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The smartphones contain an integrated GPS receiver. The devices used are marketed as Assisted GPS ('AGPS'). Performance requirements are defined in GSM/GPRS 3GPP TS 25.171, CDMA 3GPP2 C.S0036-0. There is some discussion available as to what significance that "A" might have.
The external antenna for the GPS uses an MMCX connector. More information about external antennas on the GPS antennas page. The connector for the internal GPS antenna also uses an MMCX connector. The external connector is located on the side of Freerunner.
The two current models (Neo 1973 and Neo Freerunner) use different GPS chipsets. The Neo 1973 used the Hmamerhead. The Neo Freerunner GTA02 GPS device contains the u-blox ANTARIS 4 ATR0635.
A critical problem with early (current) GTA02s is that accesssing the SD card generates RF noise, which causes very long TTFF (time to first fix) (10min+ or longer). See this page for more discussion and suggested fixes. Using an external antenna is one.
The Neo 1973 uses a separate userland driver to access the Hammerhead GPS. See this article for more information on this driver: gllin
The gllin driver itself is available here: http://3rdparty.downloads.openmoko.org/gllin/ It can be run from a command line. It outputs the NMEA data stream from the Hammerhead chip on a pseudotty device, so that it can be read as if the data were coming in on a serial port.
Here is email from Michael Shiloh about it. http://lists.openmoko.org/pipermail/community/2007-November/011916.html
There was an effort to write a Free Software program that could be used instead of this binary-only program, but this stalled after the decision to change GPS chips in GTA02. The Iphone 3G uses the same GPS chip. It's not inconceivable that this might lead to further effort.
See Hammerhead/Protocol for details and the latest status.
Some scripts for those with the binary are on Manually_using_GPS
Please see the important information on gllin!
There is no userland driver required for the GTA02, the driver is built into the kernel.
To turn on the GPS, echo 1 to the sys file:
echo 1 > /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/neo1973-pm-gps.0/pwron
To read from the GPS, simply read /dev/ttySAC1. Use the gpspipe command like this:
gpspipe -r 127.0.0.1 2947
You will find gpspipe in the package gps-utils. You can also just "cat /dev/ttySAC1" but it produces the unknown msg*58; This doesn't happen with gpspipe.
Before getting a fix, the GPS spits out lots of "$GPTXT,01,01,01,NMEA unknown msg*58", though these stop once a fix is obtained.
A position without a fix looks like this:
$GPGGA,235946.99,,,,,00,00,5.0,,M,0.0001999,M,0.0020199,*57
One with a fix:
$GPGGA,065852.00,5613.022527,N,00306.725890,W,1,05,0.5,158.0,M,0.277000,M,-0.010 0515,*7A
(The given position is in central Scotland.)
--Speedevil 11:52, 7 April 2008 (CEST)
If you are having GPS problems with your Freerunner, please document them on the page GPS Problems. FreeRunner GPS antenna repair SOP documents a possible solution.
In Openmoko projects, there is a GPS test program called agpsui that provides graphical and text dump of GPS information. See Howto Test Your GPS with agpsui. The project is called Openmoko AGPS UI project.
Aside from accessing the GPS data in applications programs running directly on the smartphone, you can also access the GPS data stream from another gadget such as a laptop.
Here are a couple ways to do that. You can use a network connection to pull data from the gpsd daemon, or you can make the smartphone appear to be a generic Bluetooth-connected GPS receiver.
Using gpsd requires a program that understands its protocol, such as GPSdrive. Using Bluetooth would allow using just about any program that understands the NMEA protocol.
This procedure depends upon being able to set up a network connection between your Neo and your laptop. The connection can be over either WiFi or USB cable.
First be sure you have gllin (on Neo 1973) and gpsd installed. Some Neo Freerunner images don't have gpsd, they use a different GPS stack called gypsy.
Tested with RoadNav. Works great!
If you have an unlimited GPRS data package you could make your gpsd service accessible over the Internet. This opens up many possibilities. For example, you could implemented AVL (Automatic Vehicle Location) by having a web server somewhere query your gpsd server for your position and write it to a KML file which would then display your location on a Google map.
Here is how to make your smartphone appear to be a Bluetooth GPS.
As people develop more sophisticated GPS applications, please note them here.
See [http://lists.openmoko.org/pipermail/community/2007-July/007252.html for another collection of ideas.
Please note if a program works or if it's vapourware.
here.