Differences

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--- mcimx6q-sbc [2017/10/04 17:55] – [Playing sample mono .wav files] rpjday
+++ mcimx6q-sbc [2017/10/04 18:34] (current) – [Headphone mixers] rpjday
@@ Line 56: / Line 56: @@
 </code>
-==== Playing sample .wav files ====
+==== Playing sample .wav files (both mono and stereo) ====
 With no other sound or CODEC configuration, first, turn up headphone volume:
@@ Line 78: / Line 78: @@
 For ''.wav'' files under ''/home/root/'', mono files play only on left HP channel, stereo ''.wav'' files play on both channels, so this verifies that both HP channels work, at least with stereo files.
-==== Playing stereo files ====
-Copy more sample files to target:
-<code>
--rw-r--r--    1 root     root         53544 Oct  3  2017 pcm0808m.wav
--rw-r--r--    1 root     root        107042 Oct  3  2017 pcm0808s.wav
--rw-r--r--    1 root     root        107042 Oct  3  2017 pcm1608m.wav
--rw-r--r--    1 root     root        214040 Oct  3  2017 pcm1608s.wav
-</code>
-Mono files play only on left, stereo files play on both.
 ==== Switching channels for mono files ====
-By default:
+To verify we can send digital input to the right channel, the digital audio interface supports swapping the channels immediately upon input:
 <code>
@@ Line 102: / Line 91: @@
 </code>
-Switch, so mono files play on right headphone:
+Switch, so mono files play only on right headphone:
 <code>
@@ Line 111: / Line 100: @@
 </code>
-Turn off for now.
+Verified that that works, so turn this off. All this verifies is that we can route digital input to the right headphone.
 ==== Headphone mixers ====
@@ Line 131: / Line 119: @@
 </code>
-For the left channel, we can use the mixer and just feed the left channel into the mixer, effectively getting the same result:
+The above represents bypassing the headphone mixers on both channels. Experiment with just mono files and try to set the left channel to come through the mixer for that channel.
+First, switch to have HPOUTL come from the mixer, not directly from DACL. This should kill the output to the left HP channel (until we configure the mixer properly):
+<code>
+# amixer cset name="HPOUTL PGA" Mixer
+numid=95,iface=MIXER,name='HPOUTL PGA'
+  ; type=ENUMERATED,access=rw------,values=1,items=2
+  ; Item #0 'DAC'
+  ; Item #1 'Mixer'
+  : values=1
+</code>
 <code>
-# amixer set "HPOUTL PGA" Mixer
+# amixer get "HPOUTL PGA"
 Simple mixer control 'HPOUTL PGA',0
   Capabilities: enum
@@ Line 141: / Line 140: @@
 </code>
-This effectively kills the left output channel until we set the mixer properly:
+Indeed, playing mono files now produces no output at all (which is expected).
+Now configure HPMIXL to get input from DACL:
 <code>
-# amixer sget "HPMIXL DACL"
+# amixer set "HPMIXL DACL" on
 Simple mixer control 'HPMIXL DACL',0
   Capabilities: pswitch pswitch-joined
   Playback channels: Mono
-  Mono: Playback [off]
+  Mono: Playback [on]
 </code>
+But playing a mono wav file ... no sound. Not good. Oh, wait, must turn on headphone mixer:
 <code>
-# amixer sset "HPMIXL DACL" on
+# amixer set "Headphone Mixer" on,on
-Simple mixer control 'HPMIXL DACL',0
+Simple mixer control 'Headphone Mixer',0
-  Capabilities: pswitch pswitch-joined
+  Capabilities: pswitch
-  Playback channels: Mono
+  Playback channels: Front Left - Front Right
-  Mono: Playback [on]
+  Mono:
+  Front Left: Playback [on]
+  Front Right: Playback [on]
 </code>
+In short:
+  * switch ''HPOUTL PGA'' to "Mixer"
+  * enable ''HPMIXL DACL''
+  * enable "Headphone Mixer"
+==== Playing mono .wav files on both headphone channels ====
+Seems simple enough:
+  * Switch ''HPOUTR PGA'' to "Mixer"
+  * Make sure "Headphone Mixer" is enabled
+  * Enable ''HPMIXR DACL''