Do-it-yourself projects and technology updates

DIY Garmin GPS Connector

Well, I have been really interested in GPS units lately. I was working for a family practice doctor, and he had a Garmin eTrex GPS. He did not need it, and sold it to me for $50. It may not have been the best deal around, but it was my first GPS, and I wanted to play with it.

Well, it turns out that this lame GPS does not have any map in it at all. All this thing does is give you waypoints, and tell you the direction to go to get to any programmed waypoint. I guess this would be ok if you were in the woods. It is an older GPS unit, and it does not receive the satellite signals very well.

I started thinking what I could do with this thing, and started looking for mods for it. I found this one pretty easy little hack. This unit does have a 4 pin connector that can be attached to the device.



Above is a schematic of the connector pin out for the gps. This unit can be powered externally by a 3 VDC power supply.

The actual connector is not available, so it has to be made. This can be done using a credit card. See the below picture.



The data in and out are standard R232 serial lines. This GPS uses several different protocols for talking, one is called NMEA.

This GPS can actually be used to connect to a PDA. This is what I originally wanted to do with my device. You can buy a scrolling map software for your PDA for street navigation, and then connect any GPS source. Unfortunately my PDA is part of my phone, and does not have a serial port. I would have to buy a bluetooth adapter for this GPS which is expensive. Anyway, that is not the point, the point is you could use this GPS as a cheap alternative to buying a Garmin streetpilot 330 (Which I did finally buy.)

Garmin eTrex GPS receiver is a cute little thing that does not cost you a fortune. Although it does not have a scrolling map (unless you have one of those newer, more expensive models), and offers somewhat limited functionality compared to more expensive models, but it has a connector for attaching it to serial port of your PC or laptop. So, the connector:

Data in and data out are RS232 compatible signals for talking to GPS. eTrex knows several protocols, including generic NMEA and Garmin proprietary protocol that can be used to upload/download waypoints, tracks and routes. eTrex also has a firmware in FLASH, so you can update it over the serial cable, too.

Read more about this great DIY project here . This site also includes a schematic for making your own 3 VDC power supply.

This entry was posted on Sunday, May 6th, 2007 at 4:50 pm and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.