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--- en:bpi-r4:start [2024/04/27 09:24] – [rtc] frank
+++ en:bpi-r4:start [2024/04/27 10:20] – [rtc] frank
@@ Line 150: / Line 150: @@
 Battery connection looks like charging circuit for ml2032. You should not connect non-rechargeable battery like cr2032.
+https://forum.banana-pi.org/t/bpi-r3-bpi-r4-does-the-bpi-r3-r4-have-a-rtc/17763/36
 Connector is JST with 1.25mm pitch
+RTC time will survive software reboot
+<code>
+# dmesg | grep rtc
+[    1.479923] rtc-pcf8563 2-0051: low voltage detected, date/time is not relia.
+[    1.487390] rtc-pcf8563 2-0051: registered as rtc0
+[    1.493378] rtc-pcf8563 2-0051: low voltage detected, date/time is not relia.
+[    1.500771] rtc-pcf8563 2-0051: hctosys: unable to read the hardware clock
+root@bpi-r4-v11:~
+# date -s "2024-04-27 09:55 CEST"
+Sat Apr 27 07:55:00 UTC 2024
+root@bpi-r4-v11:~
+# hwclock -w
+root@bpi-r4-v11:~
+# hwclock -r
+-04-27 07:56:23.979830+00:00
+root@bpi-r4-v11:~
+# reboot
+...
+root@bpi-r4-v11:~
+# dmesg | grep rtc
+[    1.480067] rtc-pcf8563 2-0051: registered as rtc0
+[    1.486061] rtc-pcf8563 2-0051: setting system clock to 2024-04-27T07:56:53 )
+root@bpi-r4-v11:~
+# date
+Sat Apr 27 08:00:46 UTC 2024
+root@bpi-r4-v11:~
+</code>
 ===== uboot/ATF =====