Real Time Clock DS1307 and Libraries

Other Hardware Sensors
1

I am experiencing apparently strange behaviours when using the following functions to access the DS1307 chip, I am able to write and read back from the DS1307 using the RTC.set and RTC.get functions and the low level functions makeTime, breakTime and CalendarYrtotm and tmYeartoCalendar, using the libraries DS1307RTC.h, Time.h and Wire.h.
My understanding is that the functions set the Year as offset since 1th-January-1970 and I guess that this is correct, if a set aYear that is greater than 2000 and I read it back everything seems to work properly, the problem arises if I set a Year that is less than 2000 for example 1999, in these cases I read back a Year that is completely wrong, but the value read from the Year register of the DS1307 chip is correct (it is the offsey since 1-Jan-1970), I think that the problem is in the libraries that performs some operations using Year 2000.
Is somebody aware about this problem, is this a real problem or it is caused by a wrong use of the library functions or I need some other setup?
If needed I can attach the simple sketch I wrote to test Time Functions.

I look forward to hear from somebody
thank you

Salvatore Sapia

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3

Yes, in fact I am asking to Adafruit (Really the chip is from Dallas Semiconductor, but I think that Adafruit that sells the RTC board knows exactly how the chip works) if they have some answer; I know that this RTC stuff works if I set a Time greater than 2000; but because the Year offset reading from the chip is correct for both year settings (>2000 or <2000) I would be sure I am correctly using the library functions, otherwise a trap could (maybe yes or maybe not) manifest in someway and sometime, this usually happens when software is written using functions that are not completely clear.
thanks

4

Page 8 in the Product Description for DS1307 (http://datasheets.maximintegrated.com/en/ds/DS1307.pdf) might be of help. The problem is the library that adjusts the year. The chip handles 00-99 year value (in BCD). The library adjusts to 20XX.

Depending on what you are looking for you will have to at least have to modify the library, find another library or write your own.

Cheers!