I2S input on ADAU1702

ADAU1702 I2S Slave configuration

 

When the ADAU1702 is used as an I2S slave, the stream is not read in as should. The audio data is however not clearly received.

 

This is a simplified design of our system:

 

Description of setup:

We have DSP1 (ADAU1701), generating an I2S bit stream, which is then sent via a TI CC8531 wireless audio link to DSP2 (ADAU1702).

 

Problem:

The problem we experience is lots of pops and clicks on our analog outputs of DSP2.

 

Analysis:

  • We have modified DSP1 to send out on one of the 2 I2S channels only a “1” in 5.23 format. We can trace this value easily up till the input of DSP2, so it shows that the signal chain up till here is working ok.
  • We have a board with only an CC8531 receiver and a DAC, this works perfectly.
  • When DSP2 is configured to directly send the value of the I2S input stream to its digital I2S output, there is rubbish coming out on the I2S data line (clock lines seem OK).
  • DSP2 is configured to output a value of “-1” in 5.23 format on the other I2S slot and this is OK.
  • When an RMS level meter is placed in DSP2, and read out via SigmaStudio, this level meter shows a very nervous reading, indicating that the read-in value is also not OK.

This leads to believe that the I2S input of DSP2 is not working as supposed to.

(Attached: “LA Output.png”, logic analyser measurement of DSP2 in- and outputs)


 

Settings of DSP2:

 

What could be wrong here?

Parents
  • I have tried the same configuration on a second board and I get exactly the same result:

    I2S data input seems to be almost random, however when I send a stream of data with only zeroes I can see only zeroes coming in. When there is one bit set in the stream, the I2S input read 5 or five bits which are jumping around to random 1 or 0.

    It seems there is some correlation between input and output . With numerical data input (constant) the read data doesnt even look like what is sent.

    To rule out some different problems I Also performed the following measurements:

    - Clock stability: I connected the MCLK input pin to a phosphor scope and there is no occurrence of double or skipped clocks. There is also no significant jitter.

    - I verified the input data up to pin 11, MP0. Data is read in on audio input 2 and 3 inside SigmaStudio. (Also tried on other channels with the same result).

    - I double checked signal levels and integrity, these seem ok.

    - I double checked the connections and measured all I2S and clock pins up to the pins on the DSP itself.

    - Double check the pin connections:

    MCLK (12,288 MHz to pin32, MCLKI)

    LRCLK to MP4 = pin8

    BCLK to MP5 = pin9

    SDATA to MP0 = pin11

    I have no more options to investigate.

Reply
  • I have tried the same configuration on a second board and I get exactly the same result:

    I2S data input seems to be almost random, however when I send a stream of data with only zeroes I can see only zeroes coming in. When there is one bit set in the stream, the I2S input read 5 or five bits which are jumping around to random 1 or 0.

    It seems there is some correlation between input and output . With numerical data input (constant) the read data doesnt even look like what is sent.

    To rule out some different problems I Also performed the following measurements:

    - Clock stability: I connected the MCLK input pin to a phosphor scope and there is no occurrence of double or skipped clocks. There is also no significant jitter.

    - I verified the input data up to pin 11, MP0. Data is read in on audio input 2 and 3 inside SigmaStudio. (Also tried on other channels with the same result).

    - I double checked signal levels and integrity, these seem ok.

    - I double checked the connections and measured all I2S and clock pins up to the pins on the DSP itself.

    - Double check the pin connections:

    MCLK (12,288 MHz to pin32, MCLKI)

    LRCLK to MP4 = pin8

    BCLK to MP5 = pin9

    SDATA to MP0 = pin11

    I have no more options to investigate.

Children
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