[Thumbgps-devel] Article -- Macx-1: GPS receiver with standard USB connector and PPS support

[Dave Hart]

On Wed, May 9, 2012 at 9:38 PM, Eric S. Raymond <esr at thyrsus.com> wrote:
>>                                                             Also,
>> are there other applications which expect the pps to be coming
>> though another handshaking pin besides DCD?
>
> Note that GPSD will actually notice PPS over RI and CTS as well.
> It doesn't care - a transition on any handshake line is treated
> as a PPS event, because the onlty thing it ever means from a GPS.

While I appreciate GPSD's flexibility, I advise against exercising it
needlessly.  All of the PPSAPI implementations which support serial
port control line input that I'm aware of want to see it on the
carrier detect line.  If you know you'll only ever care about using
the hardware with GPSD, any control line will do for PPS, but to use
it directly with ntpd, the PPSAPI implementations dictate using the
DCD line.

I had a vague recollection GPSD could use PPSAPI where it's available.
 If that's true, when GPSD is using PPSAPI, isn't it restricted to
using carrier detect in practice?

Cheers,
Dave hart