Testing Jetson Nano RTC Battery health

Autonomous Machines Jetson & Embedded Systems Jetson Nano
1

Hello!
We are using a Jetson Nano on a carrier board with a RTC battery. In production, we have had 1-2 boards that, despite having the battery installed, don’t seem to advance the time when powered off.

Is there a command or some other way to verify the RTC circuit is functioning properly?

We have noticed an RTC voltage in dmesg (vdd-rtc: 850 <–> 1100 mV at 1000 mV ) which is always 1000mV, even if the battery is physically missing.

Powering off the system for 5 minutes and checking the time does work but this a slow/highly disruptive step for verifying something this specific.

Thanks in advance!

4

What’s the voltage got from a scope on backup battery? Is it 2.5V or …? The typical voltage of BBat is 2.5V, if it is then the backup battery side is OK.

6

Not sure if this command “cat /proc/driver/rtc” can get the battery status.

8

Hello,
I work with @sergeil (OP).

Please find attached the content of /proc/driver/rtc on one of our systems.
Is it possible to infer battery health from it?

Thanks,
Simon

developer@fotokite:~$ cat /proc/driver/rtc 
rtc_time	: 10:31:16
rtc_date	: 2020-10-05
alrm_time	: 00:00:20
alrm_date	: 1970-01-02
alarm_IRQ	: no
alrm_pending	: no
update IRQ enabled	: no
periodic IRQ enabled	: no
periodic IRQ frequency	: 1
max user IRQ frequency	: 64
24hr		: yes
name		: 7000e000.rtc
10

Does your device have install coin battery?
Should have batt_status report like below.

rtc_time        : 01:37:02
rtc_date        : 2005-08-30
alrm_time       : 00:40:04
alrm_date       : 2005-01-02
alarm_IRQ       : no
alrm_pending    : no
update IRQ enabled      : no
periodic IRQ enabled    : no
periodic IRQ frequency  : 1024
max user IRQ frequency  : 64
24hr            : yes
periodic_IRQ    : no
update_IRQ      : no
HPET_emulated   : yes
BCD             : yes
DST_enable      : no
periodic_freq   : 1024
batt_status     : okay