STM32CubeIDE generates bad GPIO initialization code for Ethernet peripheral

[crazy88]

Post edited by ST moderator to be inline with the community rules especially with the code sharing. In next time please use </> button to paste your code. Please read this post: How to insert source code

# STM32CubeIDE ETH Configuration Bug Report

 

## Issue Summary

STM32CubeIDE fails to generate proper GPIO initialization code for Ethernet peripheral, resulting in non-functional MDIO/MDC communication with PHY chips.

 

## Environment

- **STM32CubeIDE Version**: 1.19.0

- **MCU**: STM32F407ZGT6 (LQFP144 package)

- **PHY**: YT8512C

- **Interface**: RMII mode

- **Date**: September 28, 2025

 

## Problem Description

 

### Configuration in .ioc File (Correct)

The STM32CubeIDE project configuration file (`.ioc`) shows correct pin assignments:

```

PC1.Mode=RMII

PC1.Signal=ETH_MDC

PA2.Mode=RMII  

PA2.Signal=ETH_MDIO

ETH.MediaInterface=HAL_ETH_RMII_MODE

```

 

### Generated Code Issue (Incorrect)

However, STM32CubeIDE **fails to generate the required `HAL_ETH_MspInit()` function** in `stm32f4xx_hal_msp.c`. This results in:

 

1. **Missing GPIO configuration**: PC1 and PA2 pins are not configured as alternate function AF11

2. **Default GPIO state**: Pins remain in their default configuration (typically AF0)

3. **Non-functional MDIO interface**: PHY register reads always return 0x0000

4. **Network connectivity failure**: Cannot establish Ethernet communication

 

### Symptoms Observed

- PHY register reads via `HAL_ETH_ReadPHYRegister()` always return 0x0000

- PHY not responding to MDIO commands

- Network interface fails to initialize properly

- Cable insertion/removal has no effect on link status

 

### Root Cause Analysis

Investigation revealed that the GPIO registers showed incorrect configuration:

- PC1 (MDC): Mode=0x0, AF=0x0 (should be Mode=0x2, AF=0xB)  

- PA2 (MDIO): Mode=0x0, AF=0x0 (should be Mode=0x2, AF=0xB)

 

The missing `HAL_ETH_MspInit()` function should contain:

void HAL_ETH_MspInit(ETH_HandleTypeDef* heth)
{
 GPIO_InitTypeDef GPIO_InitStruct = {0};
 if(heth->Instance==ETH)
 {
 /* Peripheral clock enable */
 __HAL_RCC_ETH_CLK_ENABLE();
 __HAL_RCC_ETHMAC_CLK_ENABLE();
 __HAL_RCC_ETHMACTX_CLK_ENABLE();
 __HAL_RCC_ETHMACRX_CLK_ENABLE();
 
 __HAL_RCC_GPIOA_CLK_ENABLE();
 __HAL_RCC_GPIOC_CLK_ENABLE();
 /* ... other GPIO clocks ... */
 
 /**ETH GPIO Configuration
 PC1 ------> ETH_MDC
 PA2 ------> ETH_MDIO
 /* ... other ETH pins ... */
 */
 GPIO_InitStruct.Pin = GPIO_PIN_1;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF11_ETH;
 HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_2;
 HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 /* ... */
 }
}

 

## Workaround Solution

Manual GPIO configuration in user code successfully resolves the issue:

 

// Enable GPIO clocks
__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_GPIOC_CLK_ENABLE();


// Configure PA2 (MDIO) as AF11
GPIOA->MODER = (GPIOA->MODER & ~(0x3 << 4)) | (0x2 << 4);
GPIOA->AFR[0] = (GPIOA->AFR[0] & ~(0xF << 8)) | (0xB << 8);


// Configure PC1 (MDC) as AF11 
GPIOC->MODER = (GPIOC->MODER & ~(0x3 << 2)) | (0x2 << 2);
GPIOC->AFR[0] = (GPIOC->AFR[0] & ~(0xF << 4)) | (0xB << 4);

 

After applying this workaround, PHY communication is immediately restored and network functionality works correctly.

