Hardcore Programming Question re: Garmin Interface

[+wiredcur]

OK... so this is post might be pretty geeky even for this group

 

Out of morbid curiousity, I've written up a small program that opens and closes the COM1 serial port on my PC. Of course, my eTrex Venture is connected to the PC, powered up, locked on and set for "NMEA In/NMEA Out".

 

I've actually had some success, every once in a while, I'll get a full NMEA sentence in my buffer. Most times, I'll get a partial sentence or a huge amount of garbage characters.

 

I've also sneaked a peek at the communications between ExpertGPS and the GPS when I've enabled GPS Tracking in ExpertGPS. There's never any garbage in that communication.

 

First Question is simply, If I've got my GPS set for NMEA Out and it's powered up. It's going to be spitting out NMEA sentences every second or so, right?

 

Thanks

 

FINALLY!!! Something useful I can do with that Geography degree. :-D

[able2ru]

Haven't experimented with your device, but other things to check are the "handshake", RTS parameters. If you are not getting a continous stream, it might be that your communications protocol with the serial port settings may need to be turned off, set so that it accepts anything and no response. CTS, needed. What you're trying should work, and if I find the website that goes into better detail about the data stream, it should enable you to write code that will assemble and calculate your position. Not too hard to do, but can be a problem since some newer computer com port protocols, can have some problems. It's amazing that an old 386 can do things that a state of art XP can do only with considerable tweaking.

 

Able2ru?

[Nelle & Jay]

Yes it will be spitting out NMEA sentences at regular intervals.

 

Try running Hyperterminal and just watch the NMEA strings spew from the GPS. That'll at least let you make sure you have the ports, baud, handshaking, etc. set up correctly.