For the most ultra-accurate time, a GPS with PPS (packet per second)
setup will be the most accurate.? The next most accurate would be a
machine using NTP via the Internet.? A GPS receiver without a PPS
signal might be a bit more accurate but I'm not a time expert (a
very very deep topic btw). ? The least accurate would be to solely
use an RTC setup for accurate time.
To your second question about if an RTC's time gets updated from
NTP, the answer here is rather convoluted as it depends on your
chosen time synchronization tool (usually chosen by your choice of
distro).? If you're using a modern systemd based distro, the
systemd-timesyncd tool currently does NOT have a feature to keep the
RTC's time current.? You can work around this with simple cron or
shutdown scripts (this is what I do).? For example:
The crony system DOES have the ability to do this via it's "rtcsync"
option -
Anyway, here is a decent high level read about the various NTP tools
with Linux:
--David
KI6ZHD
On 10/29/2022 03:42 PM, Douglas Pervine
wrote:
toggle quoted message
Show quoted text
I have RPi setups with RTC or GPS w/PPS.
I'm just wondering which is the better setup for maintaining
accurate time.
Does the RTC get updated regularly via the NTP source on the
Internet?? Or is the time stored in the RTC only provide time
during boot/lack of NTP source?
On my other system.? GPS w/PPS provides accurate time but it takes
a few minutes to achieve this fix.
I was just wondering.? I'd like to configure my RPi's the same.
Any assistance would be greatly appreciated.?
