RevPi Connect+ RTC clock read error when booting up

[BergControls]

I am testing a RevPi Connect+ unit in my office WITHOUT internet connection.

Kunbus claim the RTC will hold power for 24 hours, however my time is lost when the unit has been down for much shorter time than that.

When I start the unit after a short time without power (just tested now with 30 minutes) the time is set correctly (from the RTC) and:
dmesg | grep rtc
[ 1.619515] rtc-pcf2127-i2c 1-0051: rtc core: registered rtc-pcf2127-i2c as rtc0
[ 1.623352] rtc-pcf2127-i2c 1-0051: setting system clock to 2021-05-05 08:18:31 UTC (1620202711)

so that looks ok.

However when power has been off a longer time (tested with 1hour 12 min) the time is incorrect (I get an old time) and:
dmesg | grep rtc
[ 1.606660] rtc-pcf2127-i2c 1-0051: pcf2127_rtc_read_time: read error
[ 1.607594] rtc-pcf2127-i2c 1-0051: rtc core: registered rtc-pcf2127-i2c as rtc0
[ 1.609207] rtc-pcf2127-i2c 1-0051: pcf2127_rtc_read_time: read error
[ 1.609983] rtc-pcf2127-i2c 1-0051: hctosys: unable to read the hardware clock

[BergControls]

I have myself done more testing and I notice that when dmesg says:
rtc-pcf2127-i2c 1-0051: pcf2127_rtc_read_time: read error
[ 1.609983] rtc-pcf2127-i2c 1-0051: hctosys: unable to read the hardware clock
the RTC time is not transferred to system clock at system boot.

But I tried:
sudo hwclock -r
and the hwclock does actually show correct time (power had been off for ~15 hours)

I don't understand why the RTC gives read_error at boot during these circumstances, maybe it is not ready yet?
However, when this happens, as a workaround I can myself execute:
sudo hwclock --hctosys
to get correct system time.

[->Johannes<-]

Hi,

we have discussed your case internally.
Could you please run the SOS Report, please make sure that the error "rtc-pcf2127-i2c 1-0051: pcf2127_rtc_read_time: read error" is in the kern.log.

Instruction for SOS report:

Code: Select all

sudo apt update
sudo apt install revpi-tools
revpi-sos


pi@RevPi40302:~ $ revpi-sos
The report will be generated under folder /tmp in a .tar.xz file, which
can be extracted with command: tar -Jxvf xxx.tar.xz in linux or 7zip in Windows.
And then some inspection can be done before it is sent to support@kunbus.com.
Are you going to continue (N/y)?y
report generating...

Your report has been generated and saved in:
/tmp/sosreport-RevPi40302-20201102163308.tar.xz

To make the report have better accessibility, the ownership of the report
can be changed to the current user.
Are you going to proceed(N/y)?y
The ownership of /tmp/sosreport-RevPi40302-20201102163308.tar.xz has been changed to user:pi

Please have in mind that you agree to send us private data i.e. IP address.

At first view, it seems to be a hardware problem. Maybe the capacitor.

Regards
Johannes