Kobo mini GPS mod with 3D printed case


XCSoar is an amazing software for sailplane, hang-glider and paraglider. But lack the proper hardware with the following features:

  • sun readable ( eink)
  • usable with gloves (anything but capacitive)
  • long battery life
  • running android/linux
  • GPS and/or bluetooth
  • dirt cheap (yes 50€/£/$ for this hardware is dirt cheap)

The Kobo Mini is a very good eReader (unfortunately no more retailed) appears to be meeting all theses requirements except the GPS.


Component list

You will need for this mod:

  • Kobo Mini reader
  • GPS module with serial output or a BlueFlyVarioTTL
  • 3D printed spacer
  • extra battery
  • iron solder (a good one, I use this)
  • solder wire and a piece of flat ribbon cable

( By the way, the way Kobo handles the first boot is just crap: no I don’t want to register my device online or anything, just to drag and drop my own ePub books, thanks! )

GPS module instructions

Solder the MTK3339 GPS breadboard (with a piece of flat ribbon cable such as IDE, Floppy, whatever..)

KOBO to GPS MTK3339 wiring

KOBO - MTK3339
TP2 <-> BACKUP (TP2 is just below the battery connector)
RX  <-> TX
TX  <-> RX

Don’t forget to cross RX<->TX and TX<->RX (the eternal embedded engineer question, RX TX….)

Just in case you wondered, yes the BACKUP does accept 4.2V (TP2 is battery test point, so not regulated), and not just 3.3V (have a look on the MTK3339 datasheet)


You can download the STL of the “Kobo mini Case Spacer II” on Thingiverse

And download the gps cover

The STL (in mm) file is then printed by Shapeways for just 22€ incl P&P, delivered in about a week: very cool!


You will need 5screws, size M1.6 and 8mm (my 10mm were too long, I had to cut them with a pair of pliers)

All fit snugly, even the original back cover.

Add ON/OFF button to switch the GPS power (a simple SMD switch to the GPS’s VCC)

So I can still use it as a regular eBook without draining the battery and without the blue led blinking in the dark.

The switch is accessible by nails as it’s quite recessed.

Add a label for even more clarity.

BlueFlyVarioTTL instructions

Or this set for the BlueFlyVarioTTL, download the cover: And download the spacer for the battery:

The file STL (in mm) is then printed by Shapeways for just 19€.

You will need 5screws, size M1.6 and 8mm (my 10mm were too long, I had to cut them with a pair of pliers)

Solder 0.1″ header

And remove the black plastic from the header

Drill 5 holes with a 1mm bit, using the module as guide

Insert it

Then solder the 5 wires

Use 2 parker 3mm screws

That’s it

Battery for GPS module or BlueFlyVarioTTL

The original battery of 1000mAh gives from 4 to 6h, which can be quite a limitation.

The original 1000mAh beside the new 3800mAh battery

The new battery li-ion from AliExpress measure 4x75x86mm, with 3.7V and 3800mAh. Warning, you need the 3D printed spacer to use this battery.

I removed the original one and harvested it’s connector for the new one.

To remove the original double side taped battery, use an air dryer or so (warning not a hot air gun, it would be too hot)

The new battery is held firmly with double sided tape and now it last about 20hours of flight: perfect. (but the drawback: it is quite heavy to read in the bed now….)


They are tons of tutorials on the web, I wont describe it any further, but simply put, it works this way:

Download XCSoar KoboRoot.tgz: http://www.xcsoar.org/download/data.html

And place it on the kobo root file system using any file browser, restart and you are done.

GPS configuration

GPS module

For the GPS module, set the device to /dev/ttymxc0 at 9600bauds, generic drivers.


For the the BlueFlyVarioTTL, set the device to /dev/ttymxc0 at 57900bauds, blueflyvario drivers.

“GPS waiting for fix” should appear, note that the first fix can take up to 15min (30s later on, thanks to BACKUP power supply to keep the RTC and ephemeris)

You can change the sink alarm and volume:

  • Enable Wifi, and Telnet,
  • Connect to with telnet to the Kobo,
  • send the following commands:

stty ospeed 57600 ispeed 57600 -F /dev/ttymxc0 #configure baudrate

stty -F /dev/ttymxc0 raw #set device as raw

echo ‘$BFS 2500*’>/dev/ttymxc0 # sink alarm to -2500cm/s

echo ‘$BVL 70*’>/dev/ttymxc0 # volume to 70%



Then download the map: http://www.xcsoar.org/download/data.html

Download hotspot (probable thermal) as way-points (wpt format), and set the file in way-points configuration): http://thermal.kk7.ch/, save all this map file to the correct XCSoar folder.

