Because of accuracy of 32.768khz crystals, you’d have to set the time regularly. Just not worth thinking about it any other way. OR… you could just ignore the fact that it’s time is 10 secs different to “real” time. It’s not like it actually needs time sync, does it ?
If you need accurate time for encryption, then connectivity isn’t a problem.
If you need accurate time for logs, then it’s all relative, and accuracy is not needed to the second. If you’re trying to correlate logs between two sources, then more important than absolute time is accuracy between the sources. How often does the other source actually change it’s time ? And really, do you have that many log entries that you won’t be able to sync them ?
@ Brett - Well I don’t need to be accurate to the millisecond, and yes there would be more than 2 log sources that need to correlate. All the robots upload their logs to the central servers periodically. As a software guy, I know the importance of having accurate time on a class 1 computing device.
With only weekly log collation, you are unlikely to be interested in “real time” event correlation, so I would expect that the RTC on it’s own will probably be good enough (but will still drift differently on each bot based on the accuracy of the crystal and circuit, which are not that accurate ).
Accuracy of the timestamps on a set of information sources is directly related to the time between an event and when you can act on that event information. If there’s a gap of a week compared to a gap of a minute, it’s clearly more important to have accuracy and synchronicity in timestamps in the second scenario. With a gap of a week, you may well only be looking for events in the same minute, or 5 minutes… It won’t really help you to know that these things happened a second apart on Bot A, then B, then C, a week after it happened, will it ?
If something happens on more than one machine at a specific time, at a specific customer, then I’ll be able to tell that customer hey it’s something in the environment, not the machines themselves. “Look all 3 machines started recording errors at exactly 8:25:15 AM.” But if one happened at 8:25 and another happened at 8:30 and another at 8:10, then I’ll have to look much deeper to figure out what went wrong. The accurate time stamp would help me to quickly determine if the problem is internal or environmental.