Incorrect hour rollovers on Adafruit Feather M0 board.

[cavemoa]

Hi, have just started using your library on the adafruit Feather M0 board which has a SAMD21.

I get some strange behavior with the roll over of hours when I set the using the simplertc example:

12:00:00 rolls over to 28:00:00 !
28:59:59 then rolls over directly to 17:00:00
It then runs correctly for a few hours to 23:59:59 which rolls over to 24:00:00 and does not increment the day/date.

Another board user has confirmed they have the same behavior.

I'm guessing it must be chipsetup as I presume the issue doesn't arise on the Arduino Zero. Any thoughts?
Cheers Jon

[GabrielNotman]

The register bit RTC.MODE2.CTRL.CLKREP is being set incorrectly.
That bit should only be set for 12hr mode.

In 12 hour mode, the highest bit is used to specify AM/PM. If this is read as a 24 hour value, it results in all PM values having 16 added to them.

[sandeepmistry]

@GabrielNotman is this resolved now that #3 has been merged?

(In particular this line https://github.com/arduino-libraries/RTCZero/pull/3/files#diff-6ed0013c42219b7dc3d3d5d163434a8fR55)

[GabrielNotman]

I haven't test the post merge version.
But, yes It should be.

[sandeepmistry]

@GabrielNotman yes, looks good to me. I tried the following initial time values with the SimpleRTC examples:

/* Change these values to set the current initial time */
const byte seconds = 55;
const byte minutes = 59;
const byte hours = 11;

/* Change these values to set the current initial time */
const byte seconds = 55;
const byte minutes = 59;
const byte hours = 23;

With 1.3.1 saw the same issues @cavemoa noted, with 1.4.0 rollover works as intended.

@cavemoa could you please try the latest release (1.4.0)?

[cavemoa]

Yes all seems good post merge to me.

[sandeepmistry]

@cavemoa great! Thanks for verifying!