jack & full duplex possible

I was wondering if it's possible to use Jack?

Yes.

If yes, is full duplex (in & out) possible?

Yes.

What can I expect for the latency (less than 20ms, more than 100 ms)?

Don't know, I've never tested latency in Jack. ALSA gives me 6 - 7 ms.

If not, with Alsa is it possible to have analog in & analog out working at the same time?

Yes.

--

Ragnar

Wonderful! Is it better to use Alsa (less CPU, lower latency)? I was wondering if it is also a good idea to run everything in root (I know it's never a good idea normally) - but for getting the best performance out of the raspberry pi... Should I try to apply those modifications: http://wiki.linuxaudio.org/wiki/raspberrypi

Thanks!

Hi Georg,

I guess it's not an easy task... Did you post more information about your setup somewhere? Could you spare some time to explain a bit more? Here's some questions:

• What distribution do you use
• Do you use Jack if yes what are the settings (period, nperiod, samplerate)
• Do you get glitches / drops
• Are you running X11 or headless
• What software are you using (amsynth, ...?)
• Do you use a special power supply (some people recommend some expensive one, I just have a basic cell phone charger 5V / 700ma)

Thank you!

Hi Pat,

it's not soooo difficult. Here some answers to yor questions:

• Ubuntu Studio 14.04
• yes, jack
• no glitches or drops!!!
• headless
• linuxsampler, amsynth yoshimi
• testing with easy acc powerbank  pb 12000A, and cellphone charger 5V / 1A

Some days ago I tested a setup with a tablet,a smartphone and another midi instrumented connected at the same time via wifi. It was possible to play all 3 without any glitches.

I'll post a little howto, a little video and the necessary patches when I've tested everything so far, that I think it's somehow stable.

Ubuntu Studio 14.04?

I don't see an ARM11 release:

Ubuntu Studio 14.04 LTS (Trusty Tahr)

If you want I can review your tutorial - trying to follow and add to it if something is missing (or adding how to run pure data for example). That would be nice!

yes, reviewing is really welcome! Thank you.

Answer: cross compiled on ubuntu 14.04

kernel  3.12.y and 3.14.y (from which only the first one works so far) for raspbian. Details will come soon.

Have fun

Georg

Ok make sense (using Ubuntu Studio for cross compiling and raspbian for the actuel distro)! In the meantime I found this tutorial: Talk Unafraid » Real Time kernels and audio on the Raspberry Pi - but I have to say that I would very much like to use your solution because I also want a similar setup (usb midi, pure data).

Keep in touch!

Hi Pat,

next weekend there will be more information on how to compile the 3.12 kernel with rt-preemption and wolfson drivers included on my website. Please be patient and

Have fun.

Here we go:

http://blog.georgmill.de/2014/04/26/compile-wolfson-audio-card-driver-for-kernel-3-12-y/

Have fun.

I have problem:

git reset --hard 4639d2b773b318d4b0409f67d3d5e73a513ba64b

fatal: Could not parse object '4639d2b773b318d4b0409f67d3d5e73a513ba64b'.

Hi Georg!

Thank you so much for this. Will try to find the time asap to confirm that it's working. With your permission, I will upload the rt-kernel with module so that people can simply do Step 53 (or maybe you already share the files somewhere)?

Talk to you soon

@ Jan Tomasik

Hi Jan,

what does

git status

say?

Georg

@ Jan Tomasik

Hi Jan,

what does

git status

say?

Georg

I tried both, of course, it's always the same:

git reset --hard 4639d2b773b318d4b0409f67d3d5e73a513ba64b

fatal: Could not parse object '4639d2b773b318d4b0409f67d3d5e73a513ba64b'.

the object does not exist.

git status

# On branch rpi-3.12.y

nothing to commit (working directory clean)

Hi Jan,

you are right. Maybe I made a mistake with git and now have the gravity (movie) effect: Detached sources and lost in space? ;-)

Hope there is time enough to find a solution for that soon. I'll let you know.

Georg (without having fun)

Hi Jan,

please have a look at http://blog.georgmill.de/2014/04/29/compile-wolfson-audio-card-driver-for-kernel-3-12-y-a-new-try/

Test and report,  please. Here I'm able to use the Wolfson card full duplex with jackd and calf-plugins. I routed the two onboard mics through calf reverb and then trough calf phaser to system playback. What an echooooooooo ;-)

With much more fun than ever !

Many thanks Georg

I used your kernel source code to create patch for Runeaudio with Wolfson Audio Card and Power-on-off circuit.

The only problem is in boot with "vc_cma: dma_declare_contiguous (11800000, d400000) failed", I used the workaround described in http://archlinuxarm.org/forum/viewtopic.php?f=31&t=6432

Otherwise, it works great, thanks for the great work.

Re: Instructions for compiling the wolfson audio card kernel drivers and supported use cases

Hi Georg,

So sorry. I am pretty new to Linux and the RPi. Is there a benefit to using your method over just flashing my pi with Wolfson's distro of raspbian with the drivers already installed? I understand by cross compiling the kernel, you can add the Wolfson drivers to an existing distro that you have on your RPi, but I am a new user. Am I better off just using Wolfson's prepackaged distribution? I want to use JACK on a headless setup for an audio FX unit. I will be writing the .cpp files using JACK's process callback. Thank you so much for your help

-Rob

Hi Rob,

it depends on what you want to do. If you want to develop your files on a stable kernel version (which you should do) you should make use of the precompiled image provided by wolfson. My version is an unofficial version for testing purposes only built upon an git snapshot. If you use my version you are ALONE! You will get no support from wolfson and from me. Sorry.

-Georg

"Happiness is lack of information"

Hi Georg,

Thank you so much for sharing the precompiled rt-kernel for raspbian! It works very well, but I do get a lots of:

delay of 228987.000 usecs exceeds estimated spare time of 11549.000; restart ...

...

I am wondering if you get the same output in the console (I am starting jackd1 headless). Here's the full story:

Wolfson Audio Card for Raspberry Pi - linux.autostatic.com

Do you have any idea how to fix this?

Thanks again!