I created custom map content to have paragliding skyways displayed on XCS:

More detail here: http://www.dotmana.com/weblog/2014/07/xcsoar-generate-custom-maps/

And here you are, you have a comp GPS for less than 100€/$/£ for paragliding/sailplane, in about an hour of work.

Result with GPS module

Result with BlueFlyVarioTTL

(note the green led flashing when lifting)

leGPSBip: solar vocal GPS alti vario

This device is ready to use with the Kobo or any smartphone, simply connect it and voila! You have a fully GPS/altimeter enabled smartphone.

It also act as a standalone vocal GPS variometer when not connected, pretty convenient:

More info here: http://www.lebipbip.com/legpsbip-solar-vocal-gps-alti-vario/

Links and references

XCSoar forum: http://forum.xcsoar.org/viewtopic.php?f=3&t=1242

Kobo GPS mod on another blog: http://www.extreme-nature.de/?p=9114

M1.6×8 screws: http://www.ebay.co.uk/

Commercial Kobo mod: http://www.goflyinstruments.com/gofly-project-v4/

XCSoar forum about this mod: http://forum.xcsoar.org/viewtopic.php?f=3&t=1404&start=10

Li-ion battery on AliExpress: http://www.aliexpress.com/item/L002-3-7V-3800mAH-457992-PLIB-polymer-lithium-ion-battery-Li-ion-battery-for-tablet/1477811584.html

BlueFlyVarioTTL http://blueflyvario.blogspot.com.au/2014/11/blueflyvariottlgpsv10-released.html

BlueFlyVarioTTL case: http://blueflyvario.blogspot.com.au/2014/07/blueflyvariottlgps-simple-case.html

Mini Solar vario: http://www.lebipbip.com/

STL archive: Kobo_Mini_case

Why FLARM protects it’s radio protocol

The FLARM device is definitely useful for avoiding collision in sailplane.

But the company behind maintains it’s monopoly position arguing that’s it’s safer and cheaper for the users:

We fundamentally believe that our low cost collision warning technology and its licensing procedures are in the
best interests of the sport and its participants.

To ensure safety, full compatibility and interoperability are essential. Experience shows that it is impossible to
be compatible just by following a written specification.


This text is just regular company’s crap, to reassure themselves (and the shareholders) they can maintain a high level of monopoly (and profit).

They also state the radio protocol is patented:

FLARM applies for the radio communication between the units a proprietary and copyright-protected protocol

Unfortunately, there is no such thing as copyrighted radio protocol!

My prefered part is it when the founder respond this accusation of being obscure and avoid implementation in many hardware device, and in software such as XCSoar:


The best part it: they managed to impose the device, not only in competition but for any sailplane in France. How comes the FFVV (French Gliding Federation) can make a device mandatory without any alternative?

One person, Hiram Yaeger seemed to have reverse engineered the protocol:



If interoperability by documentation or standardization would not be possible, even in RF, there would be no GSM, no GPRS, no WIFI, no Bluetooth.

What do you thing you are FLARM? You are just making a simple electronic device broadcasting GPS position in the free RF band, and it’s not even EASA / CAA / FAA certified! (just like any regular babyphone)

Step down while you can and publish this RF protocol, or the community will do it for you sooner or later! (and no update of the 10k units released in the world will save you)

Service en ligne La Banque Postale: client mécontent

Voici un mail envoyé aux services en ligne de La Banque Postale dont je suis très mécontent.

Bonjour, je suis client à la Banque Postale, aussi bien à titre
personnel que pour mon entreprise.

Je vous écris car je suis TOUT SIMPLEMENT LAS de votre service, digne de
l'URSS, souvent non fonctionnel, toujours minimaliste, pas intuitif pour
un sou.

