Interface #1 (Isochronous-Out Interface)
Interface #2 (HID Interface)
Endpoints
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SLES081F – JUNE 2003 – REVISED JANUARY 2009
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Interface #1 is for the audio-streaming data-out interface. Interface #1 has the following three alternative settings.
Alternative setting #0 is the zero-bandwidth setting. All other alternative settings are operational settings.
ALTERNATIVE
TRANSFER
SAMPLING RATE
DATA FORMAT
SETTING
MODE
(kHz)
00
Zero bandwidth
01
16-bit
Stereo
2s complement (PCM)
Adaptive
32, 44.1, 48
02
16-bit
Mono
2s complement (PCM)
Adaptive
32, 44.1, 48
Interface #2 is the interrupt-data-in interface. Interface #2 comprises the HID consumer control device.
Alternative setting #0 is the only possible setting for interface #2.
On the HID device descriptor, eight HID items are reported as follows for any model, in any configuration.
Basic HID Operation
Interface #2 can report the following three key statuses for any model. These statuses can be set by the
HID0–HID2 pins (PCM2704/6) or the SPI port (PCM2705/7).
•
Mute (0xE2)
•
Volume up (0xE9)
•
Volume down (0xEA)
Extended HID Operation (PCM2705/6/7)
By using the FUNC0–FUNC3 pins (PCM2706) or the SPI port (PCM2705/7), the following additional conditions
can be reported to the host.
•
Play/Pause (0xCD)
•
Stop (0xB7)
•
Previous (0xB6)
•
Next (0xB5)
Auxiliary HID Status Report (PCM2705/7)
One additional HID status can be reported to the host though the SPI port. This status flag is defined by SPI
command or external ROM. This definition must be described as on the report descriptor with a three-byte usage
ID.
AL A/V Capture
(0x0193) is assigned as the default for this status flag.
The PCM2704/5/6/7 has three endpoints:
•
Control endpoint (EP #0)
•
Isochronous-out audio data-stream endpoint (EP #2)
•
HID endpoint (EP #5)
The control endpoint is a default endpoint. The control endpoint is used to control all functions of the
PCM2704/5/6/7 by standard USB request and USB audio-class-specific request from the host. The
isochronous-out audio data-stream endpoint is an audio sink endpoint that receives the PCM audio data. The
isochronous-out audio data-stream endpoint accepts the adaptive transfer mode. The HID endpoint is an
interrupt-in endpoint. The HID endpoint reports HID status every 10 ms.
The HID endpoint is defined as a consumer-control device. The HID function is designed as an independent
endpoint from the isochronous-out endpoint. This means that the effect of HID operation depends on host
software. Typically, the HID function is used to control the primary audio-out device.
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Copyright © 2003–2009, Texas Instruments Incorporated
Product Folder Link(s):
PCM2704 PCM2705 PCM2706 PCM2707
