GPS from TomTom Go 300 (Cirocomm G100/300 580)

Aug 17, 2010
Category:Arduino Electronics 

My mate kindly donated his old broken TomTom Go 300 from which I was hoping to steal the GPS chip and antenna for use in my Arduino projects. I opened it up and found the GPS unit, it was labeled Cirocomm G100/300 580 but I couldn't find much info about this on the net, there were several posts of people with them asking about the pin outs and one site where someone had apparently got it to work but unfortunately hadn't detailed the pin outs. So, I had to resort to trial and error at the risk of blowing it up... It seems luck was on my side and I soon got it working, I will detail the pins I used as others seem to be after the info, I can't grantee they are the "correct" pins, but they work for me...

I soldered to the small gold TP circles that were dotted over the board, rather than the ribbon cable connector its self. I'm guessing these are test points connect directly to the ribbon connector and other interesting places. There is a large group of them on the board on the opposite side to the ribbon connector. These are the connection I used:

TP28 = VCC (+5V)
TP4 = TX (4800 baud)

And thats it, if all goes well, on the TX line you should be receiving this kind of data:

$PSRFTXT,Version: *5F
$PSRFTXT,TOW: 160126*17
$PSRFTXT,WK: 1597*6F
$PSRFTXT,POS: 4043192 -123430 4914862*32
$PSRFTXT,CLK: 95692*2C
$PSRFTXT,Baud rate: 4800 System clock: 24.553MHz*76

Thats NMEA data and some of those lines will constantly repeat every second or so with updated geo coords and other interesting info.

The $GPGGA line is the interesting line containing 5043.9983,N,00144.8843,W which = 50° 43.9983' N and 1° 44.8843' W. If you are looking to plot this on google maps dont be fooled by the fact that its in degrees and decimal minutes and that google maps uses decimal degrees so some conversion is required.

Hope this helps and let me know what cool devices you make from this unit :)