Re: MM Location API and MBM GPS

[Bastien Nocera <hadess hadess net>]

On Sun, 2010-09-05 at 15:15 +0100, Sjoerd Simons wrote:
> Hey,
> 
> I'm wondering how to best integrate my MBM 3G modems GPS with MM and
> Gypsy. The GPS on this device works as follows: The modem exposes three
> serial ports that all support AT commands, one can use AT commands to
> turn on the GPS, query it's status (e.g. whether it has a lock) and
> adjust some other settings. To read the actual location information from
> the GPS another AT command can be send to any of the three serial ports
> to turn it into an NMEA streaming port. At this point you can point any
> normal GPS application (like gypsy or gpsd) to this serial port an
> everything works nicely.
> 
> 
> Looking at the recent Location interface of MM the ``suggested'' way to
> implement this seems to be that MM turns one port into the NMEA port and
> relays the NMEA information over dbus in the Location property, which
> seems somewhat over the top. It seems more natural to be able to ask MM
> nicely whether one can have a serial port with NMEA enabled and just use
> that, at which point Gypsy can take care of everything else.
> 
> Assuming i'm not the only one that thinks that's a nicer way of doing
> things, i'd be happy to propose a GpsDevice interface with the needed
> functionality. I wouldn't put it in the Location interface as that feels
> more like: the modem itself provides location information instead of the
> modem has a slave device which gives raw nmea. 
> 
> Comments, suggestions, flames ? :)

Dan, rightly so, didn't like the idea of just handing out a socket to
Gypsy. There are multiple reasons for that:
- you want MM to still have complete control over the ports offered
- it would make it hard to push vendor specific hacks to Gypsy
- a lot of modems don't actually give you NMEA data at all, so it
wouldn't make sense to parse the proprietary format, put it into NMEA,
just to have it parsed again

The right way to implement this would be through a Geoclue provider,
which you could hit directly from your application if you're so
enclined, or just let it be one more provider amongst others.

Cheers