RTC

Introduction

The AIO-1126BJD4V0 development board uses the RV1126B chip's internal peripherals as the RTC (Real Time Clock). It provides year, month, day, weekday, hour, minute, and second based on a 32.768 kHz crystal oscillator. Second and hour count compensation is supported. BCD indicates time, calendar, and alarm. It supports 12 or 24-hour format, with AM and PM in 12-hour mode.

• Interrupts can be individually masked by software.
  • Alarm interrupt
  • Periodic interrupt
  • Chip power-off interrupt
  • Battery power atypical interrupt

This RTC peripheral does not support timed sleep/wake-up.

Driver RTC

DTS configuration reference in Linux SDK: kernel-6.1/arch/arm64/boot/dts/rockchip/rv1126b-firefly-aio-1126bjd4v0.dts

&rtc {
        rockchip,rtc-suspend-bypass;
        status = "okay";
};

Driver Reference: kernel-6.1/drivers/rtc/rtc-rockchip.c

Interface usage

Linux provides three user-space call interfaces. The corresponding path in the AIO-1126BJD4V0 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

PROCFS Interface

Print RTC related information:

# cat /proc/driver/rtc
rtc_time        : 06:53:50
rtc_date        : 2022-06-21
alrm_time       : 06:55:05
alrm_date       : 2022-06-21
alarm_IRQ       : yes
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