USB Repeater Power Saving via Packet Interception
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Solution Overview
Problem
USB repeaters face challenges in reducing power consumption during idle states without compromising data throughput, as keeping receiving circuitry active to anticipate incoming data packets is power-intensive and requires complex protocol interception.
Innovation Solution
The USB repeater intercepts host packets to predict data flow direction, disabling peripheral receive circuitry during idle states when a start-of-frame packet is detected and re-enabling it for non-SOF packets, thereby optimizing power usage without requiring extensive protocol analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the repeater keeps receiving circuitry active during idle states to anticipate incoming data packets, then data throughput is maintained, but power consumption increases substantially
Solution Approach 1:
The repeater implements periodic monitoring of USB data lines instead of continuous reception. The receive circuitry is activated only during specific USB transaction phases (when tokens or data packets are expected) and deactivated during idle periods, creating a periodic on-off pattern that reduces power consumption while maintaining data throughput capability
Solution Approach 2:
The repeater uses USB protocol knowledge to predict when data packets will arrive and activates receiving circuitry in advance during idle states. By anticipating upcoming transactions based on protocol state, the repeater prepares receive buffers and enables circuitry before actual data arrival, ensuring no data is missed while allowing extended idle periods with reduced power consumption
2Use of energy by moving object
If the repeater intercepts data packets to determine host/device data transaction protocol for predicting idle states, then power saving opportunity arises, but device complexity and overhead increase substantially
Solution Approach 1:
The repeater extracts and monitors only specific, critical USB protocol fields (such as token packet types, endpoint addresses, and data stage indicators) rather than intercepting and analyzing complete data packets. This selective extraction of necessary protocol information enables idle state prediction without the complexity of full packet interception and protocol analysis
Solution Approach 2:
The repeater uses a simplified protocol state machine as an intermediary that tracks USB transaction phases based on minimal packet header information. This state machine acts as a mediator between raw USB packets and power management decisions, translating complex protocol sequences into simple idle/non-idle state indicators without requiring full protocol interception capability
Data Source
AI summary
Disclosed are techniques for saving power in a Universal Serial Bus (USB) repeater/re-timer between a USB host and a peripheral device by intercepting packets received from the host to predict the direction of data traffic to selectively turn off/on circuitry of a peripheral port used to receive packets from the peripheral device. If a host port determines that the host is sending a start-of-frame (SOF) packet, the direction of data flow is from the host to the peripheral device, and the repeater may turn off the peripheral port such as squelch circuitry. If the host port determines that the host is sending a non-SOF packet, such as an address token that precedes a host-to-peripheral-device data transfer or a peripheral-device-to-host data transfer, the direction of data flow is anticipated to be from the peripheral device to the host, and the repeater may re-enable the deactivated circuitry of the peripheral port.