PPS input on a generic GPIO pin on Raspberry Pi.

Peter Ankerstål peter at pean.org
Thu Mar 3 18:57:34 UTC 2016


I have sort of exactly the same question as Erik:

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
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