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LAN8720 With NUCLEO H723ZG

JohnReese
Associate

Hello everyone,

I have a NUCLEO-H723ZG board and I would like to establish Ethernet communication with it. The board already includes a LAN8742 chip as the physical layer. However, in my system there is an external LAN8720 magnetic Ethernet module.

At the moment, I can successfully ping the board using the on-board LAN8742 with the LwIP_UDP_Echo_Server application example. What I want to do is disable the on-board LAN8742 and instead use the external LAN8720 for Ethernet communication. I could not find any example where an external PHY is used together with an STM32 board that already has an on-board PHY.

First of all, is such a setup actually possible? If it is, can I connect the external LAN8720 to the ETH header pins in RMII mode and make it work by adding the LAN8720 PHY driver? I have seen some discussions stating that this cannot be done without physically removing the LAN8742 chip, possibly due to pin conflicts.

Could you please clarify this for me? Is it possible to achieve Ethernet communication with an external PHY only by software changes and library configuration, without any physical modification to the board? If it is possible, I am not sure which parts of the software need to be changed, especially since the example application does not include the .ioc file and therefore cannot be easily reconfigured.

Thank you in advance.

1 REPLY 1
mbarg.1
Senior III

YES BUT: ethernet is a high speed device and wiring to an external device is not very reliable - will work  @ 10MB, have some problems @ 100MB - you can make a proof of concept but not evaluate performances - you will have to build a custom board.

0 ohm resistors are there for similar applications.

Have a look at the board schematic - you can download from st site in docs related to nucleo-h7232 - en.MB1364-H743ZI-E01_Schematic.pdf