[time-nuts] looking for low-power system for gps ntp timekeeping
David J Taylor
david-taylor at blueyonder.co.uk
Mon Jul 1 01:31:13 EDT 2013
From: Dennis Ferguson
You aren't necessarily showing the part where the Raspberry Pi is a bit
weak, though. How well do clients which receive their time via the
USB ethernet interface do?
The Beaglebone Black has about three advantages going for it in this
For a $5-$10 difference in price for the board I think these are worth it.
The RPI makes a fine, low-power replacement for Intel hardware for this,
but the Beaglebone Black has the raw material to do significantly better at
this than either of them. The only problem with the Beaglebone is that it
is not as popular as the Raspberry Pi, so making use of the former is going
to require one to do more work on one's own to take advantage of it.
I've tested with 75 clients (simulated load) and not seen any problems with
the Raspberry Pi's own time keeping. I'll set my FreeBSD PC to look at the
the three Raspberry Pi cards and report back....
A first report is that the offset is shown as 0.091 ms from one RPi and
0.065 ms from the second, and 0.056 ms on the third RPi which is operating
over Wi-Fi. This is far better than I see from any Internet servers on my
Cable Modem ISP service. Jitter is 0.022 and 0.027 ms for the LAN connected
devices, again much better than the best Internet device which shows 0.110
ms (at what is the middle of the night for many - 06:00 clock time here).
Here the two units are similarly priced, so you can take your choice.
There is one write-up here:
for using the BeagleBone Black as an NTP server, but he seems to have an
offset of -0.281 ms from his PPS source, which is rather high.
SatSignal Software - Quality software written to your requirements
Email: david-taylor at blueyonder.co.uk
More information about the time-nuts