Hi Alan, Thank you for the tips! Yes, SDIO looks pretty involved compared to SPI or I2C. I'll try reading the specification like you suggested.
The BCM2711 datasheet doesn't document it at all, however the EMMC interface is supposedly the exact same from the BCM2835 and the registers there are at least documented. All I know is that it is using an interface by Arasan. I'm not as familiar with NuttX, but if this at all looks like something that's already been supported, please let me know. In the meantime, I'll look through the SDIO implementations to check: https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf (page 65) Thanks again! Matteo On Tue, Sep 16, 2025 at 9:49 AM Alan C. Assis <acas...@gmail.com> wrote: > HI Matteo, > > I implemented the SDIO support for LPC43 some years ago and what helped me > most was reading the SD/MMC specification, the LPC43 reference manual and > enabling the NuttX SD/MMC debug messages. > > There are many details to take care of: clock enable for the controller, > interrupts, pins configuration, etc. > > Unfortunately, the BCM2711 doc is not good. You can start verifying the > registers, maybe it is based on some SD/MMC core IP already supported by > NuttX. > > BR, > > Alan > > > > On Mon, Sep 15, 2025 at 6:34 PM Matteo Golin <matteo.go...@gmail.com> > wrote: > > > Hi everyone, > > > > Now that I2C has been tackled, I am moving on to SDIO interfaces so the > SD > > card can be interacted with from NuttX. > > > > The NuttX SDIO documentation is a little bare, and I'm not the most > > familiar with SDIO. Does anyone have any recommendations for > > implementations to look at (besides the STM32 one that is linked in the > > docs), resources to read (any blog posts from when you ported SDIO) or > > advice in general? It would be much appreciated. > > > > Thank you, > > Matteo > > > > On Fri, Sep 5, 2025, 11:15 AM Matteo Golin <matteo.go...@gmail.com> > wrote: > > > > > Got another response from my earlier request to Raspberry Pi through > > their > > > website: > > > > > > Hi Matteo > > > > > > > > > > > >> Thanks for getting in touch. We don't actually have any more > > >> documentation that we can release on this. My usual recommendation is > > for > > >> SW people to take a look at the Linux drivers to get a closer > > understanding > > >> of how the HW works. Not ideal, but the best I can offer. > > > > > > > > > So I guess everyone is telling us the same thing! > > > > > > > > > On Mon, Sep 1, 2025 at 3:49 PM Tomek CEDRO <to...@cedro.info> wrote: > > > > > >> Sure! Public now :-) > > >> Tomek > > >> > > >> On Mon, Sep 1, 2025 at 9:24 PM Matteo Golin <matteo.go...@gmail.com> > > >> wrote: > > >> > > > >> > I have populated the RPi 4B project with some starting issues to > > tackle > > >> for > > >> > the 4B implementation. I see that the project is marked as private; > is > > >> > there any way to make it visible to potential contributors just > > visiting > > >> > the GitHub page? I think if they can see a list of issues in one > place > > >> when > > >> > they go to the page it might help. > > >> > > > >> > Thanks, > > >> > Matteo > > >> > > > >> > On Mon, Sep 1, 2025 at 3:02 PM Tomek CEDRO <to...@cedro.info> > wrote: > > >> > > > >> > > Thank you Linguini, good luck and have fun! :-) > > >> > > Tomek > > >> > > > > >> > > On Mon, Sep 1, 2025 at 8:48 PM Matteo Golin < > matteo.go...@gmail.com > > > > > >> > > wrote: > > >> > > > > > >> > > > To update the community, we've been told by Gordon that the Pi > > >> Foundation > > >> > > > doesn't have any documentation for the chip beyond what was > > written > > >> in > > >> > > the > > >> > > > peripheral datasheet. Broadcom themselves has written the Linux > > >> drivers > > >> > > and > > >> > > > Raspberry Pi has only made some slight bug fixes, etc. We've > been > > >> > > suggested > > >> > > > to read the source to discover undocumented > > registers/configuration > > >> > > options. > > >> > > > > > >> > > > I plan to still continue with the port until the feature set on > > >> NuttX is > > >> > > > equal or greater to what is available on QNX. I at least want to > > get > > >> > > > Ethernet and some graphics running after the base peripheral set > > >> (I2C, > > >> > > SPI, > > >> > > > UART) are supported. > > >> > > > > > >> > > > Matteo > > >> > > > > > >> > > > On Sun, Aug 31, 2025 at 6:10 PM Matteo Golin < > > >> matteo.go...