USB HID Usage Tables详解：理解报告描述符的关键

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本文档是关于Universal Serial Bus (USB) 的Human Interface Device (HID) 使用表（HID Usage Tables）的版本1.11，发布于2001年6月27日。USB Implementers' Forum 提供了这份文档，旨在为理解和设计符合USB标准的人机交互设备提供基础规范。HID Usage Tables定义了一系列预定义的标识符，用于指示USB Human Interface Devices (HID) 的输入和输出功能，如键盘、鼠标、游戏控制器等设备。学习和操作USB设备时，了解这些表格至关重要，因为它们规定了设备如何向USB主机报告其状态和接收命令。文档详细列出了多个贡献者，包括来自ELO Touchsystems、LCS/Telegraphics、Microsoft Corporation、Symbol Technologies、Intel、Logitech International等公司的工程师，他们在USB HID设计和规范的制定中起到了关键作用。文档的历史修订记录从1.1版开始，直至1.11版，期间包含了对多个HID Review Request的整合，如请求号1至18，反映了标准持续改进和适应新技术需求的过程。1.11版的发布日期为2001年8月7日，rc1版本则是在同年2月进行了部分修正，比如改正了barcode Usage Page ID和页码问题。通过学习和参考这份HID Usage Tables，开发者能够确保他们的USB HID设备遵循统一的标准，从而实现兼容性和互操作性。无论是硬件制造商还是软件开发者，在设计和实现USB接口的HID设备时，都应参考这些表格，以确保设备功能的正确描述和有效的通信。这份文档对于USB设备的开发者和维护者来说，是不可或缺的技术参考资料。

16 Universal Serial Bus HID Usage Tables

Version 1.11 June 27, 2001

Page ID Page Name Section or Document

91 Arcade Page

OAAF Definitions for arcade and

coinop related Devices

92-FEFF Reserved

FF00-FFFF Vendor-defined

A bold usage definition in the following sections identifies a collection. Non-bold definitions are specific

features related to a device that would be applied to individual controls that generate data. In many cases,

specific usages can be used by a number of device types.

3.1 HID Usage Table Conventions

Usage ID 0 should always be reserved.

Usage ID 1 through 0x1F are reserved for “top level” collections. These usage IDs are not necessarily

application-level but are used to identify general device types.

Usage page values are limited to 16 bits.

Usage ID values are limited to 16 bits.

Usages are 32-bit identifiers, where the high order 16 bits represents the usage page and the low order 16

bits represents the usage ID. To allow more compact Report descriptors, Usage Page items can be declared

to specify the high order bits of the Usage item and the Usage items can declare only the ID portion of the

usage, as follows:

• If the bSize field of the Usage item equals 1 or 2, the entire 1- or 2-byte data portion of the item is

interpreted as a usage ID.

• If the bSize field equals 3, bits 16-31 of the 4-byte data portion of the item are interpreted as a usage

page, and bits 0-15 of the data portion are interpreted as a usage ID. This interpretation of usages

applies to Usage, Usage Minimum, and Usage Maximum items.

The notation for a 32-bit usage (sometimes called an extended usage) in the examples is

Usage(Usage Page: Usage ID).

3.2 Handling Unknown Usages

If a usage is unknown to an application then the application should ignore it.

If the usage attached to a collection is unknown to an application, then the application should ignore the

collection and all usages contained in the collection. A collection can be used to modify the meaning of the

usages that it contains, therefore “known” usages within an unknown collection may not represent their

original meaning. An example of this is the Usage Selected Indicator on the LED page.

System software provides capabilities for parsing HID Report descriptors. In some cases the usage

associated with the top level application collection can be used by the system software as a key to load an

application-specific driver or a mapping driver for legacy compatibility.

Universal Serial Bus HID Usage Tables 17

Version 1.11 June 27, 2001

3.3 Usages and Units

For usages that declare data items as a measurement of time, distance, force, and so forth, an application

must look at the units to properly interpret the value defined by a usage, unless:

1. The usage specifically declares Units as optional.

2. The usage description defines the units in which the value will be presented.

If Units are set to Optional or set to None (have not been declared) then an application can assume the usage

represents a dimensionless value. Any application that ignores Units does so at its own risk.

A usage that declares itself to be a measurement of time would specify whether it was seconds or

milliseconds by declaring Units and Unit Exponent prior to the respective Main item declaration. An

example of this is the Flash On Time usage on the LED page, which is described as the duration that the

indicator is illuminated in flash mode. The duration would be qualified by the values of Units and Unit

Exponent.

When declaring Units for a main item, the Logical Minimum, Logical Maximum, Physical Minimum,

Physical Maximum, and Unit Exponent items must also be declared.

