STM32CubeIDE generates bad GPIO initialization code for Ethernet peripheral

[crazy88]

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# 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**: 1301621323@qq.com

[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