CM119B
USB Audio Single Chip
6.5 HID Feature and Descriptor
The HID class consists primarily of devices that are used by humans to control the operation of computer systems.
HID feature is provided by t h e CM119B, so user settings ( volume up, volume down, and playback mute button pin)
were all reported to the host to synchronize host side setting. In addition, all the CM119B internal registers can be
accessed via HID function call.
USB protocols can configure devices at start up or when they are plugged in at run time. These devices are broken
down into various device classes. Each device class defines the common behavior and protocols for devices that has
similar functions. The HID (Human Interface Device) class is one of the device classes.
.
6.5.1 HID Interface Descriptor
Offset
Field
Size
Value(Hex)
Description
0
1
2
3
bLength
1
1
1
1
09
04
03
00
Sizeofthisdescriptor:9byte
INTERFACE descriptor type
Number of interface: 3
Alternate 0
bDescriptorType
bInterfaceNumber
bAlternateSetting
Number of endpoints used by this
interface:1
4
bNumEndpoints
1
01
5
6
7
bInterfaceClass
bInterfaceSubClass
bInterfaceProtocol
1
1
1
03
00
00
HID Interface Class
No Subclass
Must be set to 0
Index of a string descriptor that characterizes this
interface
8
iInterface
1
00
6.5.2 HID Descriptor
4.
Offset
Field
Size
Value(Hex)
Description
Total 9 bytes
HID descriptor type
HID class version 1.00
-
0
1
2
4
5
6
bLength
1
1
2
1
1
1
09
21
bDescriptorType
bcdHID
0100
00
bCountryCode
bNumDescriptors
bDescriptorType
01
-
22
Report descriptor
Numeric expression equal to the total size of the
optional descriptor: 60 Bytes
7
wDescriptorLength
2
003C
6.5.3 Interrupt in Endpoint Descriptor
5.
Offset
Field
Size
Value(Hex)
Description
Total 7 bytes
0
1
bLength
1
1
07
05
bDescriptorType
ENDPOINT descriptor type
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Revised: Aug. 2013 Copyright© C-Media Electronics Inc.
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