Help with digital audio processing project (ALC5616 Codec + STM32F4)

[giovanicauzzi]

Hello guys,

I'm developing a board to process digital audio (see block diagram attached). The board has a STM32F405 and a Realtek ALC5616 audio Codec.
Between both ICs, there is a I2C interface for Codec registers configuration and a I2S interface of full-duplex audio data transfering.
The I2S is configured as described bellow:
- Sampling Frequency: 48kHz
- 16bits stereo data
- STM32 as master, generating MCLK 12.5MHz (48.828kHz * 256)

The problem that I have is that the Codec always return the same audio data via I2S, 9353 for one channel and 28061 for the other.
(See the logic analyzer print screen attached)
Even if I ground the input, this values doesn't change.
I review the audio path inside the Codec several times, making sure that both single ended inputs are reaching the internal ADC.

I want to know if some of you already developed something with an audio Codec and could share some common issues or probable causes for this kind of problem.
I also attached the circuit schematic for the Codec.