CM108AH Datasheet, PDF (16/27 Pages) C-Media Electronics – Highly Integrated USB Audio I/O Controller

CM108AH
Highly Integrated USB Audio I/O Controller
7.3 HID Feature
The CM108AH’s HID feature allows users to set volume up, volume down, playback mute and recording mute
button pins, and reports the changes to the host to synchronize host side settings. In addition, all CM108AH
internal registers can be accessed via HID function call.
7.3.1 What’s HID?
USB protocols can configure devices at startup or when they are plugged in at run time. These devices are
categorized into various device classes. Each device class defines the common behavior and protocols for
devices that serve similar functions. The HID (Human Interface Device) class is one of the device classes.
The HID class consists primarily of devices that are used to control the operation of computer systems.
Typical examples of HID class devices include:
 Keyboards and pointing devices: mice, trackballs and joysticks
 Front-panel controls: knobs, switches, buttons and sliders
 Controls that might be found on VCR remote controls, games or simulation devices: data gloves,
throttles, and steering wheels
 Devices that may not require human interaction but provide data in a similar format to HID class
devices: bar-code readers, thermometers or voltmeters
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