NetMF Gadgeteer SeeedStudio GPS module driver oddness

A few months ago I built a proof of concept NetMF 4.2 application for a client which uploaded data to a Windows Azure Service. Recently we had been talking about extending the application to include support for tagging of the uploaded data with position information.

I purchased a Gadgeeter GPS Module from SeeedStudio and did a trial integration of the module into the client’s application. Initially it was working but I noticed that after a while (I monitored the application using MF Deploy) it would start displaying buffer overflow messages. I did the usual thing and went looking for “slow” code in the GPS events, removed debug print statements and made sure my application and the GPS were “playing nice” but the problem persisted.

My modifications seemed to make little difference so I downloaded the Microsoft Gadgeeter source code from codeplex so I could have a closer look at how the GPS driver worked. (I also personally would also like the driver to return the HDoP, VDoP or PDoP so there is an indication of the accuracy of the position data)

I noticed that there was a GPSTestApp and fired it up to see what would happen. I connected to my FEZ Spider device using MF Deploy and below is the output. The GPS Test application threw an exception shortly after I started it, then started displaying “Buffer OVFLW”. (Odd thing is I it must still be processing some NMEA1803 strings)

I need to do some digging to figure out what’s going on as initially thought it was my code but as the demo application fails I’m not so sure 🙂

Found debugger!
Create TS.
Loading start at a0e00000, end a0e1383c
Assembly: mscorlib (4.2.0.0)     Assembly: Microsoft.SPOT.Native (4.2.0.0)     Assembly: Microsoft.SPOT.Security.PKCS11 (4.2.0.0)     Assembly: System.Security (4.2.0.0)  Loading Deployment Assemblies.
Attaching deployed file.
Assembly: Microsoft.SPOT.IO (4.2.0.0)  Attaching deployed file.
Assembly: GTM.Seeed.GPS (1.6.0.0)  Attaching deployed file.
Assembly: Microsoft.SPOT.Graphics (4.2.0.0)  Attaching deployed file.
Assembly: Microsoft.SPOT.Hardware (4.2.0.0)  Attaching deployed file.
Assembly: Microsoft.SPOT.Hardware.PWM (4.2.0.1)  Attaching deployed file.
Assembly: GHI.Premium.Hardware (4.2.9.0)  Attaching deployed file.
Assembly: System (4.2.0.0)  Attaching deployed file.
Assembly: Gadgeteer.Serial (2.42.0.0)  Attaching deployed file.
Assembly: Microsoft.SPOT.TinyCore (4.2.0.0)  Attaching deployed file.
Assembly: GHI.Premium.System (4.2.9.0)  Attaching deployed file.
Assembly: GPSTestApp (1.0.0.0)  Attaching deployed file.
Assembly: Microsoft.SPOT.Net (4.2.0.0)  Attaching deployed file.
Assembly: System.IO (4.2.0.0)  Attaching deployed file.
Assembly: GHI.Premium.IO (4.2.9.0)  Attaching deployed file.
Assembly: Gadgeteer (2.42.0.0)  Attaching deployed file.
Assembly: Microsoft.SPOT.Hardware.SerialPort (4.2.0.0)  Attaching deployed file.
Assembly: GHIElectronics.Gadgeteer.FEZSpider (1.1.1.0)  Resolving.
GC: 1msec 28272 bytes used, 7311396 bytes available
Type 0F (STRING              ):     24 bytes
Type 15 (FREEBLOCK           ): 7311396 bytes
Type 17 (ASSEMBLY            ):  28176 bytes
Type 34 (APPDOMAIN_HEAD      ):     72 bytes
GC: performing heap compaction...
Ready.

Using mainboard GHI Electronics FEZSpider version 1.0
Program Started
#### Exception System.InvalidOperationException – 0x00000000 (4) ####
#### Message:
#### System.IO.Ports.SerialPort::set_ReadTimeout [IP: 0009] ####
#### Gadgeteer.Interfaces.Serial::ReadLineProcess [IP: 0015] ####
Uncaught exception
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
Buffer OVFLW
Buffer OVFLW
Buffer OVFLW
Buffer OVFLW
Buffer OVFLW

95 x Buffer OVFLW

Buffer OVFLW
Buffer OVFLW
Buffer OVFLW
Buffer OVFLW
GPS last position NO POSITION FIX age 10675199.02:48:05.4775807
Buffer OVFLW
Buffer OVFLW

4 thoughts on “NetMF Gadgeteer SeeedStudio GPS module driver oddness

    • Hi,

      I’m planning on writing my own thread based GPS driver just need to get some spare time.

      I was planning to slow device down to 4800 baud etc. so NMEA string processing workload reduced.

      Will post when I have got something to show

      Bryn

    • Is it possible to write a version of this that is for netmf 4.2? I can’t open Visual Basic on my PC. (sorry!)

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