BBB: Add "mmc" command that interfaces to the onboard eMMC

Jarielle Catbagan jcatbagan93 at
Tue Aug 4 23:26:23 UTC 2015

On Tue, Aug 4, 2015 at 4:17 PM, Ed Sutter <edsutterjr at> wrote:
> Jarielle,
> Great!  Looks good.  Couple of thoughts...
> - Similar to the sd command, the outer edges of the mmc command code should
> probably be in the main/common
>   directory as mmc.c; but for now I pushed it as is.

Definitely, I'll be looking into optimizing the MMC code in the future.

> - I turned on INCLUDE_XMODEM in config.h just so that we can update without
> pulling the uSD card all the time.

Great! Sound good.

> - Should the 'write' command for sd and mmc include a "are you sure?"
> prompt?  I'm mixed on that one.

Honestly, I think it's a good idea to have a prompt to alert the user
before writing as I would suspect that unintentionally overwriting
data could be possible.  Just my opinion.

>   That was optionally covered by the user levels in uMon a while ago, so
> maybe we just leave it for that
>   (making it up to the user).
> Hey, this is really shaping up!!!
> Good work.  Its all pulled into the master.
> Ed

Thanks! Next up, Ethernet!
>> I just want to add that I was able to transfer the uMon image from the
>> SD card to the eMMC.  I then removed the SD card and power-cycled the
>> BBB, and I was able to boot uMon from the eMMC.
>> The sequence steps I took are as follows:
>>          sd init
>>          mmc init
>>          sd read 0x80100000 0 102
>>          mmc write 0x80100000 0 102
>> The '102' is the number of 512 byte blocks required to transfer the uMon
>> image.
>> On Tue, Aug 4, 2015 at 11:03 AM, Jarielle Catbagan
>> <jcatbagan93 at> wrote:
>>> These series of patches add the "mmc" command which is the interface to
>>> the onboard eMMC on the BBB.
>>> The "mmc" command is implemented with initialization, reading, and
>>> writing functionality.
>>> Furthermore, the MMC0 and MMC1 clock enable are moved to initCPUio() in
>>> cpuio.c to ensure that the
>>> MMC modules are enabled before they are accessed.
>> _______________________________________________
>> umon-devel mailing list
>> umon-devel at
>> .
> _______________________________________________
> umon-devel mailing list
> umon-devel at

More information about the umon-devel mailing list