Real-time clock (RTC) support for Raspberry Pi 5

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1

Hi,

I’m wondering whether info-beamer hosted supports the RTC to Raspberry Pi 5, and if so: 1) what needs to be done to enable it, and 2) is the device set to charge the RTC backup battery by default, or not? (Can that be changed?)

https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#real-time-clock-rtc

I’m planning to use info-beamer at an upcoming conference, and Wi-Fi access requires certificates, so I’m looking into enabling RTC on the devices, so that the OS has a viable wall clock before NTP is available.

Thanks!

2

I think it should work out of the box. On a test Pi5, I see the following kernel output, even before control is handed to the userland:

[    0.372580] rpi-rtc soc@107c000000:rpi_rtc: registered as rtc0
[    0.373993] rpi-rtc soc@107c000000:rpi_rtc: setting system clock to 2026-07-28T12:30:27 UTC (1785241827)

So not only is the time set when the Linux kernel starts, the time was also persisted in the previous boot cycle. I’m not entirely sure when that happened though, but it’s definitely not something done by the info-beamer OS. I guess the kernel persists the time on reboot?

I currently don’t have a battery connected, so having an RTC time requires me to not remove power between reboots, but with a battery that obviously should be the case.