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COMPUTER ACCESS TECHNOLOGY CORPORATION USB DESCRIPTOR DEFINITION (.DSC) FILES

Reference Manual

USB DESCRIPTOR DEFINITION

(.dsc) F

ILES

Descriptor definition (.dsc) files are used to configure decoding of class- or vendor-

specific descriptors of any protocol. A .dsc file is a set of instructions that contains

definitions that describe, in USB-specific terms, how to take blocks of data and

break them into fields with consecutive decoding of each field. The descriptor def-

inition files are text-based files that are identifiable by their .dsc extension. Custom-

ized decoding of USB descriptors is possible by editing or creating new definition

files.

The .dsc files work in conjunction with .req files in order to display descriptor in-

formation in a trace. A descriptor can be referred to by its DescriptorType

when a GET_DESCRIPTOR standard request (or any class- or vendor-specific Get

or SetDescriptor request, such as GET_HUB_DESCRIPTOR) is executed.

Also, when a CONFIGURATION descriptor is requested by the

GET_DESCRIPTOR standard request, a set of descriptors is supposed to be

returned by the USB device. This includes some standard descriptors (e.g.,

INTERFACE and ENDPOINT) and also can include class- and vendor-specific de-

scriptors. The .dsc definitions will work for both of those cases, using the

DescriptorType values and/or some other defined values, such as

DescriptorSubtype, ClassCode and Subclasscode.

This document describes the components of a .dsc file and the format for writing or

editing a .dsc file.

Please refer to the Universal Serial Bus Specification, version 1.1 for details about

USB protocol. The USB specification is available from the USB Implementers

Forum (USB-IF) at http://www.usb.org/.

Structure

Descriptor definition files are structured very similarly to request definition files;

however, a .dsc file can contain multiple descriptor definitions (inlcuding the

header, AllOffsets, and Offset structures), whereas a request file can contain

only one set of definitions.

Here is the basic structure for a .dsc file:

DescriptorName=<name>

DescriptorType=<wValue>

[DescriptorSubtype=< ? >]

opt

[ClassCode=<class code>]

opt

[SubclassCode=<subclass code>]

opt

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