Jetson TX2i - RTC reset time and value


Couple of questions regarding RTC on TX2i (JetPack 3.2.1) :
a) If the TX2i module is unplugged from the Jetson devkit/carrier board and left unpowered (no RTC supercap/backup power in this case), how long should it take for RTC to go off (and reset date/time?

b) In my tests, I’ve tried leaving the module unplugged and unpowered for 12 to 48 hours and after that when I plug in the module in the devkit and power on the unit (without network connection), observed the time gets reset in the range of ‘00:06:xx UTC’ but not the date. It remembers/keeps the current date. I would’ve expected the date to reset to some old value too.

Hi FM2461,

The module has a small decoupling cap connected to the BBATT pin as is suggested as a minimum. It may be that this is why the date/time might stay for a short time. As to why the date seems to last longer than the time, that may just be that the date area consumes less leakage power. Actually, we don’t see where it tells how long the date/time would stay valid based on a certain size super-cap/battery. It does have a small leakage power I believe, which may allow the calculation to be made, but we never did the test and no guarantee for the RTC behavior at unplugged state.