401kill's Content

#57986 Adafruit Ultimate GPS with N+2. Any experiences?

Posted by 401kill on 07 May 2014 - 08:43 AM in Netduino Plus 2 (and Netduino Plus 1)

And if a low-pass filter is installed in the GPS module�s power supply ripple should also not be a problem. How do you set up the low-pass?

I used the same wiring layout as shown in your pictures previously:

Which is really strange, because it works for you - but I've now tested it on 2 N+2 boards and get nothing at all!

#57985 Send data from netduino 2 plus to a Service with xml serialization

Posted by 401kill on 07 May 2014 - 08:32 AM in Netduino Plus 2 (and Netduino Plus 1)

RESTful services will get you up and running, but URLs have a maximum length.

Correct - so if you are sending a lot of data, send a POST request with the message body containing JSON (or similar) serialized data. The max POST size is defined by your web server, not by the HTTP spec (and is usually adjustable).

XML serialization is anything but short! JSON is more lightweight, so faster to process and transmit. Less RAM usage too.

#57777 Send data from netduino 2 plus to a Service with xml serialization

Posted by 401kill on 26 April 2014 - 11:47 PM in Netduino Plus 2 (and Netduino Plus 1)

For my project (somewhat similar, N+2 reporting to a WCF web service), I tried to use DPWS. Sending a request worked fine, but the firmware doesn't implement the XmlReader class, so DPWS can't deserialize the response. This might work for you if your service calls are one-way only.

As jrlyman3 said, XML generation is comparatively slow due to the verbosity of the language. I configured my WCF services to use JSON instead (exposed via RESTful URLs), and used Json.NetMF to (de)serialize the data sent / received.

I did eventually end up forking the library to strip out the bits that I didn't need, but its a good starting point.

#57774 Adafruit Ultimate GPS with N+2. Any experiences?

Posted by 401kill on 26 April 2014 - 07:54 PM in Netduino Plus 2 (and Netduino Plus 1)

Still no luck - I've got the low pass filter and backup battery, and tried on two different N+2 boards, but never shows any sign of getting a fix. It's configured for hot start and quickly obtains a good fix using both the gen-1 Netduino and a USB TTL connection.

Think I'm out of options - unless anyone has anything to add?

#57490 Adafruit Ultimate GPS with N+2. Any experiences?

Posted by 401kill on 11 April 2014 - 10:11 PM in Netduino Plus 2 (and Netduino Plus 1)

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.

#57231 Adafruit Ultimate GPS with N+2. Any experiences?

Posted by 401kill on 31 March 2014 - 11:17 AM in Netduino Plus 2 (and Netduino Plus 1)

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.

#55908 Newbie Question - WCF Service

Posted by 401kill on 06 February 2014 - 11:50 PM in Netduino Plus 2 (and Netduino Plus 1)

I started out using the DPWS client to call the WCF service. However, I discovered that the Netduino firmware does not include an XML reader. This means that the Netduino can send a message to the WCF service, but can't receive a reply (throws a NotSupportedException).

My solution was to expose the WCF service methods as web methods using JSON serialization - you can then use the built in HTTP library to call the service, and there are some fairly good JSON libraries available for NETMF to deal with data transfer (such as Json.NetMF).

#55837 EM-406 GPS works on Netduino but not Plus 2

Posted by 401kill on 03 February 2014 - 06:00 PM in Netduino Plus 2 (and Netduino Plus 1)

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.

#53748 EM-406 GPS works on Netduino but not Plus 2

Posted by 401kill on 31 October 2013 - 08:15 AM in Netduino Plus 2 (and Netduino Plus 1)

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

#53741 EM-406 GPS works on Netduino but not Plus 2

Posted by 401kill on 30 October 2013 - 05:05 PM in Netduino Plus 2 (and Netduino Plus 1)

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