RTC Introduction The ROC-3399-PC-PLUS development board has an RTC(Real Time Clock) integrated into the RK808. The main functions are Clock, calendar, alarm Clock, periodic interrupt, dual channel 32KHz Clock output. After J2 is connected with CR2032 button battery, it can ensure that the RTC can run normally after the power of the board is lost. The location of J2 is as follows: RTC drive DTS configuration information is stored on the rk808 node. Driver code path : drivers/rtc/rtc-rk808.c Interface usage Linux provides three user-space call interfaces. The corresponding path in the ROC-3399-PC-PLUS development board is: SYSFS Interface : /sys/class/rtc/rtc0/ PROCFS Interface : /proc/driver/rtc IOCTL Interface : /dev/rtc0 SYSFS Interface You can directly use the interface below cat and echo operations /sys/class/rtc/rtc0/ . For example, check the date and time of the current RTC: # cat /sys/class/rtc/rtc0/date 2013-01-18 # cat /sys/class/rtc/rtc0/time 09:36:10 Set the startup time, such as starting up after 120 seconds: #Start the machine regularly after 120 seconds echo +120 > /sys/class/rtc/rtc0/wakealarm # View boot time cat /sys/class/rtc/rtc0/wakealarm #To turn it off reboot -p PROCFS Interface Print RTC related 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 Interface You can use ioctl to control /dev/rtc0 . Please refer to the document rtc.txt for detailed instructions. FAQs Q1: The time is out of sync after the development board is powered on ? A1 : Check that the RTC battery is properly connected