The new D415 and D435 RealSense cameras feature a set of four pins called GPIO (General Purpose Input Output). These are pins that have no default purpose and can be used to connect the RealSense camera via the pins to other forms of hardware, including sensors (e.g a compass). The Raspberry Pi development board has such a pin set.
Assuming that devices are somehow connected to the GPIO with a cable like on Raspberry Pi boards, this offers intriguing possibilities, both for DIY electronics fans and for harnessing old retro hardware for providing logic inputs to a RealSense D415 / D435 camera application.
I was inspired to write this article by a browse through my archive of articles on retro hardware such as laser-disc players, super-geeky micro-computer homebrew devices and early-1980's DIY electronics blueprints for projects such as home environmental control with a home computer.