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PCM2903C: S/PDIF in to USB out not work

AJ Cheng
Genius 3615 points
Part Number: PCM2903C
Other Parts Discussed in Thread: PCM2902C,

Hello.

We used PCM2902C EVM check S/PDIF in to USB out function is not work. S/PDIF input is from Audio pattern Gen. Audio input to USB is OK.

I think S/PDIF maybe is not lock. How can I know S/PDIF is lock or not lock in PCM2902C. Please kindly help us. Thanks~

  • 0
    TI__Guru 57800 points

    Hi , AJ,

    As you mention, it seems the S/PDIF signal that is going to the device is not locked, hence he audio data sent through USB interface is coming from the ADC. The device will change the audio output source to the S/PDIF input as soon as the signal is locked.

    Unfortunately, this part doesn't  have a way to identify if the S/PDIF source is locked or not. Another thing to try would be to check if the input signal has the copyright bit asserted, if so, then the device will select the ADC as the source.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Genius 3615 points

    Dear Diego.

    I do not understand "copyright bit asserted". I think the S/PDIF signal is from Audio Generator are Standard signal.

    Below are more information for you reference. Please kindly give me some advice. Thanks for help~

  • 0 in reply to AJ Cheng
    TI__Guru 57800 points

    Hi, AJ,

    My comment was based on the fact that S/PDIF signals have the capability of adding a copyright bit for the data transmission, but actually it seems it is not the cause of this issue. I responded yesterday to this post, I guess is part of the same issue. Once Shu-Cheng posted the test setup, I was able fo identify the root cause.

    For the PCM2903C, the S/PDIF input used should have the same sampling rate as the record sampling rate of the PCM2903C, this is configured by the host. For example, in Windows, you need to go to Recording Devices, then select the USB AUDIO CODEC [PCM2903C], then go to the Advanced tab and change the Default Format to match the sampling rate of the S/PDIF input. By default, it seems that the PCM2903C is configured by windows to have a sampling rate of 44.1KHz, so you can also try changing the sampling rate of the S/PDIF signal to 44.1KHz.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer