NRF5340 AUDIO DK, USB audio output Headset device & Microphone input on Gateway

[O_Hndfrd99]

Hello,

I'm using two NRF5340 Audio DKs — one as a Gateway and one as a Headset — running the nrf5340_audio example.

1. Is it possible to configure the Headset device to output audio via USB while maintaining audio input through I2S (LINE IN) on the Gateway?
2. How can I integrate an external electret microphone on the Gateway to replace the built-in PDM MEMS microphone?

Currently, I'm using LINE IN on the Gateway with an external microphone, but the audio is sent to the Headset as audio data. When output through the Headset, it is recognized as audio data rather than microphone data. I'm currently using an external DAC on the Headset device in this set up but I would like to use the NRF5340 to do this task instead.

Thanks!

[Øyvind]

Hello, 

Could you please provide an illustration to what you are trying to achieve? 

Which version of the nRF Connect SDK are you working with?

Kind regards,
Øyvind

[O_Hndfrd99]

I'm using SDK v2.8.0. I have attached an illustration to give more context, essentially my current problem is getting USB audio out the Headset device. An ADC on the LINE OUT of the Headset is my temporary solution which works, but I would like the NRF5340 to do DAC and output via its USB-C. I'm aware the Gateway device is capable of this but I would like to use the Headset device..

[O_Hndfrd99]

Apologies when I said 'DAC' I meant ADC. Thank you

[Øyvind]

Hello, here is the answer I got from our Audio team: 

In CIS bidirectional mode, the gateway consumes almost all the CPU resource (USB audio stack and LC3 enc/dec)
Not sure if gateway still have chance to split the input/output to different interface, since CPU now need to handle the interrupt from USB and also I2S.

Kind regards,
Øyvind

[O_Hndfrd99]

Thank you for the response. My question specifically refers to the Headset and not the Gateway. By default the Headset outputs through the I2S (Line Out), is it possible to output through the USB on the Headset device instead of the I2S (Line Out)?

[Øyvind]

Hello again, sorry, there was a slight misunderstanding here. Please ignore my last comment. Still working on an answer to this. 

O_Hndfrd99 said:

My question specifically refers to the Headset and not the Gateway. By default the Headset outputs through the I2S (Line Out), is it possible to output through the USB on the Headset device instead of the I2S (Line Out)?

That said, it is still not clear what you are trying to achieve. Is there a reason for why you have the headset connected to the computer and not the gateway? As the head-set is what you have on you head/in your ear?

What exactly are you trying to achieve with your setup? Please provide more details for our audio team to understand.

Is it possible to configure the Headset device to output audio via USB while maintaining audio input through I2S (LINE IN) on the Gateway?

The headset and the gateway are two different devices. As far as I know there is nothing preventing the user from configuring the inputs and outputs of the two devices differently

How can I integrate an external electret microphone on the Gateway to replace the built-in PDM MEMS microphone?

the audio is sent to the Headset as audio data. When output through the Headset, it is recognized as audio data rather than microphone data.

What exactly does this mean? The output of the microphone is an audio signal, i.e. audio data.

I'm currently using an external DAC on the Headset device in this set up but I would like to use the NRF5340 to do this task instead.

Can't you use the microphone input on the kit i.e. line in?

O_Hndfrd99 said:

I have attached an illustration to give more context, essentially my current problem is getting USB audio out the Headset device.

The figure also says "bidirectional audio", but the arrow is going in one direction only. Are you expecting sound both ways? 

Kind regards,
Øyvind