Custom Board OSError: ethernet enable failed

[GruppD]

Hi all together,

I have a problem with a custom made Board which contans a ESP32-WROOM 16 MB and a LAN8720.
With this Pin connection:
RMII_INT --> GPIO36
RXER/PHYAD0 --> GPIO39
RXD0 --> GPIO25
RXD1 --> GPIO26
CRS_DV --> GPIO27
RMII_RST --> GPIO2
RMII_CLK_IN --> GPIO0
MDIO --> GPIO4
MDC --> GPIO5
RMII_CLK_EN --> GPIO18
TXD0 --> GPIO19
TXD1 --> GPIO22
TXEN --> GPIO21

The important Pins for the RMII-Interface are connectet according to the IO_MUX which ist declared by Espressif

I build a Custom Firmware based on the Micropython Version 1.21.0 the SIL_WESP32 with the following Board parameters.

board.json:

{
    "deploy": [
        "../deploy.md"
    ],
    "docs": "",
    "features": [
        "BLE",
        "Ethernet",
        "External Flash",
        "WiFi"
    ],
    "images": [
        "esp32_devkitc.jpg"
    ],
    "mcu": "esp32",
    "product": "ESP32 / WROOM",
    "thumbnail": "",
    "url": "https://www.espressif.com/en/products/modules",
    "variants": {
        "IDF3": "Compiled with IDF 3.x",
        "D2WD": "ESP32 D2WD",
        "SPIRAM": "Support for SPIRAM / WROVER",
        "UNICORE": "ESP32 Unicore",
        "OTA": "Support for OTA"
    },
    "vendor": "Espressif"
}

mpconfigboard.cmake

set(SDKCONFIG_DEFAULTS
    boards/sdkconfig.base
    boards/sdkconfig.ble
    boards/sdkconfig.240mhz
    boards/ExtruderControlV0_2/sdkconfig.board
)

mpconfigboard.h

#define MICROPY_HW_BOARD_NAME "ExtruderControl"
#define MICROPY_HW_MCU_NAME "ESP32"

sdkconfig.board

# 16 MB flash

CONFIG_ESPTOOLPY_FLASHSIZE_4MB=
CONFIG_ESPTOOLPY_FLASHSIZE_8MB=
CONFIG_ESPTOOLPY_FLASHSIZE_16MB=y
CONFIG_ESPTOOLPY_FLASHSIZE="16MB"

# Fast flash

CONFIG_ESPTOOLPY_FLASHMODE_QIO=y
CONFIG_ESPTOOLPY_FLASHFREQ_80M=y
CONFIG_ESP32_REV_MIN_1=y

# OTA

CONFIG_PARTITION_TABLE_CUSTOM=y
CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions-16MiB-ota.csv"# OTA

# Network name

CONFIG_LWIP_LOCAL_HOSTNAME="ExtruderControl"

The Firmware was build with the esp-idf Version 5.0.4.

Buiding works fine and flashing to the ESP32 was no problem.
To test the Ethernet connection i used the following code.

import network
from machine import Pin
import os

print(os.statvfs("/"))
reset=Pin(2, Pin.OUT)
CLK_EN=Pin(18, Pin.OUT)

reset.value(1)
CLK_EN.value(1)

lan = network.LAN(mdc=Pin(5), mdio=Pin(4), power=None, id=0, phy_addr=0, phy_type=network.PHY_LAN8720)

print('ifconfig :', lan.ifconfig())
print('status : ', lan.status())
print('isconnected : ', lan.isconnected())
print('active : ', lan.active())

lan.active(True)
# by default (no parameters), ifconfig() will request DHCP
lan.ifconfig()
# set fixed IP (address, netmask, gateway, dns)
#lan.ifconfig(('192.168.18.190', '255.255.255.0', '192.168.18.254', '192.168.18.254'))

If I run the sketch it outputs the following informations.

MPY: soft reboot                                                                
(4096, 4096, 2832, 2828, 2828, 0, 0, 0, 0, 255)                              
ifconfig : ('141.18.38.85', '255.255.255.0', '141.18.38.253', '141.18.30.1') 
status :  5                                                                  
isconnected :  False               
active :  False                    
Traceback (most recent call last): 
  File "main.py", line 45, in <module>                                          
OSError: ethernet enable failed                                                 
MicroPython v1.22.0-preview.246.g4365edb81 on 2023-12-11; ExtruderControl with E
SP32                                                                            
Type "help()" for more information.

I am a bit confused because the device has a IP-Address and I am able to Ping and trace it from my computer.
If i try the basic Ethernet example from Espressif in the ESP-IDF which is written in C, I am able to run it without any error message.

Has anybody a similar problem or a solution for my problem?

Thanks for your help