描述

Global items describe rather than define data from a control. A new Main item assumes the characteristics of the item state table. Global items can change the state table. As a result Global item tags apply to all subsequently defined items unless overridden by another Global item.

全局项用于描述而非定义来自控制器的数据。一个新的主项会继承项状态表中的特性。全局项可以改变这个状态表。因此，全局项标签适用于其后定义的所有项，除非被另一个全局项覆盖。

格式

• Usage Page (bit[7,0] = 0000 01nn)
  Unsigned integer specifying the current Usage Page. Since a usage are 32 bit values, Usage Page items can be used to conserve space in a report descriptor by setting the high order 16 bits of a subsequent usages. Any usage that follows which is defines 16 bits or less is interpreted as a Usage ID and concatenated with the Usage Page to form a 32 bit Usage.

  这是一个用于指定当前用途页的无符号整数。由于用途是32位的值，通过设置后续用途的高16位，用途页项可用于节省报告描述符中的空间。其后定义的任何16位或更少位数的用途，都将被解释为用途ID，并与用途页拼接，共同组成一个32位的完整用途。

单词
usage - 美[ˈjusɪdʒ]英[ˈjuːsɪdʒ]
n.使用；利用；利用率；惯用法
网络翻译为: 用途(★)；使用方法；习惯

• Logical Minimum (bit[7,0] = 0001 01nn)
  Extent value in logical units. This is the minimum value that a variable or array item will report. For example, a mouse reporting x position values from 0 to 128 would have a Logical Minimum of 0 and a Logical Maximum of 128.

  逻辑最小值
  以逻辑单位表示的数值范围下限。这是一个变量或数组项将报告的最小值。例如，一个报告x轴位置值范围为0到128的鼠标，其逻辑最小值为0，逻辑最大值为128。

• Logical Maximum (bit[7,0] = 0010 01nn)
  Extent value in logical units. This is the maximum value that a variable or array item will report.

  逻辑最大值
  以逻辑单位表示的数值范围上限。这是一个变量或数组项将报告的最大值。

• Report Size (bit[7,0] = 0111 01nn) 报告大小
  Unsigned integer specifying the size of the report fields in bits. This allows the parser to build an item map for the report handler to use. For more information, see Section 8: Report Protocol.

  报告大小
  指定报告字段大小的无符号整数，单位为位。这使得解析器能够为报告处理程序构建一个项映射以供使用。更多信息，请参阅第8节：报告协议。

含义：每个字段单元的大小（位）

• Report ID (bit[7,0] = 1000 01nn) 报告ID
  Unsigned value that specifies the Report ID. If a Report ID tag is used anywhere in Report descriptor, all data reports for the device are preceded by a single byte ID field. All items succeeding the first Report ID tag but preceding a second Report ID tag are included in a report prefixed by a 1-byte ID. All items succeeding the second but preceding a third Report ID tag are included in a second report prefixed by a second ID, and so on.

  一个指定报告ID的无符号整数值。如果在报告描述符中的任何位置使用了报告ID标签，则该设备的所有数据报告前面都会带有一个单字节的ID字段。位于第一个报告ID标签之后，但在第二个报告ID标签之前的所有项，都包含在一个以第一个1字节ID为前缀的报告中。位于第二个报告ID标签之后，但在第三个报告ID标签之前的所有项，都包含在一个以第二个ID为前缀的报告中，依此类推。

This Report ID value indicates the prefix added to a particular report. For example, a Report descriptor could define a 3-byte report with a Report ID of 01. This device would generate a 4-byte data report in which the first byte is 01. The device may also generate other reports, each with a unique ID. This allows the host to distinguish different types of reports arriving over a single interrupt in pipe. And allows the device to distinguish different types of reports arriving over a single interrupt out pipe. Report ID zero is reserved and should not be used.

此报告ID值指示了添加到特定报告的前缀。例如，一个报告描述符可以定义一个报告ID为01的3字节报告。该设备将生成一个4字节的数据报告，其第一个字节是01。该设备还可以生成其他报告，每个报告都有唯一的ID。这允许主机区分通过单个中断输入管道到达的不同类型的报告，也允许设备区分通过单个中断输出管道到达的不同类型的报告。
注意：报告ID 0 是保留值，不应被使用。

• Report Count (bit[7,0] = 1001 01nn) 报告数量 ★
  Unsigned integer specifying the number of data fields for the item; determines how many fields are included in the report for this particular item (and consequently how many bits are added to the report).

  一个无符号整数，用于指定该项的数据字段数量；它决定了报告中为此特定项包含多少个字段（从而决定了向报告中添加多少位数据）。

含义：连续的字段单元的数量

笔记

• bit[3,2] = 01 - 全局项(global item)