ADAU1442 SPDIF Lock Bit

Beni Question

Jun 19, 2013 00:00

Hi,

When connecting a SPDIF Signal to the ADAU1442 the first time after power on there is a nasty click.

Question: Is it possible to access the SPDIF Lock Bit ( Reg 0xE0C9) from inside the ADAU1442 program to trigger a delayed UnMute ?

Bernd

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ADIApproved Reply

Jun 19, 2013 00:00

Hi Bernd,

Will the S/PDIF source be "hot-plug" in your system, meaning that the user can plug it in and out at any time?

Any time there is a discontinuity in a signal, there will be an associated pop sound. So, if the S/PDIF source can be hot-plugged, this is kind of unavoidable.

The S/PDIF lock bit cannot be read from the DSP core itself.

However, you could do some smart auto-muting if the signal is not present on the input.

Perhaps something like this would work. It uses a DC blocker and peak envelope on the input to detect if the signal is present, and uses a slew volume control to un-mute the signal when it appears.

b2e94be173a785b6ce317a371934f773.jpg-450x213.jpg

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Beni Reply

Jun 19, 2013 00:00

Hi Brett,

thanks for your fast response.

Yes there is of course a little pop and click when hot-plugging the S/PDIF input but this is not a problem.

The problem is the extremely loud noise when a S/PDIF signal ( even with no audio ) is connected the first time after power up.

I have a workaround by reading the S/PDIF Lock bit and do a delayed un mute from outside the dsp with a uC.

It just would have been nice to have access to the dsp registers from the dsp itself because it would be much faster than the management from an external Controller.

Anyway thanks for your help.

Best regards

Bernd

Von: BrettG analogvm-admin@analog-vm.hosted.jivesoftware.com

Gesendet: Mittwoch, 19. Juni 2013 15:45

An: Nimmrichter, Bernd

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Re: ADAU1442 SPDIF Lock Bit

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ADIApproved Reply

Jun 19, 2013 00:00

Hi Bernd,

I assume you are routing the S/PDIF input signal through the ASRCs, since external S/PDIF sources are generally asynchronous to the DSP.

I think this pop noise is from the ASRCs themselves, as they automatically detect the incoming sample rate. In that case, you could use either the S/PDIF lock bit or the corresponding ASRC lock bit to trigger the delayed un-mute.

I hope that helps.

Thanks,
Brett

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