How does Jetson Nano expand EMMC

I want to connect to eMMC on the SDMMC interface, but the SDMMC interface reserved by Jetson Nano itself is 4bit, while the interface of eMMC is 8bit. How should I connect to this extra 4bit hardware and how should it be configured on this application software?

Simply use the lower 4 data lines and leave the upper 4 EMMC data lines open. The driver should use 4 bit EMMC mode automatically.

You can try this with an external EMMC module like this one

and the matching adapter for uSD-Slot

on an DevKit.

Thank you for your reply, but whether using 4bit alone will affect its transmission rate, I expect its transmission rate to be similar to that of the module itself.

Using 4 bit instead of 8 bit will reduce the theoretical transfer speed by 2 and the practical speed somewhat less. Also using the uSD slot will reduce the maximum frequency.

This is what I am worried about, because my customers are more concerned about the transmission speed of EMMC. Does Jetson Nano have a way to achieve the application of 8Bit eMMC?

No, there is no way to have a second 8 bit EMMC connected directly to the Nano.
You could add an SATA interface via PCIe or use the PCIe x4 for an NVME SSD, or you could use an USB2642 USB 2.0 High Speed to EMMC bridge chip (this USB bridge does support 8 Bit EMMC connections).

It seems that I can only use EMMC for 4bit mode, because our customers must use EMMC or UFS, so both SATA SSD and PCIE SSD can only be abandoned.
I still want to reconfirm that Jetson Nano’s SDMMC interface is an application that supports 4bit eMMC?
Because I saw feedback in the forum that apps like them didn’t work properly, which worried me.

I showed you EMMC modules and the matching uSD adapter board. Just buy and try them on a Devkit. If it works then it should work on your board as well. Otherwise the USB2642 USB-EMMC bridge is you only remaining solution.

Thank you very much for your answer. In addition, I would like to ask whether any special configuration is required in the software if EMMC modules and the matching uSD adapter board is used for verification.

The combination of EMMC module (there are different sizes available) and uSd-Adapter is known to work out of the box on PC hardware. So just plug in and see what happens.

The hardware design to be used is emmc mode, and the combination of emmc module and uSd adapter should be sd mode.Can we draw any conclusions from this test?

Electrically and low-level protocol-wise EMMC and SD are identical, since SD evolved from MMC cards. (E)MMC and SD just have slightly different command sets, but most drivers know both variants.

We use the EMMC adapter shown in the figure, which can be recognized by OS under Windows and can successfully load the SD card version of Linux into it.
But I plugged it into the TF card of P3448, the system did not start, and displayed the following screen, do you know which link went wrong?

Sorry. I’ve got absolutely no idea.

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