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Original question:

PCM2906C Digital Input not working

PCM2906CEVM-U: S/PDIF input doesn’t work.

Michael Sirkis
Prodigy 47 points
Part Number: PCM2906CEVM-U
Other Parts Discussed in Thread: DIT4192, PCM2906C

I’m testing a new pcb which uses a  DIT4192 to send S/PDIF to a PCM2906C. The PCM2906c is supposed to output the S/PDIF via USB.

Except I can’t get it to work.

 The analog inputs and outputs of the PCM2906c both work. But I don’t have any use for them.

 USB in to S/PDIF out works fine.

S/PDIF in to USB our doesn’t work.

Using a scope, I can see signal on the S/PDIF in pin. Using an audio analyzer on the same pin, it indicates that the signal is not copy protected and that it is 16 bits. Connecting a DAC to the same pin — the DAC outputs audio.

Can someone please explain why I am not getting a USB output?    

Regards,

Michael

  • 0
    TI__Mastermind 28705 points

    Hello Michael,

    Thanks for reaching out. 

    From my understanding your connection is as follows

    Since the DIT4192 is a SPDIF transmitter it can only output a SPDIF signal to the DIN of the PCM2906C. The DIT4192 would be transmitting the SPDIF signal as shown in datasheet figures 11-14.

    Based on the description in the post above, it seems like there is a packed mismatch between the DIT4192's data packet an the PCM2906C. I would recommend providing the PCM2906C with a packet that works and using a logic analyzer to assess the differences between the working packet and the DIT4192's packet which doesn't work. 

    The difference will likely be in the VUCP bits of the data packet shown in the figure below.

    These bits are set by the CUV data buffer shown in figure 2 of the datasheet.

    I hope this helps.

    Best,
    Andrew

  • +1
    Prodigy 47 points

    There is also a chip if front of the DIT4192. It is a DIR + SRC. This chip is the Master, the DIT4192  and PCM

  • +1 in reply to Michael Sirkis
    TI__Mastermind 28705 points

    Hello Michael,

    When the "resolve" button is clicked this closes the thread which means I didn't see this. Did you have follow-up questions? 

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 47 points

    I still can’t get audio to move from PCM2906 to computer via USB. How can I send you a schematic confidentiality?

    Thanks,

    Michael

  • 0 in reply to Michael Sirkis
    TI__Mastermind 28705 points

    Hi Michael, 

    I will reach out to you at the email listed in your myTI account.