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EM-406 GPS works on Netduino but not Plus 2

netduino netduino plus 2 power gps em-406

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#1 401kill

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Posted 30 October 2013 - 05:05 PM

Hello

 

I have a Sparkfun EM-406 GPS shield which is giving me some problems on a Netduino Plus 2.

 

It was originally working correctly on a classic Netduino, it gets a fix (even indoors) and the LED flashed to indicate this. The serial output was all good.

 

I have now moved to a Plus 2 unit instead, and the GPS never finds a fix. The LED stays solid indicating that it is seeking. The $GPGSV string is always $GPGSV,1,1,00*79, which I believe indicates that it can see one satellite. This would account for the fact that the time string it sends seems to be accurate.

 

My question is whether anyone has any experience of the EM-406 on a Plus 2, or if there is a difference in platform that may account for the behavior? From my own reading of various threads around the internet, I'm currently suspecting that the GPS is not able to draw enough current (data sheet says  it needs ~70mA IIRC).

 

Thanks

Ben



#2 Chris Walker

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Posted 30 October 2013 - 08:37 PM

Hi Ben, Are you powering your Netduino Plus 2 via USB or the power barrel? If via USB, try powering via the power barrel and check your results. Chris

#3 401kill

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Posted 31 October 2013 - 08:15 AM

Hi Chris

 

Thanks for getting back to me. The GPS works with the original Netduino on both USB and 4x D batteries through the power jack. It doesn't work with either on the Plus 2.

 

Thanks

Ben



#4 r1ch4rd

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Posted 30 December 2013 - 08:45 AM

Hi Ben,

 

I have just come to the exact same conclusion...

Did you get it working on the Plus 2?

 

Thanks,

Rich.



#5 Chris Walker

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Posted 30 December 2013 - 01:27 PM

Hi Ben, Rich: Which SparkFun shields do both of you have, including revision? Hand-assembled? Which modules (by PN)? Do you know much 5V power does the GPS receiver consume? How much 3.3V power? Any chance you can plug it into external power, to isolate that as an issue? Netduino Plus 2 has a nice power subsystem including filtering--but there are limits in regards to mA supply and ripple. I also saw some notes on SparkFun's page about users having issues using the shield with Arduino...there may be posts in some Arduino forums about how to solve the issue as well. Chris

#6 r1ch4rd

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Posted 12 January 2014 - 07:42 PM

Hi Chris,

 

Thank you for your reply!

Unfortunately I am a complete beginner when it comes to microcontrollers and electronics in general.

 

I am using the Sparkfun GPS Shield (GPS 10710) with the EM0406 receiver.

 

On the GPS shield it has a port for 'AREF' which connects to a blank port on the Plus 2, however on the original Netduino board there was an 'AREF' port, that appears to be the only difference.

 

Many thanks

Richard.



#7 401kill

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Posted 03 February 2014 - 06:00 PM

Chris,

 

I don't have a revision number for the Sparkfun shield - it is marked 5-17-11 underneath though.

I believe it was originally hand assembled (looking at the solder), but I inherited it for my honours project.

 

I had my suspicions about the power draw on the N+2, so I replaced the EM-406 with an Adafruit Ultimate GPS Breakout V3 board (GTPA013 chip), which cites rather lower power requirements - particularly, it runs on 3.3V. I don't have a multimeter at the moment and can't remember the numbers off the top of my head though. IIRC, the Adafruit board draws ~90mA during operation.

 

This new chip also works correctly with the original Netduino, but cannot find a fix on the N+2. A slight improvement though - it once found a single satellite for about 5 minutes!

 

I also found this thread which seems to suggest that the N+2 emits enough EMI to mess with GPS. I don't know if this is true, or why the N+2 should be so bad for EMI compared to the original, but could it be a possibility?

 

I'm going to try running the Adafruit board on the N+2 with an external power supply and see what difference that makes.

 

Does any of this help?

 

Thanks
Ben

 

EDIT: The plot thickens...

 

- I just ran the Adafruit board on the old Netduino until it picked up 4 satellites.

- I then hot-swapped the TX/RX pins onto the N+2, leaving the power supply coming from the Netduino.

- The GPS continued to spit out $GPGSV string indicating 4 satellites for several iterations.

- I then temporarily unplugged the Netduino, thereby de-powering the GPS.

- When the GPS came back on, it no longer found any fix, even after several minutes (when fully connected to the old Netduino, it picks up at least 1 satellite within about 30 seconds).

 

I'm not really sure what this means in terms of solving the problem - if anything, it's more confusing!

 

EDIT 2: I also ran the GPS on the old Netduino with the N+2 powered up next to it. This didn't cause any problems. So if there is any electrical noise issue, it's within the wires.







Also tagged with one or more of these keywords: netduino, netduino plus 2, power, gps, em-406

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