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PCM1794A: Sharing PCM1794 between DIR9001 and PCM2707

Nebojsa Zdravkovic
Prodigy 90 points
Part Number: PCM1794A
Other Parts Discussed in Thread: DIR9001, , SN74LVC157A

Hi, is it possible to simply share I2S bus between DIR9001 and PCM1794A with resistors in the path, or is it necessary to use multiplexer? In case of multiplexer, which part would be recommended, assuming auto switching is required, with priority given to DIR9001 with toslink input.

  • 0
    TI__Guru 53633 points

    Hi Nebojsa,

    You will need to have some kind of switch between the two.  If both devices were sourcing a signal (which they usually do, just with zero data), then there will be conflicts.  I recommend a simple digital switch, and you can try to use the DIR9001's ERROR flag as the input.  This way when a valid TOSLINK input is applied, the switch will change sources.  A simple device like the SN74LVC257ARGYR can be used for the switch.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 90 points

    Hi Paul,

    Thanks for the answer. Do you think ERROR flag is a good indication for present audio signal, or should I use !AUDIO instead? Also, I guess I could also use SN74LVC157 instead of *257?

    Thanks,

    Neb.

  • 0 in reply to Nebojsa Zdravkovic
    TI__Guru 53633 points

    Hi Neb,

    If you expect the input to always be audio (linear PCM data), which i think is reasonable given your application, then AUDIO will work for the logic switch as well.  The SN74LVC157A will work as well.  Seems like a pretty cool project!

    I'm following the thread over at DIYaudio as well. :)

    Thanks,

    Paul