NAS kit w/ NEO LTS: RTC not surviving reboots

[Makda Mujji]

The 1-bay NAS kit v1.2 has an RTC with option to add CR2032 button cell to keep HW time when system is shut down. But running `timedatectl` when device is booted in offline mode shows RTC is set to 1970-01-01 00:00:00 which defeats the purpose of having the option of CR2032. And yes, the button cell have juice; I've bought it a week ago and tested it before putting it in the kit.

[Makda Mujji]

Allwinner H3 CPU has an in-built RTC which is mounted at /dev/rtc0. This is the reason the RTC doesn't save current time when CPU powers off. The RTC present on the NAS kit (DS1307) needs to be accessed using i2c interface which itself needs to be enabled before doing anything else, and all time sync done with DS1307.

 

Enable i2c (i2c-tools is present in Armbian bullseye by default) by editing /boot/armbianEnv.txt file:

sudo nano /etc/armbianEnv.txt

in the line

 overlays=...

where "..." means there are already some overlays mentioned, append " i2c" (notice a space before i2c) so that the line should look like

overlays=... i2c

Save and close. Next, make sure DS1307 module is present in your kernel (it is present in Armbian bullseye by default)

sudo modinfo rtc-ds1307

If you see some description and a signature, it is present. Load the module on system start up by adding line to /etc/modules:

sudo echo rtc-ds1307 >> /etc/modules

 Run the following command:

sudo i2cdetect -y 0

If you see something like this:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

then you can see rtc1 in /dev:

sudo ls -al /dev/ | grep rtc

You need to initialize rtc1 (one time):

sudo hwclock --rtc /dev/rtc1 --systohc

Create a new file called rtc_ds1307 and add following text (copied from here) by following command:

sudo cat <<EOF > rtc && sudo mv rtc /etc/init.d/rtc_ds1307 && sudo chmod +x /etc/init.d/rtc_1307
#! /bin/sh
### BEGIN INIT INFO
# Provides: rtc_ds1307
# Required-Start: $remote_fs $syslog
# Required-Stop: $remote_fs $syslog
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: DS1307 real-time clock usage script
# Description: This file should be used to construct scripts to be
# placed in /etc/init.d.
### END INIT INFO
# PATH should only include /usr/* if it runs after the mountnfs.sh script
PATH=/sbin:/usr/sbin:/bin:/usr/bin
DESC="ds1307_rtc maintenance service"
do_start() {
	echo "Selecting correct RTC instance"
    	echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-0/new_device
    	sudo ln -f -s /dev/rtc1 /dev/rtc
	echo "Syncing system time to RTC"
    	#You need to sync from rtc1 instead of default (rtc0)
	sudo hwclock -s -f /dev/rtc1
}
do_stop() {
	echo "Syncing RTC to system time"
	sudo hwclock -w
} 
case "\$1" in 
	start) 
		do_start 
		;; 
	stop) 
		do_stop
		;; 
	status) 
		echo "RTC time:" hwclock -r 
		echo "System time:" date
		;; 
	restart|force-reload)
		do_stop 
		;; 
	*) 
echo "Usage: rtc_ds1307 {start|stop|status|restart}" >&2 exit 3 
;; 
esac
EOF

Update rc.d then reboot:

sudo update-rc.d rtc_ds1307 defaults
sudo reboot now

Check your system time by following command:

timedatectl

 

Edited April 27, 2023 by Makda Mujji
Added code blocks

[Makda Mujji]

Few changes to above answer:

Edit armbianEnv.txt by

sudo nano /boot/armbianEnv.txt

And append i2c0 instead of i2c

overlays=... i2c0

install i2c-tools

sudo apt install i2c-tools

If your "sudo i2cdetect -y 0" returns 68, run the following commands first:

Load rtc-ds1307 by

sudo modprobe rtc-ds1307
sudo echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-0/new_device