ErosQ (both): avoid clipping due to DC offset bandaid

Set the maximum volume on both hosted and native ports
to -2 dB.

Verified behavior here on native and by borkitall on irc
for hosted.

Change-Id: I3aebc2bb4b9294a4137a33694c83139c0d76099a

2 files changed, 16 insertions, 3 deletions

diff --git a/firmware/export/eros_qn_codec.h b/firmware/export/eros_qn_codec.h
index ae04c66799..851ab63362 100644
--- a/firmware/export/eros_qn_codec.h
+++ b/firmware/export/eros_qn_codec.h
@@ -23,10 +23,16 @@
 #ifndef _EROS_QN_CODEC_H
 #define _EROS_QN_CODEC_H
 
+/*
+ * Note: Maximum volume is set one step below unity in order to
+ *       avoid overflowing pcm samples due to our DC Offset.
+ *
+ *       The DAC's output is hot enough this should not be an issue.
+ */
 #define PCM5102A_VOLUME_MIN -740
-#define PCM5102A_VOLUME_MAX 0
+#define PCM5102A_VOLUME_MAX -20
 
-/* a small DC offset appears to prevent play/pause clicking */
+/* a small DC offset prevents play/pause clicking due to the DAC auto-muting */
 #define PCM_DC_OFFSET_VALUE -1
 
 AUDIOHW_SETTING(VOLUME, "dB", 0, 2, PCM5102A_VOLUME_MIN/10, PCM5102A_VOLUME_MAX/10, 0)
diff --git a/firmware/export/erosqlinux_codec.h b/firmware/export/erosqlinux_codec.h
index 2ed1ae11cf..ecc10be924 100644
--- a/firmware/export/erosqlinux_codec.h
+++ b/firmware/export/erosqlinux_codec.h
@@ -3,9 +3,16 @@
 
 #define AUDIOHW_CAPS (LINEOUT_CAP)
 
+/* a small DC offset prevents play/pause clicking due to the DAC auto-muting */
 #define PCM_DC_OFFSET_VALUE -1
 
-AUDIOHW_SETTING(VOLUME, "dB", 0,  2, -74, 0, -40)
+/*
+ * Note: Maximum volume is set one step below unity in order to
+ *       avoid overflowing pcm samples due to our DC Offset.
+ *
+ *       The DAC's output is hot enough this should not be an issue.
+ */
+AUDIOHW_SETTING(VOLUME, "dB", 0,  2, -74, -2, -40)
 
 //#define AUDIOHW_NEEDS_INITIAL_UNMUTE