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

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

Karl Ylvisaker — Mon, 05 Feb 2024 12:03:46 GMT

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.

[quote user="MontBlanc"]After reviewing the source code again and rewriting it, the sound now plays correctly.[/quote]

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.

[quote user="MontBlanc"]Referring to the post below, is the bitrate of LC3 default to 96kbps?[/quote]

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

[quote user="MontBlanc"]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?[/quote]

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

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

MontBlanc — Wed, 27 Dec 2023 05:49:54 GMT

Hello,

After reviewing the source code again and rewriting it, the sound now plays correctly.
Referring to the post below, is the bitrate of LC3 default to 96kbps?

devzone.nordicsemi.com/.../range-of-config_lc3_bitrate

I'm making the same changes, but the build doesn't work.
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?

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

MontBlanc — Mon, 04 Dec 2023 08:08:25 GMT

In addition, the specifications of I2S are
LRCK=48kHz
BCLK=64Fs
16bit I2S (Left alignment)
is input to nrf5340 on the sending side.

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

MontBlanc — Mon, 04 Dec 2023 08:01:30 GMT

Hello,

CONFIG_TRANSPORT_BIS=y was set extra.
When this setting was removed, L/R monaural transmission was possible.
The results are below.

.format = NRF_I2S_FORMAT_I2S
.alignment = NRF_I2S_ALIGN_LEFT

.sample_wodth = NRF_I2S_SWIDTH_16BIT
Lch Silent, Rch OK, No noise

.sample_wodth = NRF_I2S_SWIDTH_16BIT_IN32BIT
Lch Silent, Rch OK, No noise

.sample_wodth = NRF_I2S_SWIDTH_24BIT
Lch OK, Rch Silent, small noise mixed

.sample_wodth = NRF_I2S_SWIDTH_24BIT_IN32BIT
Lch OK, Rch Silent, small noise mixed

.sample_wodth = NRF_I2S_SWIDTH_32BIT
Lch OK, Rch Silent, No noise

I'd like to send and receive in stereo, but it's not working.
What should I fix?

Best Regards.

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

MontBlanc — Tue, 28 Nov 2023 08:57:08 GMT

I made the changes below.

main.c
#include <hal/nrf_gpio.h>

and added
nrf_gpio_cfg_output(21);
nrf_gpio_pin_set(21);
inside
int main(void){}

audio_system.c
"ret = hw_codec_init();"
delete

hw_codec.c
Change all "return ret" in to "retuern 0"

Are there any other changes?

audio_i2s.c

.mode = NRF_I2S_MODE_SLAVE, // MODIFIED
.format = NRF_I2S_FORMAT_ALIGNED, // MODIFIED
.alignment = NRF_I2S_ALIGN_LEFT,
.ratio = NRF_I2S_RATIO_256X, // MODIFIED
.mck_setup = NRF_I2S_MCK_DISABLED, //0x66666000, MODIFIED

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

Karl Ylvisaker — Thu, 23 Nov 2023 12:12:31 GMT

Hello,

Thank you for your extreme patience with this, and for the clarifications.

[quote user="MontBlanc"]nrf5340-audio-dk RX(Right) - I2S(Rch audio is Lch packet) - External DAC(I2S MASTER) - Rch audio is output from Lch[/quote]

Is the only issue here that the R channel audio is output from the L channel? Is the audio quality as expected, and equal to the audio output on the nRF5340-audio-dk RX(left) that is acting as the I2S master?

[quote user="MontBlanc"]I2S(L/R ch packet is incorrect) - External DAC(I2S MASTER) - L/R ch audio is output from L/R ch, However, the sound is mechanical[/quote]

Are you here configuring the headset device to be an I2S slave to the External DAC as the I2S master? In this case, I would assume that the output could be distorted since the nRF5340 is not in control of the I2S interface, and so it can not adjust the frequency of the MCLK to compensate for the drift in the reception timestamp.
Could you share some of your implementation here, so that I can take a look at how you are handling the packet reception and output?

