Real Time Clock in STM32

Written in November 11, 2025

2025   ·   TIL

What is Real Time Clock (RTC)?

  • It refers to a hardware component (peripheral).1
  • Features timekeeping such as calendar with alarms, when the device is running in a low-power mode (e.g. run on a coin battery).2
  • In STM32 board, it is clocked by the low-speed external oscillator (LSE) at 32.768 kHz, the RTC is functional even when the main supply is off. However, the VBAT (Voltage of Battery) domain needs to be supplied by a backup battery.3

Reference

  1. https://wiki.st.com/stm32mcu/wiki/Getting_started_with_RTC ↩

  2. https://controllerstech.com/internal-rtc-in-stm32/ https://www.st.com/resource/en/product_training/stm32l4_wdg_timers_rtc.pdf ↩

  3. https://www.st.com/resource/en/product_training/stm32l4_wdg_timers_rtc.pdf ↩