Microphone input on efus A9 starterkit

    Hi all,


    I'm testing audio input and output on efus A9 starterkit. I upgraded the board to the latest image (V2.1) and output works (well, only the left speaker but it will be mono anyway). But I'm not able to record any usable sound.


    I'm using arecord for recording:

    Code
    1. arecord -f cd -d 3 recording.wav


    and aplay for playback:

    Code
    1. aplay recording*


    I was trying tu use different audio settings via 'alsamixer' (mic level, input source, (un)mute sources, ...) but without effect. I think that connection is somehow correct because when input is set to LINE_IN there is nothing (i.e. clear silence). With MIC_IN input there is at least some small noise and touching the jack (on the male-male audio cable) makes noise.


    I already tried:
    - two different headsets (both work on my dekstop PC)
    - playback recording from efus on my desktop PC
    - upgrade to the latest image - it helped with playback and error when switching input via alsamixer from MIC_IN to LINE_IN is gone


    I probably miss something so could you please help me? Maybe my mixer setting is just wrong, so output of 'alsactl store' on your board will help me.


    Thanks a lot,


    Tomas Novotny

    We are evaluating this at the moment. As soon as we have any information, we will let you know.


    Your F&S Support Team

    F&S Elektronik Systeme GmbH
    As this is an international forum, please try to post in English.
    Da dies ein internationales Forum ist, bitten wir darum, Beiträge möglichst in Englisch zu verfassen.

    Hi,
    We found the problem. There is a hardware bug on the efus skit that concerns the mic input.
    The female connector on efus starterkit uses the signal provided by the middle ring (=right signal) of the jack.
    (imagine a stereo jack with three rings tip=left signal, middle ring=right signal, last ring=ground)


    If you have a mono jack you only have two rings: tip=left, rest=ground.
    So where the right signal was before you now have ground signal too.
    Because the left signal is not connected signals we want to record get lost.


    As a workaround you can use a microphone with 'stereo' jack if you have or you can build an adapter that connects the middle ring of a male stereo jack to the 'tip of a female jack'
    With a workaround like this we could record sound with default settings of amixer using arecord.
    (e.g.: arecord -c 2 -r 48000 -f s16_le -d 3 test.wav).


    Please note that this bug only affects the efus skit not the efus module. So on your baseboard its no problem.


    If this should not work for you please let us now.


    Your F&S Support Team

    F&S Elektronik Systeme GmbH
    As this is an international forum, please try to post in English.
    Da dies ein internationales Forum ist, bitten wir darum, Beiträge möglichst in Englisch zu verfassen.

    Hi,


    thanks, that was it. I'm able to record the sound using my microphone. The recording is very silent and there is noise, but it is most probably caused by my microphone (it some microphone from other board and requires some electronics around).


    I also tested recording with standard Logitech headset with "stereo" 3.5 mm jack but it doesn't work. I don't care there because I won't it use that way.


    Thanks for the support and best regards,


    Tomas