USB Extension Endpoint Configuration Latency Compensation
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Solution Overview
Problem
USB communication is limited to short distances due to timing requirements, necessitating a method to extend SuperSpeed USB connections beyond the conventional 3-meter limit without compromising compliance with USB specifications.
Innovation Solution
The implementation of upstream and downstream USB extension devices that use a non-USB extension medium to communicate, hiding the extension medium from the host and USB devices and compensating for latency, allowing seamless communication over longer distances while maintaining USB standard compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If USB cable length is extended beyond 3 meters, then communication distance is improved, but timing requirements and signaling integrity deteriorate
Solution Approach 1:
The USB extension system divides the communication path into multiple segments: host device to UFP device via USB cable, UFP device to DFP device via extension medium, and DFP device to USB device via USB cable. Each segment operates within timing requirements, allowing overall extension beyond 3 meters while maintaining reliability.
Solution Approach 2:
The extension medium acts as an intermediary between the UFP device and DFP device, enabling long-distance communication without directly violating USB timing constraints. The intermediary handles protocol translation and timing compensation, masking the extended distance from the USB protocol layers.
2Length of stationary object
If extension medium is introduced, then communication distance is improved, but system complexity increases
Solution Approach 1:
The extension medium is introduced as a dedicated intermediary component with defined functionality for protocol translation and timing management. This structured approach to complexity allows the system to achieve extended distance while maintaining manageable system architecture through clear separation of concerns.
Solution Approach 2:
The UFP device and DFP device serve multiple functions: they act as USB interface devices for connected devices, extension medium interface devices for the non-USB medium, and protocol translation entities. This multi-functionality reduces overall system complexity by consolidating roles into existing components rather than adding dedicated functionality.
3Adaptability or versatility
If USB protocol compliance is maintained, then standard compatibility is improved, but extension capability is limited
Solution Approach 1:
The extension medium serves as a mediator that enables long-distance communication while keeping the USB protocol layers compliant with standards. The intermediary handles the non-compliant aspects (distance, timing) at the physical layer, allowing upper protocol layers to maintain full USB standard compatibility.
Solution Approach 2:
The system segments USB compliance requirements from physical layer constraints by separating USB communication (host to UFP, DFP to device) from extension medium communication (UFP to DFP). This segmentation allows USB protocol compliance to be maintained in the compliant segments while achieving extension through the non-USB segment.
Data Source
AI summary
In providing USB communication functionality over a non-USB-compliant extension medium, increased latency and processing delays may be introduced, including during configuration of endpoints. In some embodiments of the present disclosure, an upstream facing port device (UFP device) and a downstream facing port device (DFP device) are used to extend USB communication across an extension medium. In some embodiments, the UFP device extracts information from packets sent between a host device and a USB device during configuration of an endpoint. In some embodiments, the UFP device sends a synthetic NRDY packet to the host device in response to a STATUS Transaction Packet to provide the UFP device and DFP device additional time to complete configuration for servicing the endpoint.