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 >>>>> >>>>> >>> >>>
