ALSA input error (snd_pcm_open): No such file or directory - Problem with running Pd with ALSA

Question

I am pretty new to Raspberry Pi, so sorry if I might be not clear on something. I am trying to set the Raspberry Pi 3 to work running a Pure Data patch while communicating with two Arduino UNO, and getting it work just plugging it, so running the patch auto-starting after boot. There are so many things I would like to ask, but I'll remain strict to the topic, also one of my first problem. I switched to Patchbox OS cause I need a minimal system for audio working. I am now using Pure Data running with jack (Pd->media->jack) cause it is not working with ALSA, but it seems to me that running jack is not the properly way: clicks and pops are showing up also if CPU meter is between 15% and 25%. So I started searching for some solution. I found in this site another related-question with a well explained answer: here. The problem with that comes just in the first steps, after calling

 patch@patchbox:~ $ cat /proc/asound/cards
 0 [ALSA           ]: bcm2835_alsa - bcm2835 ALSA
                      bcm2835 ALSA
 1 [USB            ]: USB-Audio - Scarlett 2i4 USB
                      Focusrite Scarlett 2i4 USB at usb-3f980000.usb-1.5, high speed

I call amixer this is the results:

amixer -c 1
Simple mixer control 'Internal Validity',0
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [on]

So the system is not recognising real ins and outs of my audio interface. Also there is this problem with Pd, that when I chose ALSA as driver (Pd->media->ALSA) I get the problem reported on the title [ALSA input error (snd_pcm_open): No such file or directory] I hope I have been clear, Thanks to all

Answer 1

I've searched the Pd mailinglist archive for this ALSA error and found this post, Re: [PD] alsa : Invalid value for card, by IOhannes zmölning:

iirc, there's a problem if the cards are not in consecuritve order, starting with 0.

e.g. my devices are

$ cat /proc/asound/cards
 0 [DSP            ]: H-DSP - Hammerfall DSP
                      RME Hammerfall HDSP 9652 at 0xf3100000, irq 22
 1 [MID            ]: HDA-Intel - HDA Intel MID
                      HDA Intel MID at 0xf3420000 irq 33
 2 [NVidia         ]: HDA-Intel - HDA NVidia
                      HDA NVidia at 0xf3000000 irq 17
$

which means I have 3 devices with IDs 0, 1 & 2.

if however, you have something like

$ cat /proc/asound/cards
 1 [NVidia         ]: HDA-Intel - HDA NVidia
                      HDA NVidia at 0xf3000000 irq 17
$

then you are missing the device #0, and Pd gets into trouble.

a couple of workarounds:

• use jack to talk with the soundcard, so Pd doesn't need to know

• make sure that the card numbers start with 0 (and are consecutive, in case you want to access a not-first card); this most likely involves tweaking some kernel module parameters (for the soundcards to be loaded), and maybe some udev rules.

a reply by Nicolas Montgermont shows a solution:

editing /lib/modprobe.d/aliases.conf and changing:

options snd-usb-audio index=-2

to

options snd-usb-audio index=0

make the card number to 0 and works in pd with alsa.

That said, in your provided cat /proc/asound/cards output the cards are in consecutive order, so the problem might actually be different.