A fixed installation of a Nexus 7 (2013) may in some cases require external access to the power and volume buttons. My first attempt to achieve this, was to modify and solder wires directly to the flexible PCB.
Although possible, this is probably not the best and easiest way. A simple and reliable alternative (if you do not need the onboard microphone) is to get hold of the following parts from eBay:
- 8 Pin 0.5mm Pitch Flexible Flat Cable (FFC) [about 6$ for 10, 150mm]
- 8 Pin 0.5mm to DIP 2.54mm Breakout PCB with connector [about 2.50$]
Connecting the flat flex cable between the Nexus 7 and the breakout board, gives the following pinout, and makes it simple to add whatever interface needed: