PPS Troubleshooting
Posted by John Lindberg, Last modified by
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on 22 May 2007 04:24 PM

PPS Troubleshooting

To use the PPS signal from a GPS for time sync you must use a HYPACK PPS box interfaced between the GPS and you computer serial port. There are three different drivers that can be selected in HYPACK Hardware: GPS with NMEA-0183 Output (GPS.DLL) Kinematic Real-time Tides (KINEMATIC.DLL) APPLANIX POS/MV Network (POSMV.DLL).

To sync to PPS with one of these device drivers the driver responsible for synching must be the first driver installed in HYPACK Hardware. Also, the option SYNCHRONIZE COMPUTER CLOCK WITH GPS CLOCK must be checked. This option is located under HYPACK CONFIGURATION in HYPACK Hardware. ZDA must also be output from the GPS at 1 Hz.

To confirm that you are getting the PPS pulse into your computer:

  • Is the light on the PPS box blinking, 1 second on and 1 second off? If so, the PPS signal is coming into the box.
  • You also need the serial output from the GPS going right into the PPS box serial input, and the serial output of the PPS into the PC. Be sure this is a standard 9 pin cable because we use pin 6 of the serial cable to send the PPS pulse.
  • To be sure you are receiving the PPS signal into the PC, go into HYPACK, go to UTILITIES-COMMUNICATIONS-COMTROL’S WCOM32. This is a terminal program. Click on PORT-OPEN PORT and connect to the com port your PPS box is connected to. You then should see a little CTS light blinking one second green, one second grey. If so then the PPS is getting into the PC.
  • What is the baud rate set for your GPS? A lower baud rate of 9600 or 19200 seems to work best for time synching to PPS.