Shortly about the BADGEr board (http://wyolum.com/projects/badger/) and connecting it to Jolla (reminder to self)

• It is Arduino compatible, and has I2C routed to "shield" connector, however it is connected through level converter TXS0108. It can only convert to higher voltages (as it is connected in such way). So I2C needs to be wired to SDA_3V3/SCL_3V3 signals
• ATMEGA328 datasheet has promising figure 31-309 showing VIH close to 1.8V when VCC=3.3V, but then table 29-19 gives VIH specifically for I2C 0.7xVCC (might or might not need level conversion)
• Powered by 3V coin cell, so connecting external 3.3V is no problem.
• Hook a opendrain GPIO to drive interrupt when display has been updated, and allow to shutdown.
• Eats WIF format from SD card, should be easy to modify to get that over I2C in some sort of packets. I think "streaming" is not feasible here (dunno)
• About Arduino Wire slave receiving data: http://arduino.cc/en/Tutorial/MasterWriter