RTC
Update time：2018-04-13 Views：3086
Introduction
There are one RTC(Real Time Clock) integrated in RK808 on the Firefly-RK3399 .The main capabilities are clock, calendar，alarm, timer, and two 32KHz clock ouput.
Connect CR2032 to J2 for providing rtc power if want to keep rtc running when main power goes off. connect like the following picture:
Driver
RTC's DTS information integrated in rk808 note
driver path: drivers/rtc/rtc-rk808.c
Interface
Linux has three main userspace RTC API:
SYSFS：/sys/class/rtc/rtc0/
PROCFS： /proc/driver/rtc
IOCTL： /dev/rtc0
SYSFS
you can use cat/echo to operate the interfaces in /sys/class/rtc/rtc0/.
for example， you can check date/time like this:
# cat /sys/class/rtc/rtc0/date 2013-01-18 #cat /sys/class/rtc/rtc0/time 09:36:10
and set the boot time, such as boot after 120s:
echo +120 > /sys/class/rtc/rtc0/wakealarm cat /sys/class/rtc/rtc0/wakealarm reboot -p
PROCFS
List RTC information:
# cat /proc/driver/rtc rtc_time : 09:34:59 rtc_date : 2013-01-18 alrm_time : 08:52:45 alrm_date : 2013-01-18 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
IOCTL
The ioctl() calls supported by /dev/rtc0 are also supported by the RTC class framework.
Please refer to rtc.txt for detailed instructions.
FAQs
Q1: RTC clock does not synchronize after power on
A1: check whether the battery connect to the J2.
