[alsa-devel] [PATCHv4 0/2] McBSP: OMAP3: Add sidetone feature

[Eero Nurkkala]

On Fri, 2010-02-19 at 14:39 +0100, ext Jarkko Nikula wrote:
> On Fri, 19 Feb 2010 10:34:32 +0200
> Peter Ujfalusi <peter.ujfalusi at nokia.com> wrote:
> 
> > I'm not sure, but you might need to configure the taps as well to have the 
> > correct sidetone.
> > Also I have a recollection, that the McBSP sidetone requires DSP mode (TDM) in 
> > order to operate correctly, so on Beagle you might need to set up 4 channel 
> > mode. And how the channel mapping in 4 channel mode works in McBSP sidetone is 
> > another matter...
> > 
> It seems to work with I2S too.
> 

For both channels? I don't recall so.. and for the one channel only, the
FIR doesn't behave expectedly? (maybe this works [1,0,..0], but more
sophisticated ones may not..)

> I think I forgot to enable control 'McBSP2 Sidetone' when I last time
> tried this set (v1 or v2). But now my null test below works and I can
> hear that the level is changing when I adjust the volumes with amixer.
> 
> echo 32767 >/sys/devices/platform/omap-mcbsp.2/st_taps
> 
> arecord -f dat >/dev/null |aplay -f dat /dev/zero
> 
> amixer set -D hw:0 'McBSP2 Sidetone Channel 0' 32700
> amixer set -D hw:0 'McBSP2 Sidetone Channel 0' 327
> amixer set -D hw:0 'McBSP2 Sidetone Channel 0' -- -32700
> 
>