HID Switch Emulation via Report Descriptor Analysis
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Solution Overview
Problem
The lack of a standard structure for reporting additional features in USB human interface devices (HIDs) makes it difficult to emulate these devices while switching between hosts, leading to delays and compatibility issues.
Innovation Solution
A method and system that analyze the HID report descriptor to create mask tables for buttons, X coordinates, and Y coordinates, allowing the creation of a switch report that can be interpreted by the host, enabling seamless switching and emulation of HID devices with enhanced features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switch uses standard USB enumeration to recognize HID devices, then the host can identify the device type, but switching between hosts introduces delays due to repeated enumeration
Solution Approach 1:
The switch performs preliminary analysis of the HID report descriptor during the initial enumeration phase, extracting and storing device-specific information (button mappings, coordinate systems, wheel configurations) in mask tables. This preliminary action enables the switch to rapidly translate HID reports without re-enumerating the device when switching hosts, thus eliminating switching delays while maintaining accurate device recognition.
2Adaptability or versatility
If the switch emulates HID devices with enhanced features, then more functionality is supported, but there is no standard structure for reporting these features making emulation difficult
Solution Approach 1:
The patent introduces an intermediary translation layer between the HID device and the host computer. The switch contains a report translator that converts non-standard HID reports (with enhanced features like media controls, navigation buttons, and custom coordinates) into standard USB HID reports that the host can understand. This intermediary mechanism enables support for diverse enhanced features without requiring changes to the host system, resolving the complexity of emulation while maintaining versatility.
Solution Approach 2:
The switch dynamically changes report parameters by using mask tables to extract specific fields from incoming HID reports and reformat them according to the target host's expected format. The mask tables store parameter mappings for different HID device types, allowing the switch to adapt report structures (button codes, coordinate ranges, wheel directions) to match standard USB specifications, thereby enabling versatile feature support through parameter transformation.
3Adaptability or versatility
If the switch creates mask tables for each HID feature, then enhanced features can be emulated, but the processing complexity increases
Solution Approach 1:
The patent implements a universal mask table structure that can handle multiple HID device types (keyboards, mice, game controllers, media players) through a single standardized framework. The mask tables use consistent field names and formatting rules across all device types, allowing the same translation machinery to process diverse enhanced features. This universal approach enables comprehensive feature emulation capability while keeping processing complexity manageable through reuse of the same processing logic.
Data Source
AI summary
The present invention relates to a system and method for switching keyboard human interface devices (HIDs) and video displays. Provided is a switch with emulation support for advanced HID features. The switch uses information contained in HID report descriptors to extract information contained in HID reports and insert the extracted information into a switch report, which is sent to a host computer.