TLV320DAC3120: Biquad not working

Alan Ball

Prodigy 110 points

Part Number: TLV320DAC3120

Hello,

I am trying to implement a biquad filter on the TLV320DAC3120. My initialization sequence is as follows:

hardware reset
wait 1ms
set P1R60 = 6 (DAC signal processing block PRB_P6)
set P8R1 = 4 (Adaptive filtering enabled in DAC miniDSP)
10ms delay
do a block write of the 10 bytes of biquad A coefficients for buffer A (P8R2 and following)
do a block write of the 10 bytes of biquad A coefficients for buffer B (P12R2 and following). If I don't do this, P8R2 and following registers have their default value.

After the above I configure the other audio amplifier settings.

To verify that the biquad is working I initially set the cutoff frequency to 1.5 kHz and then play a 1kHz tone and check that it is audibly attenuated. I then repeat this experiment with the cutoff frequency set to 3 kHz.

When I program my microcontroller with a Debug build, the above tests work as expected. However if I program a release build, the tone sounds the same (no attenuation). In both cases when I read back the contents of the audio amplifier registers, they look correct.

Is there something else I could have missed?

Thanks in advance for some feedback,

Regards.

Alan

over 2 years ago

0 Jeff McPherson over 2 years ago

TI__Mastermind 46805 points

Hi Alan,

What's the difference between the debug build and the release build?

Thanks,
Jeff McPherson

0 Alan Ball over 2 years ago in reply to Jeff McPherson

Prodigy 110 points

Hi Jeff,

The code for the 2 builds is the same, except the Debug/Release configuration.

My microcontroller has 2 code banks. In the 1st bank I put code with the 3kHz fc and in the 2nd I put the 1kHz fc code (to facilitate jumping between the 2).

The debug version of this works as expected. However when I run the Release version of the 2nd code bank code, the biquad coefficients are set to the 3kHz values and not the 1 kHz values despite power cycling my board.

If I make a release build with a 1 kHz filter in each code bank, the audio amp works as expected.

Regards,

Alan

0 Ivan Salazar over 2 years ago in reply to Alan Ball

TI__Guru** 109745 points

Hi Alan,

One thing I would double check is if the device is properly changing between the coefficients buffers, you may have to toggle bit 0 from page 8 register 1 twice to write the coefficients and use these for the active playback path.
Perhaps the one that has 2 different sets is working because you do this toggle to configure both buffers.

Best regards,
-Ivan Salazar
Applications Engineer

0 Alan Ball over 2 years ago in reply to Ivan Salazar

Prodigy 110 points

Hi Ivan,

Thank you for your comments. I will try this out.

Regards,

Alan

0 Ivan Salazar over 2 years ago in reply to Alan Ball

TI__Guru** 109745 points

Hi Alan,

You can let us know if this solves it.

Best regards,
-Ivan Salazar
Applications Engineer

0 Alan Ball over 2 years ago in reply to Ivan Salazar

Prodigy 110 points

Hi again,

I'm still having problems. The tables below are in the datasheet. The DAC stage of my audio amp should be off, so that's rows 2 and 3 of table 5-7.

In my code do the following:

set page to 8
set P8R1 to 4
write the biquad coefficients to buffer A
set page to 12
write the biquad coefficients to buffer B

Every time I read back P8R1, bit 1 is 0. I've tried setting bit 0 to 1.

What have I missed? Thanks advance for any pointers.

Regards,

Alan

0 Ivan Salazar over 2 years ago in reply to Alan Ball

TI__Guru** 109745 points

Hi Alan,

I'll take a look at your comments and provide further comments by tomorrow.

Best regards,
-Ivan Salazar
Applications Engineer

0 Alan Ball over 2 years ago in reply to Ivan Salazar

Prodigy 110 points

Thanks in advance.

Alan

+1 Ivan Salazar over 2 years ago in reply to Alan Ball

TI__Guru** 109745 points

Hi Alan,

If you're not using the adaptive filter mode, you should follow the sequence suggested in data sheet section 5.6.7: https://www.ti.com/lit/ds/symlink/tlv320dac3120.pdf#page=38

Otherwise, I would suggest enabling the adaptive filter mode as mentioned in data sheet section 5.6.1.3: https://www.ti.com/lit/ds/symlink/tlv320dac3120.pdf#page=26
In this case, you don't have to write buffer A and B separately, instead you should just swap between them by setting page 8 regsiter 1 bit 0 to 1, this is a self-clearing bit so you just write value of 1 to it. When you write the coefficients one, you should toggle this bit twice, first to write the buffered coefficients and a second time to load the coefficients that were written the first time this bit is enabled.

If you have an EVM and the GUI, you can use the I2C record tool to inspect all the I2C transactions needed to perform the biquad settings adjustment.

Best regards,
-Ivan Salazar
Applications Engineer

0 Alan Ball over 2 years ago in reply to Ivan Salazar

Prodigy 110 points

Hi Ivan,

Thank you for your help. I was able to successfully implement option 2 above, once the DAC was turned on.

Thanks again,

Alan

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TLV320DAC3120: Biquad not working