Testing the GPS module


The GPS module that I ordered arrived on Friday. This is the Adafruit Ultimate GPS Breakout v.3 which is built around the MTK3339 chipset. Adafruit has published a library and set of example codes to interface the module with an Arduino, which makes it really easy to get the device up and running in under 10 minutes.

GPS module

Detailed instructions are also available at the Adafruit Learning Center. To test the module, I mounted the GPS unit on a breadboard and connected the RT and TX pins on the module to the Arduino digital pins 0 and 1. By uploading this basic sketch on the Arduino, the data from the GPS unit is sent directly to the Serial Monitor and bypasses the Arduino completely.

GPS unit wired to Arduino

Even though I was inside the house, within two minutes of being powered on the  GPS module locked on to three satellites and started displaying positron data through the Serial Monitor. This first example code just pulls data right from the GPS module, even if the unit has not connected with satellites yet, so its an easy way to test to see if everything is working correctly. By looking though the output lines and reading the $GPRMC string I was able to determine the longitude and latitude values and verify my position with google maps to within 3 meters.

Screenshot 2013-12-21 10.55.31

For the next step, I would like to integrate the GPS module with a digital temperature sensor and SD card to create a basic GPS datalogging unit. This will give me something to do while I wait for the solar panel charging PCB and GPRS shield to ship. I’m also researching potential antennas to boost the sensitivity of the GPS chip, but need to ensure that they are waterproof and tough enoguh to  withstand the saltwater environment.


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