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I bought a RTC DS3231 because of the accuraty of time (2ppm, I was searching an accurate RTC). When I received it, I checked that in the encapsulating it is as well marked like DS3231.

But, after install the RTC, I realized that it seems DS 1307. I executed:

dmesg | grep rtc
[    4.129921] rtc-ds1307 1-0068: registered as rtc0

Why the response is DS1307 instead of DS3231? Is it more or less the same RTC (having the same ppm)?

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    What's in your /boot/config.txt to activate the device? IIRC it should be dtoverlay=i2c-rtc,ds3231. See /boot/overlays/README for detailed info – Dirk Jan 17 at 12:38
  • yes, I put exactly dtoverlay=i2c-rtc,ds3231 at the end of the file (/boot/config.txt) @Dirk – user940969 Jan 17 at 12:53
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If two devices are compatible to the point they can share the same driver, the driver usually gets the name of the first device it was implemented for. Additionally, in your case the driver specifically states

We can't determine type by probing.

Simply put, there is no way for the driver to tell whether you got a DS1307 or a DS3231.

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Most of the RTC modules supported use the same commands as 1307 so use the same driver.

They may operate on different voltages and have additional features, but none are supported by the driver (and not needed for basic RTC function).

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