Real Time Clock (CM-i.MX27)

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The PMIC MC13783 contains a Real Time Clock. You have to populate a LiCell on the DEV Board for supply of the RTC in power-off mode.

Linux kernel configuration

Device Drivers  --->
  Real Time Clock  --->
    <*> RTC class
    [*]   Set system time from RTC on startup and resume
    (rtc0)  RTC used to set the system time
    [*]   /sys/class/rtc/rtcN (sysfs)
    [*]   /proc/driver/rtc (procfs for rtc0)
    [*]   /dev/rtcN (character devices)
    <*>   Freescale MXC Real Time Clock
  MXC support drivers  --->
    MXC PMIC support  --->
      <*>   MC13783 Real Time Clock (RTC) support

Test in Linux

The Linux device driver reads the time from the PMIC RTC at Linux boot and stores the value into the on-CPU RTC. At Linux shutdown, it saves the current time to the PMIC RTC which is powered always by the LiCell.

  • Boot Linux
  • Set any date:
root@btmxc27:~# date -s "2010-03-01 20:00:00"
Mon Mar  1 20:00:00 GMT 2010
  • Shutdown Linux and disconnect all power sources:
halt
  • Re-connect power and boot Linux again
  • Check the date:
root@btmxc27:~# date
Mon Mar  1 20:01:31 GMT 2010
  • You have successfully tested the RTC.
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