About nRF5340 Audio I2S SCLK settings

RE: About nRF5340 Audio I2S SCLK settings

dejans — Mon, 15 Jul 2024 09:04:12 GMT

Hi,

For getting exactly 12.288 MHz for MCLK you should use bypass mode which selects audio PLL as clock source. In this case MCKFREQ would be ignored.

Best regards,
Dejan

RE: About nRF5340 Audio I2S SCLK settings

dejans — Fri, 05 Jul 2024 13:37:33 GMT

Hi,

I have not got an update on this yet. I will try to provide an update during next week, but please note that it is summer vacation period and delayed replies can be expected during this period.

Best regards,
Dejan

RE: About nRF5340 Audio I2S SCLK settings

dejans — Mon, 01 Jul 2024 08:41:59 GMT

Hi,

I have requested more information on this internally. I expect to get back to you by the end of this week.

Best regards,
Dejan

RE: About nRF5340 Audio I2S SCLK settings

Junichi — Thu, 27 Jun 2024 07:28:16 GMT

This is because I want to output a 12.288MHz MCLK to the IC on the other end of the I2S.

The IC I'm connecting to is an AK4432, and I want to output a 12.288MHz MCLK to it.

RE: About nRF5340 Audio I2S SCLK settings

dejans — Thu, 27 Jun 2024 07:09:46 GMT

Hi,

Could you please provide information about your use case? Can you please also provide information why you need to set MCLK value directly in the code and what you try to achieve?

Best regards,
Dejan

RE: About nRF5340 Audio I2S SCLK settings

Junichi — Mon, 24 Jun 2024 05:07:38 GMT

Thank you for your reply.

The current setting of 48kHz for LRCK is fine, so to change the bit width to 32bit I added the following to the prj_release.conf file:

CONFIG_AUDIO_BIT_DEPTH_32=y

I was also able to check the waveform with an oscilloscope.

I still don't know how to change MCLK.

Which part of which file should I change, and how?

Please tell me specifically.

RE: About nRF5340 Audio I2S SCLK settings

dejans — Thu, 20 Jun 2024 11:42:50 GMT

Hi,

I would first recommend that you update to the NCS v2.6.1.

For setting the clock and bit width to the ones supported by the application, please refer to the nrf\applications\nrf5340_audio\src\audio\Kconfig and specifically to AUDIO_SAMPLE_RATE_HZ and AUDIO_BIT_DEPTH. This would result in correct I2S settings without further actions from your side. However, if you have requirements that does not fall within supported settings, you can look at the nrf\applications\nrf5340_audio\src\modules\audio_i2s.c file. This file contains configuration for I2S. There you can find MCLK configuration. Currently, clock supports only 16 KHz, 24 KHz and 48 KHz sampling rates. By selecting the ratio located in the Kconfig file in combination with sample width from the same Kconfig file, LRCK and BCLK can be obtained. If you want to have a different ratio then you can refer to CS47L63 TRM in nrf\application\nrf5340_audio\src\drivers\cs47l63_reg_conf.h and modules\hal\nordic\nrfx\hal\nrfx_i2s.h for register settings. New sample ratio would need to be defined in nrf\applications\nrf5340_audio\src\modules\audio_i2s.c and the Kconfig mentioned above should be updated to allow that frequency to be selected.

Best regards,
Dejan

RE: About nRF5340 Audio I2S SCLK settings

Junichi — Wed, 19 Jun 2024 00:49:29 GMT

Thank you for your reply.

I checked, but I don't quite understand.

Please tell me specifically which parts of nRF5340 Audio I should change and how.

RE: About nRF5340 Audio I2S SCLK settings

dejans — Tue, 18 Jun 2024 06:57:51 GMT

Hi,

nRF5340 product specification provides information about I2S peripheral in its chapter 7.15. In master mode, both serial clock (chapter 7.15.3) and left right clock (chapter 7.15.4) are generated from the master clock (MCK, chapter 7.15.5). MCK is generated from the clock source selected in the CONFIG.CLKCONFIG and CONFIG.MCKFREQ registers. The clock source for the master clock generator can be selected in the register CONFIG.CLKCONFIG. Depending on which clock source you use PCLK32M or ACLK, there are tables (chapter 7.15.5, Table 83 and 84) which provide configuration examples. Additionally, you can refer to nrfx I2S driver and its nrfx_i2s_config_t configuration structure. One example of using this structure can be found in this discussion.

Best regards,
Dejan