https://devzone.nordicsemi.com/f/nordic-q-a/118474/nrf5340-i2c-master-clock-generator-fractional-divider-possible-with-mckfreqWe want to generate 8.200 MHz as I2S MCK with an nRF5340. This could be achieved with 12.300 MHz ACLK as source for MCK, and then dividing by 1.5 in the Master clock generator. An MCKFREQ register value of 0xAAAAA000 = 2863308800 looks like it coulden-USTelligent Community 13Tue, 04 Feb 2025 12:50:10 GMThttps://devzone.nordicsemi.com/thread/521303?ContentTypeID=1Tue, 04 Feb 2025 12:50:10 GMT137ad170-7792-4731-bb38-c0d22fbe4515:9b72f2c9-5092-4e96-8b1f-f3feb0146b77Wolfgang R<p>Well, thanks anyway.</p> <p>Regards,<br />Wolfgang</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/521291?ContentTypeID=1Tue, 04 Feb 2025 12:07:07 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4ccca0c0-8719-491f-a0fc-5c83f8fc0523Maria Gilje<p>Hello,</p> <p>Bad news: The I2S MCK can not be used to get to a frequency of 8.2 MHz. You will need to have an external clock source to reach your goal.</p> <p>Best regards,</p> <p>Maria</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/520917?ContentTypeID=1Fri, 31 Jan 2025 15:03:08 GMT137ad170-7792-4731-bb38-c0d22fbe4515:281b497d-46ba-4f0e-9e0d-f5006197977dMaria Gilje<p>Thank you for the explanation. I will have a chat with said experts and let you know if it is possible. My apologies in advance for this leaking over to next week timing-wise.</p> <p>Best regards,</p> <p>Maria</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/520767?ContentTypeID=1Thu, 30 Jan 2025 16:07:19 GMT137ad170-7792-4731-bb38-c0d22fbe4515:05d93773-fca5-4adc-b0bb-f3d105290e94Wolfgang R[quote userid="116814" url="~/f/nordic-q-a/118474/nrf5340-i2c-master-clock-generator-fractional-divider-possible-with-mckfreq/520762"]if you can explain why you need 8.200 MHz I would like to know.[/quote] <p>The 8.2 MHz are needed for&nbsp;an ultrasonic transducer. And also 64 kHz in sync with it, which could easily be generated by LRCK = MCK / 128.<br />It is not an I2S application. I only found no way to generate 8.2 MHz with the PWM units.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/520762?ContentTypeID=1Thu, 30 Jan 2025 15:40:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:c3d5768f-0cce-4b23-8b1a-09443143cefaMaria Gilje[quote user=""]Is this true? Can the Master clock generator only do integer ratios despite its MCKFREQ configuration register suggesting many more possibilities and fractional division?[/quote] <p>Yes, this is the correct interpretation of the documentation. The I2S peripheral on the nRF5340 does cover the most common clock frequencies, so if you can explain why you need 8.200 MHz I would like to know. </p> <p>Let me have a chat with some of our experts and then I will get back to you after I know what options are available to generate 8.2 MHz MCK.</p> <p>Best regards,</p> <p>Maria</p><div style="clear:both;"></div>