ok, the system uses the external RTC, not the RTC on/in the SoC.
I will use the chip Toradex uses on the IRIS board, but in the manual of the chip, the I²C address reads as 0xD0. But no problem, I don’t have a divice with this address or 0x68 as you wrote in your post.
We will always try to have a connection to mobile Internet, so the time will be correct, but if we can’t do so, we need a reasonable correct time for about a day or two and a ±10ppm crystal will hopefully do that job. Otherwise the user has to correct the time once a day, which is aceptable for a measurement System used in the field.
And there is a GNSS Receiver included too, so I can take the time from there with just some line of codes and a task starting lets say every hour or so.
With best regards