Best regards,
Karl

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

MontBlanc — Wed, 08 Nov 2023 23:52:38 GMT

Hello,
The environment I tried is as follows.

Environment of external CODEC without using nrf5340
External HOST(I2S SLAVE) - I2S(L/R) - External DAC(I2S MASTER) - L/R ch audio is output from L/R ch

Customized nrf5340 software for external CODEC
External HOST(I2S SLAVE) - I2S(L/R) - nrf5340-audio-dk TX - nrf5340-audio-dk RX(Left) - I2S(Lch) - External DAC(I2S MASTER) - Lch audio is output from Lch
|
- nrf5340-audio-dk RX(Right) - I2S(Rch audio is Lch packet) - External DAC(I2S MASTER) - Rch audio is output from Lch

Environment where I tried to send/receive L/Rch this time
External HOST(I2S SLAVE) - I2S(L/R) - nrf5340-audio-dk TX - nrf5340-audio-dk RX - I2S(L/R ch packet is incorrect) - External DAC(I2S MASTER) - L/R ch audio is output from L/R ch, However, the sound is mechanical

Best Regards.

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

Karl Ylvisaker — Wed, 08 Nov 2023 13:12:23 GMT

Hello,

[quote user="MontBlanc"]Thank you for answering.[/quote]

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

[quote user="MontBlanc"]Confirmed that the sound is played correctly in external I2S SLAVE mode with v2.4.0,
After that, I implemented all the changes you suggested.[/quote]

Does this mean that you verified the audio going into the nRF5340 (i.e verified that your external codec provided the correct audio to the nRF), or does it mean that you were able to hear the stereo audio correctly through the LE Audio link when you used the referenced branch as provided, prior to any changes?

[quote user="MontBlanc"]The result is an interrupted mechanical sound that is linked to the played sound.[/quote]

If there are glitches on top of the received audio then there is a chance that something has gone wrong in the handling of the received audio frames.
Could you elaborate further on the question above, so that I better can understand the issue you're seeing?

Best regards,
Karl

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

MontBlanc — Wed, 08 Nov 2023 08:23:08 GMT

Hello, Karl.

Thank you for answering.

Confirmed that the sound is played correctly in external I2S SLAVE mode with v2.4.0,
After that, I implemented all the changes you suggested.

The result is an interrupted mechanical sound that is linked to the played sound.
When there is no sound, there is no sound.
It seems that I2S transmission and reception are not being performed correctly.

If only prj.conf is restored to the original external I2S settings, the audio will be played in monaural with the correct sound.

Therefore, we assume that there is a problem somewhere in the processing branched at HEADSET.
Don't you know what the reason is?

Best Regards.

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

Karl Ylvisaker — Mon, 06 Nov 2023 14:59:39 GMT

Hello again,

Thank you for your patience with this.
Please have a look at this sample based on v2.4.0 as a reference to see the necessary changes to make it a stereo demo.

Best regards,
Karl

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

MontBlanc — Thu, 02 Nov 2023 02:23:22 GMT

Hello,
The latest version when I started working on it was v2.4.2. Since the current latest version is v2.5.0, I will make the same modifications here and try external I2S connection. Please check the modifications to the stereo conversion source code in v2.5.0.

Best Regards.

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

Karl Ylvisaker — Wed, 01 Nov 2023 12:54:58 GMT

Hello,

Thank you for your extreme patience with this.

[quote user="MontBlanc"]Modifying the source code to use external I2S in v2.4.2 worked fine.
I modified the source code to use external I2S in v2.2.0 using the same procedure, but noise is always output to I2S DATA. (At this time, I have not yet modified the source code to make it stereo.)

I want to send and receive external I2S in stereo with v2.4.2.[/quote]

I understand this to mean that it is working to sending and receiving external I2S stereo audio in v2.4.2, is this correct?
If not, could you elaborate and clarify on the issues you are currently facing with this approach using v2.4.2?

