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Audio intermittently plays out of wrong ad1939 D/A output

Question asked by svacca@valcom.com on Jan 2, 2018
Latest reply on Jan 12, 2018 by DaveThib

My system includes a bf537, ad1939 CODEC, uClinux bf537-0.3-3.0.8-ADI-2011R1, and ALSA.

 

Audio is continuously sent out of all 8 of the ad1939 CODEC's D/A output channels,
with no problems, except, occassionally, maybe once per day, the audio channels
seem to get shifted, with audio playing out of the wrong D/A output channel(s).
For example, a tone, which normally is constantly playing out of output 8,
starts playing out of output 1, instead. And the audio, which was normally playing
out of output 1, is not playing, though, possibly it is playing out of another unused
output. This can stay in this condition, for minutes, and then it always (eventually)
self-corrects, and all is back to normal.

 

The Volume (gain), of the ad1939 output channels, is frequently updated, to change
a channel's gain to a certain level, for a few secs, and then it is changed back
to its normal operating Volume (gain) level.

 

Twice, when the above-mentioned condition occurred, I executed a piece of test
code, which writes to the ad1939, to change the Volume (gain), for output 1,
for example, and immediately, all audio started playing normally, again, out of the proper
output channels.

 

- Are there any constraints, regarding changing the ad1939 Volume (gain) levels?
- Does anything have to be disabled, before a channel's Volume (gain) register
  is written to?
- Is there a time duration, before and after the change is made? Special timing?

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