[ntp:questions] Linux/Raspberry Pi: PPS driver loaded, but no PPS devices

Ralph Aichinger ralph at pangea.at
Tue Feb 12 13:59:03 UTC 2013

james machado <hvgeekwtrvl at gmail.com> wrote:
> you should not need to load the ktimer module to get your PPS working.
> That is the debug module and fakes PPS to the kernel.  Verify that
> the kernel you installed was an uncompressed kernel.  Did you compile
> it yourself or did you get it off the net? The kernels that come as
> part of the Raspberry Pi Linux distributions are not able to do PPS
> and must modified and then recompiled.  You can check if your running
> kernel supports the PPS_GPIO by looking in the /proc/config.gz file
> (zcat /proc/config.gz | less ) and search for CONFIG_PPS_CLIENT_GPIO
> it is probably equal to 'm'.  If it "is not set" or doesn't exist then
> the kernel you are running can not support PPS on the RPi.

A delayed thank you for this posting! It was truely helpful, as I was
almost going crazy, because my PPS pulse seemingly was placed at a
random position against NTP time. Now I know why :)

My mistake was compiling the stock Raspbian kernel without the
specific gpio-pps patch. The stock kernel can be recompiled to
have PPS, only one that did not work for me. The specific patch


did it for me.


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