SAM4E, can't mount eMMC in Windows (can mount SD card)

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I'm fairly new to Atmel chips. This question pertains to the ATSAM4E16E chip used on the EK dev board and on a proprietary board.

I used the EK dev board and ASF to create a project using USB and MMC mass storage that would mount the SD card image to Windows 10 explorer. The SD card showed up for reading and writing.

On the other board, there is an eMMC chip that essentially takes the place of the SD card — the LUN (logical unit number) is the same for the eMMC as it was for the SD card (#2).

The eMMC does not show up in Windows Explorer, but I do see it show up in the Device Manager.

In the Device Manager, is appears in a directory called "Other devices".

Inside that directory is a device called "Unknown device" with a yellow triangle with exclamation mark.

If I unplug the USB cable it is removed from the Device Manager. When plugged in, it comes back.

I have stepped through the initialization code and everything seems to be fine.

The "type" is set to 0xA (0x8 for high capacity, 0x2 for MMC)

The "version" is set to 0x40 (MMC4)

The "bus width" is set to 4.

The speed is set to "high speed".


I set the new project up similarly to the (working) EK project.

Differences are the new project uses RTOS for some actions.

And the USB part of the project is set to "composite", using both mass storage and CDC.


I have read through some of the forums here and the new board does use pull-up resistors.

68K for the data lines and 10K for the control line. Nothing on the clock line.


Please let me know if there is anything I missed in the configuration, or anything that I should try to get the eMMC mounted.

Also, I am curious if the eMMC can be mounted as a mass-storage device and as a CDC (serial) device at the same time.


Thank you!