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High Accuracy Pi RTC (DS3231) installation in Ubuntu 19.10 in Raspberry Pi 4 Model B Rev 1.1
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| Base instructions are here: | |
| http://wiki.seeedstudio.com/High_Accuracy_Pi_RTC-DS3231/ | |
| But I've diverted my setup procedure somewhat because Ubuntu boot setup is different than Raspbian and setup does some things not needed. | |
| To use RTC early in the boot add "fixrtc" to kernel boot command line. Correct file is "/boot/firmware/nobtcmd.txt". | |
| This is implemented in "/usr/share/initramfs-tools/scripts/local-premount/fixrtc". | |
| To add the at at device tree, add "dtoverlay=i2c-rtc,ds3231" to "/boot/firmware/usercfg.txt". | |
| Uninstall possible "fake-hwclock". | |
| There should not be need for configuring any kernel modules or udev/systemd and other initscript changes. | |
| If changes work correctly you should see correct time at start of the boot when looking messages "journalctl -b0". If not, date is "Apr 11" (mine was 2019-04-11T16:28:37.384186+0000). | |
| There should be no (minimal) change in time when your time server starts. | |
| Some lower level debugging helpers, install i2c-tools. You should get UU at location 68 in i2cdetect. | |
| $ ls -l /dev/i2c* | |
| crw-rw---- 1 root i2c 89, 1 Jan 19 20:47 /dev/i2c-1 | |
| $ sudo i2cdetect -y 1 | |
| 0 1 2 3 4 5 6 7 8 9 a b c d e f | |
| 00: -- -- -- -- -- -- -- -- -- -- -- -- -- | |
| 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | |
| 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | |
| 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | |
| 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | |
| 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | |
| 60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- -- | |
| 70: -- -- -- -- -- -- -- -- | |
| Syslog says: | |
| kernel: hctosys: unable to open rtc device (rtc0) | |
| kernel: rtc-ds1307 1-0068: registered as rtc0 | |
| The module manages many models: modinfo rtc-ds1307 | |
| $ sudo hwclock -v | |
| hwclock from util-linux 2.34 | |
| System Time: 1579463067.337580 | |
| Trying to open: /dev/rtc0 | |
| Using the rtc interface to the clock. | |
| Assuming hardware clock is kept in UTC time. | |
| Waiting for clock tick... | |
| ioctl(4, RTC_UIE_ON, 0): Invalid argument | |
| Waiting in loop for time from /dev/rtc0 to change | |
| ...got clock tick | |
| Time read from Hardware Clock: 2020/01/19 19:44:28 | |
| Hw clock time : 2020/01/19 19:44:28 = 1579463068 seconds since 1969 | |
| Time since last adjustment is 1579463068 seconds | |
| Calculated Hardware Clock drift is 0.000000 seconds | |
| 2020-01-19 21:44:27.819024+02:00 | |
| If you use systemd-timesyncd, | |
| $ timedatectl status | |
| Local time: Sun 2020-01-19 21:45:54 EET | |
| Universal time: Sun 2020-01-19 19:45:54 UTC | |
| RTC time: Sun 2020-01-19 19:45:54 | |
| Time zone: Europe/Helsinki (EET, +0200) | |
| System clock synchronized: yes | |
| NTP service: inactive | |
| RTC in local TZ: no | |
| If you use chrony, add to /etc/chrony/chrony.conf: | |
| # This directive enables kernel synchronisation (every 11 minutes) of the | |
| # real-time clock. Note that it can’t be used along with the 'rtcfile' directive. | |
| rtcsync |
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Also check https://github.com/rgl/rtc-i2c-ds3231-rpi in conjunction with above (for future visitors)