Using a Raspberry PI with FreeBSD 10 for NTP with PPS Sync

Erik Sejr eriks at
Thu Jul 3 16:47:35 UTC 2014

Hello List,
I was thinking of attempting to get a GPS synchronized NTP server
running on a raspberry PI using FreeBSD 10. I had no issues getting
FreeBSD 10 up and running on the rpi using crochet-freebsd, but I think
i've hit a wall when it comes to making use of the PPS signal from the
GPS reciever to sync the clock.

The kernel has the PPS_SYNC option compiled in, but I can't seem to find
anything indicating where/on what pin the PPS signal is expected? I
would think this would be hardware-specific and my original intent was
to use one of the GPIO pins for this purpose. Looking though the
bcm2835_* kernel driver files in /usr/src/sys/arm/broadcom there seems
to be no support for this on this board. From what I can tell, there
seems to be no way to map a particular GPIO pin to be used as a PPS
input in a manner similar to what the gpio-pps driver provides in Linux.

I took a quick look at gpsd to see if this was gad been done in
userspace, but it seems to require that the PPS comes in from one of the
unused hardware handshaking pins on the serial port, and the RPI only
has a 3-wire serial port (rx, tx and ground).

I'm wondering if anyone on the list knows if there is something I've
missed/overlooked here, or if the hardware support in FreeBSD is just
not there for this application with the raspberry pi?


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