SparkFun Forums

[bms20]

Guys,
I've wired an EB-85a to a technologic systems TS7400 cpu board. From this board I can see the NMEA data streaming off of the GPS, but I never see any real coordinate information.

I see some people reporting problems with noisy power preventing a lock - what do I need to do to either measure this noise and filter it?

What $PMTK messages do I need to send to configure it?

This is a sample of the output I receive:
$GPGGA,223525.624,8960.000000,N,00000.000000,E,0,0,,137.000,M,13.000,M,,*42
$GPGSA,A,1,,,,,,,,,,,,,,,*1E

Note: the time is correct, but the location doesn't make any sense. I'm in Cambridge UK...

Any help would be greately appreciated!

-bms20

[leon_heller]

Have you tried taking it outside so that it gets a better signal? I think it gets the time from a single satellite but it needs data from several to get a proper location fix.

Leon

[bms20]

Indeed - The recorded segment was from the GPS running outside.

It seemed to find the time very quickly, like within about 20 seconds, but it never reported the correct coordinates.

-bms20

[leon_heller]

The GPS might be getting interference from the TS7400.

Leon

[bms20]

Ok, I measured the voltage ripple on the device, and it is tiny, probably about 0.001V. I've added a 0.1uF capacitor on the connector to the GPS, and additional electrolytic capacitors on the daughter board that attaches to the TS7400 - again, the same results - no satelites. I will try shielding the TS7400 shortly.

-bms20

[NukWaste]

I was getting the very same thing, even with a battery. I RMAed it back to Sparkfun, they tested it and they said it was ok (Got a lock in 20 Sec. ).

I was so frustrated that I gave up and decided to wait on the DEMO board.

...

Still waiting.

[ClausT]

Same experience here - but today i changed my supply regulator from 5.0 to 3.3V, and now the Gps gets a lock in a few seconds

[rmsteele]

We have had the same problem from time to time.

I have found that if I place the EB-85A on a larger metal, copper or aluminum plate to act as a ground plane until it gets a lock usually within a couple of minutes, seems to fix the problem. Once it has a lock I can move it anywhere without the ground plane and it will continue to maintain the lock and update with correct data.

Other times we can bring it up cold and it will lock in a few seconds... Weird...

Rick

[NukWaste]

Got the DEMO board and ALWAYS get a lock.

I'm really confused.

[busonerd]

Power supply filtering / battery supply is real important I've found.

Cheers,

--David Carne