Adding Hardware Security with the CryptoCape - BeagleBone for Secret Agents - page 84

You will have to set the RTC time initially after installing the CryptoCape. First, you'll
need an accurate system time. Refer to the project from Chapter 2 , Circumventing Censor-
ship with a Tor Bridge , on how this is done. Set the RTC from the system time with the
following command:
hwclock -w -f /dev/rtc1
Cross-check the time to ensure it was set properly:
hwclock -r -f /dev/rtc1
This should produce something like the following:
Tue 13 May 2014 07:29:27 PM UTC -0.198319 seconds
If you use the coin cell battery from SparkFun Electronics, it has a stated capacity of
47mAh. The DS3231m draws 2 micro Amps when on the battery. Ideally, this would res-
ult in 23,500 hours of run time on the battery or about 2.7 years . In actuality, you see
much less run time from your battery, but even if the battery dies in half of the ideal time,
you should still see plenty of battery life from your RTC.