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How to configure Android 4.4.2 to work with two RTCs in the system

Question asked by Jeffrey Chang on Mar 14, 2018
Latest reply on Mar 14, 2018 by Diego Adrian Cuevas

I am using iMX6 to build a system based on Android Kit-Kat. On the system I have an external RTC chip which is powered by a separate battery. The external RTC chip does not have an interrupt line connected iMX. The external RTC chip is registered under /sys/class/rtc/rtc0.


I have also enabled the internal SRTC on iMX by enabling CONFIG_RTC_DRV_MXC_V2 to build the rtc-mxc_v2.o. The internal SRTC is under /proc/driver/rtc.


Two questions:

  1. When I have both an external RTC and SRTC on iMX enabled on the system, how do I synchronize the SRTC with the external RTC? The time will be kept on external RTC because it is powered by a separate battery so SRTC has to be synchronized with the external RTC.
  2. How do I configure Android so that when it needs to get time, it gets time from the external RTC; and when it needs to set an alarm to wake up the system in suspend, it sets the alarm using the SRTC on iMX not the external RTC?