How to Config Alsa Mixer Controls for a DFSDM Sound Card

[Farid Azhar]

We’ve successfuly configured a digital Microphone on our custom board (based on OSD32MP1-RED) as a “STM32MP15DK” dfsdm sound card and able to record audio using “arecord” command. The recorded audio volume is very low and we find no way to increase it.

We added the /etc/asound.conf file

The contents of amixer utility are empty.

The /var/lib/alsa/asound.state configuration file is also empty.

There is no STM32MP15DK card specific alsa-lib configuration file “STM32MP15DK.conf” in /usr/share/alsa/cards/ directory as stated in Soundcard_configuration wiki

How do we assign the “amixer” contents for the STM32MP15DK dfsdm sound card to modify the audio recording volume.

Here are some of the audio commands output:

debian@device-1293a743:~$ sudo arecord -v -r 16000 -f S16_LE -d 20 sound_S16_16khz.wav Recording WAVE 'sound_S16_16khz.wav' : Signed 16 bit Little Endian, Rate 16000 Hz, Mono Plug PCM: Hardware PCM card 0 'STM32MP15-DK' device 0 subdevice 0 Its setup is: stream : CAPTURE access : RW_INTERLEAVED format : S16_LE subformat : STD channels : 1 rate : 16000 exact rate : 16000 (16000/1) msbits : 16 buffer_size : 6144 period_size : 1024 period_time : 64000 tstamp_mode : NONE tstamp_type : MONOTONIC period_step : 1 avail_min : 1024 period_event : 0 start_threshold : 1 stop_threshold : 6144 silence_threshold: 0 silence_size : 0 boundary : 1610612736 appl_ptr : 0 hw_ptr : 0 debian@device-1293a743:~$ debian@device-1293a743:~$ ls -al *.wav -rw-r--r-- 1 root root 640044 Mar 20 20:55 sound_S16_16khz.wav debian@device-1293a743:~$ => Volume is very low in this audio debian@device-1293a743:~$ sudo arecord -l **** List of CAPTURE Hardware Devices **** card 0: STM32MP15DK [STM32MP15-DK], device 0: 4400d000.dfsdm:filter@0:dfsdm-dai-dmic-hifi dmic-hifi-0 [] Subdevices: 1/1 Subdevice #0: subdevice #0 debian@device-1293a743:~$ debian@device-1293a743:~$ sudo arecord -L null Discard all samples (playback) or generate zero samples (capture) default mic hw:CARD=STM32MP15DK,DEV=0 STM32MP15-DK, Direct hardware device without any conversions plughw:CARD=STM32MP15DK,DEV=0 STM32MP15-DK, Hardware device with all software conversions sysdefault:CARD=STM32MP15DK STM32MP15-DK, Default Audio Device dsnoop:CARD=STM32MP15DK,DEV=0 STM32MP15-DK, Direct sample snooping device debian@device-1293a743:~$ debian@device-1293a743:~$ sudo amixer -v amixer version 1.2.4 debian@device-1293a743:~$ debian@device-1293a743:~$ sudo amixer debian@device-1293a743:~$ debian@device-1293a743:~$ sudo amixer scontrols debian@device-1293a743:~$ debian@device-1293a743:~$ sudo amixer scontrols debian@device-1293a743:~$ debian@device-1293a743:~$ sudo amixer scontents debian@device-1293a743:~$ debian@device-1293a743:~$ sudo amixer controls debian@device-1293a743:~$ debian@device-1293a743:~$ sudo amixer contents debian@device-1293a743:~$ debian@device-1293a743:~$ cat /var/lib/alsa/asound.state state.STM32MP15DK { control { } } debian@device-1293a743:~$ debian@device-1293a743:~$ cat /etc/asound.conf pcm.!default { type asym capture.pcm "mic" } pcm.mic { type plug slave { pcm "hw:0,0" } } debian@device-1293a743:~$ debian@device-1293a743:~$ sudo alsactl -v alsactl version 1.2.4 debian@device-1293a743:~$ debian@device-1293a743:~$ cat /sys/bus/iio/devices/iio:device9/name dfsdm-pdm0 debian@device-1293a743:~$ debian@device-1293a743:~$ ls -al /usr/share/alsa/cards/STM32*.conf ls: cannot access '/usr/share/alsa/cards/STM32*.conf': No such file or directory debian@device-1293a743:~$ Any help is much appreciated. /Farid.

