Quoting folkert <[email protected]>: ...
Linux has this PPS interface for a while so now that it is easy configurable in config.txt on the rpi, I thought I give that a try. The strange thing now is that using that I get very bad jitter. So bad that ntp discards it as a false ticker!remote refid st t when poll reach delay offset jitter ============================================================================== x127.127.22.1 .PPS. 0 l 2 16 377 0.000 0.161 0.001 x127.127.22.1 .PPS. 0 l 7 16 377 0.000 0.148 0.006 x127.127.22.1 .PPS. 0 l 13 16 377 0.000 0.147 0.007 x127.127.22.1 .PPS. 0 l 2 16 377 0.000 0.146 0.006
Your kernel pps RPI has a ~147us offset compared to your other time sources. I assume you have the two configured as peers over a local lan. I think ntpd is rejecting the local source because your other source is low enough latency (probably in the 100-200us range).
You could try adjusting the fixed offset of the userland pps to account for the latency between the pps happening and the user process being run.
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