Ultimate GPS No Fix

[adafruit_support_rick]

Is the GPS obstructed in any way? Do you have anything mounted over it? It should be facing upwards, with a clear, unobstructed view of the sky.

[wd6cmu]

It's facing upwards on a window sill, right against the glass with no screen. The external antenna is in the same position.

[adafruit_support_rick]

OK - let's replace it. Please email [email protected] with a link to this thread and ask for a replacement

[bdevore]

I am seeing similar behavior with my Ultimate GPS and Beaglebone Black. If I use power from the Beaglebone, I get GPS strings on the serial port with no fix and no satellites. If I use a separate battery power source with a common ground I get a fix quickly and can read good GPS data. Any thoughts?

[adafruit_support_rick]

I am seeing similar behavior with my Ultimate GPS and Beaglebone Black. If I use power from the Beaglebone, I get GPS strings on the serial port with no fix and no satellites. If I use a separate battery power source with a common ground I get a fix quickly and can read good GPS data. Any thoughts?

What voltage levels are we talking about from the BBB and the battery?

[bdevore]

I tried both the 3.3V and 5V pins on the Beagleboard without success. For the successful run I used three AAA batteries.

[adafruit_support_rick]

It's facing upwards on a window sill, right against the glass with no screen. The external antenna is in the same position.

Try it without the external antenna. Also, try taking it outside if you can.

[adafruit_support_rick]

I tried both the 3.3V and 5V pins on the Beagleboard without success. For the successful run I used three AAA batteries.

That's just wacky. I'm going to have to ask around about this one...

[bdevore]

I agree.. It was a bit confusing to me. I'm wondering if it is a line noise or current issue. I'll measure the current levels this evening both using USB and external power to the BBB and see what that looks like.

[adafruit_support_rick]

Sometimes, it just seems to take a loooong time to get a lock. With the backup battery installed, it should get a fix much faster the next time you power it up.

[1chicagodave]

Have you "played with" the PMTK codes at all? It should come to you with certain default settings which usually result in decent acquisition times. But, those option are changeable. You might want to take a look at the "Confidential" document in downloads section of Ultimate GPS tutorial. (http://www.adafruit.com/datasheets/PMTK_A08.pdf)
You should be able to query the module & determine how it's set up. Or, send a single command to ensure the defaults are set.
Example: To reset to "factory status" & force a 'Cold Start', send this via serial monitor
$PMTK104*37<CR><LF>

Further explanation -

There are options/instructions to tell the module when/if to do a "cold start" (don't use any saved information to help acquire GPS fix), "warm start", "hot start" (use all saved information and ephemeral data from last acquisition), etc....sometimes based on different variables. If it's trying to do a Hot Start with outdated/incorrect ephemeral data, it may take forever to get a GPS fix.

[adafruit_support_rick]

That's good info - I didn't know that.

[square002]

I'm having a hard time getting a fix in one of my gps modules. I have two gps modules. I bought the first one on the local store here and I bought the second one in adafruit online. My first gps gets a cold start within just ~17 secs. However, the second one takes ~400 secs with just 5 or 6 satellites. The two gps are both placed at the balcony of our house. I did a factory reset on both by using MT3339 PC tool v1.3 but the problem still persists. What may be the cause? Im using external gps antenna by the way.

The pc tool output of my first gps:


And the second one:


Please help.

[adafruit_support_rick]

Do you have the backup battery installed? That will make cold starts much faster.

[square002]

Yes. I have battery on both.