Problem starting a GPS module

Forum 2005-2010 (read only) Hardware Interfacing
1

I'm using the ET-332 GPS module, the communication is working well, but I receive incorrect datas from GPS, like those:

$GPGGA,003650.740,,,,,,0,00,,,M,0.0,M,,0000*50 (look the gps is using 00 satelites to acquire the information!)
$GPRMC,003653.740,V,,,,,,,250708,,*27 (look the data is invalid V)

I tried to send $PSRF104,my lat,my long,my alt,9650,timeofweek,weeknumber,channelcount,3*Checksum just for initialization but this don't work, after some seconds the GPS lost the information (lat,lon and alt) that I`ve send, and still showing $GPGGA without lat,lon and etc. :-/

2

Can your GPS see the sky? Does it have an antenna? 0 satellites and an invalid fix may well be correct.

If a GPS has not been used in some time (especially if it doesn't have a battery backup for the almanac) it can take several minutes to acquire all the data it needs for a position fix.

random thought for today: I always thought V for invalid was pretty dumb - shouldn't V mean valid?

-j

3

Good

1-No my GPS is in my bedroom, I will try to put outdoor. :wink:
2-Yes, I bought an active antenna with the module.

3-The module has a 3,3V battery, put the weeknumber is incorrect (1489) put today is 14895 http://www.ngs.noaa.gov/CORS/gpscal08.html Jul 25 2008

4- I thought that V means valid but when I read http://www.usglobalsat.com/downloads/NMEA_commands.pdf I discovered that A means data valid and V data not valid

Thanks for replay.

4

the weeknumber is incorrect (1489) put today is 14895

Based on that (and the fact you have a 3.3V battery), I'm guessing that it's doing a cold start, which can take a while.

Take it out for a walk, so it can see the sky. It'll feel better. :slight_smile:

-j

5

Thanks kg4wsv :), I turnned on the circuit outdoor, took about 1 minute for the GPS recognize the satellites avaliable and more 30s to find the altitude,lat. and long. .

Now the module is working fine.!!!! ;D

6

Daniel_FEI,

I told you. We have less users on portuguese forum, many not logged, so harder questions must be posted in "english" forum, when in portuguese nobody answer. I think it's the same with spanish, french and italian forums. More brains, more knowledge.

7

Glad you got it working!

A couple of notes: GPS signals are weak and easily blocked. It is unusual in my experience for a GPS to maintain a lock indoors, except maybe near windows.

The GPS will send sentences even without a valid fix, as you've already seen. You will want to watch for the "V" and "A" to know when the GPS has (or has lost) lock.

-j