In many cases the coordinate system assumes that the values can vary both positively and

negatively from zero (0).

3.4 Usage Types

Usages define a wide variety of device features. However, the way an application treats the data that they

generate falls into a relatively small set of categories. This section provides descriptions of frequently used

types of usages, primarily to save redundant text throughout this document. This list is not an exhaustive list

of the possible usage types. Individual usage pages can declare their own usage types.

Each usage type describes how an application should treat the data generated by the Main item that the

usage is attached to.

Usage type names are followed by an abbreviation that is used in the detailed usage description to identify

the default type of a usage. In some cases usage types do not apply and the detailed description will identify

how the usage is to be interpreted.

There are three basic types of information that are described by usages: controls, collections, and data. In

this context, controls are identified with the state of a device (on/off, enable/disable, and so forth),

collections group related controls and data together, and data comprises the remaining information that is

passed between a device and the host.

Usage types are always considered to be the recommended method of handling a usage.

Consult the usage’s definition to determine whether alternative usage types may apply.

Note

18 Universal Serial Bus HID Usage Tables

Version 1.11 June 27, 2001

3.4.1 Usage Types (Controls)

The following table summarizes the control related usage types.

Table 2: Usage Types (Controls)

Control

Type

Logical

Min

Logical

Max

Flags Signal Operation

–1 1 Relative,

Preferred

State

Edge 1 increments the control’s value.

–1 decrements the control’s value.

–Min Max Relative,

Preferred

State

Level

n increments the control’s value. –n

decrements the control’s value.

Linear

Control

(LC)

Min Max Absolute,

Preferred

State

N/A The value reported by the control is

used directly by the host.

-1 1 Relative,

No Preferred

Edge 1 asserts an On condition.

–1 asserts an Off condition.

0 1 Relative,

Preferred

State

Edge A 0 to 1 transition toggles the current

On/Off state.

On/Off

Control

(OOC)

0 1 Absolute,

No Preferred

Level 1 asserts an On condition.

0 asserts an Off condition.

Momentary

Control

(MC)

0 1 Absolute,

Preferred

State

Level 1 asserts a condition.

0 deasserts the condition.

One Shot

Control

(OSC)

0 1 Relative,

Preferred

State

Edge A 0 to 1 transition triggers an event.

A 1 to 0 transition must occur before

another event can be triggered.

Re-trigger

Control

(RTC)

0 1 Absolute,

Preferred

State

Level 1 triggers an event. When an event

completes, if the value is 1 then the

event will be triggered again.

3.4.1.1 Linear Control (LC)

In many cases, a control of a linear value is implemented as a pair of increment/decrement buttons, a jog

wheel, or a linear control such as a knob or a slide.

When implemented as an increment/decrement control, the two buttons must be translated into a single, 2-bit

signed value and declared as a Relative Main item with a Report Size equal to 2, where –1 decrements the

value, +1 increments it, and no change occurs when 0 is asserted.

A jog wheel is normally implemented as a spring-loaded knob that returns to a fixed center position when

released. This control reports a single value of two or more bits which are reported as a signed value and

declared as a Relative Main item where –n decrements the value, +n increments it, and no change occurs

when 0 is asserted. A jog wheel control is implemented with a resolution of +/–n, where the offset of the

knob from the center position is proportional to the reported value. The Report Size must be declared large

enough to contain the signed value n.

When implemented as a linear knob or slide, the control must be declared as an Absolute Main item. For an

example, see Section A.1, “Volume Control,” in Appendix A, “Usage Examples.”

Universal Serial Bus HID Usage Tables 19

Version 1.11 June 27, 2001

3.4.1.2 On/Off Control (OOC)

An On/Off Control can be implemented in any of the following ways:

• Two buttons, On and Off. The two buttons are encoded into a 2-bit signed value and declared as

a Relative, No Preferred Main item with Logical Minimum and Logical Maximum of –1 and 1,

respectively. The transition from 0 to –1 generates an Off condition and the transition from 0 to +1

generates an On condition. No change occurs when 0 is asserted.

• A single button that toggles the On/Off state each time it is pressed. (single throw momentary

switch The single button is encoded into a 1-bit unsigned value and declared as an Relative,

Preferred Main item with a Logical Minimum and Logical Maximum of 0 and 1, respectively.

The transition from 0 to 1 toggles the current On/Off state. No change occurs on the 1 to 0

transition.

• A toggle switch that maintains the On/Off state mechanically. (toggle switch) This control is

encoded into a 1-bit unsigned value and declared as an Absolute, No Preferred Main item with a

Logical Minimum and Logical Maximum of 0 and 1, respectively. The assertion of 1 generates an

On condition and the assertion of 0 generates an Off condition.

