I also use a DS3231 RTC except it's on a Pi3B+.
All I have in my /boot/config.txt which applies to the RTC:
Code: Select all
I would try commenting out everything but those, then work from there. After a reboot, try the
i2cdetect -y 0
command and see if it reports 'UU' in place of 0x68. If port 0 no longer works, try
i2cdetect -y 1
Two possible issues stand out to me. For the first - I'm not familiar with the CM3+, but my basic understanding is it's essentially a 3B+ in a different form factor. Per this page
(at the bottom), beginning with the 512M Pis the i2c port was changed from 0 to 1. FYI, my Pi3B+ uses i2c port 1. Your current config file specifies running i2c on port 0. Possible misconfiguration there.
As to the second possible issue, I would try running the default 100KHz on the i2c until you get the RTC working, then experiment running the higher rate if you actually need it. Although I cannot find the link at the moment, I also seem to recall reading some chatter over at the RPi forums about how there was/is a bug with the i2c configuration regarding rate; the gist was that the config file required using a higher value to get an actual 400KHz rate. Since I did not have a reason to run 400KHz, I didn't pursue it further. That issue may have already been solved, but it's something to keep in mind.
Running with the config.txt parameters I listed above should have the i2c run on the correct port for your device as well as the default 100KHz. See where that gets you, and we can go from there.