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Tips and questions relating to the GPS modules from SFE
By ezflyr
alex2wr wrote:Are you talking about this? ... mo3.87.pdf

If so, I haven't tried it. I didn't know about it, so I will try it.
Hi Alex,

That's the manual for the software. Sparkfun hosts the actual code here: ...

I'm not sure if running this software will solve your problem, but you can view a lot of extra data from the module once you switch from 'NMEA' output mode to 'SiRF Protocol' output mode. You do this under the 'View' menu.

This software can be a little bit 'quirky', but it does get the job done!

By alex2wr
Hello John,

It seems like I'm making progress here. I was able to lock satellites as long as I don't have it hooked to the Netduino. So I tried multiple things to figure our what was happening and this is what I noticed. If I give power to the PS shield ( one pin at a time, the GPS locks on satellites. But if I power everything at once, I cannot lock to satellites.

I don't know what is happening
By alex2wr
More discoveries

When I power the GPS unit by itself with the laptops USB 5v, it lock on satellites like a charm. The moment I hook it up to netduino, it craps out. I've tried to disconnect certain pins to see if it helps, and when I think it did help it looses lock again.

So it seems to me that the problem is with the netduino, I just don't know were.

By the way, I'm using netduino plus with wichever firmware it came with.
By ezflyr
Hi Alex,

OK, I'm glad to hear you are making progress!

I took a brief look again at the GPS Shield schematic/docs to see if there was anything obvious that might explain your observations, but I really didn't see anything......

I'd say that there are three possibilities for what you are seeing, so this might help a bit:

1. Noisy/Inadequate Power Supply. If you have a scope it would be worth taking a look at the +5V connection right at the GPS module. You might also try adding a decoupling cap (0.1uf), and a filtering cap (10uf) as close to the GPS module as possible.

2. Excessive loading on one or both the TxD and RxD connections from the GPS. There are 'solder jumpers' on the GPS Shield that allow you to isolate these connections, so you might see if that helps? This scenario isn't likely unless you've got an assembly error, or a failed/failing input on the Arduino, but it's worth a check.

3. Some sort of EMI/RFI interference from the Netuino board. It's possible that the Netuino is generating a lot of EMI/RFI that is coupling into the power supply or serial connections going to/from the GPS module. Perhaps as a test you can physically separate the two boards by using wire connections instead of the headers. Also try shielding the Netuino board by putting your hand over it while running these tests.

My bet is that a combination of #1 and #3 is going to move you along towards a solution.

Good luck!

By alex2wr
John Morley wrote:Alex,


Hey John,

Is not quite solved yet but I have to put the GPS down for a while. Most of the testing I've done has been by my window, and sometimes I get a lock and others I don't., so I don't know if the trouble I'm having is a combination of issues like you mention before.

The original plan was to log GPS data, engine rpm, throttle position and air fuel ratio on my race bike before race day an the end of October, so now I'm out of time to mess with the GPS and start preparing the bike.

I thought I was going to be able to pull it together with in 2 weeks time, but my ambition exceeded my ability. My background is mechanical, though I do quite a bit of coding, I though this project was going to be a breeze. My electrical skills are not so good either, so when I don't understand something, which is mostly everything, I have to do quite a bit of reading before I understand enough and continue troubleshooting. Now that I ditched the GPS and I'm only running netduino, I was able to calculate RPM from the pulse that goes to the gauges and the voltage coming from the air fuel ratio sensor, but when I connect them together, the voltage from the air fuel ratio sensor is different. I did split the voltage to get it down from 10v to 3.3v, but now I don't know if the pulse is throung the rest of the circuit voltage off.

So you see, I need to put this project down and prepare the bike. This is the last race of the season and I'm after some money so I need to have the bike in optimal conditions. Unfortunetly, this project was going to help me achieve that by logging air fuel ratio, so at the end is not going to be perfect but is all I can do for now. I will rethink this project during the winter time, or I just may buy a system already developed.

I want to thank you for your help figuring out the GPS, is the first time I do this and you help was appreciated.
By ezflyr
Hi Alex,

OK, glad to be of some help!

Frequently in a multi-function project, getting everything to work correctly can seem a bit daunting. The key is to break the project into manageable bits, get them working alone, and then integrate them together! Even things that worked alone will no longer work together, so it's a continual process, but it's always fun!!

One of EM-406A modules is used to collect telemetry for model airplanes. In addition to measuring position via GPS, it measures dynamic air pressure via a pitot (airspeed), static air pressure (altitude), a variety of voltages and currents, and cylinder head temperature. Everything is stored to SD card for post-flight analysis, and I'm currently working on a 900 MHz data downlink system for "real-time" measurements!

Good luck!

By ekoy
if the led is blinking then for sure , you have acquire the gps data already
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