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ADAU145x Flexible TDM

Question asked by jlevro1 on Jul 8, 2015
Latest reply on Jul 24, 2015 by DaveThib

I have an application where I'm processing a 2-channel TDM input stream in an ADAU1451. I've never used TDM before, so please bear with me for what may be a stupid question.

 

In SigmaStudio 3.12.1, I enable the FTDM registers in the hardware config as follows, per Fig. 70 of the data sheet:

 

For the "left" input channel:

 

FTDM IN0 - Position 0, MSB

FTDM IN1 - Position 1, 2nd MSB

FTDM IN2 - Position 2, 3rd MSB

FTDM IN3 - Position 3, LSB

 

And for the "right" input channel:

 

FTDM IN4 - Position 0, MSB

FTDM IN5 - Position 1, 2nd MSB

FTDM IN6 - Position 2, 3rd MSB

FTDM IN7 - Position 3, LSB

 

The resulting output waveform looks like 8-bits resolution, which I verified with a controlled input level. It's sort of like the 3 lower byte positions are being ignored.

 

In order to get full resolution, I had to change the "Position" tab on all IN's to "0". The byte assignments were not changed from the above listing.

 

What am I not getting?

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