According to the data sheet (
[
^]) there are different versions with different serial interface specifications:
GPS 18x USB, GPS 18x PC, GPS 18x LVC, and GPS 18x-5Hz.
If you have the 5Hz version you must use 19200 baud.
Quote:
GPS 18x LVC and GPS 18x-5Hz: 0 V dc to Vin, between 4 and 5.5 V dc (Asynchronous Serial, TIA-232-F (RS-232) Compatible Polarity)
indicates that the interfaces use logic voltage levels (TTL, GND and 5 V) while RS-232 uses +/- 3 to 15 V (see
RS-232 - Wikipedia[
^] ). So it can't be connected to the serial port of a PC. Instead, a RS-232 level shifter must be used.
Finally, it might be necessary to invert the received data ("Compatible Polarity" indicates that the output is inverted like with RS-232 but RS-232 level shifters will invert again and serial TTL inputs will not invert).