Can I make speaker by using 'USBD AUDIO' library?

RE: Can I make speaker by using 'USBD AUDIO' library?

Karl Ylvisaker — Fri, 01 Sep 2023 12:37:01 GMT

Hello,

[quote user="heavyjo"]Thanks for answer[/quote]

No problem at all, I am happy to help! :)

[quote user="heavyjo"]But ble part is not a problem. And it looks unreasonable, I have to write the code with the above structure.
The problem is between (analog to digital converter) and nrf52840 on my diagram.
it doesn't work. in this case, function called app_usbd_event_queue_process, p_event_item is always null.
so app_usbd_event_execute is not called anymore.

When i tested that, i used usbd_audio example.
what's my missing part?[/quote]

As I understood it you previously you have said that you successfully tested the USBD input:

[quote user="heavyjo"]Additional when i used usbd_audio example (...\examples\peripheral\usbd_audio), it was work.
The logic below is an example that I checked first. it was worked.[/quote]

What was the difference between the inputs when the usbd_audio application worked as expected and when it did not?
Do you have an alternate USB source that you could use to test this application again, so that we can isolate if the issue is with the nRF's setup or the analogue to digital converter you are using?

Best regards,
Karl

RE: Can I make speaker by using 'USBD AUDIO' library?

heavyjo — Fri, 01 Sep 2023 07:55:08 GMT

Thanks for answer

This, along with the diagram, tells me that you will just be receiving USB audio on the nRF52840, and then output it somewhere else, presumably over BLE, is this correct?

>> YES.
But ble part is not a problem. And it looks unreasonable, I have to write the code with the above structure.
The problem is between (analog to digital converter) and nrf52840 on my diagram.
it doesn't work. in this case, function called app_usbd_event_queue_process, p_event_item is always null.
so app_usbd_event_execute is not called anymore.

When i tested that, i used usbd_audio example.
what's my missing part?

RE: Can I make speaker by using 'USBD AUDIO' library?

Karl Ylvisaker — Thu, 31 Aug 2023 13:08:19 GMT

Hello again,

Thank you for your extreme patience with this. I have been out of office for some time, but now I am back.

[quote user="heavyjo"]I'm sorry to keep giving you an unclear explanation.[/quote]

No need to apologize - I will just ask whenever something is unclear :)
Thank you for providing the diagram, this makes things much more clear.

[quote user="heavyjo"]*And the above adc converter supports digital signal output of 48 kHz, 16 bits.[/quote]

This, along with the diagram, tells me that you will just be receiving USB audio on the nRF52840, and then output it somewhere else, presumably over BLE, is this correct? Your diagram only mentions 'data -> client', could you confirm that this is intended to be transferred over BLE?
If so, you will just need to merge the usbd_audio application that you currently have working into one of the BLE applications to do the transfer. For this, I recommend the BLE Nordic UART service application, since this just acts as a generic service that lets you transfer byte arrays across the BLE link.

One last consideration will then be the throughput that your audio stream requires for the BLE connection.
Do you intend for the audio to be played back in real time, or just to be transferred to the client?
In case of the latter you should be able to use BLE just fine - it will just take a lot of time - but in case of the former you will quickly run into issues with the throughput of your link.

Essentially, regular BLE communication is not dimensioned to be used for live playback of audio streams - its throughput is not high enough for this, and the innate lossless feature of the BLE protocol also causes issues for live audio playback when packets are dropped and needs to be retransmitted.
This is why the BT SIG recently came out with the LE Audio specification, which is the future of wireless audio playback.
Unfortunately, we only support development of LE Audio on the nRF5340 devices, but I have seen some third-party vendors offer solutions to run LE Audio on nRF52840 devices as well, such as Packetcraft - if this is interesting to you.

Best regards,
Karl

RE: Can I make speaker by using 'USBD AUDIO' library?

heavyjo — Tue, 08 Aug 2023 11:20:10 GMT

I'm sorry to keep giving you an unclear explanation.
The logic below is the logic I am asking.

Is your intention to use the USB-C <-> 3.5 mm jack cable to transfer an analogue signal to a nRF52840 SoC,
-> no. I must use digital source on nRF52840.
so that using 3.5mm <-> USB-C jack to transfer digital audio signal to nRF52840 SOC.

But as you watched in my questions, it doesn't worked.

*And the above adc converter supports digital signal output of 48 kHz, 16 bits.

Additional when i used usbd_audio example (...\examples\peripheral\usbd_audio), it was work.
The logic below is an example that I checked first. it was worked.

RE: Can I make speaker by using 'USBD AUDIO' library?

Karl Ylvisaker — Tue, 08 Aug 2023 10:34:31 GMT

Hello,

I will be handling this support request while Simon is out of office.

Like my colleague Simon I too am unfortunately not sure I have understood your intended configuration fully.
Is your intention to use the USB-C <-> 3.5 mm jack cable to transfer an analogue signal to a nRF52840 SoC, which then should relay this to another device (speaker or otherwise) over audio USBD?
Please correct me if any part of this understanding is incorrect.

If my understanding is correct you could indeed use the nRF52840's SAADC to sample the received analogue signal, and output this signal over the USBD interface, but you would have to make sure that the quality of the output is good enough for your application.
For instance, the bit depth for digital PCM streams are typically 16- or 24- bit, while the SAADC on the nRF52840 only has 10.5 ENOB, so you will see a pretty stark degradation of the audio quality with this approach, since the SAADC on the nRF52840 is not made for the audio sampling use-case, and we do not recommend using it for high quality audio sampling.

