USB Audio Design Guide
3.1
The USB Audio System Architecture
The XMOS USB Audio platform consists of a series of communicating components.
Every system is required to have the shared components listed in Figure
Component
Description
XMOS USB Device Driver (XUD)
Handles the low level USB I/O.
Endpoint 0
Provides the logic for Endpoint 0 which handles
enumeration and control of the device including DFU
related requests.
Endpoint buffer
Buffers endpoint data packets to and from the host.
Decoupler
Manages delivery of audio packets between the
endpoint buffer component and the audio components.
It can also handle volume control processing.
Audio Driver
Handles audio I/O over I2S and manages audio data
to/from other digital audio I/O components.
Figure 7:
Shared
Components
In addition Figure
shows components that can be added to a design:
Component
Description
Mixer
Allows digital mixing of input and output channels. It can also
handle volume control instead of the decoupler.
S/PDIF Transmitter
Outputs samples of an S/PDIF digital audio interface.
S/PDIF Receiver
Inputs samples of an S/PDIF digital audio interface (requires the
clockgen component).
ADAT Receiver
Inputs samples of an ADAT digital audio interface (requires the
clockgen component).
Clockgen
Drives an external frequency generator (PLL) and manages
changes between internal clocks and external clocks arising from
digital input.
MIDI
Outputs and inputs MIDI over a serial UART interface.
PDM Microphones
Receives PDM data from microphones and performs PDM to PCM
conversion
Figure 8:
Optional
Components
Figure
shows how the components interact with each other. The green circles
represent cores with arrows indicating inter-core communications.
This section will now examine these components in further detail.
3.2
XMOS USB Device (XUD) Library
All low level communication with the USB host is handled by the XMOS USB Device
(XUD) library.
The
XUD_Manager()
function runs in its own core and communicates with endpoint
cores though a mixture of shared memory and channel communications.
XM0088546.1
Содержание xCORE-200 Multi-channel Audio board
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