NR5340 AUDIO DK Microphone

[O_Hndfrd99]

Hello, I have several development-related questions about the microphone functionality of the NRF5340 AUDIO DK in headset mode:

1. Is it possible to configure the device as a microphone-only LE Audio headset using the available configurations?
2. How can I integrate and use a custom I2S microphone, such as the Adafruit ICS43434 MEMS, with the NRF5340 AUDIO DK?
3. Can the "Line In" input be used as a microphone input while in headset mode? If so, what code modifications would be necessary to enable this functionality?
4. I have the device successfully connected to a Google Pixel 9, and it works perfectly for general audio, but I am unable to use the microphone as an LE Audio input while simultaneously outputting Bluetooth audio to another pair of headphones. Is there a way to achieve this?
5. Ultimately, I aim to create a high-quality microphone solution using the NRF5340 AUDIO DK. What would be the best approach to accomplish this?

Any guidance or recommendations would be greatly appreciated!

[Hieu]

Hi O_Hndfrd99,

As you are discussing a product idea, I would like to check, do you want to discuss in private, or are you fine with the case being public?

Regarding your product, I am a little confused. Do you want to create a microphone peripheral for smartphones? Or do you want to create a headset with microphone, supporting bidirectional audio?

Am I right to understand that you are only interested in one-to-one connection?

Hieu

[O_Hndfrd99]

I’m working on a personal project and am happy to discuss it publicly if it can benefit others. The project involves using the NRF5340 AUDIO DK as a microphone. My goal is to send audio captured by the NRF5340 AUDIO DK to my Pixel 9 smartphone and then listen to it through Bluetooth headphones connected to the same device. However, the Pixel only supports connecting one headset device at a time. In this setup, the NRF5340 AUDIO DK would serve as the microphone input while the Bluetooth headphones act as the audio output. I’m facing challenges with routing the audio correctly in this configuration. Is there a way to resolve this issue?

Additionally, I’m aiming to implement a I2S MEMS microphone on the NRF5340 AUDIO DK or using the ‘LINE IN’ port as the microphone input. Any help or guidance on this would be much appreciated, thankyou.

[Hieu]

Is it possible to configure the device as a microphone-only LE Audio headset using the available configurations?

In that case, I will interpret this question as whether it is possible to configure the device as a microphone accessory or not.

Please allow me some time to confirm this.

How can I integrate and use a custom I2S microphone, such as the Adafruit ICS43434 MEMS, with the NRF5340 AUDIO DK?

The nRF5340 Audio DK has an integrated microphone, connected via PDM. Does this work for you, or do you need to connect a different MEMS mic via I2S?

Can the "Line In" input be used as a microphone input while in headset mode? If so, what code modifications would be necessary to enable this functionality?

I suppose you are working with the nRF5340 Audio sample application. The Line In input can be used as a microphone input. You can read more about it in the documentation here:

nRF5340 Audio applications

I have the device successfully connected to a Google Pixel 9, and it works perfectly for general audio, but I am unable to use the microphone as an LE Audio input while simultaneously outputting Bluetooth audio to another pair of headphones. Is there a way to achieve this?

It seems you are using the Unicast server configurations. Referring to the configuration documentation, you can use the CONFIG_AUDIO_SOURCE_I2S Kconfig to use the audio jack for input instead. The jack is connected to the CS47L63 headphone driver, which connects to the nRF5340 via I2S.

Ultimately, I aim to create a high-quality microphone solution using the NRF5340 AUDIO DK. What would be the best approach to accomplish this?

Do you want to use the Audio DK itself, or a custom board with the nRF5340?

Also, what degree of "high quality" are you aiming for here?

[O_Hndfrd99]

Thank you for your response; it addresses my questions about implementing a microphone on the nRF5340 Audio. The PDM microphone on the board is currently working.

While there's potential for a custom board, I haven't reached that stage yet.

I do have another question regarding the PDM microphone on the board: Is it possible to configure the microphone on the nRF5340 for noise cancellation?

Hope to hear back from you soon with regards as setting up the device as a microphone accessory. Thank you.

[cyw]

Hi, can you elaborate more on what do you mean by "The Line In input can be used as a microphone input" ?

Can you point me to the documentation for the api to call? Or the sample code in some of the samples?

Thank you.

[Hieu]

Hi cyw,

It is mentioned in the Configuring page under the overall documentation that I link. In particular, here: Configuring the nRF5340 Audio applications.

[Hieu]

Hi O_Hndfrd99,

I have been looking into the nRF5340 Audio application source code and understood its setup a little more. I believe that if you enable CONFIG_STREAM_BIDIRECTIONAL, you should be able to start using the microphone. Could you please try this and let me know if it works?

What I haven't been sure of is whether it can be just a microphone or not. I can tell right away that the nRF5340 Audio application doesn't support this case by design. However, the building blocks are there, from the bidirectional support, so I think it should be possible.

From what I have seen, I also think that the code modification shouldn't be too hard but also isn't trivial.

I am trying to be more certain of both the code and the specs before asking for a review from our developers. It's here that the lack of a LE Audio enabled smartphone has made it a bit difficult for me.

I will continue looking into it and keep you updated.

By the way, are you familiar with the nRF Connect SDK environment yet? If not, you might want to look this online course: nRF Connect SDK Fundamentals. It unfortunately isn't designed for the Audio DK though...

[O_Hndfrd99]

Hello Hieu,

The PDM is functioning for me in bidirectional mode. I will try to modify the code and configure the device as a microphone-only audio device. However, upon further consideration, would it be possible to set it up as a ‘BIS’ ‘Source’ device, effectively acting as an Auracast transmitter?

Yes, I believe a mobile device would need direct support for LE Audio and Android 13 or higher. Thank you for sharing the link to the online course and the updates.

[Hieu]

Hi O_Hndfrd99,

I am glad to hear that you have the PDM mic working in bidirectional mode.

I got information from our developer that while our stack can support setting up a microphone device, currently Android unfortunately only support headset peers for LE Audio, and microphones aren't supported yet. Thus, the closest we can do right now is what you already have working, a headset with bidirectional audio stream.

Shall we put a pause on this until Android supports LE Audio microphones?