Pi Zero PWM sound

[MikkelM]

I am trying to get audio to work over PWM pins, but without luck

I have followed the tricks described here, by setting GPIO pins.

http://forum.tinycorelinux.net/index.php?topic=20550.0

My image (the SDcard) works as intended on an Pi 3 model B

I get this error on the Pi Zero

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tc@box:~$ aplay -l
aplay: device_list:268: no soundcards found...

Here is my config.txt

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# For more options and information see
# http://www.raspberrypi.org/documentation/configuration/config-txt.md
# Some settings may impact device functionality. See link above for details

[PI0]
initramfs 9.0.3.gz followkernel
kernel kernel4922.img
cmdline cmdline.txt

[PI1]
initramfs 9.0.3.gz followkernel
kernel kernel4922.img
cmdline cmdline.txt

[PI2]
initramfs 9.0.3v7.gz followkernel
kernel kernel4922v7.img
cmdline cmdline.txt

[PI3]
initramfs 9.0.3v7.gz followkernel
kernel kernel4922v7.img
cmdline cmdline3.txt

[ALL]

#----------------------------------------------------
# Enable peripheral buses

dtparam=i2c=on,spi=on,i2s=on

# Enable serial console

enable_uart=1

[PI3]
dtoverlay=pi3-disable-bt

[ALL]
 dtparam=audio=on
 dtoverlay=pwm-2chan,pin=18,func=2,pin2=13,func2=4
 gpu_mem=16

Cheers

Mikkel

[Paul_123]

Did you add the appropriate kernel driver.  It is not included by default.

AFAIK, it is not included in any extension, but would be in the module tar package.

[MikkelM]

Hi Paul.

Thank you. Can you hint me were to find modular tar package and how to add the right kernel driver.

Yes I am a newbie.

Cheers

Mikkel

[Rich]

Hi MikkelM

... Can you hint me were to find modular tar package ...

ARM6:
http://tinycorelinux.net/9.x/armv6/releases/RPi/src/kernel/
ARM7:
http://tinycorelinux.net/9.x/armv7/releases/RPi/src/kernel/

[MikkelM]

Ok, and how do I do it? Do I need to compile a new kernel?
And what do I need to include from the modular package, I can see there is a folder called sound.

I have used the newest build from here http://tinycorelinux.net/9.x/armv6/releases/RPi/

As I mentioned above, it works perfectly with PWM sound on the RPI 3, which I started out to use.

The whole setup is for an art project where we are going to use Pi zeros.

Thanks

Mikkel

[Paul_123]

I would compare drivers loaded using when everything is working on the Pi3, then again with the zero, and compare.

I have no experience with PWM audio.

[MikkelM]

I can see I miss this on the Zero compared to the Pi3

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snd_bcm2835            23123  0
snd_pcm                97468  1 snd_bcm2835
snd_timer              23881  1 snd_pcm
snd                    70476  3 snd_bcm2835,snd_pcm,snd_timerI am just swapping the SDcard around on the two boards.

when I write this on the Zero

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modprobe snd
modprobe: module snd not found in modules.depI get no failure on the Pi3.

But the PiZero and Pi3 is loading different kernels in the config.txt, and the lib/modules are way different.

Any ideas?

Cheers

Mikkel

[Rich]

Hi MikkelM
If you unpack:
http://tinycorelinux.net/9.x/armv6/releases/RPi/src/kernel/4.9.22-piCore_modules.tar.xz
you'll find it contains:

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lib/modules/4.9.22-piCore/kernel/sound/core/snd.ko
lib/modules/4.9.22-piCore/kernel/sound/core/snd-timer.ko
lib/modules/4.9.22-piCore/kernel/sound/core/snd-pcm.ko
lib/modules/4.9.22-piCore/kernel/sound/arm/snd-bcm2835.koYou'll need to either copy them to  /lib  and back them up or create an extension out of them.

[Rich]

Hi MikkelM
I'm not certain, but you may also need to run:

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sudo depmodafter adding the files to the file system.

[MikkelM]

Hi Rich.

I have copied the files and ran the depmod command, but how do I get the files to stay in the /lib folder.

Or simply how do I add the needed modules to the Kernel package.

It seems I am getting closer.

Thanks.

Mikkel

[Rich]

Hi MikkelM
After copying the files to  /lib  you could add the following lines to  /opt/.filetool.lst:

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lib/modules/4.9.22-piCore/kernel/sound/core/snd.ko
lib/modules/4.9.22-piCore/kernel/sound/core/snd-timer.ko
lib/modules/4.9.22-piCore/kernel/sound/core/snd-pcm.ko
lib/modules/4.9.22-piCore/kernel/sound/arm/snd-bcm2835.koand then run a backup like this:

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filetool.sh -b

[MikkelM]

Yeah. It works.
My bootlocal is somehow a mess now

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depmod
and then modprobe to the individual modules
amixer cset numid=3 1
gpio -g mode 18 ALT5
gpio -g mode 13 ALT0

Are there anyway to use dtoverlay when loading drivers?

[Rich]

Hi MikkelM
You shouldn't need to  "modprobe the individual modules".  Try:

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modprobe snd-bcm2835Since  snd-bcm2835  depends on the other 3 modules,  modprobe  should be loading the other 3 automatically.

[Paul_123]

Are you sure you loaded the alsa-modules-KERNEL.tcz package.

When you download the sound stuff on your RPI 3, it would have only downloaded the package for the armv7 boards.