@Alan, Thanks for the hints.
From your message I will assume that this direct mode is not supported by default, so I need to start looking into it. I already have a basic hardware setup includes a STM32F7 custom board and an imx8m custom board, all prototypes. So it would be easier for me to start from these platforms @Nathan. As the GPIO resources are always against us, RMII would be a more realistic choice to me. In general level I have known it is possible, as I can find some successful cases in other platforms. And I will not worry too much about imx8m side which running Linux, which supports direct mode through RMII as claimed. I will be appreciated that if any Nuttx specific information/discussion about this feature that you can also share? This may prevent me from wasting time on something you may already explored. On hardware level, not sure if you can help to confirm my following understanding, 1. MDIO pins are not mandatory, so these 2 pins are not used on current prototypes in order to save GPIOs for other purposes. 2. 50MHz Reference clock is provided from a shared crystal to feed into both side. All the best, /Roland > On Mar 1, 2024, at 3:14 AM, Alan C. Assis <acas...@gmail.com> wrote: > > Hi Roland, > > We had a discussion about it a few months ago! > > We know it is possible, but nobody until now tried to do it. > > Basically you will need RMII support on both chips, I don't remember the > details why MII will not work (or will be more difficult to work) > > There is a discussion about it here, maybe you can get more insights: > https://stackoverflow.com/questions/39503466/can-two-ethernet-mac-chips-be-connected-directly-without-going-thru-phy > > Best Regards, > > Alan > > > On Thu, Feb 29, 2024 at 2:11 PM Roland <ning.rol...@mindpx.net> wrote: > >> Hi, >> >> I would like to directly connect a STM32F7 processor running Nuttx, to an >> external MCU (i.e., NXP imx8m) through RMII directly, without the need for >> PHY IC in between. >> Is this supported by Nuttx? I checked into the documents but this direct >> mode seems not been mentioned anywhere. >> Can anyone please confirm if this is supported, or I have to change >> something by myself? >> >> Thank you. >> >> /Roland >> >>
