Ethernet does not work if uC starts with the cable disconnected

[#1]

When starting uC (or performing a reset) with the cable connected to the router, ping.exe receives a response normally. If the cable is removed, ping.exe does not receive a response, but after reconnecting, ping.exe receives a response.

The problem is that if the cable is disconnected, and the uC is initialized, then ping.exe does not receive a response, obviously due to the disconnected cable. But after connecting the cable, ping.exe still doesn't get a response.

I tried to force the execution of MX_LWIP_Init () but it didn't work, even if the Ethernet is already responding to ping.exe, it will stop responding if I call MX_LWIP_Init () again.

I noticed that MX_LWIP_Init () has a long timeout, 5000ms, but even so, I can't get it to work without restarting uC.

Note: DHCP: off. External PHY: LAN8720. uC: STM32F407VG.

I tested a code made with Arduino IDE, and it happens the same way it happens in STM32CubeIDE.

How to reset the Ethernet, without having to restart the uC?

[Pavel A.]

Do you use an existing example from the ST library (which are by the way created not in Cube or Cube IDE),

or you generate from scratch in Cube new code with LwIP?

If the latter - please, do study the LwIP examples. Even for different/newer STM32 families. There are examples how to deal with reconnect.

Do NOT call MX_LWIP_Init () again.

-- pa

[#3]

They were created with STM32CubeMX or STM32CubeIDE, which alias use the same base.

This artifice of using other tools to generate examples, in my view, is not a good sign, since users will use the available tools, and preferably they are free, which means that the examples need to be done with the same tool, even that are just identical copies.

About the reconnection, would you know how to say a search term, a key word, or a subroutine name to be searched?

[Piranha]

So, you've made a thousand topics with million images with "something doesn't work", but haven't found and read my report?

Post edited to adhere to community guidelines.

https://community.st.com/s/question/0D50X0000BOtfhnSQB/how-to-make-ethernet-and-lwip-working-on-stm32

[#5]

Well, I was already thinking about using ESP32 instead of STM32, I'll see if ESP works better with Ethernet.

Thank you.​

[Pavel A.]

> About the reconnection, would you know how to say a search term, a key word, or a subroutine name to be searched?

Detection of link state changes.

See here for example (in 'H7 library, but should be similar for F4).

Note that the PHY is responsible for link up/down detection. If you have a different PHY, need to adapt. There can be more states than in the LAN8742 example: auto-negotiation in progress, etc,

Regards,

-- pa

[#7]

Since MX_LWIP_Init () cannot be called again, I added a flag that prevents the first call until the cable has been connected, it seems to have worked well.

Before testing the PHY status, it was necessary to initialize it.

lwip.c

/* USER CODE BEGIN 0 */
#define  ETH_UsrLog(...)   do { \
		printf(__VA_ARGS__); \
		printf("\n"); \
} while (0)
 
uint8_t eth_is_initialized = 0;

void MX_LWIP_Init(void)
{
	if(eth_is_initialized != 0) return;
 
	ethernetif_init(&gnetif);
 
	uint32_t phyreg = 0;
 
	if(HAL_ETH_ReadPHYRegister(&heth, PHY_BSR, &phyreg) != HAL_OK)
	{
		ETH_UsrLog("HAL_ETH_ReadPHYRegister: error");
	}
 
	if((phyreg & PHY_LINKED_STATUS) != PHY_LINKED_STATUS) return;
 
	/* IP addresses initialization */
	IP_ADDRESS[0] = 192;
	IP_ADDRESS[1] = 168;
	IP_ADDRESS[2] = 1;
	IP_ADDRESS[3] = 111;
	NETMASK_ADDRESS[0] = 255;
	NETMASK_ADDRESS[1] = 255;
	NETMASK_ADDRESS[2] = 255;
	NETMASK_ADDRESS[3] = 0;
	GATEWAY_ADDRESS[0] = 192;
	GATEWAY_ADDRESS[1] = 168;
	GATEWAY_ADDRESS[2] = 1;
	GATEWAY_ADDRESS[3] = 1;
 
	/* Initilialize the LwIP stack without RTOS */
	lwip_init();
 
	/* IP addresses initialization without DHCP (IPv4) */
	IP4_ADDR(&ipaddr, IP_ADDRESS[0], IP_ADDRESS[1], IP_ADDRESS[2], IP_ADDRESS[3]);
	IP4_ADDR(&netmask, NETMASK_ADDRESS[0], NETMASK_ADDRESS[1] , NETMASK_ADDRESS[2], NETMASK_ADDRESS[3]);
	IP4_ADDR(&gw, GATEWAY_ADDRESS[0], GATEWAY_ADDRESS[1], GATEWAY_ADDRESS[2], GATEWAY_ADDRESS[3]);
 
	/* add the network interface (IPv4/IPv6) without RTOS */
	netif_add(&gnetif, &ipaddr, &netmask, &gw, NULL, &ethernetif_init, &ethernet_input);
 
	/* Registers the default network interface */
	netif_set_default(&gnetif);
 
	if (netif_is_link_up(&gnetif))
	{
		/* When the netif is fully configured this function must be called */
		netif_set_up(&gnetif);
	}
	else
	{
		/* When the netif link is down this function must be called */
		netif_set_down(&gnetif);
	}
 
	/* USER CODE BEGIN 3 */
	eth_is_initialized = 1;
 
	//tcp_echoserver_init();
	/* USER CODE END 3 */
}

void MX_LWIP_Process(void)
{
/* USER CODE BEGIN 4_1 */
	if(eth_is_initialized == 0) return;

main.c

while (1)
	{
		/* USER CODE END WHILE */
 
		/* USER CODE BEGIN 3 */
		MX_LWIP_Process();
 
		MX_LWIP_Init();

[ABOSTM]

As per Arduino is concerned, it works like a charm with the setup below.

Board: NUCLEO_F429ZI which embed PHY: LAN8742

Sketch: WebServer.ino (provided with https://github.com/stm32duino/STM32Ethernet library)

see details https://github.com/stm32duino/STM32Ethernet/issues/42

[#9]

Please test again, the wait time I'm using is 10 seconds or more. The LwIP startup has a long timeout, 5 seconds if I'm not mistaken.

[Pavel A.]

> The LwIP startup has a long timeout, 5 seconds if I'm not mistaken.

??? Perhaps only if DHCP is enabled, and it does several retries before failing.

@rtek1000

>  I added a flag that prevents the first call until the cable has been connected

In your code above the initialization still may occur several times.

Line 5: ethernetif_init called

Line 14: if the link is not detected, it returns and next time ethernetif_init called again.

-- pa