[ntp:questions] NTP strategy for Linux embedded system?
dave-gnus at bfnet.com
Tue Jan 20 20:16:51 UTC 2004
I am working on a consumer electronics embedded system running Linux.
It needs accurate system time, but I'm currently seeing system clocks
lag up to about 800PPM. This is probably because the kernel does a
very large amount of PIO and therefore misses many jiffy timer
I would like to tune the clock using ntpd, and here is what I have to
1. many units are not connected to the Internet
2. all units have a real-time clock chip that I can query using an
3. the real-time clock chip accuracy is better than the system timer,
but it is still not as accurate as Internet NTP servers
My idea is this: Write a reference clock driver to query the real-time
clock chip. This will be a big improvement over a free-running system
counter. If an Internet connection is available, periodically set the
real-time clock using NTP.
1. Is this a good strategy?
2. Is the SHM driver a good place to start for implementing my
reference clock driver?
3. Setting the RTC chip has a completely different API than setting
the system clock. Is there a way to easily integrate the setting
of the RTC into my configuration?
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