DAC - mxmxmx/terminal_tedium GitHub Wiki

#testing the codec / setting up the PCM5102a (or wm8731)

to set up the codec, either run the install.sh script or do it manually, specifically:

1) /boot/config.txt

  • make sure you've added the codec device tree overlay to /boot/config.txt (see here)

2) asound.conf

  • configure /etc/asound.conf:

sudo nano /etc/asound.conf

  • then add:
pcm.!default  {
  type hw card 0
}

ctl.!default {
  type hw card 0
}
  • save.

3) amixer

  • if/when using wm8731, open alsamixer and unmute "Output Mixer HiFi Playback Switch" manually. or do:

amixer cset numid=13 on

  • which should result in:
numid=13,iface=MIXER,name='Output Mixer HiFi Playback Switch'
  ; type=BOOLEAN,access=rw------,values=1
  : values=on

  • (also double-check the master-volume and ADC settings: run amixer and look out for Master Playback Volume, Line Capture Switch, and Capture Volume). alternatively, run alsamixer, press tab to go the capture settings and select Line (first select the column saying Line, then press the space bar).

  • store the settings:

alsactl store

4) aplay/test

  • reboot. running aplay -l you should now see:
**** List of PLAYBACK Hardware Devices ****

card 0: sndrpihifiberry [snd_rpi_hifiberry_dac], device 0: HifiBerry DAC HiFi pcm5102a-hifi-0 [] 
  Subdevices: 0/1
  Subdevice #0: subdevice #0
  • or corresponding message for wm8731:
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpiproto [snd_rpi_proto], device 0: WM8731 HiFi wm8731-hifi-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
  • if that's not what you see (but some additional cards), blacklist the onboard audio: create a file called raspi-blacklist.conf in /etc/modprobe.d/ (if it's not already there) and add this line:

blacklist snd_bcm2835

  • reboot.

5) play test wav

  • let's test the DAC is working. move a wav file (stereo, 16 bit/44.1kHz) onto your rpi/odroid (with scp, say). plug a patchcable(s) into the L and/or R outputs.

  • run aplay /path_to_file/file.wav. you should see this:
    Playing WAVE 'file.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo.

  • respectively

Playing WAVE 'file.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo.

  • ... more importantly, you should also hear some sound, nice and clean, from both the L and R outputs

  • alternatively, use the speaker-test app, eg. speaker-test -t sine -f 440 -c 2 -Dplug:sysdefault ; that should result in a 440Hz test tone sent to the left and right outputs, alternatingly.

6) testing the ADC (wm8731 only)

  • make sure you've got the alsa settings right (see above, #3), and you have the patch called passthru.pd ready.

  • start the patch: eg. sudo pd -rt -r 48000 -nogui passthru.pd. this is basically just feeding the signal through pd (plus some high-pass and attenuation):

  • now, feed a signal into the left input, say a sine wave; as there's no onboard attenuation, typically it'll make sense to use an attenuator such as A183-1. the signal should be present at both the left and right outputs (R_in is normalled to L_in); next, the right input (in which case the signal should be present at R_out only). it shouldn't clip and not look distorted (when you look at it with, say, a scope).

  • alternatively, to inspect things, you can record the input signal with arecord. e.g. arecord -f dat -vvv test.wav; record it for a few seconds, then play the file with aplay test.wav (and listen to it / look at it with a scope / inspect the recording in your DAW). you can also record/loopback the output signal. for instance, say you have prepared a file called sinetest.wav. then run a cable from the left output back into the left input and do arecord -f dat -vvv test.wav | aplay -Dplug:default sinetest.wav. aplay test.wav will play the recording.