Intro, transferring the GPS-module
Intro
The GP2X is an handheld running Linux. It has 2 arm-processors and a few peripherial interfaces: Available on the ext-port is a serial port which normally is used as a debugging port. Other hardware can be connected to it too, though. I've used it to build a GPS-receiver into the GP2X, while keeping the original debugging-function.
The beginning
It all started when I saw a SDIO-GPS-card in the sale-basket of a local
computerstore. The beastie was only E49,-, which isn't too expensive, and it
came with an internal antenna and an external antenna with 5M coax-cable.
Even if the device itself wasn't usable, I always would have 2 nice
GPS-antennas.
Opening the device
As soon as I came home, I decided to void the warranty and open up the device.
The contents were as I hoped: the device was made of a
SDIO-to-serial-port-device and a generic (but tiny!) GPS module with a serial
port at TTL-levels.
After a bit of measuring, I found out which of the connections was the gnd, which
one was the +3.3V and which one carried the signal. I then decided to test my
findings and connected the thingy to the computer.
The weather was nice and I picked up about five sattelites: the device seemingly
worked the way I thought it would.
Into the GP2X
From my experiences with the
USB-port
I built into my GP2X, I knew the unit still had some spare room to put things
in. I opened my GP2X and found myself a nice location for the GPS-pcb:
I then started connecting wires. I'd only need three: power, ground and serial.
The serial pin was available as a via at the underside of the PCB:
The gnd and 3.3V is retrievable at U13, pin 7 and 14 respectively. After
connecting everything and booting up the GP2X, it worked!
I got some serial output too:
The serial output is damaged a bit, because the gp2x-menu tries to read from the
serial port, too, but the NMEA-strings are recognisable.
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