@gmail.com> > > >> > > wrote: > > >> > > > > > >> > > > > Very interesting Sebastian. I got that impression from > Broadcom > > >> when I > > >> > > was > > >> > > > > initially trying to port NuttX to the Pi. The inability to > > submit > > >> > > forms on > > >> > > > > their website seems like it might be by design... > > >> > > > > > > >> > > > > I'm hopeful the Raspberry Pi Foundation will have something > more > > >> for > > >> > > us to > > >> > > > > work with, they seem more positive to FOSS. Otherwise I will > > still > > >> > > continue > > >> > > > > with reverse engineering until at least the point where the > > >> > > functionality > > >> > > > > driver-wise is on par with QNX. > > >> > > > > > > >> > > > > On Sun, Aug 31, 2025, 10:46 AM Tomek CEDRO <to...@cedro.info> > > >> wrote: > > >> > > > > > > >> > > > >> James Dougherty contacted us with Gordon Hollingworth from > > >> Raspberry > > >> > > > >> Pi Foundation recently :-) We are waiting for response :-) I > > >> really > > >> > > > >> hope we can get some sort of documentation and/or code > samples > > to > > >> > > > >> write high quality NuttX port for the big raspberries :-) > > >> > > > >> > > >> > > > >> Open-Source matters even more in this crazy world. Thanks for > > >> > > > >> interesting article Sebastien! Personally I think we should > > >> focus only > > >> > > > >> on vendors that support Open-Source. What is the reason for > > >> bumping > > >> > > > >> sales for companies that in the end can sue you for > reversing? > > :D > > >> > > > >> > > >> > > > >> Have a good day folks :-) > > >> > > > >> Tomek > > >> > > > >> > > >> > > > >> > > >> > > > >> > > >> > > > >> On Sun, Aug 31, 2025 at 10:15 AM Sebastien Lorquet < > > >> > > sebast...@lorquet.fr> > > >> > > > >> wrote: > > >> > > > >> > > > >> > > > >> > Hello, > > >> > > > >> > > > >> > > > >> > I just found this interesting document: > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > > >> > > > > >> > > > https://fastcode.io/2025/08/30/the-69-billion-domino-effect-how-vmwares-debt-fueled-acquisition-is-killing-open-source-one-repository-at-a-time/ > > >> > > > >> > > > >> > > > >> > In a summary, if you expect anything cool from broadcom: > > dont. > > >> > > > >> > > > >> > > > >> > go go go reverse engineering! > > >> > > > >> > > > >> > > > >> > Sebastien > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > On 8/29/25 15:37, Tomek CEDRO wrote: > > >> > > > >> > > No response from #infra@slack, I just sent request to > > >> > > > >> > > dev@community.apache mailing list maybe someone can > reply > > >> over > > >> > > there > > >> > > > >> > > :-) > > >> > > > >> > > > > >> > > > >> > > > > >> https://lists.apache.org/thread/n9y5vrvjm23npwgbr45f7zq5ys5l8dok > > >> > > > >> > > > > >> > > > >> > > We should also know the official stance from Broadcom and > > RPI > > >> > > > >> Foundation :-) > > >> > > > >> > > > > >> > > > >> > > Thanks :-) > > >> > > > >> > > Tomek > > >> > > > >> > > > > >> > > > >> > > On Thu, Aug 28, 2025 at 9:35 PM Tomek CEDRO < > > >> to...@cedro.info> > > >> > > wrote: > > >> > > > >> > >> I just asked question at #asfinfra / slack, maybe > someone > > >> can > > >> > > help > > >> > > > >> > >> there or recommend someone who can, waiting for response > > :-) > > >> > > > >> > >> > > >> > > > >> > >> For a good start you can contact Broadcom and > RaspberryPi > > >> > > Foundation, > > >> > > > >> > >> introduce yourself as Apache NuttX RTOS developer that > > want > > >> to > > >> > > port > > >> > > > >> > >> NuttX to rPI boards, and just ask if DataSheets are > > >> available > > >> > > :-) We > > >> > > > >> > >> will know then first hand if this is possible or are > there > > >> any > > >> > > > >> > >> problems / requirements :-) > > >> > > > >> > >> > > >> > > > >> > >> You can ask for 4B and probably Zero-2W SoC > documentation > > >> these > > >> > > seems > > >> > > > >> > >> most popular nowadays :-) > > >> > > > >> > >> > > >> > > > >> > >> Thanks :-) > > >> > > > >> > >> Tomek > > >> > > > >> > >> > > >> > > > >> > >> > > >> > > > >> > >> > > >> > > > >> > >> On Thu, Aug 28, 2025 at 8:45 PM Matteo Golin < > > >> > > matteo.go...