If you’re like me you have found that the GPS accuracy of Android phones and tablets leaves something to be desired when used in the car. My Sony Android tablet can barely get a fix from inside the FJ.
I have been wanting to get away from my Windows based CARpc with the built in GPS and use either my Android tablet on my new touch screen laptop for the moving maps in the FJ. The laptop does not have any GPS.
To remedy these problems I started looking for a bluetooth GPS and found a number but none of them had the capability to use an external GPS antenna. To get the best accuracy from inside the car an external antenna works best. I also do want to have the GPS installed in an out of the way place, not on the dash.When I completed the original FJ Cruiser build I included an external antenna to feed the GPS that I built into the CARpc. I figured that I would just repurpose this antenna.
Well, the hobbyist came out and I just figured that I would build it myself. I am happy to say that I now have a functioning Bluetooth GPS that has an external antenna jack on it. The total cost was about $70.00 for all the parts and the time, with a little experimentation, was about 6 hours.
The parts are listed here:
- Garmin GPS15xL OEM low voltage GPS
- HC-05 Bluetooth radio installed on component board
- 12 volt to 3.7 volt power supply
- GPS Antenna Pigtail
- Project Box
- LED
- Power addapter
The garmin GPS is configured using the Garmin X-Series Sensor Configuration Software. The GPS is directly connected to the PC through the serial interface. The key setting is the baud rate which must match the speed that the Bluetooth serial adapter is set to. The GPS also needs to be configured for standard NMEA sentences.
GPS Configuration Utility
For configuration the Bluetooth adapter is also hardwired to the PC with a serial cable. Traditional AT commands are used to configure the adapter. Again the baud rate of the interface is key and I set mine to the max rate the GPS will run at which is 38400. I also used an AT command to change the name of the Bluetooth to “GPS”
Both the Bluetooth adapter and the GPS can run on 3.7 volts which is supplied by the prebuilt power supply.
Bluetooth and power supply
System with GPS INstalled
With the system built my Laptop will connect and mapping applications can be configured to get the GPS data stream from the Bluetooth serial port. Android applications are not a simple. The Android GPS interface is built into the operating system. For an external GPS to be used the operating system must be fooled into using it. I install a Bluetooth GPS app that sets up a Mock GPS Provider and enables the mapping applications to use the external GPS.
Android NMEA Data stream
Satellite Status
GPS data output
I use Backcountry Navigator for Topo mapping on my tablet. In the FJ the only way I could get a GPS lock was to set the tablet on the dash. It also would take minutes to show my location on the map. With the external GPS it takes no more than 2 seconds to show my location. This will now make the Android Tablet a functional navigation tool inside the FJ.
With the GPS no longer tied to one specific system I will now be able to use both my windows and Android systems with no problem. Next in the project is to get the RAM Mount in the FJ setup to accommodate either the Laptop or tablet and remove the built in CARpc.
I know these are not specific build instruction but are intended to inspire and provide a general direction. I purchased all the parts off eBay.