USB AUDIO 2.0 REFERENCE DESIGN XMOS, USB AUDIO 2.0 REFERENCE DESIGN Datasheet - Page 20

• Manufacturer Part Number: USB AUDIO 2.0 REFERENCE DESIGN
• Description: USB AUDIO 2.0 REFERENCE DESIGN
• Manufacturer: XMOS

Specifications of USB AUDIO 2.0 REFERENCE DESIGN

• Design Resources: USB AUDIO Schematic
• Main Purpose: Audio, Audio Processing
• Embedded: Yes
• Utilized Ic / Part: XS1-L1
• Primary Attributes: Audio data up to 24-bit @ 192kHz
• Secondary Attributes: I²S and S/PDIF
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 880-1017

The audio system sends a word over a channel to the decouple thread to request
The first operation the interrupt handler does is to send back a word acknowledging
The complete communication scheme is shown in the table below (for non sample
USB Audio Software Design Guide
Decoupler/Audio thread interaction
system, the decoupler thread must respond to requests from the audio system
to send/receive samples immediately. An interrupt handler is set up in the de-
coupler thread to do this. The interrupt handler is implemented in the function
handle_audio_request .
sample transfer (using the build in outuint function). The receipt of this word in the
channel causes the
the request (if there was a change of sample frequency a control token would instead
be sent—the audio system uses a testct() to inspect for this case).
Sample transfer may now take place. First the audio subsytem transfers sam-
ples destined for the host, then the decouple thread sends samples from the host
to device. These transfers always take place in channel count sized chunks (i.e.
NUM_USB_CHAN_OUT and NUM_USB_CHAN_IN ). That is, if the device has 10 output chan-
nels and 8 input channels, 10 samples are sent from the decouple thread and 8
received every interrupt.
frequency change case):
handle_audio_request interrupt to fire.
To meet timing requirements of the audio
Document Revision 1.2
20/57