
Building my own 64GB memory card with a $6 eMMC chip (2016) - nfriedly
https://ripitapart.com/2016/10/28/emmc-adventures-episode-1-building-my-own-64gb-memory-card-with-a-6-emmc-chip/
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userbinator
Given the compatibility between SD/MMC, one thing I'd like to see on the
market, but haven't, is an Android phone which has no "internal storage" to
speak of, but instead replaces the soldered-in eMMC with a microSD socket.
That would make expanding, brick-recovery, as well as backing up and
controlling access to the data very easy; like taking the hard drive out of a
computer before giving it to someone else.

It's not difficult at all to do from the hardware perspective, but no one
seems to have produced such a thing on the mass market.

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mschuster91
You dont need a hw mod, all you need is an Android phone with a sdcard slot
and the option to do raw read/write to the embedded flash from the bootloader
as you WILL fuck up many times during experimentation. Havent tried with
qualcomm stuff, but successfully converted my Mediatek-based CAT B15Q to
sdcard-only.

All you need to modify is /etc/fstab, /init.rc (or, in some cases,
/init.XYZ.rc), split the sdcard into three partitions (OS, /data, /sdcard),
copy the existing partitions from flash to the sdcard et voila.

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awiesenhofer
I would love to read more about your experiments! any chance for a blog post?

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v_lisivka
If you have root, just replace init with something like that:

    
    
        #!/bin/sh
        mount /dev/mmcblk1p1 /root
        exec chroot /root /bin/init

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Hello71
although you probably want `|| sh`

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jpm_sd
This is so gloriously horrible. Please note that if you want to get the
maximum speed out of an eMMC device, you need proper PCB layout: ground and
power planes, decoupling caps right under the appropriate BGA balls, traces
length matched and impedance controlled, etc.

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AstralStorm
A single chip will forgive a lot of mess. A big array though will not.

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cornholio
Maybe a dumb question: If 64GB chips are $6, why aren't we seeing terabyte-
sized tablets and netbooks for $100 more than the baseline version? I would
imagine the idle power draw is negligible and the extra size and weight well
worth it.

Producers take the exact opposite approach, and use storage size as a price
discriminator: a 64GB version might cost $300, while the 128GB is "only" $499,
pure profit margin an order of magnitude higher than the cost of the actual
storage.

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jlebrech
so you could technically upgrade an ipad?

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zymhan
You can technically replace any chip on any device with a better, pin- and
voltage- compatible chip. But you need soldering equipment easily tens of
thousands of dollars.

For example, a Dell desktop I had a while back was the lowest-end SKU, and
therefore they left the AGP connector off of the board, even though the BIOS
knew about AGP and there were the AGP solder points/vias on the motherboard.
Had I had the ability to solder the dozens of points at the same time, I could
have added my own AGP slot.

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jlebrech
I was thinking you could have a laptop company that uses the same board for a
few years (for it's whole range) everything would be soldered on but could be
sent back for generously priced upgrades.

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aexaey
There are ready-made boards for this being sold for less than $2. Just search
"eMMC Adapter 153 without flash" on ebay.

153 is number of balls on the eMMC chip OP is using. You might need a
different adapter for different eMMC chip.

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chocolatebunny
Are there cost effective ways for hobbyists to solder BGAs? I remember back in
the day, it wasn't that expensive to get an etching kit and create some single
layer prototype boards but they all used through hole components. Now-a-days
it doesn't seem like that kind of stuff is possible anymore.

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throwaway2048
You can get perfectly acceptable results on everything except large BGA
layouts with only a toaster oven, or for smaller jobs even a hot air gun is
enough.

A lot of people will insist you absolutely need a massive multi-thousand
dollar peice of kit, but its nonsense, and gear of that grade is only of much
use if you are doing large batch jobs and you want to minimize your failure
rate, for one off projects a few percentage points either way in terms of
failure rates is completely irrelivant, especially considering you can just
rework it anyways.

if you want to go the full 9 yards though, you could spring for something like
this and get real professional level results, for around $300ish USD + a
little DIY.

[http://www.whizoo.com/](http://www.whizoo.com/)

And in regaurds to the boards themselves, its true you cant very easily make 4
layer PCBs with Vias and other sensitive alignment constraints at home,
however the good news is that they can be ordered even cheaper than it would
typically cost a home maker in materials for even single sided boards!.

[https://dirtypcbs.com/store/pcbs](https://dirtypcbs.com/store/pcbs)

[https://pcbshopper.com/](https://pcbshopper.com/)

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tawayway
The very popular 858D temperature controlled hot air stations only run about
50usd. Performance is much better than a hardware store heat gun.

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baobrien
I love seeing that kind of crazy soldering. I would have had to make an SD-
shaped PCB and heat gun the part on.

Also (2016)

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sctb
Thanks, we've updated the title.

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jhallenworld
We used eMMC in a design recently: I learned that the unused balls are
essential for breakout on low layer count boards.

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Quequau
This actually might be worthwhile for ODROID or Pine owners because both of
those companies demand premiums for their eMMC boards.

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jacquesm
A lot of the bandwidth of a 'proper' SSD device comes from running a bunch of
operations in parallel.

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rwmj
I love how these (assuming they are not fake) have at least half a billion
addressable bits.