Additionally, if my understanding of the intentions are correct then you will essentially be using the nRF52840 as a ADC (since I dont see any mentions of wireless activity, or usage of other peripherals), and so I am not sure if the nRF52840 SoC would be a good fit for your application.
What else will your application be doing during the regular operation?

Best regards,
Karl

RE: Can I make speaker by using 'USBD AUDIO' library?

heavyjo — Fri, 04 Aug 2023 02:42:02 GMT

1. GOAL : make the nRF be the brain. - that means use digital audio source and control it.

2. Sub GOAL : verificate that it is possible that nRF52840 communicated with ADC cable's output.

3. Reason : Want to use host(mobile, pc)'s digital and analog output at the same time. and want that nRF52840 communicated with host's digital output. but, when host use digital audio output. then, they can't use analog output.
So i make host use analog audio output. then make output distribute with y jack. and make output that be distributed convert to digitial output with ADC cable.

4. Result : failed. nRF52840 can't take the DRV_SOF event.

EXAMPLE THAT I USED : ...\examples\peripheral\usbd_audio - DIGITAL audio commuication

* ADC cable : Analog to Digtal converter cable.
- USED cable Link :
www.amazon.com/.../ref=sr_1_4

RE: Can I make speaker by using 'USBD AUDIO' library?

Simonr — Thu, 03 Aug 2023 06:58:31 GMT

I'm sorry, but this block diagram doesn't add much clarity I'm afraid. As I am not sure I understand your intentions correctly, please elaborate thoroughly on exactly what it is you would like to implement. For example, what is this "ADC cable" you mention, and what protocols are you transferring the audio to/from the mobile and nRF52 device with?

Is the end goal here to make the nRF52840 be the "brain" or wireless radio chip of a speaker?

Best regards,

Simon

RE: Can I make speaker by using 'USBD AUDIO' library?

heavyjo — Wed, 02 Aug 2023 05:09:12 GMT

- it seems to just output an analog signal to a "black box" that is supposed to output two digital signals, is that right?

No. Sorry to mistake. I thought that diagram make you confused.
Here is the diagram that make sure your understand.

RE: Can I make speaker by using 'USBD AUDIO' library?

Simonr — Tue, 01 Aug 2023 11:00:53 GMT

Thank you for your description. I'd recommend that you check out the USB audio class module and the specification documentation to better understand how to use this. Yes, I think it's possible to do something like what you're explaining, but I don't really understand the block diagram you uploaded, since it seems to just output an analog signal to a "black box" that is supposed to output two digital signals, is that right?

Will the mobile also in this scenario use the USBD audio class, or will it be converted to this class in the "black box"?

Best regards,

Simon

RE: Can I make speaker by using 'USBD AUDIO' library?

heavyjo — Fri, 28 Jul 2023 06:43:43 GMT

wanted

1. I want to take digital audio input on nRF,
2. also I wanna heard audio signal from the host(PC, mobile).

-> So I thought that SAADC peripheral example is not suited for my case.

are there any advise for my case?

RE: Can I make speaker by using 'USBD AUDIO' library?

heavyjo — Fri, 28 Jul 2023 02:07:28 GMT

I wanted to connect to the nRF by digitally converting one side to ADC with an analog 1:2 connection because when I get the DIGITAL signal from my PC, it's only 1:1 connection.

Do you have any recommendations in this case?

RE: Can I make speaker by using 'USBD AUDIO' library?

Simonr — Wed, 26 Jul 2023 14:02:44 GMT

Due to the summer vacation period we are currently understaffed, so delayed replies must be expected. I am sorry about any inconvenience this might cause.

Are you still using a USB cable from this ADC device to the nRF52840 device at this point?

If you are to transmit just analog data to the nRF52840, I think it's easier to just do that to the analog pins on the nRF52840 and use the onboard SAADC peripheral to convert it into digital data on the nRF end.

Best regards,

Simon

RE: Can I make speaker by using 'USBD AUDIO' library?

heavyjo — Mon, 24 Jul 2023 11:44:18 GMT

1. yes i used sample of yours. ...\examples\peripheral\usbd_audio
but there were some code changes to test.

2. when i saw the memory that temp_buffer is located. it didn't be changed.

and there is other 2 reasons that i thought that is not work.

in using one cable,
in function called app_usbd_event_queue_process, p_event_item is always null.
so app_usbd_event_execute is not called anymall.

in using other cable,
DRV_SOF event is not called anymore in app_usbd_event_execute.

3. here is the test structure.

it is a orignal one.

it is test

RE: Can I make speaker by using 'USBD AUDIO' library?

Sigurd Hellesvik — Mon, 24 Jul 2023 11:16:17 GMT

Hi,

I see that this is your first case.
So I should mention that for new projects we recommend the nRF Connect SDK instead of the nRF5 SDK.

[quote user=""]and I could see that digital audio communication operate well. [/quote]

Did you use one of our samples for this, or something custom?

[quote user=""]then it doesn't work anymore.[/quote]

Can you describe how you see this?

Regards,
Sigurd Hellesvik