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ADV7612 I2S Audio Machine Gun Sound

Question asked by jasonuy on May 2, 2017
Latest reply on May 5, 2017 by mattp

Hi,

 

Wasn't sure how to properly describe what I'm hearing other than it sounding like machine gun firing.  I have an EVAL-ADV7612-7511P board.  Everything works fine within the board. I can send audio from HDMI input (7612) to HDMI output (7511) and to a TV.

 

The next step in my project is to connect the 7612 to my ARM based board.  I have jumper cables connected to the J3 and J4 header for LRCLK, I2S0, and SCLK.  The device transmitting the audio via HDMI is an xbox but I used a laptop as well and the behaviour is the same.

 

I tried to capture the I2S data on my board and when I play it, I get a machine gun sound.  It doesn't sound like a sampling issue.  I verified using scope and logic analyzer that the LRCLK is 48k and SCLK is 3M.  There seems to be adequate transitions on the I2S0 pin to suggest there is normal data activity.

 

To configure the 7612 chip, I used this script found in ADV7612-VER.2.9c_AVEB.txt

 

:6-4b - 1920 x 1080p60, Any Colorspace In (YCrCb 444 36bit from ADV761x) Through HDMI Out 36-bits 444 YCrCb 48kHz 8 Ch VIC 16

 

To simplify my test, I connected a laptop running audacity software.  I created a short pulse waveform and output that to the 7612.  I sometimes see glitches on the bus.  For example, when I only populate the left channel with audio (right channel is muted), I still see occasional transitions on the I2S bus.

 

I'm wondering if I have some sort of signal integrity issue sending data form the eval board to my own board.  I checked and the drive strength is at max.  Do you have any suggestions on how I can further debug this?  Would you know what would be the likely cause of the "machine gun" audio?  Is it possible I'm not capturing the data on the correct clock?

 

Regards,
Jason

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