Cis mode - Mic issues

[Abdulmohaimen]

Hi,

With this setup in Issue with Stereo Sound from External Codec on nRF5340 DK (SDK v2.6.2) , I successfully built a CIS mode using my nRF5340 DKs, enabling stereo sound while the microphone is active.

However, I am currently experiencing several issues:

• The recorded microphone signal is accelerated, playing back faster than it was recorded.
• The input signal quality is poor when using an analog microphone, but it improves significantly with a digital microphone.
• When using the microphone and playing audio through the headset simultaneously, the recorded sound is barely audible (very low signal strength).
• Occasionally, one of the DKs disconnects, causing a complete loss of audio.

Any insights into what might be causing these issues? and how might they be solved?

Thank you in advance—I truly appreciate your time and support.

Best regards,
Abdulmohaimen Algamoudi 

[dejans]

Hi,

On which specific board do you experience issues?

Do you still use NCS v2.6.2?

Best regards,
Dejan

[Abdulmohaimen]

Hey Dejan,
The nrf5340 audio DK as well as the BC40C from Fanstel.
The sdk is V2.8.0

Thank you in advance

Best regards,
Abdulmohaimen Algamoudi 

[Abdulmohaimen]

Hi Dejan,

When I use the microphone to record a voice signal on my computer, the playback (of the microphone recorded signal) sounds faster than the original recording. This affects the signal quality, making it appear accelerated—roughly by a factor of 1.25 to 1.3 (an estimation).

The microphone is connected to the DA7212 hardware codec. I haven’t modified the sample rate, so I assume it's the same for both recording and playback.

Additionally, I measured the clock signal from the NRF DK and noticed:

• MCLK: 3.471 MHz
• BCLK: 1.536 MHz
• WCLK: 48,000 Hz

This is the set up i am using for the HW codec as salve setup:

  ret = da7212_write_reg(DA7212_PLL_CTRL, DA7212_PLL_EN_MASK | DA7212_PLL_SRM_EN_MASK |  DA7212_PLL_INDIV_2_10MHZ); 
     if(ret < 0)
     printk("da7212 write operation failed\n");
       // Set the frame length to 32.
     ret = da7212_write_reg(DA7212_DAI_CLK_MODE, DA7212_DAI_BCLKS_PER_WCLK_BCLK32 ); 
     if(ret < 0)
     printk("da7212 write operation failed\n");   
 
 
     // Enable Digital Audio Interface (DAI)
     ret = da7212_write_reg(DA7212_DAI_CTRL, DA7212_DAI_EN_MASK | DA7212_DAI_OE_MASK); 
     if(ret < 0)
     printk("da7212 write operation failed\n");
 
     
     ret = da7212_write_reg(DA7212_SR, DA7212_SR_48KHZ);
     if (ret < 0) printk("Sample rate configuration failed\n");

Best regards,
Abdulmohaimen

[dejans]

Hi Abdulmohaimen,

Abdulmohaimen said:

I have applied the modifications from the GitHub link and made changes to the hardware codec file to configure the codec. Additionally, I enabled the I2S configuration to utilize the external HW codec.

Can you show all your modifications/changes and provide GitHub link?

Best regards,
Dejan

[Abdulmohaimen]

Hi Dejan, i have showed them to this privat artical.
Can you check it?
 
Thank you in advance
Best regards,
Dejan

[dejans]

Hi Abdulmohaimen,

Thank you for showing your code changes in another ticket.

Before looking into it, I have some questions related to your previous reply where you provided additional details about microphones. I also need some clarifications and additional information.
1. For two DKs that you use for left and right channel (described as headsets), do you want to use them as earbuds, one channel per ear with a single channel to each?
2. It looks like you have 2 microphones. Are these 2 microphones connected to the same DK or to different DKs?
3. How many DKs do you use in total?
4. Which kit do you have connected to the computer - headset kit or microphone kit?
5. Is the recorded signal audio that has been sent over LE Audio and then recorded, or is it tapped directly from the microphone DK?
6. Can you provide picture/diagram of all devices involved, how they are connected, and which signals are transferred between them? Please label external HW codec, the microphone kits, the headset kits, the computer used for the recording, any other devices involved and the connections/signals going between them.
7. Do you want to have stereo bidirectional communication?
8. Did you try to use demo branch provided in the previous ticket which you linked in your initial post?
9. Are you trying to use USB (not I2S) as audio interface?

Best regards,
Dejan

[Abdulmohaimen]

Hi Dejan,

1. Yes, 2 channels in CIS mode are used to provide stereo sound while also supporting on-device microphone input.

2. The microphones are connected to the DA7212 evaluation board, which is connected to the nRF5340 DK via I²S.

3. There are 3 nRF5340 Audio DKs in the setup (2 headsets and 1 gateway), with each gateway connected to a DA7212 evaluation board over I²S.

4.The gateway is connected to the computer via USB.

5. Audio is recorded from the microphones using the DA7212, then sent over I²S to the headset and over BLE to the gateway.

6

7 as far as i know yes.
8 yes 
9 the gateway is connected to the computer via usb.

I believe the issue may be related to the USB interface. I tested recording an input signal using the unmodified configuration of the nRF5340 Audio DK from the SDK. I used the on-board codec in two scenarios:

1. Connecting the gateway to the computer via USB.

2. Using the I²S source in prj.conf and feeding the signal through the line-in input.

I noticed that the signal recorded via USB was accelerated. Is it possible to change the data format or sampling rate of the USB configuration?

Thank you in advance
Best regards,
Dejan

[dejans]

Hi Abdulmohaimen,

I am not able to open your picture/diagram for point 6. Which format is you picture/diagram in? Can you please try to upload it again by first zipping the file and then upload it using Insert->Image/video/file->Upload?

Best regards,
Dejan

[Abdulmohaimen]

Hi Dejan,
Sure. can you see it know?
Best regards,
Dejan

[dejans]

Hi Abdulmohaimen, 

Thank you for additional information.

Abdulmohaimen said:

Sure. can you see it know?

I can see it now. I will look into this. I expect to get back to you by the end of the week.

Best regards,
Dejan

[Abdulmohaimen]

Hi Dejan,
Thank you so much—Looking forward to your feedback. 

I truly appreciate your time and support.

Best regards 
Abdulmohaimen 

[dejans]

Hi Abdulmohaimen,

Previous demo worked for combining L and R into one frame and sending it to a single headset. I have checked internally the requirements which could be supported by the CPU. 
Scenario of having CIS gateway sending stereo channel stream (combined left and right into a frame) to 2 headsets and having USB as interface to collect MIC from both headsets, will probably (i.e. can be expected to) overload available bandwidth. Unfortunately, it cannot be expected that gateway side will be able to handle
- encoding 2 streams for 2 headsets
- decoding 2 streams from MIC in both headsets
- use USB as audio interface

Best regards,
Dejan