RTC on OrangeCube

Cube Autopilot
1

I’m trying to get a clearer understanding of how the RTC (Real-Time Clock) works on the CubeOrange, specifically when the flight controller is powered off.

1. How does the CubeOrange maintain its RTC when unpowered?

My understanding is that the STM32H7’s RTC can run from the VBAT domain using the LSE 32.768 kHz crystal, but I’m not sure what the CubeOrange/Cube carrier board actually uses for backup power (coin cell, supercap, etc.) or how long the RTC can realistically retain time without main power.

If anyone has measured or documented:

  • How long the CubeOrange can keep accurate time when unpowered

  • Whether the carrier board uses a coin cell or supercapacitor for VBAT

  • Any practical retention duration you’ve observed

…I’d really appreciate the details.

2. Is there any information available about RTC drift on the CubeOrange?

I’m also trying to find out what kind of clock drift to expect from the Cube’s RTC. Since drift depends on the 32.768 kHz crystal tolerance, temperature, and aging, I’m hoping someone knows:

  • The ppm tolerance of the LSE crystal used on the CubeOrange

  • Typical drift per day/week/month

  • Whether ArduPilot applies any RTC calibration

  • Any measurements users have made in real-world conditions

2

The Cube Orange does not have an RTC.
Time is supplied by a GNSS unit, or optionally a ground station. Drift and accuracy depends on the constellations selected, or the time source of the GCS.

If you power up without a GNSS unit (or without a fix) and generate a log file you’ll notice the name of the file will be “1/01/1980 10:00:00 AM”
Time and date will be set correctly once there is a GPS fix.

3

Thanks for the answer.

I was just a bit confused because I thought the CubeOrange might still have an RTC available, since the STM32 itself includes one if I understood the documentation correctly.

My main question is really about how the system time is counted on CubeOrange when no GPS is connected. Is the time purely software‑based, or does CubeOrange use any hardware timer internally? And is there any data on how much this internal time drifts when the system starts from “0” without GNSS time sync?