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RTC accuracy
Posted:
Thu Oct 09, 2014 9:42 amby Jostikas
Hi all!
I'm wondering what the accuracy of the built-in LFC is? Could I rely on it for an accuracy of no more than 1 min/24 h drift (~0.05%)? Or should I add an external XO (As I understand, there's no option to just add a crystal for the LFC).
Re: RTC accuracy
Posted:
Thu Oct 09, 2014 11:02 amby Bert
It might as well be a simple RC oscillator (as in other cheap MCUs), in which case a 5% accuracy would already be better than expected.
Re: RTC accuracy
Posted:
Thu Oct 09, 2014 11:27 amby jonsmirl
I am aware of three schemes:
1) use the main crystal (20Mhz esp?) and divide to get 32Khz for RTC
2) use two crystals. In deep sleep 20Mhz is turned off. Running 32Khz uses far less power
3) An internal RC for a low power 32Khz clock. That RC is periodically tuned by comparing it to the 20Mhz crystal. So the 20Mhz crystal can be turned off. This mode is not very accurate and you have to turn the 20Mhz crystal on a lot to check.
Unknown which of these modes esp8266 is using.
Re: RTC accuracy
Posted:
Thu Oct 09, 2014 11:51 amby Jostikas
Thanks, I guess an external LFC is in order.