I would like to use a STM32H743XIH6U with a KSZ8863RLLI switch connecting directly though the RMII MAC registers.

[STM32 User]

https://www.digikey.com/en/products/detail/microchip-technology/KSZ8863RLLI/2426202 - switch

Any1 have experiance with using these two components?

If not are they're any known plug and play switches that will achieve this?

[Piranha]

Apart for a bit more configuration, there are no technical problems using such a PHY+switch.

Almost all of the real problems are in software:

https://community.st.com/s/question/0D50X0000C6eNNSSQ2/bug-fixes-stm32h7-ethernet

https://community.st.com/s/question/0D50X0000AhNBoWSQW/actually-working-stm32-ethernet-and-lwip-demonstration-firmware

[STM32 User]

My hope is to remove the PHY to gain spacing on a board.

[Piranha]

You are not removing PHY but replacing it with an integrated PHY+switch. :)

[STM32 User]

Interesting so even though the registers seem to be similar on the STM32 and the 3 port switch they can't be connected to each other.

[Piranha]

What registers are you comparing between STM32 and a PHY? That's a nonsense. You are misunderstanding something.

STM32 has a MAC peripheral, which can be connected to anything supporting MII/RMII interfaces. To use wired Ethernet you need an external PHY chip with one of those interfaces. And optionally you can use an integrated PHY+switch chip if you need more than one physical port.

As I said, there are no problems using almost any PHY with MII/RMII interface (including KSZ8863) with any STM32 with Ethernet peripheral.

[Pavel A.]

@STM32 User​ Would advice to connect also I2C interface of the the KSZ8863, to be able to see all its registers.

I2C is cheap and access to entire register space can be very helpful for debugging and diagnostic.

-- pa

[STM32 User]

https://ww1.microchip.com/downloads/en/DeviceDoc/00002335B.pdf

From the data sheet on the SWITCH

"Supports RMII Interface and 50 MHz Reference Clock Output". Can I directly connect the STM32 MAC peripheral to this switch RMII interface? Will there be code required or is it just plug and play?

[Pavel A.]

Almost  just plug and play. The only thing to do with the STM32 MAC, configure it to 100 Mb/s full duplex, as this is how the switch is connected to STM32. Do not check the link state periodically on the internal port, because it never changes.

Of course, as long as it works. Otherwise you'll need to read the boring registers ;)

-- pa