by nes » June 26th, 2011, 7:59 am
In your photo it looks like the GPS radio is a separate module connected via the grey wires to the top left. You could try probing those wires to work out the pin out and then you might be able to reuse that module in something else.
As there are four wires, these are quite likely to be: GND, Power, UART Tx, UART Rx.
The computer supplies power to the radio, but you need to check the voltage (+3.3V normally, but could be +2.5V). Ground can be found by testing for continuity between the metal can and one of the pins.
The UART is likely to transmit NMEA sentences in n-8-1 serial format. If you work out which of the two remaining pins is more active when the GPS is turned on, or which is active for a short burst once per second, you could try connecting it to the serial port of a PC via a transistor inverter. Run a terminal program and try different baud rates until you see something beginning "$GPRMC," appearing regularly.
Once you have the baud rate, connect your inverter to the last remaining pin and capture any data the GPS computer sends to the radio after a reset. If there is anything, you will probably want to copy that and send the same data at start up.
Now you can remove the radio module from the GPS, supply it with a regulated power supply and connect the UART pins to a serial port on your computer and make a GPS enabled thing. Even when indoors, a GPS receiver will give you atomic precision time. When outside, as well as position it will also give you your speed in knots (or km/h if you see the $GPVTG sentences) and your heading in degrees and may tell you other useful info too.