Is there any reason why you would like to use the nRF Connect SDK v2.2.0 instead of v2.4.2? Many new features and improvements have been added in between these releases, and now the v2.5.0 is also out - I would recommend upgrading to, and using, the latest nRF Connect SDK version whenever possible.

Best regards,
Karl

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

MontBlanc — Thu, 26 Oct 2023 00:14:19 GMT

Hello,

Modifying the source code to use external I2S in v2.4.2 worked fine.
I modified the source code to use external I2S in v2.2.0 using the same procedure, but noise is always output to I2S DATA. (At this time, I have not yet modified the source code to make it stereo.)

I want to send and receive external I2S in stereo with v2.4.2.
The link you received is the source code of audio_datapath.c, but are there any other parts that need to be modified?

Best Regards.

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

Karl Ylvisaker — Wed, 25 Oct 2023 14:21:51 GMT

Hello,

[quote user="MontBlanc"]Based on the comments I received, I branched with an if statement, built and flashed at the same time, and was able to send and receive beautiful sound between external I2S.
thank you very much.[/quote]

No problem at all - I am glad to hear that the issue was resolved! :)

[quote user="MontBlanc"]Now, as a next step, I want to send stereo.
The I2S of nrf5340 on the RX side currently only outputs Lch.
Could you please tell me where to modify the source code for stereo transmission?
I'm using v2.4.2.
I tried to refer to the post below, but the version is too old and the corrections are different.[/quote]

Let me take a look at what changes are necessary here and get back to you. My initial guess would be that this primarily would require some changes to the I2S initialization in the audio_datapath.

[quote user="MontBlanc"]I also tried to include the same fix for external I2S in this version, but unfortunately the I2S DATA on the RX side had periodic pulses and was full of noise.
Therefore, could you please tell me what has been fixed in the new version?[/quote]

Do I understand you correctly that you upgraded the version to nRF Connect SDK v2.4.2, which broke the external codec/I2S functionality?
If so, could you clarify which nRF Connect SDK version you were working on prior to the upgrade, and whether or not you upgraded your application, or 'remade' it entirely in the v2.4.2?

Best regards,
Karl

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

MontBlanc — Tue, 24 Oct 2023 08:37:45 GMT

Hello,

Based on the comments I received, I branched with an if statement, built and flashed at the same time, and was able to send and receive beautiful sound between external I2S.
thank you very much.
At that time, I found out that P5 and P10 can be connected either way, and that the DIN-DOUT is reversed for P5 and P10.

Now, as a next step, I want to send stereo.
The I2S of nrf5340 on the RX side currently only outputs Lch.
Could you please tell me where to modify the source code for stereo transmission?
I'm using v2.4.2.
I tried to refer to the post below, but the version is too old and the corrections are different.

devzone.nordicsemi.com/.../387700

I also tried to include the same fix for external I2S in this version, but unfortunately the I2S DATA on the RX side had periodic pulses and was full of noise.
Therefore, could you please tell me what has been fixed in the new version?

Best regards,

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

Karl Ylvisaker — Fri, 20 Oct 2023 12:50:26 GMT

Hello,

[quote user="MontBlanc"]I wrote this because I was not confident in changing the source code and thought there might be something missing.
Does that mean that there are no mistakes in the changes made to the source code?[/quote]

No worries - this is very helpful for me to know! :)
I am not quite sure about the last change you mention - changing all returns in hw_codec_init to 0 since you are not calling the function anymore - but other than that it looks alright to me.

