GPS

Note: This article is not complete yet. I am intending to add a wiring diagram (whenever I get around to re-installing Visio on my computer) and a build video (whenever I get around to making it).

List of parts:

The links above are to the components I used but any suitable alternatives could be used.

If you are going to use a dedicated 1s lipo then the voltage buck is required to convert the LiPo voltage to a stable 5v output. Alternatively the unit can be powered from any 5v supply (e.g. flight controller 5v pin).

Build instructions:

  • Configure your data logger (the description below is for the fermion data logger linked to above).
    • Format your SD card to FAT 32 and insert it in the data logger
    • Insert the SD card into the data logger and connect a 5v power supply for a minute or two (this is to allow the data logger to write a default configuration file to the card)
    • Remove the card and insert it into your computer.
    • Edit the config.txt file to set the data rate and output filetype (CSV is preferred).
      • Baud=02,FileNum=00001,FileFormat=1,Time=0
      • The important settings is Baud=02 (or whatever baud rate your GPS module defaults to):
        • 00: 2400
        • 01: 4800
        • 02: 9600
        • 03: 14400
        • 04: 19200
        • 05: 38400
        • 06: 56000
        • 07: 57600
        • 08: 115200
        • 09: 128000
        • 10: 230400
        • 11: 512000
        • 12: 1000000
      • FileFormat=1 is for CSV output files.
    • Save the configuration file, eject the SD card form your computer and put it back in the datalogger.
  • Make the connections
    • Data logger
      • +5v to Voltage buck +5v output (or Flight Controller 5v output.
      • Gnd to Voltage buck Gnd output (or Flight Controller Gnd)
      • TX to GPS module RX (not really required)
      • RX to GPS module TX
    • GPS module
      • +5v to Voltage buck +5v output (or Flight Controller 5v output.
      • Gnd to Voltage buck Gnd output (or Flight Controller Gnd)
      • RX to Data logger TX (not really required)
      • TX to Data logger RX
    • Voltage buck (if used)
      • Make sure you configure the output for 5v. The item linked to above has a default output of 12v!
      • +5v out to +5v on Data logger & GPS module
      • Gnd out to Gnd on Data logger and GPS module
      • Vin to Battery +
      • Gnd in to Battery -

wiring for DIY GPS logger (with voltage buck)

 

  • Check the connections! (I did fry one GPS module by accidentally reversing the + & - power wires!)
  • Test
    • Power on the unit and wait for the GPS module to log onto some satellites (the GPS LED on the GPS module will illuminate or flash).
    • Walk around a bit to get some data.
    • Power off the unit
    • Remove the SD card and put it in your computer.
    • Find the data file (in my case File00001.csv).
    • Upload it to the converter program.
    • Download the converted file.
    • Open the converted file in Google Earth
    • If all is well you should see the path you took when walking around.

 

 

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The idea behind the DIY GPS logger is that you put it in your plane, drone, car or whatever, after your flight (drive) you remove the SD card (or connect via USB), upload the logfile to the NMEA to KML converter, download the resulting KML file and view the path your model took on Google Earth.

I used to use a "SkyRC GSM-015 GSS Speed meter". The problem with this is that it generates a proprietry file that can only be viewed in the SkyRC software. I did write a conversion program to convert this file to KML but SkyRC kept changing the file format between different firmware revisions and it was taking me too much time to keep re-writing the converter program.

While looking for alternatives online, I found an article on "RC Groups" by pesp with details of a homemade GPS logger he had made. It looked quite easy to build so i set about making my own. In his article pesp uses GPSVisualizer.com to convert the output to KML. I found this too restrictive so I wrote another program to do the conversion. The output from the logger is a standard NMEA GPS text file so is quite easy to convert.

My DIY logger includes a voltage buck to provide a stable 5v supply from a 1S LiPo (3.7v) but it could also be powered from a 5v pin on a flight controller or BEC.

The build time for the DIY logger is around 10 minutes.

Instructions for building it are in another article.

 

 

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