How to connect external 3.3V I/F I2S signal to nrf5340-audio-dk

[MontBlanc]

Hello,
devzone.nordicsemi.com/.../set-nrf5340-audio-dk-as-i2s-slave-over-external-bus
Based on this post, I changed I2S to SLAVE setting.
The external I2S I/F level is 3.3V.
When OB/EXT is green, it is noisy when I2S of 3.3V I/F is connected to P5, but we have confirmed that the audio signal is sent to the RX side and the sound is heard.

devzone.nordicsemi.com/.../access-to-i2s-interface-on-nrf5340-audio-dk

Based on this post, I tried changing the I2S port.
If OB/EXT lights up orange, does that mean the port has been changed to P10 instead of P5?

But when OB/EXT is orange, there is no sound even if you forcefully connect the 3.3V I/F to P10.

Also, in order to change the 3.3V I/F to 1.8V I/F, I changed the I2S signal level using TI's TXS0108E.
When I connect the nrF5340 to the enabled I2S port (P5 or P10), I checked with an oscilloscope and found that there is quite a lot of noise on the I2S signal.
Since it is a bidirectional buffer, it seems that the noise component is flowing backwards, or the GND level is not stable and crosstalk noise is being buffered.

Is there a way to run nrF5340-audio-DK with 3.3V I/F?
Or is there a good way to make I2S a 1.8V I/F?

[Karl Ylvisaker]

Hello again, MontBlanc

Thank you for your extreme patience with this. An error has occured in our system with this ticket when it was assigned between engineers due to the holiday period, and so the request was incorrectly marked as resolved until I happened upon this ticket again manually. I am terribly sorry for the incredible time it has taken to get back to you about this.

MontBlanc said:

After reviewing the source code again and rewriting it, the sound now plays correctly.

I am glad to read that you were able to resolve the issues yourself in the time that has passed since we last spoke.
Do you still require technical support with the remaining questions, or have you already found the answers you were looking for?
Just in case, I reply to the previous questions, and I hope you will raise any other questions you might have encountered in the meantime as well.

MontBlanc said:

Referring to the post below, is the bitrate of LC3 default to 96kbps?

The bitrate does indeed default to 96 kbps, you can however overwrite this configuration by setting this kconfig in your prj.conf instead.

MontBlanc said:

I would like to check the trade-off between delay and sound quality, but what should I do if I want to change the bitrate after changing to external I2S?

Which external hardware codec are you using, and what requirements does it have?
You will likely have to re-configure your hardware codec when you change the parameters of the audio stream.

Best regards,
Karl