AN726
5.6. USB Input/Output Mode
In USB input/output mode, the system samples and outputs data at 48 kHz. The USB data is 16-bit signed data.
Host PC
sound
software
Class-D RD Board
R
SiM3U1xx
USB
SARADC0
MIC
EPCA
L
Figure 12. USB Input/Output Mode Block Diagram
For playing (from PC to the board), the board receives data from the USB interface using the si32Library USB
Audio Component and outputs the PWM waveform on the EPCA0 module.
For recording (from board to the PC), the firmware measures the microphone (MK1) using one SARADC module
and sends the data to the PC using the si32Library USB Audio Component.
Figure 13 shows the data flow for the USB input/output mode.
Host PC
SiM3U1xx
sound
USB0
9-bit
R
software
quantization
hardware
gain stage
MIC
SARADC0
shift from 12
bits unsigned
to 16 signed
remainder-
weighted
dither
EPCA
L
Figure 13. USB Input/Output Mode Flow Diagram
Rev. 0.1
13