Ultimate GPS not getting a fix

[jpbot]

Have you heard many reports of the Ultimate GPS not getting a fix? When connected to the serial port on a Leonardo I observed about 2-5 minutes before it found a single GPS (time of day was reporting) and 2 hours before it had a fix. (even with just power attached and no other connections)

Eight inches away I placed a UP501 module which achieved fix in about 1 minute.

I'm open to doing a little more testing because I thought I saw the Ultimate GPS get a fix in 2-5 minutes (still a bit slow, but better) when I had it simply attached to a FTDI Friend. In addition, when running the windows software attached through the FTDI Friend I see fix in under 2 minutes, usually under 1.

[ransomhall]

I made my own breakout with the same GPS (MTK3339) and had issues with noisy power on some microcontrollers preventing it from getting a fix at all. I did not have this problem on an Uno, and have not tried it on a Leonardo yet. I used the reference circuit from the datasheet. I did notice that Adafruit beefed up the capacitors on the ultimate breakout, probably to help alleviate this issue.

[adafruit]

Have you heard many reports of the Ultimate GPS not getting a fix? When connected to the serial port on a Leonardo I observed about 2-5 minutes before it found a single GPS (time of day was reporting) and 2 hours before it had a fix. (even with just power attached and no other connections)

Eight inches away I placed a UP501 module which achieved fix in about 1 minute.

I'm open to doing a little more testing because I thought I saw the Ultimate GPS get a fix in 2-5 minutes (still a bit slow, but better) when I had it simply attached to a FTDI Friend. In addition, when running the windows software attached through the FTDI Friend I see fix in under 2 minutes, usually under 1.

We're not sure why it would take two hours - one thing that helps a lot is using the backup battery so it doesnt have to download the entire almanac. see if that helps?

[jpbot]

Thanks to ransomhall, I tried the module on the Duemilanove where the other module was working...but I didn't want to disturb the parts on the breadboard (both Arduinos are on the mounting plates sold here with half-size breadboards) so I used some female-male jumpers and everything worked fine.

Moved the Ultimate back to the Leonardo with the jumper wires attached and it worked well too (less than 2 minutes to get a fix). So I put the module back on the breadboard...no go, back on the wires go, back on the breadboard no go.

Guess this module is a little sensitive to what's around it....in this case an accelerometer and little further down 1.8" LCD w/uSD card.

Now back to my software challenges.

[mcwhorpj]

I have incorporated this ultimate GPS breakout into a high altitude balloon instrumentation package. In testing, we boot and run the system daily. Normally, we get a fix in under 5 minutes. However, there are some days the device will simply not get a fix no matter how long we wait. Even hours and hours and no fix. (We are using the small backup battery). Next day it finds a fix just fine. On the days it does not get a fix, rebooting the system over and over does not help. This happens to us maybe one day in 30, but when it happens, we can simply not make it work.

Also, it is not a hardware issue with a particular GPS unit. Swapping things out with a different GPS does not fix things.

This is a perplexing problem. We are not using an external antenna. Is there any way this could be related to the position of satellites on a particular day?

Anyway, we are pleased with the ultimate GPS and have had three successful flights with it.

[Franklin97355]

Also, it is not a hardware issue with a particular GPS unit. Swapping things out with a different GPS does not fix things.

If you change out the GPS you still don't get a fix with the new one? Sounds like a power problem or a shielding problem where access to the satellites is blocked by something, maybe a part of the payload. Have you tried moving the payload to a different location when this happens?

[mcwhorpj]

Franklin, it is on a custom board, next to two arduino nanos, both on gravitech ethernet shields (picture attached). This board sits on top, and nothing between it and the sky. On the layer below we have a raspberry pi, and the layer below that a small ethernet switch (overall a cube about 3.5 inches on a side, but gps is on top with clear view of sky). There is a 1 Watt ubiquiti 2.4 GHz radio within 2.5 feet below it. There is plenty of power from a large Lipo battery. All connections are soldered.

So, it is a mystery to me that it always works except some days. I wonder if random position of satellites leads to certain days coverage is poorer, and possibly that and interference from ubiquiti radio lead to days that it does not work.

10858061_712338895540009_9196269916327177980_n.jpg (138.32 KiB) Viewed 893 times

[LACD]

Hi,
I'm building a solar tracker that functions through GPS, using this GPS module but it's not getting a fix at all. Last week, when it was getting a fix, using the example codes, it said it was the correct date but it was 2080 or the correct date but the time was three/four hours ahead. Now, when I set it up with my actual code, it's telling me no sat or when I set it up using the example codes, it's just giving me a 00/00/00 date and 00:00 time stamp. Can someone please help me address this problem? My solar tracker project is due on 6th April and it's worth 20% of my degree, I'm kind of freaking out.

[Franklin97355]

At what rate is the LED flashing? If you output the raw data what does that tell you? Could you post some raw NMEA sentences using the blank sketch?