On 3/3/2016 12:57, Peter Ankerstål wrote: > Hi! > > I have sort of exactly the same question as Erik: > http://lists.freebsd.org/pipermail/freebsd-questions/2014-July/259055.html > > I have bought a https://learn.adafruit.com/adafruit-ultimate-gps and want to > use the PPS output to discipline my clock. > > But the only source of information on how PPS works in FreeBSD I could find > is this: https://docs.freebsd.org/doc/8.0-RELEASE/usr/share/doc/ntp/pps.html > and it clearly states the two ways to provide a PPS signal. "The PPS signal > can be connected in either of two ways: via the data carrier detector (DCD) > pin of a serial port or via the acknowledge (ACK) pin of a parallel port” > > Since the Pi doesn’t have any DCD pin i would like to use a generic GPIO for > this. There is a linux kernel module for this: > http://lxr.free-electrons.com/source/drivers/pps/clients/pps-gpio.c?v=3.6 GPIO is supported on the Pi, I'm using it on 11-Current on my home control software to drive relays on my pool hardware (e.g. valves, heater, VFD motor drive, etc) and it is working very well. I don't believe tapping into that at the kernel level to expose a pps signal (e.g. on /dev/pps or something of the like) would be very difficult at all, since the low-level driver capability is already present.
If I get some free time I'll dig around a bit and see if I can cobble something up. It's of some interest to me as well since I have a GPS clock here that currently talks to a serial port on an Intel-based machine and being able to move that to a $35 "appliance" for NTP using the Adafruit setup looks sort of attractive given that the Pi plus the module would be under $100 all-in. -- Karl Denninger [email protected] <mailto:[email protected]> /The Market Ticker/ /[S/MIME encrypted email preferred]/
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