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I2C triggers I2S issue

Question asked by dimitrisTymph on Nov 11, 2014
Latest reply on Jan 16, 2015 by dimitrisTymph

Hi forum,

 

I am working on a product that carries an ADAU1761 chip and an external MCU.

The two chips communicate through I2C protocol.

 

I am witnessing some weird behaviour however:

 

I am have set my DSP chip to output the I2C data through the ADC_SDATA pin (should be pin no 26 on an ADAU1761 chip).

When streaming music through an evaluation board then the pin 26 spits out digital audio data as it should.

When I am working on the actual product then the output is always low.

I tried deactivating the I2C communication between the MCU and the DSP so I can debug the DSP on the board.

The ADC_SDATA output was firing digital audio nicely again.

Activated I2C communication again between MCU and DSP, streamed music, the ADC_SDATA is always low again.

For some reason, it seems that the I2C is affecting the I2S output.

 

In my DSP design there is no control over the digital output. I just route the signal to output to DIG0 and DIG1 as well as to DAC0 and DAC1.

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Any idea if any settings of the DSP chip could be causing such a behaviour?

 

I am quite puzzled. I don't see how the I2C could affect the I2S pins...

Any suggestion that could lead me to the correct direction  is welcome

 

thank you

Dimitris

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