SDIO Pins not on any Carrier Board?

Hi everyone,

We are trying to use an external eMMC memory to work with the Jetson. During development, this has to be tested of course. As described in the Product Design Guide of the Xavier NX in Chapter 9 there are two SDIO interfaces. One for the internal eMMC and another one for your use (cite: “brings one to the connector pins for SD Card or SDIO use”)

As of my understanding, this means an SDIO interface can be utilized by the user, is that correct?
It appears that the SDIO interface is not available in the GPIOs of the NX DevKit. Which raises the question, how is one supposed to develop something using the SDIO if it is not accessible during development? (I also checked partner carrier boards and found no SDIO)

I assume that I am just missing something or misunderstanding the general availability of the SDIO interface.

Thanks for your help!

After Reviewing the Schematics I was able to find these pins (why are they not in other guides???)
They are at the M2 Key E slot of the WIFI card. But require some soldering to be accessible! Are we not supposed to develop something for this interface? This causes a lot of confusion.

So I would assume we have to design some kind of pinout/adapter card for our SDIO Memory to be able to use this during development. Correct?


Sorry that I don’t quite get your statement “why are they not in other guides???”.

We have one available pin for SDIO as indicated in product design guide.

Hi @WayneWWW

sorry I was a bit confused yesterday and didn’t pick my words well.

Yes, the SDMMC3 is on the pins that are named here. But those are the Jetson Pins. I am talking about the Pins (or their usage) on the development carrier board. On the carrier board we expected them to be pinned out. However they are not. The SDMMC_DAT1 is used as M2. Key M Alert. (and that’s the only mention of “SDMMC” in the whole document)

The rest of the pins is not connected and only available as solder bridges which was only found out after looking at the schematics and furthermore the PCB layout. These SDMMC pins can be connected to the M.2 Key E via the solder bridge and only then can be used for development on the devkit (alternatively one can solder cables to the 0402 sized solder bridges which is not easy)

Why are these pins not connected to a proper pinout (like the GPIO) or are they and we are missing something?

Thanks for your help!
Sorry again for my unclear post!


I cannot answer it clearly because most of my work is on software part. But I think it is just devkit does not have this pin from the beginning.

However, since the module has such pinout, you can follow the design guide to make your own carrier board as many other users already did. We have some posts on forum to tell how to enable extra sdcard slot on emmc based module.


I was afraid that we have to do that. It is very disappointing that the DevKit does not have these pins connected to any pinout. You should consider this for a future revision

Thanks for your help!