My project must work in the NYC subway, but it will get a wifi connection at least once a day. I need timestamps while disconnected accurate to about 5 seconds. (It is more important that the intervals between timestamps be correct, so if they are all off by the same amount no big deal.)
I would prefer if the device could be turned on and off while disconnected and still have timestamps. But, it could stay on the whole time if that makes things easier.
Data are saved to an SD card so flash memory is not a worry.
- connect an external RTC
- Use the built in RTC
- Use the built in RTC but mod the core so that it is powered by it’s own source?
- something else?
It’s not clear to me how sparkTime works without an internet connection. Can I still save timestamps on the SD card? Will cutting power to the core while offline reset the internal RTC? I assume yes.
So, I need to connect power to that chip on the bottom? I have a 3v coincell … any photos of how that would work?
Thanks for all the help I’m looking forward to posting this project when it’s done.