Although this page is about using a particular board to provide GPS and PPSinformation over a 9-pin RS-232 connector, I've also used other boards intendedfor small PCs such as the Arduino, BeagleBone and Raspberry Pi - the AdafruitUltimate GPS Breakout - 66 channel board is such a device. Thesetypically have a 3.3V signal output which may not be enough to drive a typicalserial port, as that level doesn't meet the RS-232 specification. In thatcase you can use a level converter such as https://www.amazon.co.uk/gp/product/B00EJ9NAKAand power it off the same 5V source as the GPS - perhaps from a USB port usingjust the ground and +5V leads. The basic steps are:

The driver and hardware ID’s are listed below so check your hardware before you download and install the driver for this popular wireless adapter from 3Com. If you are looking for a Windows 7 driver then see the sidebar of this website from Windows 7 Issues which shows you how to make most software run on a Windows 7 computer. In this project we are going one step ahead with GPS and going to track a vehicle using GPS and GSM. This Vehicle Tracking System can also be used for Accident Detection Alert System, Soldier Tracking System and many more, by just making few changes in hardware and software.

Get NTP working correctly
Procure a suitable GPS/PPS device
Find or fit a COM port on your PC and connect a suitable device
Ensure that the serial data is available (you could use PuTTY to COMx)
Check that NTP sees the serial device
Ensure that you are getting PPS data - with my Serial Port LEDs program (need to stop NTP to check)
Install the loopback DLL (from Meinberg) and edit the system environment variables
Check that NTP sees the PPS data with a low offset - look for a 'o' in the tally code field (ntpq -pn)

Using the Sure board

Some experiments using the SureElectronics GPS evaluation board for NTP. If this board appears not to be available:

BillUnruh writes: thisURL right now gives a link to their GPS modules. Of course this isCanadaeBay. I just searched for 'sure eBay store' and then typed in 'gps' intothe search box. DJT: likely you can search your local eBay for theitem SKG16A or SKG16B.

Larry Ellis hassuggested:thisboard found on eBay as an alternative. It is from seller amoj1010, andis described as: UBLOX LEA-5T high precision timing GPS module dev board 1PPS/USB/RS232/ntp .

Getting a user-mode driver rather than kernel-mode driver (much easier to configure)

Note the very bright blue Pulse Per Second LED!
It would be nice to replace the current limit resistor.
(Click for an annotated image)

Here's my boxed version.
The box isn't rusty - that's the lighting.
The box was a Maplin N90BQ

I was alerted to this board by the TimeNutslist, and inspired by TomVan Baak's Web page. The unit is not just the board, but comes with aGPS magnetic mount antenna puck, and a USB cable, so it's a ready-to-go GPSunit.

Meeting the PPS over RS-232 requirement

The purpose of the patches is to provide a true RS-232 level PPSsignal on pin 1 (DCD line) of the connector. Whilst the PPS signal ontest point TP9 could be used, it is at CMOS level and not RS-232 level,and may not be recognised correctly by the RS-232 receiver chip in your PC. You can try it if you like, of course. I have provided a SerialPort LEDs program to show the status of the RS-232 control lines. Fortunately, there is an unused CMOS-to-RS-232 level converter gateavailable in U6, with its input on pin 11 and its output on pin 14. However, as this is an inverting gate, and we want a positive going PPS signal,it should be driven with a negative going PPS signal. That available atTP9 is positive going, however it is also used to drive theridiculously bright blue LED through a CMOS inverter gate in U5, so by takingthe output from that inverter on pin 8 of U5 we have the required negative-going PPS signal to drive U6.

. or as a picture

CMOS
=> positive =>
PPS

pin 9

U5
CMOS
inverter

pin 8

CMOS
=> negative =>
PPS

pin 11

U6
RS-232 level
converter

pin 14

RS-232
=> positive =>
PPS

pin 1

RS-232
connector

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The two red patch wires shown below were added by me to provide an RS-232 level,positive-going PPS output. Note that with the Windows NTP port, theDCD line must be asserted (positive going) as provided by this patch, asthat port cannot use an inverted DCD signal.

Krysztof Zaraska notes:

USB-TTL converters (I'm using FT232) use 'assert low' logic, meaning that low DCD is seen as asserted. Your site mentions this, but you don't say that if the PPS signal is directly hooked to the DCD pin of FT232, this results in NTP detecting the PPS source, but showing that the PPS source is off by 100ms (as it is looking at the wrong edge of the PPS pulse). Seeing this behaviour can be.. confusing.
You recommend using a CMOS inverter to flip the pulse polarity. I have found that at least with the GPS receiver I am using (Neo-6M from ublox) there is a simpler way: there is manufacturer's application(u-center) which allows you to set PPS pulse polarity.

Board patches

Only two wires need to be soldered to make the required patches - one is juston the top of the board, and the other goes through the hole near the RS-232connector to connect to points on both the top and bottom of the board. Iused solid enamelled copper wire with the enamel removed at the ends forsoldering. Of course, patching the board like this invalidates theguarantee.

Bottom side	Top side
Here is the through the board lead to pin 1 of the RS-232 connector. Note: This lead is not soldered to the empty hole on the J2 outline.	There are two patch wires shown here. The first, which is purely on the top side of the board, is from U5, pin 8, carrying the negative-going PPS signal to U6 pin 11. The second goes from pin 14 of U6, through an existing hole in the the board (no connection), to pin 1 of the RS-232 connector (shown left).

You can check that the patch is working with my SerialPort LEDs program, which shows the status of the RS-232 control lines. Watch for a brief white flash of the DCD indicator once a second which shouldapproximately coincide with the timing of the brief bright blue flash of theSure board LED.

Easier alternative

One person has reported that he has obtained satisfactory results connectingthe TTL-level positive-going signal on TP9 directly to pin 1 (DCD) of the RS-232connector. This may be easier if your soldering abilities are not as goodas you wish, as the connection points are larger and easier to solder to. This does work with the serial ports on many PCs, but mayresult in a lower protection against electrical noise if you have a long leadfrom the Sure board to your PC. A couple of metres lead length should befine for this method, but possibly not an 80 metre run near interference sourcessuch as electrical machinery - i.e. anything with power switches ormotors. Try it and see, but use at your own risk.

The Sure evaluation board in use - it works well!

Initial tests were with a Windows 2000 system (PC Bacchus)running ntpd 4.2.7p97-o,from Dave Hart's site (youmay need a 64-bit version, for example) and the board worked perfectly once the NTP serial ratewas changed from the NTP default of 4800 baud to the board default of 9600baud. If you are running a different version of NTP, you may find that itdoesn't pick up the GPS properly, and the reach w

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