Mailinglist Archive: opensuse (2162 mails)

[Rodney Baker <rodney.baker@xxxxxxxxxxxx>]

On Thu, 28 Aug 2008 16:26:59 Roger Oberholtzer wrote:
> On Wed, 2008-08-27 at 20:46 +0200, Per Jessen wrote:
> > Roger Oberholtzer wrote:
> > > inertial navigation system. The PPS signal is on one of the GPS
> > > control lines. We had considered a serial->USB converter. They do work
> > > fine with the GPS - but no PPS signal.
> >
> > How do you get an accurate PPS off a serial line if you have to keep
> > polling it?  Can't you let it pull an interrupt line or something?
> > (sorry, I didn't mean to start a redesign of your system).
>
> The information is available via two different interfaces. The location
> data (NMEA strings with time) is received via read() and the PPS is via
> an ioctl() that waits for a change in the state of specified serial port
> lines before returning:
>
>       ioctl(nmeaPort, TIOCMIWAIT, TIOCM_RI);
> [...snip...]

Roger,

Can I suggest that you go to www.xastir.org and maybe correspond with some of 
the developers of the Xastir project? Xastir is a ham-radio mapping program 
that interfaces with GPS for the purposes of mobile tracking - it too uses 
the serial port for continuous monitoring of GPS NMEA strings. It also writes 
to the port to send positional beacons via a radio but nevertheless they do 
have routines for handling the GPS that may be useful to you, if nothing else 
in giving you ideas on where to look when debugging your code.

I'm sure they wouldn't mind - after all, Xastir is open source, so why 
reinvent the wheel?

Regards,

-- 
===================================================
Rodney Baker VK5ZTV
rodney.baker@xxxxxxxxxxxx
=================================================== 

Where there's a will, there's an Inheritance Tax.