Reducing system power consumption due to USB host controllers

摘要

Circuits, methods, and apparatus that reduce the power consumed by data transfers initiated by a USB host controller. Peripheral devices on a USB network are accessed with a reduced frequency in order to save power dissipated by a CPU and other circuits when reading data needed by the host controller. Instead of possibly accessing devices each frame, peripheral devices are accessed during some frames, and not accessed during others. A USB host controller may have two or more modes, such as a low power mode and a regular mode. In the low power mode, USB devices are accessed during fewer than all frames, in the regular mode, USB devices are possibly accessed each frame. Mode selection may depend on whether battery power is used.

主权项

1. A method of controlling a universal serial bus comprising:
during a first frame, querying at least one device on the universal serial bus according to a periodic schedule; then during N−1 frames, not querying at least one device on the universal serial bus according to the periodic schedule, though the device is scheduled to be queried; then during an Nth frame, querying at least one device on the universal serial bus according to the periodic schedule, wherein a value of N is progressively increased during a period of user inactivity.