[ntp:questions] linux kernel pps support on raspberry pi

A C agcarver+ntp at acarver.net
Wed Dec 17 20:56:33 UTC 2014


Is the Rpi overclocked?  When overclocked it will dynamically change the
CPU frequency.  You could potentially underclock it or heatsink the SoC
to keep the CPU frequency from changing.

Also, which version of the RPi?  A, B or B-plus?

On 2014-12-17 12:22, folkert wrote:
> This is about receiving a pps signal via one of the gpio pins of the
> raspberry pi and then feeding it to ntp.
> 
> Did a test for a while: every 5 minutes I would look at the output of
> ntpq -c pe -n for jitter of the pps source.
> This pps source was "measured" either in the kernel (this newly added
> gpio pps support in the raspberry pi) or in user space using my own
> rpi_gpio_ntp.
> 

> 
> TL;DR:
> - kernel   : 13.2us jitter on average
> - userspace:  9.6us jitter on average
> 
> 
> Folkert van Heusden
> 



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