Accessing I2S mic

RE: Accessing I2S mic

Maria Gilje — Fri, 17 Jan 2025 13:04:25 GMT

Hello,

My apologies for the delay.

Have you made any progress since your last reply?

Best regards,

Maria

RE: Accessing I2S mic

Kashyap23 — Wed, 16 Oct 2024 18:17:06 GMT

Hi,I checked without configuring any MCKFREQ , When I am doing debugging I can see MCKFREQ register has the value of 343597056.Is it compulsary to configure as it's showing the required value for respected SCK and LRCK.I think it's internally configured based on sampling frequency and bit width, when I am changing those I can see change in MCKFREQ value.And in final this may not be issue of getting wrong data.

RE: Accessing I2S mic

Maria Gilje — Tue, 15 Oct 2024 14:29:54 GMT

Thank you for sharing the new overlay file. It looks correct.

I suspect the missing piece is to configure the MCK in the source code. This is not possible with the Zephyr I2S API, but can be done by setting the CONFIG.MCKFREQ register. You can compute the value with the MCKFREQ equation (Figure 3.) from the Master Clock section of the I2S peripheral and for f_MCK = 1.024 MHz and f_source = 12.288 MHz the MCKFREQ value is 343597056 or 0x147AE000 this value can also be found in row four in the table I sent previously.

Please see this reply from my colleague on a previous case for further considerations when configuring MCK.

If you don't want to set the register directly you can use the nrfx: I2S driver to configure MCK. The result from the MCKFREQ equation is used as the mck_setup here as well, see the configuration from the nRF5340 Audio application here for reference.

Best regards,

Maria

RE: Accessing I2S mic

Kashyap23 — Tue, 15 Oct 2024 09:59:37 GMT

&pinctrl {

i2s0_default: i2s0_default {

group1 {

psels = <NRF_PSEL(I2S_SCK_M, 0, 26)>,

<NRF_PSEL(I2S_LRCK_M, 0, 25)>,

<NRF_PSEL(I2S_SDIN, 0, 7)>,

<NRF_PSEL(I2S_SDOUT, 0, 6)>;

};

i2s0_sleep: i2s0_sleep {

group1 {

psels = <NRF_PSEL(I2S_SCK_M, 0, 26)>,

<NRF_PSEL(I2S_LRCK_M, 0, 25)>,

<NRF_PSEL(I2S_SDIN, 0, 7)>,

<NRF_PSEL(I2S_SDOUT, 0, 6)>;

};

&clock {

status = "okay";

hfclkaudio-frequency = <12288000>;

};

i2s_rxtx: &i2s0 {

status = "okay";

pinctrl-0 = <&i2s0_default>;

pinctrl-1 = <&i2s0_sleep>;

clock-source = "ACLK";

pinctrl-names = "default","sleep";

};

By using this I can get SCLK==1.024MHz and LRCK=16kHz.

Is there relation b/w hfclkaudio-frequency = <12288000> and SCLK,LRCK .As if I am removing the hfclkaudio-frequency in overlay file,I able to get SCLK as 1.024MHz and LRCK =16kHz

RE: Accessing I2S mic

Maria Gilje — Tue, 15 Oct 2024 08:16:11 GMT

[quote user="Kashyap23"]To be mentioned that is not the updated datasheet [/quote]

Thank you for letting me know. I see that the frequency range is updated in the new revision to include 1024 kHz.

[quote user="Kashyap23"]Does the ACLK clock implementation\configuration correct?[/quote]

The new values looks to be correct in your written sentence. Please share your updated .overlay so I can verify that the configuration is correct there as well.

In your previous overlay, the clock node is missing status = "okay";

Also, have you investigated the timings as mentioned before?

Best regards,

Maria

RE: Accessing I2S mic

Kashyap23 — Sun, 13 Oct 2024 13:15:18 GMT

To be mentioned that is not the updated datasheet .The datasheet you are referring is REV-B but updated one is REV-C.As per updated datasheet I am using sampling rate as 16000 and Ratio 64x and source frequency 12288000 but data is not coming correctly .Does the ACLK clock implementation\configuration correct?

RE: Accessing I2S mic

Maria Gilje — Thu, 10 Oct 2024 12:20:40 GMT

Hi Kashyap,

Please check the that these requirements from the SPH0645 datasheet are met:

The screenshot is from page 8.

From the datasheet I found that having SCK/BCLK below 2.048 kHz is out of spec for the microphone.

You can check the timings with a logic analyser, for example.

Based on the datasheet for the SPH0645 and nRF5340 SoC, a possible configuration to use is marked in yellow here:

The table is from the Configuration examples section of the I2S peripheral for the nRF5340.

Best regards,

Maria