NULA ESP32-S3 external 32kHz RTC crystal configuration

TECHNICAL SUPPORT NULA Development Boards
1

Customer:

I want to use a crystal-driven 32kHz clock source for the RTC clock.

  • Is this possible on the NULA board?
  • If yes, which pins should I use?
  • Is there already such a crystal on the board (I see a 32.768 crystal)?
  • If yes, can I use it by simply selecting “External 32 kHz crystal” in ESP-IDF SDK Configuration Editor (MenuConfig)?

Originally submitted via email support on 30 November 2025. Migrated to the forum for community visibility.

2

Soldered Support:

The NULA board already has a 32kHz crystal onboard connected to the RTC. The RTC was placed on the board for precise wake times, so the ESP32 doesn’t have to use the internal clock in deep sleep mode. You can enable this by selecting “External 32 kHz crystal” in the ESP-IDF SDK Configuration Editor (MenuConfig).

Attachment omitted in migration: Soldered NULA ESP32-S3 Low-Power Schematic.pdf