Jarielle Catbagan jcatbagan93 at gmail.com
Sat Jul 18 17:45:50 UTC 2015

On Sat, Jul 18, 2015 at 10:18 AM, Ed Sutter <edsutterjr at gmail.com> wrote:
>>> Meanwhile, I'm just going to let my board soak with the memory test
>>> running..
>>> "mt -vc 0x80100000 0x1fefffff"
>>> Hopefully I'll come back in few hours and it will still be running!
>>> Next is MMC right?
>> Yes, I am currently looking into MMC right now.  It's a whole
>> different world with MMC compared to DDR3.  I hope to get it up and
>> running within the week or so which also depends on how fast I am able
>> to comprehend the MMC interface specifications.
>> For my reference, I am using the following:
>> 1. Physical Layer Simplified Specification:
>> https://www.sdcard.org/downloads/pls/part1_410.pdf
>> 2. SD Host Controller Simplified Specification:
>> https://www.sdcard.org/downloads/pls/partA2_300.pdf
>> and...
>> 3. AM335x TRM, Section 18 "Multimedia Card (MMC)"
>> I'll first target accessing an SD card and then the onboard eMMC next.
> Take baby steps. No need to implement every detail of the spec, at least not
> initially.  Start with just reading id registers and verifying that the card
> is plugged in.
> Then tackle block read and block write.  With that much working, you should
> be
> able to hook your code into the mmc command we talked about and have command
> line access to the device.  You basically need four high level functions:
> read/write/control
> just like normal device interfaces at user level.

Sounds like a good plan!  Will do!

>> >From what I have looked into so far, the interface to both is
>> practically similar with some differences on how the AM335x
>> initializes the interface and how communications take place between
>> them.
> I'm no MMC expert, but I think eMMC and uSD are essentially identical (don't
> test me
> on that) regarding the interface.  Both are in the MMC class of devices, so
> hopefully
> once you get one working, the other will just fall into place.
> SD cards used to also have an SPI-interface mode, but I think that's fading
> away.
> Anyway, keep up the good work!!
> Enjoy the weekend!
> Ed

Thanks! Same to you too!

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