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adau144x TDM8 on scope

Question asked by benybiles on Jul 14, 2018
Latest reply on Jul 30, 2018 by DaveThib

Hi , I am new to working with TDM8 24bits


I have adau144x working in master mode


The DSP is working in pulse mode in TDM8 24bit mode.


I have delayed by one set ( i2s mode )


So I calculate there should be 32 fs clocks per slot x 8 slots = 256 fs clocks for the whole frame between pulses.


It appears that I have maximum of 20bits of audio in the middle of the slots with 8 bits either side.

Also I have on the left what seams like strobing bits accross the 1st 24bits ( left to right )  with nothing in the last 8bits (right )


the sclk is 12.288mhz

FS is 48khz


The ADAU1446 is master on TDM8 bus. 


here's some pics from the scope.


the single slot,


My question really is , does anyone have a clue what could be causing the strobing across the 1st 24bits?

or is this normal for TDM8 ?





I wasn't seeing the 1st 8 - 10 bits since I never got anything load enough out of the DSP. I set tone to 100% and the full dynamic range of the 24bits is used.


So that only the question about the line across the top of the bits on the scope. Is this expected ?


I tried unconnected my ARM proto board as its quite noisy and I still get the top line from the DSP.