Adding TOSLINK / optical input to 1701 project?

I have an older design using an ADAU1701, and we'd like to upgrade it to include consumer-grade TOSLINK (optical input), but I don't want to add too much cost.  From my reading, this gets complicated, because the master clock for the ADAU won't be synchronized with the external source.  So I assume I'll need an ASRC.

I see a few options -

1.  Add a chip to convert S/PDIF to I2S as a slave to the source, then use an ASRC to sync the digital data into the ADAU1701.  This seems quite complicated, but maybe there's a cheap IC somewhere that does all this?

2.  Convert the S/PDIF into analog, which is mux'd or mixed to the ADAU analog input.  This probably requires a receiver + DAC, so $$.

3.  Switch to an ADAU1442 or similar (adds $5), which handles the digital side nicely, but requires a codec to retain my analog capability, so that's another $2 or so.  The extra processing is nice but I don't really need it.

Given that this type of input is so common in inexpensive consumer gear, I'm surprised it's turning out to be so expensive - easily $5 plus the connector in quantity.

Any other options I'm overlooking?

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  • All we need is RX.  The DIR9001 may fit the bill at ~$2, or something similar.  It need not be continuously running when switching to S/PDIF; we can afford a second or two for a reset.  And I do have a microcontroller on the board.

    Still more cost and hassle than I was expecting, but this might be the best solution.

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  • All we need is RX.  The DIR9001 may fit the bill at ~$2, or something similar.  It need not be continuously running when switching to S/PDIF; we can afford a second or two for a reset.  And I do have a microcontroller on the board.

    Still more cost and hassle than I was expecting, but this might be the best solution.

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