TE0720 VBAT_IN voltage

[bigguiness]

What is the VBAT_IN voltage supposed to be on the TE0720?

On my custom carrier board I connected a CR1220 coin cell (3V) to that pin. It appears to be working but I keep getting messages like this from the kernel:

Code Select Expand


rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.


Sometimes I don't see the message or just get one message. Other times I get a flood of the same message.

Measuring the voltage on the coin cell I get 3.144V.

Thanks

[JH]

Hi,
>1.8V and <5.5V, recommended 3V, see:
https://www.mouser.de/datasheet/2/698/REN_isl12020m_DST_20080922-1997818.pdf
page 1 and 6
from schematics it's supplied by VBAT or internal 3.3V, see:
https://shop.trenz-electronic.de/en/Download/?path=Trenz_Electronic/Modules_and_Module_Carriers/4x5/TE0720/REV04/Documents
schematic page 14

RTC is on top side (U20), see AD page 1.
https://shop.trenz-electronic.de/en/Download/?path=Trenz_Electronic/Modules_and_Module_Carriers/4x5/TE0720/REV04/Documents
Maybe measure one time what you see there.
br
John

[bigguiness]

John,

I have looked at the schematic already and saw how it is connected.

Measuring the voltage from my coin cell going to the VBAT pin of the TE0720 I read 3.144V when my carrier board power is off.

Your eyes must be much better then mine. I see no easy way to measure the VBAT (pin 7) on U20. Especially without accidently shorting to GND (pin .

All the other possible places to measure VBAT are on the bottom side of the TE0720.

I guess I have to live with the annoying kernel messages for now. Hopefully I can figure out a fix later.

Hartley

[bigguiness]

BTW, here is an example of the flood of messages I get sometimes.

Code Select Expand

urandom_read: 2 callbacks suppressed
random: udevd: uninitialized urandom read (16 bytes read)
random: udevd: uninitialized urandom read (16 bytes read)
EXT4-fs (mmcblk0p2): re-mounted. Opts: (null)
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
random: dd: uninitialized urandom read (512 bytes read)
Configuring packages on first boot....
(This may take several minutes. Please do not power off the machine.)
Running postinst /etc/rpm-postinsts/100-sysvinit-inittab...
update-rc.d: /etc/init.d/run-postinsts exists during rc.d purge (continuing)
Removing any system startup links for run-postinsts ...
  /etc/rcS.d/S99run-postinsts
INIT: Entering runlevel: 5
Configuring network interfaces... udhcpc: started, v1.31.0
udhcpc: sending discover
udhcpc: sending discover
macb e000b000.ethernet eth0: link up (1000/Full)
IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
udhcpc: sending discover
udhcpc: sending select for 10.168.0.97
udhcpc: lease of 10.168.0.97 obtained, lease time 86400
/etc/udhcpc.d/50default: Adding DNS 192.168.0.123
/etc/udhcpc.d/50default: Adding DNS 192.168.0.119
/etc/udhcpc.d/50default: Adding DNS 8.8.8.8
done.
Starting haveged: haveged: listening socket at 3
haveged: haveged starting up


Starting Dropbear SSH server: random: dropbearkey: uninitialized urandom read (32 bytes read)
Generating 2048 bit rsa key, this may take a while...
random: dropbearkey: uninitialized urandom read (32 bytes read)
haveged: haveged: ver: 1.9.5; arch: generic; vend: ; build: (gcc 9.2.0 CTV); collect: 128K

haveged: haveged: cpu: (VC); data: 16K (D); inst: 16K (D); idx: 12/40; sz: 15006/57790

haveged: haveged: tot tests(BA8): A:1/1 B:1/1 continuous tests(B):  last entropy estimate 8.00128

haveged: haveged: fills: 0, generated: 0

random: crng init done
Public key portion is:
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCm4f/MueYk1rmtwt7axcqFty8ys2V0Dli1xITKrpIGjtvP4fP2vu+tBpEBnF9lzpxCET7L53JK0oam6/zbOqCP6Po25Zt7p6Cvh90AK+efc4I3kyudPNYQVjShDjPnCvvsxpA7mxFpGi4PzHxZi8VVaHviMbZTaXRcuia1JrVd6IIgnnAacWt0Yh0VUAzItuNxRVfBSFywfjHzmt3qPM6mQycsYDJxsL2WI38bGx+F4x5MEAAmzZrC1KNAwyZwSZ1BN9UbtO4FG208SgP3xztpISRkvrlaoq17Zm4lrGry5FYLwH3GkAIZaPxG+yxCncMTpOYGaONLT2tQ9Sr5hiPH root@s6
Fingerprint: sha1!! 60:3d:d2:fe:1b:1b:3e:f7:64:b3:3d:11:21:5e:21:ca:43:52:bb:30
dropbear.
starting Busybox HTTP Daemon: httpd... done.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
rtc-isl12022 1-006f: voltage dropped below 85%, date and time is not reliable.
Starting internet superserver: inetd.
Starting syslogd/klogd: done
Starting tcf-agent: OK

PetaLinux 2020.2 s6 ttyPS0


[JH]

Hi,
do you have anything else connected to the module over your carrier? The VBAT is also powered by 3.3V, if you are not in battery mode maybe there is some problem on the HW ,which maybe works but which drop down 3.3V power rail from time to time ....
br
John