Riverdi (display) connection with external PHY

[ngrigoriadis]

Hello. I have a RIVERDI display with the STM32H757XIH6 (2MB Flash, 1MB RAM) microcontroller. I am trying to develop for this display a program  in order to connect it with an external PHY. In my research for external PHY I have found the LAN8720. Although, many topics here saying that this PHY drivers cant connect with the CubeMX and also I have read that in a lot of cases it is not working with this microcontroller. I am a bit confused and I want a feedback about this: 1) Is this LAN8720 a good solution to connect to my display and work with some protocols in order to receive messages like MQTT? If yes, is there any compatible library for this interface with this microcontroller?

2) If the LAN8720, isn't a good solution for my project, could you please provide to me some compatible and working external PHY's for developing this task, in order to buy them and start developing?

Thank you in advance!

[Issamos]

Hello @ngrigoriadis 

I suggest you to use the LAN8742 for your application with the stm32h7. This component is supported by stm32cubeh7.

Best regards.

II

[ngrigoriadis]

Thank you for your reply. I did a research on that PHY (LAN8742) and unfortunately I couldn't find a board (complete product) to buy only for PCB build.

[SofLit]

Hello,

The LAN8742A PHY is already used on ST boards, STM32H757-EVAL board or NUCLEO-H755ZI as an examples.

[ngrigoriadis]

Yes I can see that. Although my Riverdi screen does not contain a PHY as I said above to my topic and I am searching an external one in order to be compatible with the microcontroller that the screen has. I have already seen this PHY (LAN8742) but I cant find  an EV board in order to connect it with my screen. The only EV board I am finding is LAN8720 and I have read some topics, which they saying that this PHY is working with STM32H7 and other topics which are saying the opposite. Thus, I am a bit confused and the reason why I wrote this post is if someone had worked with the microcontroller that I have and the LAN8720, or maybe could suggest me something else that it is compatible and working. For example STM32CubeMX does not contain drivers for other PHY except for LAN8742, which I cant find an EV board. What should I do with that? 

[Bob S]

How do you intend to connect the display board to an external LAN8742?  Does the Riverdi have some kind of expansion connector that intended for this purpose?  Sending 50MHz clock and data over jumper wires will not be easy.

You could always buy the NUCLEO board, unsolder the CPU (or hard-wire the RESET pin low) and wire the on-board PHY to our display board (keeping in mind the caveat about 50MHz and jumper wires above).

[ngrigoriadis]

Hello and thank you for your reply. Yes the riverdi display that I have supports expansion connector but I can only use RMII and not MII. As far as the 50MHz clock speed that needs to syncronize the system, it must be through an external crystal or from internal source if the microcontroller support it? This is the riverdi screen that I have:https://riverdi.com/product/7-inch-lcd-display-capacitive-touch-panel-optical-bonding-uxtouch-stm32h7-rvt70hssnwc00-b. What do you think about that? Should I need to apply an external crystal for this purpose or not? I would appreciate if you give me a feedback. Thank you in advance!

[Piranha]

Maybe one should first look around...

https://riverdi.com/product/stm32h7-poe-add-on

[Bob S]

See also new thread https://community.st.com/t5/stm32-mcus-products/riverdi-diplay-with-stm32h7-and-external-phy/td-p/590262