with a supported Ethernet PHY chip. Up until now, ESP-IDF supports four Ethernet PHY: `LAN8720`, `IP101`, `DP83848` and `RTL8201`, additional PHY drivers should be implemented by users themselves.
* Enable `Use ESP32 internal EMAC controller`, and then go into this menu.
* In the `PHY interface`, it's highly recommended that you choose `Reduced Media Independent Interface (RMII)` which will cost fewer pins.
* In the `RMII clock mode`, you can choose the source of RMII clock (50MHz): `Input RMII clock from external` or `Output RMII clock from internal`.
* Once `Output RMII clock from internal` is enabled, you also have to set the number of the GPIO used for outputting the RMII clock under `RMII clock GPIO number`. In this case, you can set the GPIO number to 16 or 17.
* Once `Output RMII clock from GPIO0 (Experimental!)` is enabled, then you have no choice but GPIO0 to output the RMII clock.
* Set SMI MDC/MDIO GPIO number according to board schematic, by default these two GPIOs are set as below:
* If you have connect a GPIO to the PHY chip's RST pin, then you need to enable `Use Reset Pin of PHY Chip` and set the GPIO number under `PHY RST GPIO number`.
* By default Ethernet driver will assume the PHY address to `1`, but you can alway reconfigure this value after `eth_phy_config_t phy_config = ETH_PHY_DEFAULT_CONFIG();`. The actual PHY address should depend on the hardware you use, so make sure to consult the schematic and datasheet.
Enter `make -j4 flash monitor` if you are using GNU Make based build system or enter `idf.py build flash monitor` if you' are using CMake based build system.
(To exit the serial monitor, type ``Ctrl-]``.)
See the [Getting Started Guide](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.
## Example Output
### Test uplink bandwidth
* PC: run command: `iperf -u -s -i 3` to start iperf server in UDP mode, and report interval is 3 seconds.
* ESP32: run command: `iperf -u -c PC_IP -i 3 -t 30` to start iperf client in UDP mode, and the test will last 30 seconds.
* ESP32's MAC and the external PHY device need a common 50MHz reference clock (aka RMII clock). This clock can either be provided by an externally oscillator or generated from internal APLL. The signal integrity of RMII clock is strict, so it is highly recommended to add a 33Ω resistor in series to reduce possible ringing.
* ESP32 can generate a 50MHz clock using internal APLL. But if the APLL is already used for other purposes (e.g. I2S peripheral), then you have no choice but use an external RMII clock.
(For any technical queries, please open an [issue](https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you as soon as possible.)
