Re: [gpsd-users] 1PPS on the Pi - let's pool our knowledge.

[Jon Brase]

On Tue, 19 Apr 2016 12:47:15 -0500, Eric S. Raymond <address@hidden>  
wrote:

> Gary refers to GPIO pin 4.  His "dig deeper" source is David Taylor's,
> which says GPIO pin 18. Examining the traces on my Pi 3 causes me to
> suspect that it uses pin 4.  Did this vary by Pi model?  If so, we
> need to be quite clear about which pin it is on which Pi.

AFAICT, you can select whatever pin you want, as long as you're not using  
it for something else. From the sources I've found, pin 18 (logical  
scheme, not physical scheme) is recommended on the basis of physical  
adjacency to the serial pins. Pin 4 (once again logical, pin 4 physical is  
5 volt power) is also physically adjacent to the serial pins, but not on  
the same row.

See this reference for the pin numbering schemes (what I call the  
"logical" scheme it calls the "GPIO" scheme):

https://www.raspberrypi.org/documentation/usage/gpio/

> John Brase said:
> > I've been able to get [1PPS] with ppstest, but not with gpsd.
>
> That might just mean the Raspbian package of gpsd is misconfgured.
> I haven't done a source build of gpsd on the Pi yet; that's on
> my to-do list.

I have done a source build, though I have no idea if I built/configured it  
right. It worked no better.


--
Jon Brase