Extracting the Audio Signal from I2S integration

[Qwelectric]

Good day! I have a nRF52840 based board that I interfaced with a MEMS microphone (SPH0645) through I2S interfacing. I got to the point where sounds made near the microphone affects the data being fed through the board. I assumed that the interfacing is successful.

However, I want to make sure that these data are really sound. How can I extract the PCM data on the I2S buffer to listen to the sound from the microphone, in order to make sure that I was getting the right sound signals?

I am using NCS 2.6.0 and the Seeed Studio Xiao (nRF52840) BLE board. Attached below is the code I am currently using.

/cfs-file/__key/communityserver-discussions-components-files/4/echo_5F00_2.zip

Thank you!

[dejans]

Hi,

Good day! I have a nRF52840 based board that I interfaced with a MEMS microphone (SPH0645) through I2S interfacing. I got to the point where sounds made near the microphone affects the data being fed through the board. I assumed that the interfacing is successful.

Could you provide more information about the "data being fed through the board" and about the "sounds made near the microphone"?

Could you also provide more information about your application?

Best regards,
Dejan

[Qwelectric]

I use this code to print the I2S memory as int so I can check the change in values on the serial monitor.

            unsigned int* value_ptr = (unsigned int*)mem_block;
    		unsigned int value = *value_ptr;
   			printk("Received audio data: %d\n", value);

This video can help on this case. I have another ticket that might be useful too. Thank you!

[dejans]

Hi,

You might want to look at the functions i2s_read() which reads the data from Rx queue and i2s_buf_read() which reads the data from Rx queue into the buffer.

Best regards,
Dejan

[Qwelectric]

I do use i2s_read(). That is how I get the I2S data to the I2S buffer similar to the echo example from zephyr. I want to extract the PCM data from the I2S buffer into somewhere where I can hear the sound the microphone received. The ticket I referenced earlier has the code I use for this application. Idk if you saw it.

[dejans]

Hi,

To be able to hear audio data, you would need to have Digital to Analog Converter on your board. This article provides information on how to convert I2S/PCM captures into audio.

Best regards,
Dejan

[Qwelectric]

Just want to clarify on this, does i2s_buf_read() copy the data from the Rx queue into the buffer? I have been trying to make i2s_buf_read work but I can't seem to do it. Do you have any example codes where it uses i2s_buf_read so I can see? 

This is my current code and it just uses the i2s_read() function. I want to access the data per sample, not per block. With this, I think i2s_buf_read works better for my application if my assumption that it transfers the Rx queue to the buffer is right. 
 echo_2 (2).zip

[Kenneth]

Hello,

Looking at the implementation of z_impl_i2s_buf_read() I can see that there is a mempy() to the buffer supplied by i2s_buf_read(). Searching in ncs repositories I can find some usage of "i2s_buf_read(".

Kenneth