ADAU1701: Automatic analog input detection

You can sense the jack connection using one of the GPIO pins and have your software switch inputs accordingly. I'm not sure how well that would work if the 1701 was a I2S slave though, unless you are confident an I2S clock was always present. In master mode it should work reliably.

Hello, you might consider using logic to switch between the inputs based on RMS level. You would use an Envelope Detector to determine whether signal is present on the mini jack, a comparator to check against a threshold, then a multiplexer to switch the signal path.

As joe42 mentioned, you will need to ensure the I2S block always receives a valid clock; either generated internally or from an input.

Thank you!