@gmail.com> > > >> > > > >> wrote: > > >> > > > >> > >>> Hi Tomek, > > >> > > > >> > >>> > > >> > > > >> > >>> Thanks so much! I actually hadn't thought of that, > maybe > > we > > >> > > could > > >> > > > >> ask for > > >> > > > >> > >>> help from the foundation. Do you know who's the best > > point > > >> of > > >> > > > >> contact for > > >> > > > >> > >>> that? > > >> > > > >> > >>> > > >> > > > >> > >>> I know Linux must have received the datasheets to make > > >> > > Raspberry Pi > > >> > > > >> OS. No > > >> > > > >> > >>> offence to NuttX, but Linux is pretty popular in > > >> comparison. If > > >> > > > >> Broadcom or > > >> > > > >> > >>> Raspberry Pi would release us some information that > would > > >> be an > > >> > > > >> immense > > >> > > > >> > >>> help. I suspect there was some kind of deal with the > > Linux > > >> group > > >> > > > >> but I have > > >> > > > >> > >>> no idea. I believe even QNX didn't have access to the > > >> datasheets > > >> > > > >> and rather > > >> > > > >> > >>> just reverse engineered the Linux drivers. > > >> > > > >> > >>> > > >> > > > >> > >>> Matteo > > >> > > > >> > >>> > > >> > > > >> > >>> On Thu, Aug 28, 2025, 12:42 PM Tomek CEDRO < > > >> to...@cedro.info> > > >> > > > >> wrote: > > >> > > > >> > >>> > > >> > > > >> > >>>> On Tue, Aug 26, 2025 at 10:05 PM Matteo Golin < > > >> > > > >> matteo.go...@gmail.com> > > >> > > > >> > >>>> wrote: > > >> > > > >> > >>>>> I2C still needs some work unfortunately. However, I > > agree > > >> > > with you > > >> > > > >> > >>>>> generally. Personally, I think HDMI, networking > > >> (including > > >> > > WiFi > > >> > > > >> and BLE) > > >> > > > >> > >>>>> and some kind of interaction with storage (eMMC or SD > > >> card) > > >> > > are > > >> > > > >> the most > > >> > > > >> > >>>>> important. Unfortunately, those are likely going to > be > > >> the > > >> > > most > > >> > > > >> difficult > > >> > > > >> > >>>>> because of the lack of documentation on the > > peripherals. > > >> It is > > >> > > > >> definitely > > >> > > > >> > >>>>> not an impossible task, but it will be challenging. > > >> Hence my > > >> > > > >> request for > > >> > > > >> > >>>>> creating the new project roadmap, so maybe some > > >> discoveries > > >> > > can be > > >> > > > >> > >>>>> documented there and more eyes can get on the RPi > > >> > > implementation. > > >> > > > >> > >>>> The lack of documentation is a real pain, and known > > issue > > >> for > > >> > > > >> years in > > >> > > > >> > >>>> many areas, but some vendors are especially famous for > > >> that. > > >> > > > >> > >>>> > > >> > > > >> > >>>> Considering someone wants to create Open-Source > drivers > > >> for > > >> > > free > > >> > > > >> and > > >> > > > >> > >>>> bring customers to the vendor. > > >> > > > >> > >>>> > > >> > > > >> > >>>> Maybe we could ask Apache Foundation for help in > > obtaining > > >> > > required > > >> > > > >> > >>>> datasheets? :-) > > >> > > > >> > >>>> > > >> > > > >> > >>>> -- > > >> > > > >> > >>>> CeDeROM, SQ7MHZ, http://www.tomek.cedro.info > > >> > > > >> > >>>> > > >> > > > >> > >> > > >> > > > >> > >> > > >> > > > >> > >> -- > > >> > > > >> > >> CeDeROM, SQ7MHZ, http://www.tomek.cedro.info > > >> > > > >> > > > > >> > > > >> > > > > >> > > > >> > > >> > > > >> > > >> > > > >> > > >> > > > >> -- > > >> > > > >> CeDeROM, SQ7MHZ, http://www.tomek.cedro.info > > >> > > > >> > > >> > > > > > > >> > > > > >> > > > > >> > > > > >> > > -- > > >> > > CeDeROM, SQ7MHZ, http://www.tomek.cedro.info > > >> > > > > >> > > >> > > >> > > >> -- > > >> CeDeROM, SQ7MHZ, http://www.tomek.cedro.info > > >> > > > > > >
