HAL Library Development Notes - Ethernet Communication (LwIP) 🚧

/* USER CODE BEGIN PV */
extern struct netif gnetif;
/* USER CODE END PV */

ethernetif_notify_conn_changed(struct netif *netif)

ethernetif_notify_conn_changed(&gnetif);

ethernetif_set_link(&gnetif);
if (netif_is_link_up(&gnetif) && !netif_is_up(&gnetif)) {
    netif_set_up(&gnetif);
    dhcp_start(&gnetif);
}

This article is based on the self-developed RobotCtrl development kit, with the STM32F407ZET6 microcontroller as the core and the LAN8720A Ethernet PHY chip. For the schematic and detailed information, please refer to [**RobotCtrl - STM32 General Development Kit**](https://wiki-power.com/RobotCtrl-STM32%E9%80%9A%E7%94%A8%E5%BC%80%E5%8F%91%E5%A5%97%E4%BB%B6).

LwIP is a lightweight IP protocol that can run regardless of operating system support. LwIP's key focus is on reducing RAM usage while retaining the core functionality of the TCP protocol. It only requires about ten kilobytes of RAM and around 40 kilobytes of ROM to operate, making it suitable for low-end embedded systems.

LwIP provides three programming interfaces: RAW/Callback API, NETCONN API, and SOCKETAPI. They vary in ease of use and efficiency from left to right. Developers can choose the API that best suits their needs. In this article, the Raw API is used, and the following functions are called:

| API Function   | Description                                                         |
| -------------- | ------------------------------------------------------------------- |
| udp_new        | Create a new UDP PCB                                                |
| udp_remove     | Remove UDP PCB and release related resources                        |
| udp_bind       | Bind UDP PCB to a local IP address and port                         |
| udp_connect    | Establish remote IP address and port for UDP PCB                    |
| udp_disconnect | Remove remote IP and port from UDP PCB                              |
| udp_send       | Send UDP data                                                       |
| udp_recv       | Register a callback function to be called when new data is received |

## Configuration within CubeMX

1. In the `RCC` page, select an external crystal for HSE.
2. In the `ETH` page, configure the PHY mode as `RMII` and set the following parameters:
   1. Under the `Parameter Setting` tab, configure the `PHY Address` as `0` (determined by PHYAD0 pin).
   2. Under the `Advanced Parameter` tab, based on the LAN8720A datasheet, configure `PHY special control/status register Offset` as `31`; `PHY Speed mask` as `0x0004`; `PHY Duplex mask` as `0x0010`.
3. In the `LWIP` page, enable and configure the following parameters:
   1. Under the `General Settings` tab, set `LWIP_DHCP (DHCP Module)` to `Disabled` (use static IP); configure `IP_ADDRESS` as `192.168.001.100`; `NETMASK_ADDRESS` as `255.255.255.000`; `GATEWAY_ADDRESS` as `192.168.001.001`; and enable `LWIP_UDP (UDP Module)` and `LWIP_TCP (TCP Module)`.

## References and Acknowledgments

- [LwIP TCP/IP stack demonstration for STM32F4x7 microcontrollers (AN3966)](https://www.st.com/en/embedded-software/stsw-stm32070.html)
- [Developing applications on STM32Cube with LwIP TCP/IP stack (UM1713)](https://www.st.com/resource/en/user_manual/um1713-developing-applications-on-stm32cube-with-lwip-tcpip-stack-stmicroelectronics.pdf)
- [54zorb/stm32-lwip](https://github.com/54zorb/stm32-lwip)

> Original: <https://wiki-power.com/>
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