Re: [tlug] micro sdhc card recovery

[Kalin KOZHUHAROV <me.kalin@example.com>]

On Fri, Sep 13, 2024 at 9:19 AM Edward Middleton
<edward.middleton@example.com> wrote:
> Does anyone have trick for recovering a dead microsd card I was using in
> a raspberry pi.  When inserting the card the light on the reader flashes
> but the card is not recognized and no block devices are created.
>
I have a stack of various dead SD cards, usually the result of
overvoltage or other power issues in various uC and dev boards...
They have no important data, so I just keep them on my desk as a
reminder "to be careful next time"  :-D

Clean all contacts with 100% iso-propanol and lint-free cloth.
Put the card on a working reader to a proper linux PC and see if it is
properly detected (dmesg).

If not, likely the controller (inside the SD) is bad/damaged/fried.
Sometimes there is more than one way to interface to it though and
only the default/high-speed patch is borked. Generally and SD card is
like an expensive floppy - once it starts to act you simply ditch it
in the bin (or stack it on your desk), it is not (worth) repairable.
There is a chance that data can be recovered by professional data
recovery specialists, but it is costly and only worth it if data was
special (Bitcoin wallet backup ;-)
If it is not worth it, you have extra time and want to learn - there
are some videos on how to do it. the workflow involves sanding off the
back of the SD to expose a series of tiny extra contacts, solder most
of them (like 12-16) and hook to a rig that can talk to the chip
behind the controller. That said, recent SD cards employ various
tricks using encryption in the controller to maximize/randomize cell
usage of the chip, so without being able to derive the secret key,
having a full dump of the flash chip will be only "garbage".

I work with Kumanan PC-Net and they can do all that, contact them
directly https://www.kumanan-pcnet.co.jp/digitalcamera/ and AFAIK, the
initial check is free.

Cheers,
Kalin.