Raspberry Pi 4 RTC

Configuration
1

I have a relatively simple HA (just a few automations for now) running on a Raspberry Pi 4. After reading about SD card issues, I now have the Pi booting from an NVMe/USB.

So far, so good except for a nagging problem. Every time I have to reboot the Pi I have to manually reset the correct date and time. The Pi has no RTC with battery to preserve the time/date settings between boots.

There are add-on RTC boards for the Pi but I’m wondering if it’s worth it as I will eventually have to migrate to something bigger anyway.

Has anyone else found a solution for this issue?

2

HAOS tries to set the time using an NTP server. You should not need to manually set the time unless NTP is being blocked or not available.

3
  1. The cheap RTC boards don’t just work.
    Many are a DS3231 and need to be setup both on the kernel boot config.txt, and read / written with a privileged command.
    This might work if you run custom Debian with containers, but not with the deliberately locked-down HAOS.
  1. As MaxK just posted - wait 10 seconds after boot and the clock will be set from a remote Internet time server via NTP, so there’s no point (unless you’ve got no access…).

Unlike the RPi4, the RPi5 has a hardware RTC and supports battery backup, but I only added the cell as it’s £4 and a novelty. I found the DS3231 modules weren’t worth the hassle of setup, and maintaining changes to scripts across upgrades was more trouble than they’re worth.

The only use I found was fractionally improving lock times with a GPSr on a boat navigation device - and later GPSr include battery-backed RTC and ephemeris anyway.

4

When they announced the Yellow, based on a Pi 4 compute module and having a RTC, I hoped they would add support for a RTC on regular PI’s. But they did not.

5

Thanks for the info. I won’t waste my time or money on upgrading the Pi.

BTW, I did manage to get NTP working on the Pi, as described in another post.