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Adafruit Ultimate GPS with N+2. Any experiences?


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#21 remotewizard

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Posted 27 March 2014 - 12:00 PM

I hadn't tried moving it around the house.  If I get a chance over the weekend, I'll take my Netduino for a drive (I'm logging GPS changes to my SD card) and see what happens.



#22 DanielK

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Posted 27 March 2014 - 12:17 PM

I hadn't tried moving it around the house.  If I get a chance over the weekend, I'll take my Netduino for a drive (I'm logging GPS changes to my SD card) and see what happens.

 

Its not just about moving it! Could you please try this:

- remove(!) the backup battery from the GPS module

- power the GPS module using the Netduino board (5V, GND). Do not power the GPS using batteries !!!

- try to get a sat fix with the GPS powered by the Netduino

 

thanks,

Daniel



#23 remotewizard

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Posted 27 March 2014 - 12:40 PM

I'll try that too.



#24 remotewizard

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Posted 27 March 2014 - 11:07 PM

It's been cooking for over a half-hour with no battery, and I still haven't got a lock.

 

Trying next with battery inserted, but still powered from the Netduino.



#25 remotewizard

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Posted 27 March 2014 - 11:27 PM

Twenty more minutes with the battery in, and nothing,

 

Disconnecting from the Netduino and attaching the LiPo  (but not moving to the windowsill) next...



#26 remotewizard

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Posted 27 March 2014 - 11:34 PM

Less than three minutes on the LiPo (still on the desk next to the unplugged Netduino) and I have a fix.  Reattached to the Netduino and get this:

 

3D-Fix: False, Sattellites: 3, Time: 03/28/2014 23:32:48, Latitude: 4XXX.4XXX,N, Longitude: 09XXX.1XXX,W, Altitude: 190.2,M, Knots: 0.649999976 (1.26880002 km/h)



#27 remotewizard

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Posted 28 March 2014 - 10:15 PM

One last thing: I did take it out for a drive, and it tracked quite nicely!



#28 DanielK

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Posted 29 March 2014 - 12:00 AM

thanks, remotewizard!!!

Looks like you can more or less confirm the problem, right?

 

I powered my GPS module today from an old Arduino Diecimila. It got a fix after approx. 2 minutes.

Same position but powered by the N+2: no fix. Even after 30 mins.

I tried several things with capacitors, coils and resistors to filter the obviously noise N+2 votlage: no success. I was able to get a fix just once with the backup battery installed, but I could not reproduce so fare.

To me it looks like the Adafruit Ultimate GPS breakout is simply not working with the N+2.

 

Daniel



#29 remotewizard

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Posted 29 March 2014 - 02:39 PM

One last test: I enclosed my Netduino in a grounded metal box, ran twisted pair wiring out to the GPS (sans battery), and it still wouldn't lock.  I'm afraid you're right.



#30 DanielK

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Posted 29 March 2014 - 09:25 PM

One last test: I enclosed my Netduino in a grounded metal box, ran twisted pair wiring out to the GPS (sans battery), and it still wouldn't lock.  I'm afraid you're right.

 

Im pretty sure that the problem is not caused by RF noise. I tried several constellations. The problem ocurred only if the N+2 was physcally connected (wired) to the GPS module.

I run some more tests today with a 47nF capacitor and a 0.47F capacitor between 5V and GND to filter out noise. About 70% of the "cold start" experiments have been ok with a sat fix after approx. 3-10mins. 30% failed. Better than before but still not satisfying.

 

The strange thing is:if I power the GPS module from a legacy Arduino Diecimila it got a sat fix after 1-2 mins (according to the GPS LED indicator). Reproducable w/o problems. So for me the power supply of the N+2 (and maybe some more Netduinos) is too noisy for the Adafruit Ultimate GPS breakout.

Or the Adafruit Ultimate GPS breakout is too sensitive for the Netduinos power noise.

 

I have no idea....

 

Hey, Netduino guys.... what do you mean??? Its time for some research, isnt it ?

 

Daniel



#31 nhale

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Posted 30 March 2014 - 10:06 AM

 

Its not just about moving it! Could you please try this:

- remove(!) the backup battery from the GPS module

- power the GPS module using the Netduino board (5V, GND). Do not power the GPS using batteries !!!

- try to get a sat fix with the GPS powered by the Netduino

 

Normally I'm running a N1+ or N2+ (but I also tested it with the non-plus variants). Both with the same configuration.

+ Arduino Protoshield with a

-->Soldered Adafruit Ultimate GPS v3 connected to COM2

-->Soldered IC 74HC595 driving 3 bi-color LEDS (5mm)

+ Seeedstudio GPRS Shield v2 (per default because of the PCB design to COM1)

 

While debugging/development it's connected to the USB Port only and productive testing to 12V.

In both scenarios I attach an external GPS antenna, as the results are much better. And getting a valid fix is faster.

 

I tried it yesterday with and without a backup battery, after removing the battery i was waiting for about 30 minutes.

With backup battery it takes about 10-20 seconds to get a fix and a few seconds later a valid position

Without backup battery it took about 2 minutes to get a fix and shortly after i got a valid position

 

I know that you want to drive it without an external antenna, but I think the setup above should show that there is something strange going on.

Have you had the possibility to try another Netduino, just to eliminate the possibility of a problem with exactly this board.



