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[on:]

has anyone here successfully interfaced with a GPS and been able to reliably read NMEA strings from it?

thanx,
jules.

[Reply #1 on:]

Is this what you are looking for?

http://www.arduino.cc/playground/Tutorials/GPS

[Reply #2 on:]

thank you for replying so fast!

that is kind of what i'm looking for. my hardware serial port already is used for a datalogger, so i was planning on using a software serial port for the GPS. i thought it would be best this way around as there will be extra sensor data written to the logger besides the gps data. i.e. the datalogger port would be more heavily utilised. my problem is that the gps is spewing out so much data it's introducing random garbage into the datastream.

any ideas how to slow it down?

[Reply #3 on:]

The baud rate (4800bps) is part of the NMEA standard.

Depending on the particular GPS, you can sometimes select which sentences get transmitted (pare it down to the minimum you need) and also reduce the frequency - 1Hz is typical, but you can reduce it to meet your needs.

Sorry I can't be more specific, but I've never done that myself, and it's GPS-specific anyway.

-j

[Reply #4 on:]

Thank you anyway

I'm trying to throttle back the frequency of the data and not the baud rate, as you suggest. The GPS module is a GM-402 from USGlobalSat, and it uses a SiRFStarII chipset. I have the NMEA commands for reducing how often it sends the data, but it doesn't seem to be taking any notice of them!

According to the datasheet, the chipset supports 1200baud, but without the GPS module responing to commands, I can't set it to a lower speed anyway...