[quote user="MontBlanc"]Modify the TX side and build and Flash the B source code only on the TX side. →Sound comes out on the RX side.
Modify the TX side, build and Flash the C source code on the TX side. →There is no sound on the RX side because it is unclear whether the source code has been corrected.
Modify the TX side, build and Flash the source code of A to the TX side. →No sound on the RX side (cause unknown)
Build and Flash the source code of A for TX and RX at the same time. →Sound comes out on the RX side.[/quote]

The default behavior of the nRF5340 LE Audio reference application in the headset configuration is to bond with the connected device, and only look for these devices again when it connects the next time. When you reprogram the gateway it will loose its bond information, and so when it attempts to connect to the headset device it will fail the key exchange which will cause the headset to terminate the connection.

You should see this sequence in the logs from either of the devices.
The easiest fix to this is to either make sure that both devices are flashed when you reprogram one of them, or to modify the application to not use bonding and to accept connections from any gateway device.

Best regards,
Karl

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

MontBlanc — Wed, 18 Oct 2023 02:14:47 GMT

Hello,

I wrote this because I was not confident in changing the source code and thought there might be something missing.
Does that mean that there are no mistakes in the changes made to the source code?

There is one more thing that I am not confident about, but as for the Build and Flash procedures.
Build and Flash the source code of A on the TX(gateway) side and RX(Headset Left) side respectively. In this state, a sound will be heard.
After that, Flash and Build will not be executed on the RX side.

Modify the TX side and build and Flash the B source code only on the TX side. →Sound comes out on the RX side.
Modify the TX side, build and Flash the C source code on the TX side. →There is no sound on the RX side because it is unclear whether the source code has been corrected.
Modify the TX side, build and Flash the source code of A to the TX side. →No sound on the RX side (cause unknown)
Build and Flash the source code of A for TX and RX at the same time. →Sound comes out on the RX side.

In other words, if Flash and Build are repeated only on the TX side, the RX side may also be in an abnormal state.
Are my Build and Flash procedures correct?
Is it necessary to branch TX and RX using an if statement in the source code and build and flash them at the same time?

Best Regards.

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

Karl Ylvisaker — Tue, 17 Oct 2023 18:32:40 GMT

Hello,

[quote user="MontBlanc"]thank you for your reply.[/quote]

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

[quote user="MontBlanc"]I believe I have followed the steps below, but I may be missing something.[/quote]

Your changes looks alright to me - How does your logs look with these changes, and what is it that goes wrong when you say 'may be missing something'?

Could you confirm which version of the nRF Connect SDK you are working wtih?

Best regards,
Karl

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

MontBlanc — Mon, 16 Oct 2023 10:20:04 GMT

Hello, thank you for your reply.

I believe I have followed the steps below, but I may be missing something.
Actually, the LED on OB/EXT has changed to orange.

Remove hw_codec_init() and all CS47L63 related code from the project
This ay not be done correctly.

main.c
#include <hal/nrf_gpio.h>

and added
nrf_gpio_cfg_output(21);
nrf_gpio_pin_set(21);
inside
int main(void){}

audio_system.c
"ret = hw_codec_init();"
delete

hw_codec.c
Change all "return ret" in to "retuern 0"

Are there any other changes?

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

Karl Ylvisaker — Mon, 16 Oct 2023 09:42:53 GMT

Hello,

Just to aid my understanding so that I may best advice you, is your overall goal to interface the nRF5340 Audio DK with an external hardware codec that outputs I2S at 3.3V?

[quote user="MontBlanc"]Could you please give me detailed steps to use external hardware codec?[/quote]

Please follow these steps to work with an external hardware codec:

Best regards,
Karl

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

MontBlanc — Mon, 16 Oct 2023 09:28:52 GMT

Hello,

When connected to P5, I found that the output of CIRRUS's CODEC collided with the external 3.3V I/F, causing the audio to be heard mixed with noise.
With the P5 connection, even if the level shift is correct, noise (output from CIRRUS) will be mixed in the I2S DATA line and no sound will be produced.

Also, I have connected the P10 to the 1.8V I/F I2S with a software setting that turns OB/EXT orange, but there is no sound.
Could you please give me detailed steps to use external hardware codec?