[ntp:questions] Timing issue with Linux and kernel PPS?

David Taylor david-taylor at blueyonder.co.uk.invalid
Sun Nov 18 14:06:42 UTC 2012

On 18/11/2012 09:28, Uwe Klein wrote:
> David Taylor wrote:
>> Which part of the article or what keyword should I be looking for?
> UpFront: haven't played around with the raspberry yet.
> My understanding was that your /dev/pps0 entry appeared too late.
> ( instantiated late by udev )
> is the module "pps-gpio" loaded during system startup ?
> lsmod ...
> other ref:
>      https://github.com/davidk/adafruit-raspberrypi-linux-pps
>      http://www.raspberrypi.org/phpBB3/viewtopic.php?f=9&t=1970
> uwe

Thanks, uwe.  I've been using the pages you list as a guide.

On a working (with PPS pulses) system:

cat /etc/modules contains "pps-gpio"

lsmod shows:

pps_ldisc used by: 2
pps_gpio used by: 1
pps_core used by: 4 pps_gpio,pps_ldisc

On a system with nothing connected to the PPS:

cat /etc/modules contains "pps-gpio"

lsmod shows:

pps_gpio used by: 0
pps_core used by: 1 pps_gpio

I'm unsure how to interpret the difference, or what pps_ldisc does.
Web: http://www.satsignal.eu

More information about the questions mailing list