GPS Lap Timer From Secondhand Parts


Hackaday forum member [nes] was training for an endurance race, and rather than having someone verbally call out his lap times, he wanted something he could keep in-vehicle to help keep track of his performance. With the race budget running dry, he and his teammates needed something cheap, if not free, to get the job done.

He scored a “broken” GPS receiver on eBay for a measly £4 and found that the receiver worked, but corrupted software prevented the unit from mapping routes. Since he didn’t require routing functions to keep track of his lap times, he splayed the GPS receiver open and started hunting around for a serial bit stream. He found what he was looking for after a bit of probing and hooked it up to his computer to see if the data contained NMEA sentences.

He cut the receiver down to the necessary parts and then started work on the lap timer itself. The timer uses an ATMega32 to run the show, displaying relevant time and location information on an LCD panel he scavenged from the trash bin.

He admits that the wiring is a bit questionable, but says that after about seven hours of rough use, everything is still intact and working great.

3 thoughts on “GPS Lap Timer From Secondhand Parts

  1. For what it’s worth, could he have not just worked on hacking a custom firmware onto the device instead of tearing it apart just for the GPS receiver, and from what I gather, a non-standard NMEA output that had to be parsed in order to obtain JUST the coordinates.

    This man probably could have saved himself some trouble and ended up with a nicer looking end product with a COLOUR screen!

  2. @Punkguyta: You hit on the point I was making by posting this up which was was also prompted by this earlier thread:

    Basically I was pushed for time, and not having any data on the ARM / WinCE system used in the sat-nav I would have had a tough time trying to figure out a tool chain for it. Far more effective to spend a few hours building something to your own specs and concentrate on coding for that instead.

    Oh, and battery life and sunlight readability would have been issues with the colour screen. :-)

  3. Hey I’m impressed :) Good job on getting something from nearly nothing lol. I saw a split open Garmin watch at the thrift shop I need to sweep up for weekend tinkering :) Happy running and thanks for keeping it off the street :)

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