[ntp:questions] Two GPIO PPSes on Raspberry Pi

Nickolay Orekhov nowhere at mail.ru
Thu Feb 28 12:51:13 UTC 2013

The main problem of this config is that you won't be able to connect
specific PPS with specific GPS.
Some GPS devices output PPS'es even if they don't have position fix.
Sometime it can be tuned but not always.

Imagine what will happen if such device will produce PPS'es without
position fix and another will have fix?
There will be a lot of falsetickers.

Also there are another variant: you could use TSIP or NMEA reference clock
PPS as one clock source.
But I think there's an error in ntpd architecture and in this case first
unsuccessful step could stuck your clock sources
as falsetickers forever.

So It's you who will choose :-)

2013/2/28 Ralph Aichinger <ralph at pangea.at>

> Has anybody *two* GPIO PPS devices on different GPIO
> pins on their Raspberry Pi? Would a setup like this
> enable the ntpd to check the devices against eachother
> (or probably more likely give an idea of interrupt
> handling capabilities)?
> Or does more than one PPS device confuse ntpd?
> /ralph
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