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Digital mute being automatically set for SGTL5000 with no user input

Question asked by ralph__ on Sep 30, 2015
Latest reply on Oct 6, 2015 by ralph__

I'm investigating a problem with the SGTL5000 on our custom board. We are using Pulseaudio and find that if the LINE-IN of the SGTL5000 is not connected to an external earth, it will automatically enable its digital mute *on the LINE-OUT*. It is totally unclear how this happens as I am monitoring the I2C bus transactions and the last time the digital mute is unset we find it is immediately read back as correctly unset. (Digital mute == DAC_MUTE_LEFT and DAC_MUTE_RIGHT)

 

When we find the digital mute to be self-setting, we also see the VOL_BUSY_DAC_LEFT/VOL_BUSY_DAC_RIGHT bits to be staying high and never going low.

 

Has anyone else come across this or can suggest why these bits are automatically being set? It doesn't make a lot of sense that the audio input must be grounded for the audio output not to be self-muted.

 

Thanks,
Ralph

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