Using a Raspberry Pi as equaliser in between an USB source (iPad) and USB DAC

[Red@]

I provide below the starter for the gaudio_ctl daemon required to launch the script mentioned in my previous post (file set_samplerate.service under /usr/lib/systemd/system):

[Unit]
Description=Sample Rate Changer Daemon
After=multi-user.target

[Service]
ExecStart=gaudio_ctl --gadget-name "UAC2Gadget" --ccmd  "/usr/bin/python3 /home/pi/set_samplerate.py {R}"
Restart=always
RestartSec=1
StandardOutput=journal
StandardError=journal
SyslogIdentifier=set_samplerate
CPUSchedulingPolicy=fifo
CPUSchedulingPriority=10
User=pi
Group=pi

[Install]
WantedBy=usb-gadget.target multi-user.target

Note the "WantedBy" option in the [Install] section ensuring that the sample rate change daemon is started when the usb-gadget.target is reached, indicating the aviailability of a usb gadget device (this was suggested by @phofman elsewhere).

Hello @stemag,
I am not a dev per say, and would like to use this solution. since the infomation is quite scattered between posts, I am a little at lost.
Would it be possible for you to describe the steps including you're latest additions ?
It would he very much appreciate, thank you very much in advance

 

[stemag]

Hello @stemag,
I am not a dev per say, and would like to use this solution. since the infomation is quite scattered between posts, I am a little at lost.
Would it be possible for you to describe the steps including you're latest additions ?
It would he very much appreciate, thank you very much in advance

I had the same difficulty in putting all the information together. Now everything is working as expected.
I will try to write a small guide. Please allow me a few days.

 

[stemag]

Please find attached a small guide to set up a DSP box based on Raspberry Pi 4 hardware and CamillaDSP software.
I am not a native English speaker, so I apologise for any imperfect use of the English language.
Please inform me of any errors or omissions.

 

[melomane13]

is this adapter ok for gadget?

https://fr.aliexpress.com/item/1005005365356095.html?spm=a2g0o.detail.0.0.696bY6ndY6nd8T&gps-id=pcDetailTopMoreOtherSeller&scm=1007.40000.327270.0&scm_id=1007.40000.327270.0&scm-url=1007.40000.327270.0&pvid=f0083d7a-2ced-4311-9ea1-de5cc2956b52&_t=gps-id:pcDetailTopMoreOtherSeller,scm-url:1007.40000.327270.0,pvid:f0083d7a-2ced-4311-9ea1-de5cc2956b52,tpp_buckets:668%232846%238112%231997&pdp_npi=4%40dis%21EUR%218.70%214.35%21%21%2165.35%21%21%40211b61ae16958935905045948ef57b%2112000032756589673%21rec%21FR%211757239570%21

 

[DeLub]

is this adapter ok for gadget?

https://fr.aliexpress.com/item/1005005365356095.html?spm=a2g0o.detail.0.0.696bY6ndY6nd8T&gps-id=pcDetailTopMoreOtherSeller&scm=1007.40000.327270.0&scm_id=1007.40000.327270.0&scm-url=1007.40000.327270.0&pvid=f0083d7a-2ced-4311-9ea1-de5cc2956b52&_t=gps-id:pcDetailTopMoreOtherSeller,scm-url:1007.40000.327270.0,pvid:f0083d7a-2ced-4311-9ea1-de5cc2956b52,tpp_buckets:668%232846%238112%231997&pdp_npi=4%40dis%21EUR%218.70%214.35%21%21%2165.35%21%21%40211b61ae16958935905045948ef57b%2112000032756589673%21rec%21FR%211757239570%21

At least they claim it is.

 

[phofman]

That USB3 (i.e. data) connector is female (i.e. host side). You need a device side connector, to be plugged into a host.

 

[melomane13]

That USB3 (i.e. data) connector is female (i.e. host side). You need a device side connector, to be plugged into a host.

Do you want to go deeper? I'm not sure I understand

 

[phofman]

IIUC you are looking for a splitter to power your RPi while using the USB-C as a gadget (that's the subject of this topic). If so, the splitter would have to present the device side of the USB connection.

 

[Music1969]

Hi @phofman , so do you have automatic sample rate switching working with your Pi4?

So if Apple Music Hi-Res changes sample rates, you can feed it bitperfectly into Pi4, without any manual changing of sample rate?

What are the key code lines required for this to work ?

Or is it now part of some mainline kernel for RPi4?

 

[phofman]

So if Apple Music Hi-Res changes sample rates, you can feed it bitperfectly into Pi4, without any manual changing of sample rate?

Whether your host switches samplerate depends on the host, provided the device offers the required rates. If it does, then e.g. look at https://www.diyaudio.com/community/threads/sample-rate-switcher-for-camilladsp.403054/

 

[Music1969]

Whether your host switches samplerate depends on the host, provided the device offers the required rates. If it does, then e.g. look at https://www.diyaudio.com/community/threads/sample-rate-switcher-for-camilladsp.403054/

Thanks! Looking at the thread, seems only the OP was able to get it to work, and nobody else.

I'll give it a shot

 

[phofman]

Thanks! Looking at the thread, seems only the OP was able to get it to work, and nobody else.

IIUC there was only one follower who really tried and did not know how to compile C code in linux. Another guy did not use the USB gaget device.

I have not tested the project but it looks nice and the author is clearly very competent.