Haha, I'm a student as well. I study Computer Science (Technische Informatica) at the University of Twente.

I2C has no standardized shape unfortunately, so it might be difficult to detect from pictures.


Source of image: unboxing vid on youtube:
http://www.youtube.com/watch?v=VxvH_v37U04

I think the connectors may be the metal pins
1. Microsim
2. MicroSD
3. camera
4. flashlight
5. ?? (Connector?)
6. ?? (Connector?)
7. Battery
8-15. Screws
16. Sim card locking mechanism


The image you posted earlier, but with numbers.

There should be 5 pins (at least)

GND
3.3V
SDA
SCL
INT

I forgot to number a circle, I see 6 metal pins without an obvious purpose on the image.

EDIT: is there an IRC channel for jolla development, if not, do you want to claim #jollakeyboard on freenode?

Also, an idea I just had is to make peace with additional thickness and to create a standard other half style connector on the bottom. Even though it may not support everything (or anything) special, nice-looking other halves are a possibility then for your keyboard and it would be easy to change the appearance of the keyboard that way.

From left to right in that pic orientation.
6. INT (GPIO 1.8V) and 3.3V DC
5. SDA (1.8V) and SCL (1.8V) (i2c)
Unnumbered circle from top to bottom: 5V DC + GND (for example to connect wireless charger, external chargers or extra battery pack).
And the hole next to screw 13 is the rib for cover detection.

Official documentation should be coming 'soonish'.

Nice, sounds very straightforward!

Will probably carve out a wooden dock with external connectors for the i2c, something like this:


*off-topic*
Still waiting for someone else to open one of the following:
-Building crazy capacity external battery cover proto
-Building insanely fast charging 'battery' cover (ultracapacitors?) proto
-Battery hot-swappable mod
-Building e-ink display/tablet half proto
-Building boombox half proto
You can do it! Just try!
*/off-topic*

Is the 5V terminal connected 'directly' to the usb port? E.g. could you in an extreme case connect a 5 amp usb charger and pull 4 amps from the terminal?

After looking at the videos (thanks to people who have the Jolla already and took time to share them !), I have some remarks/questions about building other halves:

* Other halves looks like they need to be flexible in order to clip them to the phone. If it is really need, it will be harder to make a keyboard with the needed flexibility ?

* Pins are a bit spreaded and there is no proper connector, only the pin laying here. Does anyone know what thing we need to put on our circuit board in the other half to secure a good contact with this ? Some kind of low profile spring loaded "pogo" pin as found in circuit board test benches ? (see http://www.adafruit.com/products/394 for a big one)

* About the power connector. As I understand it, 3.3V comes after the phone regulator, and 5V is a power input that will go to the USB, phone regulator, and battery charger (then output to the battery connector). So if we have a battery in the other half, it could power the phone by the 5V connector, but couldn't be charged from the phone USB connector (it would need its own connector, which could charge both OH and phone battery), nor could the OH battery charge level been retrieved to display it with the battery icon (like the internal battery), Right ?

Looking forward for the OH documentation (some kind of schematics of the power line between 5V, 3.3V, phone battery and USB connector would be requiered) and receiving my Jolla !

TOH have not nothing common with USB.

edit: Ah, sorry .. you point to power wires from USB.
My point is: USB data not connected to TOH.

Then next question is: is 5V on this pin in case "work on internal battery and no battery in TOH"?
By Jolla, this is 5V in/out pin? Or it is 5V in and for out we must use 3,6V from i2c?

Just food for thought, came across this keyboard "Cool Leaf" interesting concept.
technically its available ..http://www.minebea.co.jp/english/coolleaf/
http://www.nmbtc.com/technologies/co...-in-Japan.html

Aside from sound when a button is pressed, the Cool Leaf doesn't seem to have any tactile feedback so its the same as a touchscreen.

Personally, i hate touchscreen keyboards and its one biggest reason why i still use my N900.

The cool leaf design is indeed interesting. It is close to the previous idea of using an e-ink display.

But it lacks the button shape, so you can see in the video people typing only with 2 fingers, and probably needing to look at it. On another video, in the comments, they say it is more for thing like hospitals where a keyboard easy to clean and disinfect is needed, than for heavy desktop use.

Anyway, if you can make a small translucent overlay with "bumps" on top of the keys, then it becomes usable. The backplane conducting light, with some holes to display the key name, is something that may be done even with small dome-like key ?