
Modifying Transcend WiFi SD Card Firmware - pearjuice
http://fernjager.net/post/modifying-transcend-wifi-sd-card-firmware/
======
fernjager
Author here! It was quite a surprise to see one of my old posts on HackerNews.

For those interested in what happened next: I managed to build and run sqlite,
rsync, and dropbear SSH on the SD card using buildroot:
[http://buildroot.uclibc.org/](http://buildroot.uclibc.org/)

I quickly moved onto other interests as I couldn't work out any practical
applications at the time.

Feel free to reach out to <me AT fernjager DOT net> if you have any ideas, or
want to pick my brain on this project.

~~~
emhart
Could you potentially still use the card in a camera, while it was running
linux?

~~~
fernjager
Yup! One of the advertised features for the SD card is being able to stream
just-captured photos automatically to the mobile app.

The SD card has a script that monitors filesystem changes, and would push the
images via curl to the client connected to it through WiFi.

~~~
emhart
Man, I thought that getting a "yes" back would lead to a Eureka moment for
some awesome use case...but the best I've got is just how cool it would be to
show off, haha. Amazing work!

------
SixSigma
The commercial WiFi power harvester I remembered would be the perfect partner
for a WiFi Spy.

Despite the announcement that "on the CES floor, they were able to charge a
BlackBerry from 30% to full in about 90 minutes, using nothing but ambient
WiFi signals as a power source. " [1]

The device has never been turned into a commercial product. [2]

[1] [http://www.ohgizmo.com/2010/01/09/ces2010-rca-airnergy-
charg...](http://www.ohgizmo.com/2010/01/09/ces2010-rca-airnergy-charger-
harvests-electricity-from-wifi/)

[2] [http://www.ohgizmo.com/2011/01/07/ces-2011-hey-rca-hows-
that...](http://www.ohgizmo.com/2011/01/07/ces-2011-hey-rca-hows-that-
airnergy-wifi-charger-coming-along-oh-no-where-to-be-seen-what-a-surprise/)

~~~
DanBC
You can make a very simple GSM signal detector using a germanium diode, an
LED, and a bit of wire. Tune the wire by cutting it to the right length (a
square with sides of 7.5 cm is fine) and solder the diodes in series. Hold a
phone near it and send a text message to the phone.

[http://www.creative-science.org.uk/mobile_LED.html](http://www.creative-
science.org.uk/mobile_LED.html)

Of course, that's a tiny amount of power but it's still there to be harvested.

Not sure what the legal situation is. In England an "artist" was asked to
remove their installation of flourescent tubes in a field below power lines.
They similarly harvested power. (I can't find that case using Google :-( but
here are plenty of others
[https://www.google.co.uk/search?q=fluorescent+tubes+power+li...](https://www.google.co.uk/search?q=fluorescent+tubes+power+lines+field&sa=X&rlz=1RMGOYI_enGB573GB573&hl=en-
GB&espv=1&tbm=isch&tbo=u&sboxchip=Images&source=univ&ei=dMFaU4r3EcGp7AbJ0IHoBw&ved=0CD0Q7Ak&biw=480&bih=300)
)

~~~
jmpe
Legal situation?!? You're creating a matched impedance point in space.

RF energy harvesting is a bit of a hot topic, there are a number of modules on
the market atm. Just search for it on mouser or farnell to get started.

Thanks btw for that LED schematic, so simple. I'm currently tuning a harvester
around a BQ25504 and super caps. I'll give it a test next week.

[http://uk.mouser.com/Embedded-Solutions/Energy-Harvesting-
Mo...](http://uk.mouser.com/Embedded-Solutions/Energy-Harvesting-
Modules/_/N-8t3zx?P=1yzotr6)

This one contains other energy sources as well:

[http://uk.farnell.com/jsp/search/browse.jsp?N=2002+225290&Nt...](http://uk.farnell.com/jsp/search/browse.jsp?N=2002+225290&Ntk=gensearch&Ntt=energy+harvesting&Ntx=mode+matchallpartial)

------
zdw
Does anyone know if the currently available versions of the hardware (
[http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-
alias%3D...](http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-
alias%3Daps&field-keywords=transcend+wifi+sd+card+16gb) ) are still compatible
with these modifications?

I ask because frequently identical outward appearance does not mean identical
internal hardware, especially on low cost consumer devices.

~~~
josteink
That's really a good question. At these prices, I would like to know before I
commit to anything.

------
tlrobinson
Why don't companies sell an open/hackable version of this? Surely they could
make a killing off the maker / Hacker News crowds.

~~~
lechatleon
Actually, Transcend released sources of the firmware : [http://www.transcend-
info.com/files/Driver/WIFISD_GPL_releas...](http://www.transcend-
info.com/files/Driver/WIFISD_GPL_release_20131219.zip)

------
kastnerkyle
For anyone who is interested, there is pretty good writeup here [1] on how to
do kernel builds for this card. I also have a WIP of crosscompiling for this
card as part of a wifi connectable (using waypoints) automated quadcopter,
though I probably won't get to do more on the copter side until the fall.

My current writeup is here [2] - I am in the process of using the 8GB
Transcend cards to save a few $$. I also did not experience any weirdness with
the first 8 bytes of the initramfs, so I will need to investigate that
further...

[1]
[http://dmitry.gr/index.php?r=05.Projects&proj=15&proj=15.%20...](http://dmitry.gr/index.php?r=05.Projects&proj=15&proj=15.%20Transcend%20WiFiSD)

[2]
[http://nbviewer.ipython.org/urls/raw.githubusercontent.com/k...](http://nbviewer.ipython.org/urls/raw.githubusercontent.com/kastnerkyle/kastnerkyle.github.io-
pelican/master/content/downloads/notebooks/hack_automated_quadcopter.ipynb?create=1)

