This page documents how to use the Garmin GPS 16/18 OEM Sensor or the Motorola ONCORE GPS Receiver and Interface Board for WinSDR time keeping. It is important to note that the actual time keeping process occurs on the A/D board or the VolksMeter Interface board, so the A/D data is time stamped before it is sent to the WinSDR system. WinSDR does not use the computer time for time keeping unless you have the Computer Time reference mode enabled in the System Settings dialog box under Time Reference Type. To use the Garmin GPS option you must have firmware version 2.0 or higher running on your Serial Output A/D board.
To use the GPS option, attach the GPS receiver to the male 9-pin DB9 connector on the Serial Output A/D or VolksMeter Interface board.
The following RS-232 lines are used by the A/D and VolksMeter boards:
Pin 1 - Data Carrier Detect. Used for the 1 pulse per second signal from the GPS receiver.
Pin 2 - Serial output data from the GPS receiver.
Pin 3 - Serial input data to the GPS receiver.
Pin 4 - +5 volt DC power for Garmin GPS 16 GPS Sensor. A/D board version 1.5 or higher.
Pin 7 - Ground signal for Garmin GPS 16 GPS Sensor. A/D board version 1.5 or higher.
Pin 5 - Ground
The Garmin GPS 16 GPS receiver and antenna combination can be connected to the A/D board using a 8 pin RJ-45 female to 9 pin RS-232 female adapter (www.jameco.com PN: 66211). The adapter should have the following pins connected together:
RJ-45 Pin 1 (Blue) to RS-232 Pin 4 - +5 V power
RJ-45 Pin 2 (Orange) to RS-232 Pin 5 - Ground
RJ-45 Pin 3 (Black) to RS-232 Pin 7 - GPS Enable
RJ-45 Pin 4 (Red) to RS-232 Pin 3 - Serial Data Input to Receiver
RJ-45 Pin 5 (Green) to RS-232 Pin 2 - Serial Data Output from Receiver
RJ-45 Pin 6 (Yellow) to RS-232 Pin 1 - 1 PPS Output
RJ-45 Pins 7 (Brown) & 8 (White) are not used.
Note: The wire colors above are for the Jameco adapter not the GPS sensor cable.
To enable this option in WinSDR, open the System Settings dialog box using Settings / System menu items. In the Time Reference Type field select either the GPS ONCORE or GPS GARMIN item. When you close the dialog box, the A/D board will attempt to lock on to GPS time.
On the Real-time window you will see the lock status of WinSDR and the A/D board. If you see a (N) after the local time display, WinSDR is not locked to the time reference. When you see a (L), WinSDR is locked to GPS or GMT time. A (?) indicates that WinSDR was locked at same time, but was unable to lock within the last 12 hours.
When you first connect up the GPS receiver to WinSDR, you should issue a reset command to the receiver. By issuing this command you will insure that that receiver is sending out accurate time information. To reset the receiver, use the Settings / GPS / Reset GPS Receiver menu items. When asked, press the Yes button. After resetting the receiver it will take 15 minutes or more, the actual time depends on how many satellites the receiver is seeing, for the almanac to be downloaded into the GPS receiver. Once the almanac is download, the receiver will start to send out time information.
To monitor the time keeping status, the user should look at the winsdr.log file. This file by default is located in the root WinSDR directory. The location of this file can be changed using the System Settings / Log File dialog box. You should also make sure that the Filter Good Time Information check box is not check in this dialog box, if you want to monitor the time keep information.
Another way of viewing the time status information, and other information messages produced by WinSDR or the A/D board is to open the Log File Viewer using the View / Log File / View Log File menu items. Once opened, this window will display any new messages added to the winsdr.log file.
Here is a typical log file produced by Version 1, 2, 3 and VolksMeter boards or our new PSN-ACCEL and PSN-ADC24 Boards. Below is information on the messages in the log file.
If you see any of the following error messages in the log file, there is a problem with the GPS receiver or RS-232 cable connection:
GPSRef: No Data from Receiver
GPSRef: No 1PPS Signal
GPSRef: Reset A/D Board Time - Sts:xx 1PPS Diff:xx
When the A/D board locks to GPS time, you will see this message:
GPSRef: First Reset - Time Diff:-0.046
Time Diff: The time in milliseconds between the A/D boards internal time and GPS time before the A/D board adjusts the time to GPS time.
Version 1, 2, 3 and VolksMeter boards will produce log message that look like this:
After the A/D board locks to GPS time you will see the following message every 5 minutes if the time difference between the A/D board and GPS time is less then 2 milliseconds:
GPSRef: Sts:2 Lck:2 Sats:06 AdjTm:12:41.6 S LckTm:00:03 MsAdj:0 MsOff:0 1PPSDif:0
Sts: This is the current time statues. 0 = No Add/Drop time interval, 1 = Calculation interval, 2 = Time interval has been calculated.
Lck: GPS Receiver lock status. 0 = not locked, 1 = 2D fix, 2 = 3D fix and 3 = differential fix using WAAS.
Sats: Indicates the number of satellites the GPS receiver is receiving. This number must be above 2 for initial lock and then above 1 after WinSDR is locked onto GPS time.
AdjTm: The current Add/Drop time interval and mode. Interval time in hours, minutes and seconds. Mode: S = Subtract time, A = Add time and ? = Unknown.
LckTm: The time in days, hours and minutes WinSDR has been locked to GPS time.
MsAdj: The number of 1 millisecond adjustments made to the time accumulator on the ADC/VolksMeter board to keep 1PPSDif: within 1 millisecond.
MsOff: This is the sum of MsAdj and 1PPSDif values.
1PPSDif: This is the time in milliseconds between the GPS time and the time accumulator on the A/D or VolksMeter board.
If you have the Set Computer Time check box checked in the Systems Settings dialog box, you will see the following message indicating that WinSDR has set the time of the computer running WinSDR. This will happen whenever the time difference between the system run WinSDR and the A/D board (or SDR server) is greater then 250 milliseconds or 1/4 of a second.
Adjusting computer time by xxx seconds
xxx = the adjustment made to the system time.
PSN-ACCEL and PSN-ADC24 boards will produce log message that look like this:
GPSRef: Sts:1 Lck:1 Sats:08 LckTm:01:14 Vco:45% VcoChg:00:33/00:02 PPSDif:0
Sts: This is the current time statues. 0 = Not Locked , 1 = Locked
Lck: GPS Receiver lock status. 0 = not locked, 1 = 2D fix, 2 = 3D fix and 3 = differential fix using WAAS.
Sats: Indicates the number of satellites the GPS receiver is receiving. This number must be above 2 for initial lock and then above 1 after WinSDR is locked onto GPS time.
LckTm: The time in days, hours and minutes WinSDR has been locked to GPS time.
Vco: The current VCO (Voltage Controlled Oscillator) percentage.
VcoChg: The time between VCO percentage changes. The first time number, in the example above 00:33, is the current elapse time and the second is the previous elapse time in hours:minutes.
PPSDif: This is the time in milliseconds between the GPS time and the time accumulator on the A/D board.