Yes, if it were I2C, that would be nice, but as I read on in those links, it seems that it’s not I2C but some proprietary protocol…
But first of all, some optional possibilities must be unlocked with some jumpers: ([LINK][1])
One of them is the possibility to use the 16 keys: It comes standard with only 8 keys activated…
Shall I put one in the mail? 
[1]: http://itimewaste.blogspot.be/2014/12/arduino-code-for-ttp229-touch-16-button.html