 

## Impact Assessment

- **Severity**: High - Ethernet functionality completely non-functional

- **Scope**: Affects all STM32F4 projects using ETH peripheral with STM32CubeIDE

- **Workaround Available**: Yes, but requires manual intervention

 

## Expected Behavior

STM32CubeIDE should automatically generate the complete `HAL_ETH_MspInit()` function in `stm32f4xx_hal_msp.c` when ETH peripheral is enabled in the .ioc configuration, including proper GPIO alternate function configuration for all assigned ETH pins.

 

## Reproduction Steps

1. Create new STM32F407ZGT6 project in STM32CubeIDE 1.19.0

2. Enable ETH peripheral in RMII mode

3. Assign pins PC1→ETH_MDC, PA2→ETH_MDIO

4. Generate code

5. Observe missing `HAL_ETH_MspInit()` function in generated `stm32f4xx_hal_msp.c`

6. Compile and run - PHY communication will fail

 

## Request for Fix

Please investigate and fix the STM32CubeIDE code generator to ensure proper `HAL_ETH_MspInit()` function generation for ETH peripheral configurations.

 

---

**Reported by**: XINYU SONG

**Project**: Dispenser Control System  

**Contact**: [e-mail]

[Ghofrane GSOURI]

Hello @crazy88 

Following your description of reproduction steps:

1. Create new STM32F407ZGT6 project in STM32CubeIDE 1.19.0

2. Enable ETH peripheral in RMII mode

3. Assign pins PC1→ETH_MDC, PA2→ETH_MDIO (This step will be automatically done  by MX )

4. Generate code

By checking stm32f4xx_hal_msp.c , the following code will be generated successfully using CubeMX 6.15.0 and IDE 1.19.0 

void HAL_ETH_MspInit(ETH_HandleTypeDef* heth)
{
 GPIO_InitTypeDef GPIO_InitStruct = {0};
 if(heth->Instance==ETH)
 {
 /* USER CODE BEGIN ETH_MspInit 0 */

 /* USER CODE END ETH_MspInit 0 */
 /* Peripheral clock enable */
 __HAL_RCC_ETH_CLK_ENABLE();

 __HAL_RCC_GPIOC_CLK_ENABLE();
 __HAL_RCC_GPIOA_CLK_ENABLE();
 __HAL_RCC_GPIOB_CLK_ENABLE();
 /**ETH GPIO Configuration
 PC1 ------> ETH_MDC
 PA1 ------> ETH_REF_CLK
 PA2 ------> ETH_MDIO
 PA7 ------> ETH_CRS_DV
 PC4 ------> ETH_RXD0
 PC5 ------> ETH_RXD1
 PB11 ------> ETH_TX_EN
 PB12 ------> ETH_TXD0
 PB13 ------> ETH_TXD1
 */
 GPIO_InitStruct.Pin = GPIO_PIN_1|GPIO_PIN_4|GPIO_PIN_5;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF11_ETH;
 HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_7;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF11_ETH;
 HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_11|GPIO_PIN_12|GPIO_PIN_13;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF11_ETH;
 HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

 /* USER CODE BEGIN ETH_MspInit 1 */

 /* USER CODE END ETH_MspInit 1 */

 }

}

 

But since you have mentioned that you are using **PHY**: YT8512C , not  using LAN8742 or DP83848 ( in those cases the GPIO code will be placed  in ethernetif.c).

Could you please provide your project?

THX

Ghofrane

[crazy88]

Dear @Ghofrane,

Thank you for your prompt response and verification! The earlier issues with pin multiplexing initialization and the uninitialized PD3 REST pin only occurred during the first code generation and were resolved after reconfiguration.

The current main problem is that the ICMP test keeps failing. I’m using a third-party development board, and the hardware has been proven functional through official examples. However, after using STM32CubeIDE with FreeRTOS + LWIP, the ICMP test has never passed, and even the ETH interrupt has not been triggered. I’ve been troubleshooting for nearly half a month and am unable to resolve it. Could you please help me identify the issue?

Thank you! I'll post my code tomorrow after my last try,lol

Best regards, crazy88