Interface system and dual-role device equipment

摘要

PROBLEM TO BE SOLVED: To provide an interface system capable of supplying electric power from a device side to a host side even when an apparatus which supplies electric power through a power supply terminal can be connected to either of the host and device.SOLUTION: An interface system (1) includes a first apparatus (100) and a second apparatus (300). The first apparatus includes a connector (21) having a VBUS terminal and an ID terminal, a power supply part (22) which supplies electric power to the VBUS terminal, and a determination part (271) which determines that the second apparatus is a host when detecting a clock signal at the ID terminal more than a predetermined number of times in a predetermined period after the electric power is supplied. Further, the second apparatus includes an oscillation part (33) which outputs the clock signal with a predetermined period to the ID terminal based upon the electric power supplied through the VBUS terminal.