#32 DanielK

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Posted 30 March 2014 - 01:01 PM

Have you had the possibility to try another Netduino, just to eliminate the possibility of a problem with exactly this board.

unfortunately not. I have tested it on an Arduino where it works perfect. Sat fix after 1-2 min w/o backup battery and w/o external antenna. And even moved for about 200 miles from the last position. So for me its clear: the/my N+2 is the troublemaker.

 

I will try with some R/C or L/C high-pass and low-pass filters in the GPS power supply in the next few days. Maybe this will help.

 

Daniel



#33 401kill

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Posted 31 March 2014 - 11:17 AM

I can also confirm this issue with multiple GPS units - see this thread for my testing.

Very interested in a fix, and happy to participate if I can help with further testing etc.



#34 DanielK

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Posted 31 March 2014 - 01:44 PM

currently my N+2 with the Adafruit Ultimate GPS is working in 99% of the tests. I added a low-pass filter (10 Ohm resistor/47nF capacity) into the power supply and now I get a sat fix in most cases. Also, I have the backup battery installed which somehow makes the whole thing more stable.

 

The strange thing now is: once Ive got a fix I can move the GPS module into a dark corner of my room (where no other GPS device is working) and it still signals my a sat fix (by its LED).

I will analyze the NMEA sentences today to see I it really has a position or if its just a(nother) bug ;)

 

Daniel



#35 DanielK

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Posted 31 March 2014 - 06:50 PM

looks like it is finally working now. The RC filter in the GPS module power supply obviously solved the problem. I havent tried it w/o the backup battery but with this battery it works more or less reliable. I write some code to analyze the NMEA sentences and simply check the "A" flag in the GPRMC sentence. If this is available (means: a valid GPS position was received) the Netduino flashs a green LED. And yes, it is flashing if the GPS modules onboard LED signals a sat fix and it is not flashing if the GPS modules LED signals "no sat fix".

 

So for all who struggling with the same issue: try a resistor (10 Ohms) in line and a capacitor (47nF) after it between 5V and GND to filter out noise. Maybe these values are not perfect but at the moment it works :)

 

netduinoGps.jpg

 

 

Thank you all for your comments and ideas!

 

Daniel



#36 DanielK

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Posted 06 April 2014 - 02:38 PM

my first NMEA sentence parser is working now and I was able to analyze data from the GPS module. Looks very good so far. As long as the NMEA sentences are marked as valid the position is right where I expected it (a few meters deviation, but thats not worse as with my Garmin).

So the RC low pass has finally fixed the problem. With the backup battery installed the module gets a fix after a few secs to some mins ...and it is reliable.

:)

netduinoGps2.jpg

 

Daniel



#37 401kill

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Posted 11 April 2014 - 10:11 PM

currently my N+2 with the Adafruit Ultimate GPS is working in 99% of the tests. I added a low-pass filter (10 Ohm resistor/47nF capacity) into the power supply and now I get a sat fix in most cases. Also, I have the backup battery installed which somehow makes the whole thing more stable.

 

Thanks for the heads up!

 

How much would you say having the battery increases stability by?

 

I've implemented a low-pass filter as you described (10 ohm in series with the GPS, 47 nF in parallel), and it has improved things (it sometimes works now!), but it is still very unpredictable.

 

As far as I can see, your implementation using the battery is the only significant difference.

 

Attached File  WP_20140412_038.jpg   298.85KB   1 downloads



#38 DanielK

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Posted 14 April 2014 - 11:02 AM

I would say its much more robust with the backup battery installed. Maybe the battery affects the "quality" of the external power somehow (?).

However, I would recommend to try it with the battery!

 

Daniel



#39 Homey

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Posted 17 April 2014 - 01:19 PM

Good info here.  I too have a similar issue with an Adafruit Ultimate GPS Logger shield.  I did try the RC circuit and a backup battery (CR1220) and still didn't get a fix after leaving the unit on a window sill with blinds raised for 24 hours.  I had to resolder the battery holder tho, the holder popped right off the board when I tried to put a battery in.   Geez!

 

One thing I noted regarding ND+2 power is that if you power from USB, the output of the ND+2 regulator is noisy.  I plugged the ND+2 into a clean 12V 0.5A  power supply instead and it looked a lot better.  Im guessing USB power - at least from my compy - is not very clean and ND+2 doesn't do any real filtering?

 

According to docs I see on the logger shield, the backup battery allows the unit to keep the satellite and ephemeris and NV data stored so it can get a fix faster.  I don't really know but I don't expect it has anything to do with prime power quality.  Do you have your unit set up for a cold start, warm start, hot start?  I was wondering if that also made any difference for you.  Thought I would ask before I complained to Adafruit. :)

 

Homey



#40 DanielK

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Posted 17 April 2014 - 06:43 PM

Homey,

 

I had this noise issue also wehen I powered my Netduino/GPS  form a 9V battery! So it looks very much like the voltage "transformation" on the Netduino board and maybe the high sensitivity of the GPS module is the problem. Anyway, with the RC filter and the backup battery my installation is very robust and reliable now. Ok, I havent tried it on the move, just outside the window. Position quality is approx. 4-10 meters.

 

I have no clue how to set up my GPS for cold/warm/hot start. I just use it as it is. Could you please give me some more information about setting the start mode? Maybe this really makes a difference(?)

 

However, its quite interessting to hear from so much more problems with this combination. Not really nice but a sorrow shared is a sorrow halved ;)

 

cheers,

Daniel






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