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debian@device-1293a743:~$ sudo arecord -v -r 16000 -f S16_LE -d 20 sound_S16_16khz.wav Recording WAVE 'sound_S16_16khz.wav' : Signed 16 bit Little Endian, Rate 16000 Hz, Mono Plug PCM: Hardware PCM card 0 'STM32MP15-DK' device 0 subdevice 0 Its setup is:   stream       : CAPTURE   access       : RW_INTERLEAVED   format       : S16_LE   subformat    : STD   channels     : 1   rate         : 16000   exact rate   : 16000 (16000/1)   msbits       : 16   buffer_size  : 6144   period_size  : 1024   period_time  : 64000   tstamp_mode  : NONE   tstamp_type  : MONOTONIC   period_step  : 1   avail_min    : 1024   period_event : 0   start_threshold  : 1   stop_threshold   : 6144   silence_threshold: 0   silence_size : 0   boundary     : 1610612736   appl_ptr     : 0   hw_ptr       : 0 debian@device-1293a743:~$   debian@device-1293a743:~$ ls -al *.wav -rw-r--r-- 1 root root 640044 Mar 20 20:55 sound_S16_16khz.wav debian@device-1293a743:~$ => Volume is very low in this audio   debian@device-1293a743:~$ sudo arecord -l **** List of CAPTURE Hardware Devices **** card 0: STM32MP15DK [STM32MP15-DK], device 0: 4400d000.dfsdm:filter@0:dfsdm-dai-dmic-hifi dmic-hifi-0 []   Subdevices: 1/1   Subdevice #0: subdevice #0 debian@device-1293a743:~$   debian@device-1293a743:~$ sudo arecord -L null     Discard all samples (playback) or generate zero samples (capture) default mic hw:CARD=STM32MP15DK,DEV=0     STM32MP15-DK,     Direct hardware device without any conversions plughw:CARD=STM32MP15DK,DEV=0     STM32MP15-DK,     Hardware device with all software conversions sysdefault:CARD=STM32MP15DK     STM32MP15-DK,     Default Audio Device dsnoop:CARD=STM32MP15DK,DEV=0     STM32MP15-DK,     Direct sample snooping device debian@device-1293a743:~$   debian@device-1293a743:~$ sudo amixer -v amixer version 1.2.4 debian@device-1293a743:~$   debian@device-1293a743:~$ sudo amixer debian@device-1293a743:~$   debian@device-1293a743:~$ sudo amixer scontrols debian@device-1293a743:~$   debian@device-1293a743:~$ sudo amixer scontrols debian@device-1293a743:~$   debian@device-1293a743:~$ sudo amixer scontents debian@device-1293a743:~$   debian@device-1293a743:~$ sudo amixer controls debian@device-1293a743:~$   debian@device-1293a743:~$ sudo amixer contents debian@device-1293a743:~$   debian@device-1293a743:~$ cat /var/lib/alsa/asound.state state.STM32MP15DK { control { } } debian@device-1293a743:~$   debian@device-1293a743:~$ cat /etc/asound.conf pcm.!default { type asym capture.pcm "mic" } pcm.mic { type plug slave { pcm "hw:0,0" } } debian@device-1293a743:~$   debian@device-1293a743:~$ sudo alsactl -v alsactl version 1.2.4 debian@device-1293a743:~$   debian@device-1293a743:~$ cat /sys/bus/iio/devices/iio:device9/name dfsdm-pdm0 debian@device-1293a743:~$   debian@device-1293a743:~$ ls -al /usr/share/alsa/cards/STM32*.conf ls: cannot access '/usr/share/alsa/cards/STM32*.conf': No such file or directory debian@device-1293a743:~$   Any help is much appreciated.   /Farid.

[Neeraj Dantu]

Hey Farid,

My apologies for the delayed response. Did you take a  look at the sound card configuration files from meta-st-stm32mp here: https://github.com/STMicroelectronics/meta-st-stm32mp/tree/kirkstone/recipes-bsp/alsa?

Since you are using the DFSDM interface same as STM32MP157C-EV1, I would look at what the STM32MP157C-EV1 is using for the configuration files that are missing in your system.

Best,

Neeraj

[Author]

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