- Par exemple, l'ajout de compte bancaire pour virement prend toujours
48h alors qu'il devrait être instantanée. (sinon on serai encore au
- Votre système d’identification est tout simplement laborieux, limité à
des chiffres.
- Je ne peux pas accéder a mes compte pro ET perso simultanément car
vous utilisez le même cookie. (alors que ce besoin est fréquent dans une
petite entreprise).
- si je ne me déconnecte pas de l'interface pro, et que je vais sur la
page perso, je me prend un message d'erreur de login, c'est pas mon
- des bannière pub pour vos services annexes qui clignotent au dessus de
MES comptes, alors que je PAYE mon compte.
- Sur les relevés, vous offrez les FRANCS, WTF? Mais ou est ma collonne
Ancien Francs!
- les virements sont limités à 3000€, vous croyez qu'une entreprise joue
aux billes? Ça fait sérieux de payer un fournisseur avec 4 virements....
- le temps que j'écrive ce message, l'identification a déjà timouté,
oui, je passe plus de 5min sur mes comptes et je n'y accède pas d'un
cybercafé en Somalie.

J'ai déjà ouvert un compte bancaire pro au Crédit Mutuel et je vous
informe que je vais faire de même pour mon compte perso.

On est en 2014, il serait temps d’être à la page, avec des service
disponible en anglais par exemple non?

A bon entendeur (si il y a quelqu'un dans votre entreprise colossale,
assez AGILE pour faire remonter ce message)

Un Entrepreneur, créateur, innovateur!
Notez que cela concerne uniquement les services en ligne, car au niveau service physique, hormis la carte bancaire, je n’en utilise aucun donc je ne peux pas m’en plaindre.



Smartphone headset standards: 2013 and still not one standard!

Believe it or not but are still two headset standards (headphone + microphone) for cellphone: TRRS_Standards

  • OMTP: old Nokia (and also Lumia starting from the 2nd gen[15]), old Samsung, old Sony Ericsson (2010 and 2011 Xperia’s), old Wiko (2012-)
  • CTI: Apple, HTC, latest Nokia, latest Samsung, latest Sony (2012+), latest Wiko (2013+), most Android phones

Skytraxx 2.0 interferences VHF radio

I’m facing this problem: I have a Skytraxx 2.0 (GPS variometer for paraglider) and a Puxing PX-888 VHF ham radio.
When the variometer emits sounds, it triggers the radio whatever the squelch setting is set on.
A quick video of the problem:

While I’m doubtful about the CE certification of this very cheap Chinese radio (a CE sticker is present in the battery tray but doesn’t mean much…).

So, as I’m not planning to change neither the radio or the variometer, I came along with this fix: put aluminum foil inside the variometer case.

Very easy to do, juste make sure the aluminium touches the usb connector when you close it and everything else is well insulated (pin with kapton tape, etc..).

Now the same test with the aluminium shield:

Much better: can use for competitions now, with the mini solar vario leBipBip.

It even seems to improve the time to fix, usualy took 5min and now about 1-2min.


Thunderbird: remove unused english dictionary

Having 5 unused English dictionary is annoying (I only need one, not en_NZ, en_US, en_AU and en_ZA)

First remove dictionary:

sudo /usr/lib/thunderbird/dictionaries.back/
sudo mv /usr/lib/thunderbird/dictionaries/* /usr/lib/thunderbird/dictionaries.back/

and prevent them from being reinstall the next update:

sudo dpkg-divert --add /usr/lib/thunderbird/dictionaries

then place only the wanted dictionary:

sudo mv  /usr/lib/thunderbird/dictionaries.back/en_GB.aff /usr/lib/thunderbird/dictionaries/en.aff
sudo mv  /usr/lib/thunderbird/dictionaries.back/en_GB.dic /usr/lib/thunderbird/dictionaries/en.dic

And restart Thunderbird.

Contact synchronisation: Android/Zimbra/Thunderbird

I do use the following combination :

  • Thunderbird (Linux or Windows)
  • Android (without any Gmail/google account)
  • Zimbra mail server

And to get my address book synchronised, I installed the following softwares:

Thunderbird: Zindus

Android: CardDAV-Sync and Contact Editor Pro (make sure to install the last one to be able to edit contacts)

And use Zimbra and in Address Book tab, right click on Contacts and select Share address book:

And copy the URL bellow:

Then use this URL to set your configuration in Zindus:

and add a CardDAV account with the URL and you mail/password

and voilà, you have the 3 places synchronised on the go!