Interfacing the Pharos GPS-500 to Mac OS X

Update 2015: This is very old. I don’t know the status of a decent OS X 10.10 driver for the Prolific PL-2303 in this GPS.

I’m stopping short of calling this “Using the Pharos GPS-500 to Mac OS X” because all I’ve been able to do is read raw NMEA sentences from the device. But that might be of use to you.

The Source is clearing out copies of Microsoft Street & Trips with GPS 2008 for $20. The GPS is a very simple USB Pharos GPS-500, which uses the SiRF III chipset. Between the USB cable and the GPS is a small black box which looks suspiciously like a serial to USB converter. I have no use for the software, but the GPS is a bargain, considering a similar bare unit costs $60.

Plugging it into a Mac does nothing beyond being recognized as a “USB-Serial Controller D” from Prolific Technology, Inc. The ancient driver on Pharos’ website identifies the serial chipset as the Prolific PL2303. The only driver I could get to work with Snow Leopard was the failberg/osx-pl2303, a fork of an earlier project from Sourceforge. You’ll know if it’s working when you get a device called /dev/tty.PL2303-something appear.

Reading the data’s pretty simple if you have GNU Screen installed. I entered the following command:

screen /dev/tty.PL2303-12345678^XX^D?^XX 4800

and very quickly started to get NMEA data scrolling in the terminal:

$GPRMC,003322.000,A,4343.8349,N,07915.8845,W,0.38,112.13,211210,,,A*7B
$GPGGA,003323.000,4343.8351,N,07915.8838,W,1,05,2.8,174.3,M,-35.1,M,,0000*65
$GPGSA,A,3,09,18,14,21,22,,,,,,,,6.9,2.8,6.3*34
$GPRMC,003323.000,A,4343.8351,N,07915.8838,W,0.89,122.04,211210,,,A*76
$GPGGA,003324.000,4343.8351,N,07915.8843,W,1,06,1.5,176.0,M,-35.1,M,,0000*62
$GPGSA,A,3,27,09,18,14,21,22,,,,,,,3.4,1.5,3.1*30
$GPGSV,3,1,12,18,78,082,28,22,61,307,27,09,56,076,30,27,40,053,19*7F
$GPGSV,3,2,12,14,38,254,18,21,32,180,21,15,27,062,16,26,12,059,*7E
$GPGSV,3,3,12,19,10,302,,12,07,119,,06,04,261,,03,02,272,*7E

To stop screen, type Control-A Control-\. Do not just unplug the GPS, as you risk your machine crashing.

These NMEA sentences can easily be converted to GPX.

8 thoughts on “Interfacing the Pharos GPS-500 to Mac OS X”

  1. I just managed to melt mine while trying to solder on leads. Incidentally, the USB-serial dongle has a screw behind the label on the back – don’t try to pry it apart.

    Actually, got it to work fine with Arduino. The unit only need three wires, and outputs TTL serial.

  2. Any chance you have the pinouts for this gps receiver? The link in the story above is broken. Any help would be GREATLY appreciated.

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