Device Configuration
Analog Out
Default
Endpoint
Endpoint #2
(IF #1)
Audio Streaming
Interface
Endpoint #0
Endpoint #5
(IF #2)
HID Interface
IT
TID1
FU
UID3
OT
TID2
Standard Audio Control Interface (IF #0)
PCM2704/5/6/7
M0024-01
Interface #0 (Default/Control Interface)
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SLES081F – JUNE 2003 – REVISED JANUARY 2009
illustrates the USB audio function topology. The PCM2704/5/6/7 has three interfaces. Each interface is
enabled by some alternative settings.
Figure 21. USB Audio Function Topology
Interface #0 is the control interface. Setting #0 is the only possible setting for interface #0. Setting #0 describes
the standard audio control interface. Audio control interface consists of a terminal. The PCM2704/5/6/7 has three
terminals:
•
Input terminal (IT #1) for isochronous-out stream
•
Output terminal (OT #2) for audio analog output
•
Feature unit (FU #3) for DAC digital attenuator
Input terminal #1 is defined as a USB stream (terminal type 0x0101). Input terminal #1 can accept two-channel
audio streams constructed of left and right channels. Output terminal #2 is defined as a speaker (terminal type
0x0301). Feature unit #3 supports the following sound control features:
•
Volume control
•
Mute control
The built-in digital volume controller can be manipulated by an audio-class-specific request from 0 dB to –64 dB
in steps of 1 dB. Changes are made by incrementing or decrementing one step (1 dB) for every 1/f
S
time interval,
until the volume level reaches the requested value. Each channel can be set to a separate value. The master
volume control is not supported. A request to the master volume is stalled and ignored. The built-in digital mute
controller can be manipulated by an audio-class-specific request. A master mute control request is acceptable. A
mute control request to an individual channel is stalled and ignored. The digital volume control does not affect
the S/PDIF and I
2
S outputs (PCM2706/7).
Copyright © 2003–2009, Texas Instruments Incorporated
17
Product Folder Link(s):
PCM2704 PCM2705 PCM2706 PCM2707
