RTC

USE STM Internal RTC	https://embedded-lab.com/blog/stm32s-internal-rtc/
Atmel RTC calibration appnote	https://ww1.microchip.com/downloads/en/Appnotes/Atmel-42251-RTC-Calibration-and-Compensation_AP-Note_AT03155.pdf

Схемотехника

Калибровка

ICs

BL5372

BL5372 - аналог Dallas DS1337, однако I2C обмен отличается ???

PCF8523TK/1,118

Clock operating voltage: 1.0 V to 5.5 V

Vth(sw)bat is the battery switch threshold voltage. Typical value is 2.5 V.

When VBAT drops below the threshold value Vth(bat)low (typically 2.5 V), the BLF flag (register Control_3) is set to indicate that the battery is low and that it must be replaced.

VBAT battery supply voltage power management function active 1.8 - 5.5 V

Vth(sw)bat battery switch threshold voltage 2.1 2.5 2.7 V