Viability Concept – nRF9151 SiP for Audio Transmission

RE: Viability Concept – nRF9151 SiP for Audio Transmission

Hakon — Wed, 01 Oct 2025 06:35:46 GMT

Sounds good. Just let me know if you need any more help.

RE: Viability Concept – nRF9151 SiP for Audio Transmission

bjesuslopezg — Fri, 26 Sep 2025 12:48:07 GMT

Hi Hakon. Really have no requirement either on audio codec. Something that can give us the best quality with the lowest amount of resources, maybe Opus.

RE: Viability Concept – nRF9151 SiP for Audio Transmission

Hakon — Fri, 26 Sep 2025 09:11:50 GMT

[quote user="bjesuslopezg"]And of course, any working example you have would be really helpful for us.[/quote]

There is the I2S echo zephyr sample, which might not work out of the box on nRF9151 DK but could probably work with some modifications. I will try to tinker with this and report back if I'm able to make it work.

[quote user="bjesuslopezg"]What protocols do you think can be used to send the audio to the network? MQTT, HTTP, or raw UDP, TCP? We're completely free to develop whatever is needed on the server/cloud reception side. [/quote]

Probably something like websocket or just pure TCP or MQTT would be fine. Depends how much data you want to send in one session. There is also a modem restriction of 2 KB TLS data (buffer limit), so keep that in mind.

Also, have you thought about what codec you are going to use?

RE: Viability Concept – nRF9151 SiP for Audio Transmission

bjesuslopezg — Tue, 23 Sep 2025 14:17:49 GMT

Hello Hakon. Yes, taking into account that nRF9151 has 256 kB of RAM, then we're perfectly aware that audio quality may take a hit, we are willing to accept that trade-off if we are able to send an audio of that duration, but of course, it would be necessary to perform tests on final audio quality.

The entire application firmware would only perform this, so we can assume the whole RAM that's left after Zephyr, modem and other configurations can be available for the audio clip. I know Nordic has released the Bare Metal SDK, I don't know if that may be a good option to release more memory that we can use for the audio.

The use case is simple, the nRF9151 would be sleep most of the time, and on certain conditions, it will receive a wake up signal to record and send the audio. We don't necessarily need to stream it, what we're interested in is that audio sending after recording happens on a reasonable time window.

What protocols do you think can be used to send the audio to the network? MQTT, HTTP, or raw UDP, TCP? We're completely free to develop whatever is needed on the server/cloud reception side.

And of course, any working example you have would be really helpful for us. We'll use any low power, small footprint microphone, for example: ICS43434 by TDK InvenSense

RE: Viability Concept – nRF9151 SiP for Audio Transmission

Hakon — Tue, 23 Sep 2025 13:33:37 GMT

Hello,

I guess it would be depend on the size of the audio clip. But if the audio data is small enough to be buffered entirely on the nrf9151, then I see no problem with this. Streaming it in real time to a cloud server can be more tricky, as the bit rate would probably be too high for an LTE-M link to handle. But that would also maybe depend on the quality of the audio file, sampling rate etc.

Sending I2S data to the nrf9151 should not be a problem at all, but I don't think we have a sample for this yet. But if you want I can try to make something work if you have time for that.