OVMS3-idf/examples/ethernet/eth2ap/README.md

# eth2ap Example
(See the README.md file in the upper level 'examples' directory for more information about examples. To try a more complex application about Ethernet to WiFi data forwarding, please go to [iot-solution](https://github.com/espressif/esp-iot-solution/tree/master/examples/eth2wifi).)

## Overview
![eth2ap](eth2ap.png)

The similarities on MAC layer between Ethernet and Wi-Fi make it easy to forward packets from Ethernet to Wi-Fi and vice versa. This example illustrates how to implement a simple "router" which only supports forwarding packets between Ethernet port and Wi-Fi AP interface. In this case, the Ethernet should play the role of WAN (i.e. it can access outside network) so that a mobile device could get access to the Internet when it gets connected to ESP32 through Wi-Fi.

**Note:** In this example, ESP32 works like a *bridge* between Ethernet and Wi-Fi, and it won't perform any actions on Layer3 and higher layer, which means there's no need to initialize the TCP/IP stack.

## How to use this example

### Hardware Required

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 three Ethernet PHY: `TLK110`, `LAN8720` and `IP101`, additional PHY drivers should be implemented by users themselves.

### Configure the project

Enter `make menuconfig` if you are using GNU Make based build system or enter `idf.py menuconfig` if you are using CMake based build system. Then go into `Example Configuration` menu.

* Choose PHY device under `Ethernet PHY Device`, by default, the **ESP32-Ethernet-Kit** has an `IP101` on board.
* Set PHY address under `Ethernet PHY address`, it should depend on the PHY configuration of your hardware. You'd better consult the schematic of the board. By default, the PHY address of **ESP32-Ethernet-Kit** is *1*.
* Check whether or not to control the power of PHY chip under `Use PHY Power (enable / disable) pin`, (if set true, you also need to give the GPIO number of that pin under `PHY Power GPIO`).
* Set SMI MDC/MDIO GPIO number according to board schematic, by default they are set as below:

  | Default Example GPIO | RMII Signal | Notes         |
  | -------------------- | ----------- | ------------- |
  | GPIO23               | MDC         | Output to PHY |
  | GPIO18               | MDIO        | Bidirectional |

* Select one kind of RMII clock mode under `Ethernet RMII Clock Mode` option. Possible configurations of the clock are listed as below. By default, ESP32-Ethernet-Kit use the `GPIO0 input` mode, which gives a good performance when enabling Ethernet and Wi-Fi at the same time.

  | Mode     | GPIO Pin | Signal name  | Notes                                                        |
  | -------- | -------- | ------------ | ------------------------------------------------------------ |
  | external | GPIO0    | EMAC_TX_CLK  | Input of 50MHz PHY clock                                     |
  | internal | GPIO0    | CLK_OUT1     | Output of 50MHz APLL clock                                   |
  | internal | GPIO16   | EMAC_CLK_OUT | Output of 50MHz APLL clock                                   |
  | internal | GPIO17   | EMAC_CLK_180 | Inverted output of 50MHz APLL clock (suitable for long clock trace) |

  * External RMII clock must be connected to `GPIO0`.
  * ESP32 can generate the RMII clock(50MHz) using its internal APLL. But if the APLL has already been used for other peripheral (e.g. I²S), you'd better choose the external clock.

* Set the SSID and password for Wi-Fi ap interface under `Wi-Fi SSID` and `Wi-Fi Password`.
* Set the maximum connection number under `Maximum STA connections`.

### Build and Flash

To build and flash the example, 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

### Step 1: Initialize Ethernet and Wi-Fi (AP mode)

```bash
I (508) example: Power On Ethernet PHY
I (518) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
I (518) emac: emac reset done
I (518) example: Ethernet Started
......
I (538) wifi: wifi driver task: 3ffc7fbc, prio:23, stack:3584, core=0
I (538) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
I (538) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
I (568) wifi: wifi firmware version: ec61a20
I (568) wifi: config NVS flash: enabled
I (568) wifi: config nano formating: disabled
I (568) wifi: Init dynamic tx buffer num: 32
I (568) wifi: Init data frame dynamic rx buffer num: 32
I (578) wifi: Init management frame dynamic rx buffer num: 32
I (588) wifi: Init management short buffer num: 32
I (588) wifi: Init static rx buffer size: 1600
I (588) wifi: Init static rx buffer num: 10
I (598) wifi: Init dynamic rx buffer num: 32
```

### Step 2: Ethernet Connects to Router/Switch/PC (with DHCP server enabled)

```bash
I (4518) example: Ethernet Link Up
```

### Step 3: Start Wi-Fi AP

```bash
I (4618) phy: phy_version: 4100, 2a5dd04, Jan 23 2019, 21:00:07, 0, 0
I (4618) wifi: mode : softAP (30:ae:a4:c6:87:5b)
I (4628) wifi: Total power save buffer number: 16
I (4628) wifi: Init max length of beacon: 752/752
I (4628) wifi: Init max length of beacon: 752/752
```

### Step 4: Wi-Fi station (e.g. mobile phone) connects to ESP32's Wi-Fi

```bash
I (10168) wifi: new:<1,0>, old:<1,0>, ap:<1,1>, sta:<255,255>, prof:1
I (10168) wifi: station: c4:0b:cb:ec:9a:84 join, AID=1, bgn, 20
I (10258) example: AP got a station connected
```

Now your mobile phone should get access to the Internet.

## Troubleshooting

* Got error message `emac: emac rx buf err` when running the example.
    * This example just forwards the packets on the Layer2 between Wi-Fi and Ethernet, it won't do any Layer3 business. So make sure you have disabled the `CONFIG_ETH_EMAC_L2_TO_L3_RX_BUF_MODE`. By default, this option is false in the `sdkconfig.defaults` file.

* Got error message `example: WiFi send packet failed: -1` when running the example.
    * Ethernet process packets faster than Wi-Fi on ESP32, so have a try to enlarge the value of `FLOW_CONTROL_WIFI_SEND_DELAY_MS`.

* Wi-Fi station doesn't receive any IP via DHCP.
    * All Layer 3 (TCP/IP functions) on the ESP32 are disabled, including the SoftAP DHCP server. This means that devices must be able to access another DHCP server (for example on a Wi-Fi router connected via ethernet) or should use statically assigned IP addresses.