Using external 32k768 crystal as default clock source instead of the …

[LieBtrau]

…inaccurate internal RC oscillator.

Signed-off-by: Christoph Tack prog.send@gmail.com

[fpistm]

Hi @LieBtrau
Even if the LSI is inaccurate, it has been chosen because not all boards have an LSE.
If your board has an LSE, simply set it before call begin:

STM32RTC/examples/RTCClockSelection/RTCClockSelection.ino

Line 63 in 1c0c41a

rtc.setClockSource(STM32RTC::RTC_LSE_CLOCK);

[LieBtrau]

Hi Frederic,
I learned the hard way that I first have to select the right clock source.
Yesterday I used the "SimpleRTC" example, where that line is not present. If it had been there, selecting either LSE or LSI, I would have realized much sooner that the wrong clock source was the source of the big time deviation with respect to my PC.

I suggest adding that line to the SimpleRTC example. After all, the examples are there to help people who don't know the innards of the library.

[fpistm]

I understand. Example could be updated to add this behaviour.