Project Tango Development Kits come with a mini-dock (see picture below).
I am controlling the iRobot Create 2 by the mounted Tablet using the USB cable provided plugged into the mini-dock. (see docs).
The USB 3.0 port on the mini-dock is only functional when the tablet is docked. The port can be used to attach an external memory drive or standard peripherals to the tablet.
I wish to recharge the tablet using the power from the iRobot. The mini dock comes with a port for external charging:
The mini-dock accepts a power adapter for faster charging (not provided). The power adapter output must be 12V, 2A, and the connector must be a barrel plug with 5.5mm outer diameter, 2.1mm inner diameter, center positive.
Ideally the charging would happen only when the iRobot is also charging, but charging all the time is acceptable.
Is this possible? If so, how?