So, Niklas tested it and submitted a PR to mainline: https://github.com/apache/nuttx/pull/12538
Next step is testing this idea on ESP32 as well! BR, Alan On Fri, Mar 1, 2024 at 12:29 PM Roland <ning.rol...@mindpx.net> wrote: > David, > > Thanks for the advice, I will check the manual. > > /Roland > > > On Mar 1, 2024, at 11:12 PM, David Sidrane <david.sidr...@nscdg.com> > wrote: > > > > Rolan, > > > > Have a look in the imx8 manual you may be able to source the clock from > that > > MAC. > > > > David > > > > > > -----Original Message----- > > From: Roland <ning.rol...@mindpx.net> > > Sent: Friday, March 1, 2024 9:55 AM > > To: dev@nuttx.apache.org > > Subject: Re: Ethernet direct RMII connection > > > > Hi Alan, > > > > Thanks for this reminder. > > > > I am using RMII, as STM32F7 can only support up to 100MHz data rate and > do > > not have any GMII interface. > > > > On imx8m side, it actually will be “downgraded” to RMII as well. > > > > /Roland > > > > > >> On Mar 1, 2024, at 9:31 PM, Alan C. Assis <acas...@gmail.com> wrote: > >> > >> Hi Roland, > >> > >> I think the page I sent earlier has more info about MII, RMII, RGMII, > >> etc that you need to know before attempting to do it. Let me put here > >> for > >> clarification: > >> > >> "There are variants of the MII (GMII; RMII; SGMII; RGMII...) interface > >> for connecting MACs to PHYs or MACs to MACs, in some of them there is > >> a MAC or PHY role. > >> > >> The RGMII interface is a dual data rate (DDR) interface that consists > >> of a transmit path and a receive path. Both paths have an independent > >> clock, 4 data signals and a control signal. This means that in RGMII > >> there is no PHY or MAC role, so no special support is needed for > >> MAC-to-MAC connection as it is the case, being both ends in RGMII mode > >> is enough for the communication to be carried out." > >> > >> Today I found a new page with more information and some details that > >> probably will help you and others trying to do it, like clock > >> shifting, otherwise it will not work: > >> > >> https://community.nxp.com/t5/i-MX-Processors/Direct-ETH-MAC-MII-to-MAC > >> -MII-connection/m-p/1042795 > >> > >> So, if you didn't include the clock skew circuit as shown on this > >> link, then you will need to use RMII. > >> > >> Best Regards, > >> > >> Alan > >> > >> On Fri, Mar 1, 2024 at 8:31 AM Roland <ning.rol...@mindpx.net> wrote: > >> > >>> @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-chi > >>> ps-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 > >>>>> > >>>>> > >>> > >>> > >
