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Table of Contents
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Kernel Setup
Enter kernel configuration
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Select submenus for USB Gadget configfs : Device Drivers > USB support > USB support > USB Gadget Support. Select <*> for “USB Gadget functions configurable through configfs“, [*] for “Function filesystem (FunctionFS)” and [*] for “Audio Class 1.0“.
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ConfigFS
Configure UAC gadget through configfs saved as a file named setup_uac.
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#!/bin/sh CONFIGFS_HOME=/sys/kernel/config VID=0xabcd PID=0x1234 serial_number="myserial" manufacturer="mymfg" product="myproduct" name="c" number="1" configuration="uac1" maxpower="500" CONFIG="configs/$name.$number" FUNCTION="uac1.0" UDC_NAME="f8102800.usb" modprobe libcomposite mount -t configfs none $CONFIGFS_HOME mkdir -p $CONFIGFS_HOME/usb_gadget/g1 cd $CONFIGFS_HOME/usb_gadget/g1 echo $VID > idVendor echo $PID > idProduct mkdir -p strings/0x409 echo $serial_number > strings/0x409/serialnumber echo $manufacturer > strings/0x409/manufacturer echo $product > strings/0x409/product mkdir -p configs/$name.$number echo $maxpower > configs/$name.$number/MaxPower mkdir -p configs/$name.$number/strings/0x409 echo $configuration > configs/$name.$number/strings/0x409/configuration mkdir -p functions/$FUNCTION echo 0x3 > functions/$FUNCTION/p_chmask echo 48000 > functions/$FUNCTION/p_srate echo 2 > functions/$FUNCTION/p_ssize echo 0x3 > functions/$FUNCTION/c_chmask echo 48000 > functions/$FUNCTION/c_srate echo 2 > functions/$FUNCTION/c_ssize ln -s functions/$FUNCTION configs/$name.$number echo $UDC_NAME > UDC |
Test Configurations for USB 2.0 Gadget Audio
Use an USB-A to Micro-USB cable to connect the Windows PC and the SP7350 platform.
Plug an USB sound card to the USB 3.0 Type C port of the SP7350 platform and plug a earphone to the sound card.
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In Device Manager of Windows PC, “Capture Input terminal (AC Interface)“ and “Speakers (AC Interface)“ will show up in Audio inputs and outputs. “AC Interface” will show up in Sound, video and game controllers.
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Test for USB 2.0 Gadget Audio
The command-line audio player (aplay) and soundfile recorder (arecord) are used for the test.
Record and Play
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Play music and choose “Speakers (AC Interface)“ in Windows PC. Then use arecord -D hw:1,0 -c 2 -r 48000 -f S16_LE | aplay -D hw:2,0 -c 2 -r 48000 -f S16_LE command to output the sounds to the earphone of the USB sound card in USB 3.0 type C port in the SP7350 platform.
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sunplus@ubuntu:~$ arecord -D hw:1,0 -c 2 -r 48000 -f S16_LE | aplay -D hw:2,0 -c 2 -r 48000 -f S16_LE Recording WAVE 'stdin' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo Playing WAVE 'stdin' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo |
Record Channel
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Play music and choose “Speakers (AC Interface)“ in Windows PC. Then use arecord -D hw:1,0 -c 2 -r 48000 -f S16_LE pc_music.wav command to record it as pc_music.wav in the SP7350 platform.
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sunplus@ubuntu:~$ arecord -D hw:1,0 -c 2 -r 48000 -f S16_LE pc_music.wav Recording WAVE 'pc_music.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo |
Play Channel
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Use aplay -D hw:1,0 -c 2 -r 48000 -f S16_LE pc_music.wav command to play pc_music.wav in the SP7350 platform. Then choose “Capture Input terminal (AC Interface)“ and record it in the Windows PC.
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