Re: [gpsd-users] PPS to gpsd from Pi GPIO pin

[Pete Nevill]

Hi Jon,

Thanks for the suggestion although I am sure I have already tried it 
once (will do again).... I have now also attached the TX and RX direct 
to the Pi GPIO pins and now when I start gpsd from the command line with 
the following:

sudo gpsd -G -N -D9 -F /var/run/gpsd.sock /dev/ttyAMA0 /dev/pps0

I get the this output (only posted the pps relevent stuff)

gpsd:INFO: stashing device /dev/ttyAMA0 at slot 0
gpsd:INFO: stashing device /dev/pps0 at slot 1........

gpsd:PROG: no /etc/gpsd/device-hook present, skipped running ACTIVATE hook
gpsd:PROG: switch_driver(PPS) called...
gpsd:PROG: selecting PPS driver...
gpsd:ERROR: /dev/pps0: device activation failed.
gpsd:ERROR: /dev/pps0: activation failed, freeing device

As such no pps offset showing up with gpsmon.

As far as I know nothing else was using that device. I even tried 
changing the permissions for /dev/pps0 with only the same result...

Does not look like a bug, just a conflict/permission issue as far as I 
can tell ...

Pete.



On 10/03/2016 04:04, Jon Brase wrote:
> On Wed, 09 Mar 2016 05:10:23 -0600, Pete Nevill <address@hidden> 
> wrote:
>
> > Hi. I wonder if anyone can help? I have a question about getting PPS 
> > to gpsd from a gps via GPIO pins using a Raspberry PI.
> >
> > I have an Ultimate GPS Breakout V3 board 
> > https://www.adafruit.com/products/746
> >
> > I have connected the PPS pin directly to my Pi via GPIO pin 18.
> >
> > I have added the following line to /boot/config.txt
> > dtoverlay=pps-gpio,gpiopin=18
> >
> > When I boot the pi I get the following:
> >
> > [    9.859705] pps_core: LinuxPPS API ver. 1 registered
> > [    9.863843] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 
> > Rodolfo Giometti <address@hidden>
> > [   10.052295] pps pps0: new PPS source pps.-1
> > [   10.054528] pps pps0: Registered IRQ 412 as PPS source
> > [   14.209399] pps_ldisc: PPS line discipline registered
> >
> > Looking good so far... Do a quick test to see if we have any ticks!
> >
> > sudo ppstest /dev/pps0
> > trying PPS source "/dev/pps0"
> > found PPS source "/dev/pps0"
> > ok, found 1 source(s), now start fetching data...
> > source 0 - assert 1457520369.538064030, sequence: 180812 - clear 
> > 0.000000000, sequence: 0
> > source 0 - assert 1457520370.538051840, sequence: 180813 - clear 
> > 0.000000000, sequence: 0
> > source 0 - assert 1457520371.538039843, sequence: 180814 - clear 
> > 0.000000000, sequence: 0
> >
> > Yes... we are cooking.
> >
> > I connected the TX and RX (of the break out) to a serial to USB 
> > adapter like this https://www.adafruit.com/products/954
>
> You have to hook up the PPS output to a GPIO pin anyways, so why not 
> hook the TX and RX lines to the UART GPIO pins on the Pi? This is what 
> I've been doing, and what every tutorial I've seen recommends doing.
>
> > Another way would be to somehow pass the PPS via the USB but its not 
> > obvious how I would do this and I actually want to take the USB out 
> > of the equation, connect the break-out board direct to the Pi GPIO 
> > pins to reduce the latency.
> >
> > Any suggestion or am I asking too much?
>
> I recently submitted a similar question here, and was told that adding 
> /dev/pps0 to the GPSD command line should do it. However, I'm having 
> some trouble with GPSD encountering errors trying to open /dev/pps0. 
> Could you try changing your DEVICES= line to DEVICES="/dev/ttyUSB0 
> /dev/pps0", and let us know what results you get? If everything works 
> for you, we can try comparing your setup to mine to see what's causing 
> my issue, if you get the same error, then we have a larger sample size 
> for the issue.