[LinuxPPS] LinuxPPS 5.0.0-rc1

[Rodolfo Giometti]

On Thu, Aug 09, 2007 at 11:58:22PM -0600, clemens at dwf.com wrote:

> This seems like another arbitrary change to the interface.

If you meant between 4.x and 5.x you are right, but 5.x is PPSAPI
compatible, even if we'll never have a device which is both a GPS data
source and a PPS data source.

The trick was here (thanks to Frank)! :)

> As it has stood up to now, linking both the GPS data and the PPS data to
> the same device was just fine.

Yes, this is allowed by the PPS API, but this not a "must".

> It is quite common with ntp (and the oncore driver) to put the following
> in the dev file
> 
> ln -s /dev/oncore.serial.0 /dev/ttyS0
> ln -s /dev/oncore.pps,0    /dev/ttyS0
> 
> linking BOTH the serial and the pps  devices used by the code to the 
> same device.  This could equally well read
> 
> ln -s /dev/oncore.serial.0 /dev/ttyS0
> ln -s /dev/oncore.pps.0    /dev/lp0
> 
> if the parallel interface were being used for the PPS signal,
> the code expects it will be able to open these two devices.

Yes! In LinuxPPS you should do instead:

   ln -s /dev/oncore.serial.0 /dev/ttyS0
   ln -s /dev/oncore.pps.0    /dev/pps0

> For a standard GPS unit, with the PPS on the DCD line what am I 
> supposed to do with this new interface?
>     (a) open it once, and use it for both GPS and PPS data?
>     (b) open it twice and use one each for GPS and PPS data?  (as I do currently)

No, you should do:

   gps_fd = open("/dev/oncore.serial.0", ...);

   pps_fd = open("/dev/oncore.pps.0", ...);

   time_pps_create(pps_fd, &handle);

and then using gps_fd for standard operations with GPS data, and
handle for PPS management. Again, the link /dev/oncore.pps.0 points to
/dev/pps0 or /dev/pps1, etc. (you can use sysfs files to discover
which is the right source.).

> I guess I just dont understand your words/example, but it appears to be
> a significant change from what we have had in the past and have in
> the previous linuxPPS.

Yes, you are right! That's why I'm sure we can get _both_ NTP and
kernel inclusion!

I'm just updating the wiki for the new 5.x series... please refere to
it in order to have further info.

Ciao,

Rodolfo

-- 

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