MAC to MAC connection without PHY layer

FAlca.1 · ‎2022-04-21

Hello,

I am desing with reference STM32MP153 and I would like connect two devices to through of MAC to MAC ports without PHY layer, Is it possible?, In attach figure connection shonw as I should do the connection between devices without phy layer:

Is it posible? could you help me?

Piranha · ‎2022-04-21

Seems you are making RGMII, not GMII connection, right? In that case you only have to cross link also the TX_CTL and RX_CTL lines and it should be fine.

FAlca.1 · ‎2022-04-26

It is true, I need RGMII conection instead of GMII.

Accoding your comment, will the connection be as I attach in file?

Thank you in advance.

Piranha · ‎2022-04-26

Now the connection seems to be OK. When designing the PCB, don't forget about an impedance matching, because 125MHz is not a joke.

Regarding the software don't forget that the speed and duplex modes have to be the same on both sides and will need to be set manually. Also, as the MDIO interface and PHY are not present, a link detection code have to be removed or disabled in one way or another. In a worst case scenario one can implement a dummy PHY driver, which just reports that the link is up and running at some specific speed and duplex configuration.