3.4.1.3 Momentary Control (MC)

A Momentary Control is a basic push button. A Momentary Control is encoded into a 1-bit value and

declared as an Absolute, Preferred Main item with a Logical Minimum and Logical Maximum of 0 and 1,

respectively. A value of 1 generates an asserted condition and 0 generates a non-asserted condition. An

example is a mouse button.

3.4.1.4 One Shot Control (OSC)

A One Shot Control is a push button that triggers a single event or action. A One Shot Control is encoded

into a 1-bit value and declared as a Relative, Preferred Main item with a Logical Minimum and Logical

Maximum of 0 and 1, respectively. A 0 to 1 transition initiates an event. Nothing occurs on a 1 to 0

transition but it is required before another event can occur. An example is degauss.

3.4.1.5 Re-Trigger Control (RTC)

A Re-Trigger Control is a push button that triggers a repeating event as long as it is asserted. A Re-Trigger

Control is encoded into a 1-bit value and declared as an Absolute, Preferred Main item with a Logical

Minimum and Logical Maximum of 0 and 1, respectively. A 0 to 1 transition initiates the first event. When

each event terminates, if the control is still asserted (1) then another event will occur. An example is an auto-

repeat fire button.

3.4.2 Usage Types (Data)

The following table summarizes the data-related usage types.

Table 3: Usage Types (Data)

Type Flags Description

Selector (Sel) Array Contained in a Named Array (NAry).

Static Value (SV) Constant, Variable, Absolute A read-only multiple-bit value.

Static Flag (SF) Constant, Variable, Absolute A read-only single-bit value.

Dynamic Value (DV) Data, Variable, Absolute A read/write multiple-bit value.

Dynamic Flag (DF) Data, Variable, Absolute A read/write single-bit value.

20 Universal Serial Bus HID Usage Tables

Version 1.11 June 27, 2001

3.4.2.1 Selector (Sel)

Selectors come in three forms:

• One selection of a set. Radio buttons are a mechanically linked set of buttons where one selection

is always valid. This is a perfect example of the “one selection of a set” form. A radio button set is

defined by a Main item with the Array flag set and the Report Count set to 1. The index returned

in the array field corresponds to the pressed button (or selection). A usage must be declared for

each selection. The array field never returns an index of NULL because one usage is always valid.

An example is Stat Not Ready on the Alphanumeric Display page.

• N selections of a set. More than one selection (button) can be valid at a time. Multiple selections

can be returned to the system at one time in a multi-byte array. The “n selections of a set” form is

defined by a Main item with the Array flag set and the Report Count set to n, where n is the

number of selections that can be reported in a single report. An example is a keyboard.

• Any selection of a set. The control is implemented as a set of bit fields in which each bit represents

a single selection. This control is defined by a Main item with the Variable flag set and the Report

Size equal to 1. The Report Count will be equal to the number of selections in the set.

Selectors therefore can be implemented in a number of ways: Array[1] (one selection of a set), Array[n] (n

selections of a set), or bitmap (any selection of a set).

Optionally, the array field or set can be named by wrapping a set of Selectors in a logical collection with a

usage attached to it. For details, see Section 3.4.3.1, “Named Array (NAry).”

3.4.2.2 Static Value (SV)

Static values are used to declare a fixed features in a device. They are defined as Constant and treated as

read-only information. Therefore, asserting this field in a Set_Report command has no defined effect.

3.4.2.3 Static Flag (SF)

Static flags are used to declare the existence of a fixed feature in a device. If a Static Flag usage is found in a

Report descriptor then the field must be read to determine whether the feature identified by the flag exists.

A value of 1 indicates existence and a value of 0 indicates non-existence. The absence of a Static Flag usage

implies that the flag is false or the feature defined by the flag is not supported by the device. A Static Flag

must be declared as a Constant. To be accessible by applications, a Static Flag must have a usage assigned to

it.

Static Flags are typically declared in a Feature report as a single-bit field where the value is always read as

1. Attempting to modify this field in a Set_Report command has no effect on a Static Flag.

3.4.2.4 Dynamic Flag (DF)

Dynamic Flags are used to declare the existence of a host-controllable feature in a device. The absence of a

Dynamic Flag usage implies that the flag is false or the feature defined by the flag is not supported by the

device.

Dynamic Flags are typically declared in a report as a single-bit field, where a value of 1 returned by the

device indicates that the feature is enabled. The assertion of 1 by the host will cause the feature to be evoked

and the assertion of 0 indicates that the feature is to be disabled or ignored if the feature is a one-time event

(such as Degauss or Clear Display). A Dynamic Flag Main item must be declared as Data.

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