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Update USB_GADGET.md

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Andrea Bondavalli 2020-09-13 11:25:00 +02:00 committed by GitHub
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USB_GADGET.md
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@ -4,7 +4,7 @@ This document describes how to use the AES67 Daemon on a board to operate as AES
The board doesn't need to have an audio codec but a USB client or OTG connector that is able to operate in device mode.
Eventually you will connect your card to your PC (*Windows* / *Linux* / *MAC*) via USB and use the PC as a player or recorder and the card to relay audio from USB to Ethernet and vice versa.
Eventually you will connect your card to your PC ( *Windows* / *Linux* / *MAC* ) via USB and use the PC as a player or recorder and the card to relay audio from USB to Ethernet and vice versa.
## Kernel configuration ##
<a name="kernel_config"></a>
@ -44,6 +44,13 @@ On the PC new audio input and output devices show up.
The name assigned to these depend on the OS.
On *Windows* a new speaker and microphone named *AC interface* get configured.
**_NOTE:_**
If the USB gadget module loads but the USB audio device doesn't show up check in the kernel ring buffer for the following message:
udc-core: couldn't find an available UDC - added [g_audio] to list of pending drivers
This means you have other USB gadgets currently active (for example g_serial).
To proceed disable the automatic load of these modules and configure *g_audio* instead.
## AES67 USB Transmitter ##
<a name="usb_transmitter"></a>
@ -51,7 +58,7 @@ Before starting make sure that the [AES67 daemon basic setup](DEVICES.ms#daemon_
On the board run the following command to relay the audio from the USB to the AES67 Source:
sudo nice -n -10 ./alsaloop -c 2 -r 48000 -f S16_LE -C plughw:UAC1Gadget -P plughw:RAVENNA
sudo nice -n -10 alsaloop -c 2 -r 48000 -f S16_LE -C plughw:UAC1Gadget -P plughw:RAVENNA
On the PC start the audio playback on the new device.
**_NOTE:_** The *ALSA RAVENNA driver* will perform the format conversion from *S16\_LE* to the *Source* format.
@ -63,7 +70,7 @@ You also need to configure a new stereo *Sink* on the daemon.
On the board run the following command to relay the audio from AES67 Sink to the USB:
sudo nice -n -10 ./alsaloop -c 2 -r 48000 -f S16\_LE -C plughw:RAVENNA -P plughw:UAC1Gadget
sudo nice -n -10 alsaloop -c 2 -r 48000 -f S16_LE -C plughw:RAVENNA -P plughw:UAC1Gadget
On the PC start the audio recording on the new device.
**_NOTE:_** The *ALSA RAVENNA driver* will perform the format conversion from *S16\_LE* to the *Sink* format.