I'm a control and automation engineer just entering the world of telecommunications.
I have questions about the Ethernet architecture, and to be more assertive in my electrical schematic, I'd like opinions on how to interconnect the Rasp CM4 and the VSC7420 Switch.
From what I understand, both devices have integrated PHYs. The CM4 exposes MDI pins on the connector, as does the VSC7420, and both should be connected to the magnetics transformer. But if both expose MDIs, can't I connect one MDI to the other and be happy?
Please keep in mind that this is the OpenWrt forum, not a hardware development board.
That said, according to the Raspberry Pi forums [1], the CM4 does not expose any MII pins but has an integrated PHY. So you need a PHY-to-PHY connection to attach the switch IC [2]. There is also the Switchberry project with Open Source schematics for your reference [3].
