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February 16, 2021 09:01
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| The use of the I2C DS3231/3232 from Armbian SBC has a few quirks, most tutorials on the internet works but only if you have internet connection. | |
| In cuba we can sometimes use Armbian on devices that are not internet connected, so most tutorial fails and after a power failure or reboot you get a non working system because some apps/soft warns and fail with a "date in the future" message. | |
| I have crafted a way to use it as a real systemd service (yes, it's a legacy service...) | |
| Create a file named: rtc_ds1307 in /etc/init.d/ you can use the command below (root privileges are required) | |
| ``` | |
| nano /etc/init.d/rtc_ds1307 | |
| ``` | |
| And paste the text below: | |
| ============================================================= | |
| #! /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 | |
| ln -f -s /dev/rtc1 /dev/rtc | |
| rm -f /dev/rtc0 | |
| echo "Syncing system time to RTC" | |
| hwclock -s | |
| } | |
| do_stop() { | |
| echo "Syncing RTC to system time" | |
| 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 | |
| ============================================================= | |
| Save it, just one comment, depending on your board and the I2C bus you use can may want to change the line than says: | |
| ``` | |
| echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-0/new_device | |
| ``` | |
| Take note, in this one we use the I2C number ZERO | |
| ``` | |
| echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-1/new_device | |
| ``` | |
| In this one we use the I2C number ONE. | |
| After this you need to disable some services about the rtc in systemd and then enable the new service, you can accomplish that by issuing this commands: | |
| ``` | |
| systemctl disable fake-hwclock | |
| systemctl disable hwclock | |
| systemctl enable rtc_ds1307 | |
| ``` | |
| If you have internet you may have good time by now, check it with: | |
| ``` | |
| date | |
| ``` | |
| If you have a bad date set it up with: (adjust your date to actual values) | |
| ``` | |
| date -s "January 16, 2020 11:54:00" | |
| ``` | |
| Now we will burn the date into the rtc. | |
| ``` | |
| hwclock -w | |
| ``` | |
| That's it, reboot or force a power failure, on reboot you will have good time on your board. | |
| A plus: if you have internet while the service is stopping it will update the system clock to the hardware clock aka: the rtc. So every time yo issue a `reboot` or `poweroff` you will be saving the system time to the rtc | |
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