USB Bus Repeater Wake-Up Mechanism for Host Power Saving
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Solution Overview
Problem
The continuous power consumption by the host's physical interface unit during low-power mode in USB communication due to frequent checks for device activity, despite the host suspending the USB interface, is inefficient.
Innovation Solution
Introducing a repeater between the host and device to monitor bus activity and generate interrupts for the host, allowing the host to maintain a low-power state without direct monitoring, converting remote wake-up events into resume events for efficient power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the host checks for device activity every 100ms during low-power mode, then the host can detect device wake-up events, but the host's PHY unit must remain powered on increasing power consumption
Solution Approach 1:
The repeater acts as an intermediary device between the host and USB device. It monitors the USB bus for wake-up events and generates interrupt signals to the host when activity is detected, allowing the host's PHY unit to remain in low-power mode while still maintaining reliable device activity detection through the repeater's monitoring capability
2Use of energy by moving object
If the host enters low-power mode to conserve energy, then power consumption is reduced, but the host cannot directly monitor wake-up events without modifying its wake-up procedure
Solution Approach 1:
The repeater autonomously monitors the USB bus for wake-up events and self-generates appropriate interrupt signals to the host without requiring the host to modify its wake-up procedure. This allows the host to enter low-power mode while the repeater handles the monitoring task independently
3Use of energy by moving object
If a repeater is introduced between host and device to monitor bus activity, then the host can stay in low-power state, but the system structure becomes more complex
Solution Approach 1:
The repeater is designed to perform multiple functions: it monitors USB bus activity, detects wake-up events, generates interrupt signals to the host, and maintains protocol compatibility. This multi-functionality justifies the added component by consolidating monitoring and interrupt generation capabilities in a single device
Data Source
AI summary
Systems, apparatuses, and methods for saving power on a bus interface are described. A system includes a host, a device, and a repeater interposed between the host and the device. While the host and device are in a low-power state, the repeater monitors a first bus to determine if the device has woken up. When the repeater detects a remote wake-up event initiated by the device, the repeater generates an interrupt which is sent to the host. The host responds to the interrupt by initiating a resume wake-up event procedure that assumes the device is still asleep. In this way, the host is able to stay in the low-power state longer while also using a wake-up procedure that does not require the host to be aware of the existence of the repeater.