custom audio card on beaglebone

[crazyiop at gmail.com]

Hi Anish,

thanks for giving me some thougt. 
Here is what I found:

On Sun, Jan 22, 2017 at 03:47:54PM -0800, anish singh wrote:
> On Sun, Jan 22, 2017 at 1:38 PM, jo <crazyiop at gmail.com> wrote:
> 
> > root at beaglebone:~# aplay -v Pom\ Pom.wav
> > Playing WAVE 'Pom Pom.wav' : Signed 32 bit Little Endian, Rate 44100 Hz,
> > Stereo
> > ALSA <-> PulseAudio PCM I/O Plugin
> > Its setup is:
> >   stream       : PLAYBACK
> >   access       : RW_INTERLEAVED
> >   format       : S32_LE
> >   subformat    : STD
> >   channels     : 2
> >   rate         : 44100
> >   exact rate   : 44100 (44100/1)
> >   msbits       : 32
> >   buffer_size  : 22050
> >   period_size  : 5512
> >   period_time  : 125000
> >   tstamp_mode  : NONE
> >   period_step  : 1
> >   avail_min    : 5512
> >   period_event : 0
> >   start_threshold  : 22050
> >   stop_threshold   : 22050
> >   silence_threshold: 0
> >   silence_size : 0
> >   boundary     : 1445068800
> >
> > #nothing play and the above stay displayed -as is- until I ctrl-c
> >
> 
> Possible that you have not turned on the mixer controls i.e.
> enabling the volume?
> 
> Check sw_ptr and hw_ptr and see if those are increasing or not?
> 
> Probe the I2S lines and see if there is any data?
> 
> 

So first, the above command in fact do finish after the length of the file (I
thought I took a much smaller test sample..)

The mixer control were all on and volume to the max.
I don't have a scope, but you made me realize that I'm clueless in front
of my problem without one... So I finnaly found an access to one. The measure
show that the input clock of the pll (mclk) is just non-existant. 
I now know what to look for.

I tried to find a reference to those sw_ptr and hw_ptr somewhere,
without success, what are they and where can I find/probe them ?

Thanks!!
Jonathan.