TLV320DAC3100EVM-U: Observing harmonics in audio played at 16KHz sampling rate.

Rahul Patil

Part Number: TLV320DAC3100EVM-U
Other Parts Discussed in Thread: TLV320DAC3100,

Tool/software:

Hi,

I am using TLV320DAC3100 hardware codec for playing an audio data sent over I2S. It is observed that there are harmonics present when audio data is of 16KHz sampling rate. But it is not observed for 48KHz sampled audio data.

For more details I have added wav file of the 16KHz sampling rate audio data.

1st channel: Audio data played on a speaker and captured by mic

2nd channel: Audio data sent to TLV320DAC3100EVM-U. As you can see there are harmonics in first channel which I was not expecting.

I have used sine wav of 1200Hz for the playback. I have tested with 500Hz and 3Khz and observed same issue as there are harmonics.

I am using below settings for TLV320DAC3100EVM-U:

- Internal PLL is turned OFF

- Processing block 16 is used as audio data is mono. Here even though audio data is mono, I2S APIs need stereo data. To achieve that we are either adding zeros' s or duplicating the first channel for second channel. Issue is observed in bot the cases.

Is there any special settings needs to be done for 16KHz? Are we missing anything for 16KHz?
Let me know if any more information needed.

Thanks!

16 days ago

0 Rahul Patil 16 days ago

Prodigy 10 points

Adding screenshot of the same file that is shared laready.

0 Daveon Douglas 15 days ago in reply to Rahul Patil

TI__Genius 13870 points

Hi Rahul,

Apologies for the delay, I will loop in an engineer to help assist with your issue.

0 Ivan Salazar 15 days ago

TI__Guru* 98185 points

Hi Rahul,

Double check your clock settings, ie. PLL, NDAC, MDAC and DOSR. Most likely all your settings are for 48kHz, so if you're using 16kHz you'll have aliasing.

Best regards,
-Ivan Salazar
Applications Engineer

0 Rahul Patil 14 days ago in reply to Ivan Salazar

Prodigy 10 points

These are the settings I am using:

The PLL internal to the TLV320DAC3100 is turned OFF. The TLV320DAC3100 codec is clocked externally from I2S IP with SCK as shown in table above.
Can u provide the information what could be the settings for the MDAC, NDAC and DOSR?

0 Ivan Salazar 6 days ago in reply to Rahul Patil

TI__Guru* 98185 points

Hi Rahul,

Is there a chance you can increase MCLK from 2048kHz to 4096kHz? If so, please try that and change DOSR = 256 instead of 128.
I would have to test this on my side as well, but my concern is data sheet mentions "2.8 MHz < DOSR × DAC_fS < 6.2 MHz" so for the 16kHz we're slightly short 2.048MHz vs required 2.8MHz.

Best regards,
-Ivan Salazar
Applications Engineer

+1 Rahul Patil 2 days ago

Prodigy 10 points

Hi Ivan,

I am able to resolve the issue by changing the processing block from 16 to 1. In addition to this, the left channel data is copied to right channel instead of having zeros.

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TLV320DAC3100EVM-U: Observing harmonics in audio played at 16KHz sampling rate.